Engineering the properties of metal nanostructures via galvanic replacement reactions

Claire M.Cobley,Younan Xia *

Department of Biomedical Engineering,Washington University,St.Louis,Missouri 63130,USA

Contents 1.Introduction ......................................................................................................452.

Template effects...................................................................................................452.1.Galvanic replacement between Ag nanocubes and HAuCl 4...........................................................452.2.Nanocages with controlled pores................................................................................472.3.Facet-selective deposition with single-crystal Ag spheres ............................................................472.4.Polycrystalline starting materials................................................................................482.5.Hollow Au-Ag nanotubes ......................................................................................482.6.Multi-walled structures .......................................................................................492.7.Hollow Au-Ag octahedrons containing gold nanorods ...............................................................492.8.Galvanic replacement with small multiply-twinned particles in organic media...........................................502.9.Synthesis of tadpole-like structures from Pd nanorods ..............................................................513.

Alloying and dealloying effects .......................................................................................523.1.Selective dealloying with ferric nitrate ...........................................................................533.2.Galvanic replacement with Pd and Pt precursors ...................................................................533.3.Effect of order of addition .....................................................................................534.Precursor effects:the case of Au(I)....................................................................................545.Optical properties:localized surface plasmon resonance ..................................................................556.

Applications ......................................................................................................576.1.Biomedical applications ................................

.......................................................576.1.1.Photothermal transducers..............................................................................596.1.2.Drug delivery.................................

.......................................................596.2.Catalytic applications .........................................................................................607.

Conclusion .......................................................................................................61Acknowledgements ................................................................................................61References ................................................

.............

..........................................

Materials Science and Engineering R 70(2010)44–62

A R T I C L E I N F O Article history:

Available online 2July 2010

Keywords:

Nanomaterials

Galvanic replacement

Localized surface plasmon resonance Alloy

Nanocage

A B S T R A C T

In this review,we will bring the reader up to date with recent advances in the use of galvanic replacement reactions to engineer highly tunable nanostructures for a variety of applications.We will begin by discussing the variety of templates that have been used for such reactions and how the structural details (e.g.,shape,size,and defects,among others)have interesting effects on the ultimate product,beyond serving as a simple site for deposition.This will be followed by a discussion of how we can manipulate the processes of alloying and dealloying to produce novel structures and how the type of precursor affects the ?nal properties.Finally,the interesting optical properties of these materials and some innovative applications in areas of biomedical engineering and catalysis will be discussed,completing our overview of the state of the art in galvanic replacement.

*Corresponding author.Tel.:+13149358328;fax:+13149357448.E-mail address:xia@https://www.360docs.net/doc/6c1184671.html, (Y.Xia).Contents lists available at ScienceDirect

Materials Science and Engineering R

j o u r n a l h o m e p a g e :w w w.e l se v i e r.co m /l oc a t e /m se r

1.Introduction

Metallic nanostructures have been extensively studied in recent years for applications in catalysis[1–4],plasmonics [5–8],sensing[9–13],and biomedicine[14–18].In order to further enhance the performance of these materials,there has been a strong effort in developing new methods for precisely engineering the structures and properties of these systems[2,19].Of the many techniques that have been demonstrated,galvanic replacement is particularly interesting due to its high tunability and the possibility to study the intricacies of alloying and dealloying in metallic nanostructures[20,21].Galvanic replacement occurs spontaneously when the atoms of one metal react with ions of another metal having a higher electrochemical potential in a solution phase.The metal atoms are oxidized and dissolved into the solution,while the metal ions are reduced and plated on the surface of the metal template.This simple reaction can be used with a wide variety of metal templates and salt precursors and is limited by little more than the requirement of an appropriate difference in the electrochemical potentials between the two metals.Based on fundamental chemistry,this reaction provides a straightforward and versatile route to a broad range of simple and complex structures including hollow nanocrystals,alloyed nanos-tructures with controllable elemental compositions,and nano-particles with tunable optical properties[20,21].

The most important factor in controlling the morphology of the ?nal structure in a galvanic replacement reaction is the shape or morphology of the starting template[22].As the newly formed metal atoms will deposit on the surface of the template,the?nal structure should closely resemble the original template.In a typical galvanic replacement reaction,the?nal structure is a hollow shell with a shape similar to that of the template and slightly larger dimensions[22].Yet as with many areas,some of the most interesting observations come from the exceptions.In the ?rst part of this review article,we will discuss the galvanic replacement reaction with a number of different types of templates,and highlight some of the engineering strategies that have come out of these comparisons.

The alloying and dealloying processes involved in a galvanic replacement reaction also have a strong impact on both the structures and properties of the?nal products[20,21].After a brief introduction to relevant processes such as atomic diffusion,we will discuss some of the ways in which these processes affect the morphology and properties of nanostructures synthesized using this approach.We will also discuss the effect that the choice of a salt precursor has on the evolution of a galvanic replacement reaction,as different morphologies have been observed when switching between a Au(III)salt and a Au(I)salt.

Finally,we will discuss some of the interesting optical properties and promising applications of structures fabricated using the galvanic replacement method.Due to the interaction between the plasmons of the inner and outer surfaces of a hollow structure,it is simple and convenient to tune the localized surface plasmon resonance(LSPR)peaks into the near-infrared(NIR) region for nanoparticles synthesized using the galvanic replace-ment reaction[23,24].Structures with strong optical absorption in this region are ideal for a number of biomedical applications,as NIR light can penetrate signi?cantly deeper into soft tissue than visible light[14–18,25–27].Particles with thin walls can also show more sensitivity to their dielectric environment,an ideal property for sensing applications[24,28,29].Though it is also possible to create hollow nanostructures with some of these properties by depositing small metal particles on the surface of a dissolvable template,this method is often limited by the dif?culty of creating smooth, continuous shells with controllable thicknesses below10nm [30,31].The resulting shells are typically less robust than those synthesized with the galvanic replacement reaction due to their polycrystallinity,and in some cases require additional synthetic steps,such as dissolution of the template[32].

In addition to biomedical applications,alloyed nanomaterials such as those generated with a galvanic replacement reaction also show great promise for catalysis—it has been shown that bimetallic nanostructures can be superior to their individual components for certain catalytic applications[4,33–36].Galvanic replacement offers a simple and controllable way to produce multi-component nanostructures with enhanced porosity and surface area,and is thus well-suited for such applications[37–39]. Furthermore,some reports have shown enhanced catalytic capabilities with hollow nanoparticles,likely due to the high surface areas.For example,Pd nanoshells were shown to retain their catalytic ability for multiple cycles,unlike their solid counterparts,for organic reactions such as Suzuki coupling [40,41].

2.Template effects

2.1.Galvanic replacement between Ag nanocubes and HAuCl4

A galvanic replacement reaction can be split into two half reactions,the oxidation/dissolution of a metal at the anode,and the reduction/deposition of the ions of a second metal at the cathode. For this reaction to occur,it is critical that the electrochemical potential of the metal ions is higher than that of the solid metal. The relevant equations for a typical reaction between Au and Ag are shown below:

Half reactions:

AgteaqTteàeaqT!AgesTe0:80V vs:SHET(1) Au3teaqTt3eàeaqT!AuesTe1:50V vs:SHET(2) Combined reaction:

Au3teaqTt3AgesT!AuesTt3AgteaqT(3) The electrochemical potentials of a number of commonly used metals are shown in Table1.Note that the potentials listed here are for ideal reactions at258C and1atm,and that the elevated temperature of this reaction(1008C),the presence of Clàions,and other non-standard conditions can all affect the actual potentials [42,43].

In recent years,the synthesis of solid metal nanocrystals having a wide variety of shapes and sizes has been achieved through careful control of the reaction conditions such as temperature,the concentrations of trace ions,and surfactant choice[19].Many of these nanocrystals can be used as templates for galvanic replacement reactions,making it possible to use this technique to synthesize hollow nanostructures with well-de?ned and controllable sizes and shapes.A typical example can be found in the reaction between Ag nanocubes and HAuCl4.This reaction is

Table1

Electrochemical potentials of relevant species relative to the

standard hydrogen electrode(SHE).

Half reaction E8/V vs.SHE a

Ag++eà!Ag0.80

Au3++3eà!Au 1.50

Au++eà!Au 1.69

Pd2++2eà!Pd0.95

Pt2++2eà!Pt 1.18

a For ideal reactions at258C and1atm.Elevated tempera-

tures,the presence of ions,and other non-standard conditions

can all affect the actual potentials[42].

C.M.Cobley,Y.Xia/Materials Science and Engineering R70(2010)44–6245

typically performed in boiling water to prevent the precipitation of AgCl onto the surface of the template [44].Fig.1shows a schematic illustration and scanning electron microscopy (SEM)images of the morphological transformations at different stages of this reaction (i.e.,after the titration with different volumes of HAuCl 4)for a sample of Ag nanocubes $100nm in edge length [22].Fig.1B shows SEM image of the starting template of solid Ag nanocubes.The inset shows an electron diffraction pattern obtained with the beam perpendicular to the surface of a nanocube.The square pattern indicates that the cube was bound by {100}facets.

When HAuCl 4was added,a small pit formed on the surface of the nanocube,likely at a defect site (Fig.1C)[45].As the titration was continued,this pit expanded into the interior of the nanocube and the resulting structure became increasingly hollow as more Ag was dissolved.Simultaneously,Au atoms plated on the surface of the nanocube,protecting the outer surface of Ag from oxidation.A small increase in size (10–20%of the initial cube size)was observed as the reaction progressed,indicating that the Au atoms were deposited on the outer surface [22].The conductive nature of the particle allows for electrons generated at the anode to move freely to the cathode where Au 3+ions are reduced and deposited.Fig.1D shows the product after enough HAuCl 4had been added to partially hollow out the Ag nanocube.The inset shows a microtomed transmission electron microscopy (TEM)image of a single particle,clearly showing the enlarged void inside the particle.

Eventually,this void expanded to ?ll the entire particle,resulting in a hollow shell with a shape similar to the original template,typically referred to as a nanobox (Fig.1E).A TEM image of a microtomed sample from this stage is shown in the inset of Fig.1E,showing the thin walled,hollow nanostructure.Notably,the pore in the surface had closed due to volume diffusion,surface diffusion,and/or dissolution and deposition [22,46].At this stage,the walls were composed of an Au–Ag alloy.Due to the close match in lattice constant and the high rate of interdiffusion between Au and Ag at 1008C,an alloy quickly formed as the Au was deposited.The details of alloying and dealloying processes will be discussed more thoroughly in Section 3.

As additional HAuCl 4was added,Ag was selectively removed from the alloyed walls,as no pure Ag remained.Due to the 3:1stoichiometric ratio between Ag and Au,many vacancies were generated during this process.In order to incorporate these vacancies,the nanobox was forced to reconstruct into a structure with a lower surface area [22].The sharp corners of the cubic box became truncated through the creation of triangular {111}facets at each corner,as shown in Fig.1F.As the dealloying process continued and additional voids were generated,they coalesced into pores on the surface,transforming the nanobox into a

Fig.1.(A)Schematic illustrating the major morphological and structural changes involved in the galvanic replacement reaction between a sharp Ag nanocube and HAuCl 4.The cross-sectional views correspond to the plane along the dashed lines.(B)SEM image of the sacri?cial templates,Ag nanocubes;and (C–G)SEM images for the hollow nanostructures obtained from sequential stages of the galvanic replacement reaction.Insets of (D)and (E)are microtomed TEM samples showing the hollow interior,and insets of (B)and (F)are the electron diffraction patterns for the corresponding nanostructures.The 100nm scale bar applies to all SEM images.Reproduced with permission from [22],Copyright 2004American Chemical Society.

C.M.Cobley,Y.Xia /Materials Science and Engineering R 70(2010)44–62

nanocage(Fig.1G).Note that the term nanocage is not shape speci?c,and can be applied to hollow and porous particles of other morphologies as well.If this reaction was continued even further, the pores became so large that the structure began to fall apart, resulting in Au nanoparticles with irregular shapes.The gradual replacement of Ag with Au allows for the creation of nanos-tructures with speci?c compositional ratios,an important ability given the strong effect that alloy composition has been shown to play in catalytic ability.

It is also important to mention that the?nal product retained the single crystalline nature of the initial nanocube due to the epitaxial relationship between the Ag nanocube and the Au shell that was deposited.This is evident in the diffraction pattern taken from a single Au nanobox,shown in the inset of Fig.1F.The square pattern of spots indicates that the nanobox was bound by single-crystal{100}facets,just like the solid Ag nanocube.The face-centered cubic(fcc)lattice constants of Au and Ag are almost identical,4.08and4.09A?,respectively,so the diffraction pattern was not expected to change after the incorporation of Au.

2.2.Nanocages with controlled pores

When more than one type of facets are present on the surface of the initial Ag nanocubes,it is possible to synthesize Au nanocages with controlled pores at the corners[47].In Fig.2,42-nm Ag nanocubes with truncated corners were used as the starting template,with six{100}facets and8{111}facets(truncation may also result in the presence of some{110}facets).Instead of forming pores randomly across the surface as seen with sharp nanocubes,both the initial pitting and the?nal pore formation occurred selectively on the{111}facets at the corners instead of on the{100}side faces,as illustrated in the schematic in Fig.2A. Fig.2B shows SEM and TEM(inset)images of the truncated Ag nanocubes used as a starting material.These cubes were generated through early quenching of a large-scale sul?de mediated polyol synthesis of Ag nanocubes,as the sharpening of the corners is the last stage of the growth process[48].It is also possible to truncate the corners of sharp Ag nanocubes through an aging process in a dilute solution of hydrochloric acid in ethylene glycol(EG)[49].

After the galvanic replacement reaction(Fig.2B),the pores in the wall were found at all eight corners and were uniform in size and shape,ideal for drug delivery applications which will be described in Section6.1.2.Due to the highly truncated nature, some of the nanocages were oriented perpendicular to the[111] direction instead of the[100]direction,and appear with a hexagonal cross-section.The facet selectivity is consistent with our observations of preferential binding of poly(vinyl pyrrolidone) (PVP)to{100}facets of Ag over{111}facets[50].This preference has been exploited in a number of syntheses of{100}capped Ag nanostructures,including the starting material of Ag nanocubes [51–54].Due to the lower binding strength in the{111}regions (or desorbing due to the low concentration of PVP in the reaction solution),it should be easier for the HAuCl4to react in the corner regions.

2.3.Facet-selective deposition with single-crystal Ag spheres

With both of the structures discussed so far,the overall morphology of the initial template was preserved throughout the reaction due to the formation of a thin shell of Au during the initial stages.However,if small,24-nm Ag spheres were used as the template,the particles underwent a morphological transformation into octahedrons[55].This process is depicted in Fig.3.Though approximated as a sphere,the initial Ag particles are more accurately described as cuboctahedrons,with a mix of{100}and {111}facets.As described above,the pitting of the galvanic replacement reaction occurred on the{111}facets,while the deposition of Au occurred on the{100}facets and the edges of the structure.Due to the small size of these particles,this uneven growth rate was signi?cant enough to cause a transformation from a cuboctahedral shape to an octahedron-like structure.The transformation of cubes and cuboctahedrons into octahedrons has been previously reported for Ag nanostructures,due to preferential overgrowth of Ag on the{100}facets[56,57].A similar shape transformation has also been reported for the

Fig.2.(A)Schematic showing the morphological changes during the different stages of the galvanic replacement reaction with a truncated Ag nanocube(or cuboctahedron). Pores formed selectively on the{111}facets instead of the{100}facets.Reproduced with permission from[20],Copyright2008American Chemical Society.(B)SEM(with TEM inset)of truncated Ag nanocubes.(C)SEM(with TEM inset)of Au nanocages synthesized from the Ag nanocubes in(B).Due to the highly truncated nature,some cages are oriented with a[111]orientation instead of a[100]orientation,recognizable by the hexagonal cross section.Inset scale bars are50nm for both images.

C.M.Cobley,Y.Xia/Materials Science and Engineering R70(2010)44–6247

galvanic replacement reaction between 11-nm Ag spheres and AuCl 3in o-dichlorobenzene with oleylamine as a surfactant [58].

The initial pitting in the reaction began on a {111}facet,which then expanded to create a hollow void in the center of the particle.As this occurred,Au was added to the {100}facets,resulting in an intermediate stage of a hollow octahedron.As the reaction progressed further,more pores began to develop due to dealloying,which coalesced into large openings on the surface of the nanocrystal.The ?nal product was either a highly porous octahedron or a ring-like structure if many pores coalesced together.Interestingly,despite the small size,it was possible to tune the SPR wavelength of these nanostructures to 790nm,within the NIR window ideal for biomedical applications,making it possible to study the effect of a wide range of sizes of Au nanocages with similar optical properties.2.4.Polycrystalline starting materials

Though highly faceted nanostructures allow for more speci?c control of the porosity of the resulting materials,the galvanic replacement reaction is not limited to single-crystal substrates and can be used with a number of different types of materials.The simplest case is the reaction with roughly spherical Ag nanopar-ticles that can be synthesized using a number of different straightforward methods,making this reaction accessible to groups without extensive nanoparticle synthesis expertise and possible to perform with commercially available starting materials [59–62].Despite the slightly non-uniform morphology,the interesting optical properties of these materials and compositional tunability are mostly preserved from the reaction with Ag nanocubes,though some broadening of the LSPR peaks is expected [59].A detailed protocol for the galvanic replacement reaction can be found in [23]for interested groups.

The different stages of the reaction between Ag nanoparticles and HAuCl 4are presented in Fig.4.The initial Ag nanoparticles were roughly spherical and some twin planes are visible as the suspension was a mixture of single crystals and twinned particles (Fig.4A).The morphological changes were very similar to those reported for Ag nanocubes above.As HAuCl 4was titrated into the suspension,Ag was dissolved from the interior and Ag and Au interdiffused,resulting in Au-Ag alloyed nanoshells (Fig.4C).As the reaction was continued further,the Ag was dealloyed from the walls,leaving behind a porous nanocage (Fig.4E).If an excess of HAuCl 4was introduced,the nanocages eventually fell apart,leaving behind irregular Au nanoparticles (Fig.4F).2.5.Hollow Au-Ag nanotubes

It is also possible to use this method to generate hollow nanotubes with diameters of $100nm and lengths of several microns [22,63].Fig.5shows the different stages of the reaction between Ag nanowires and HAuCl 4.The wires used in this reaction had ?ve twin-planes along the length of the wire together with a pentagonal cross-section (see the inset of Fig.5A).The sides of the wires were capped with {100}facets protected with PVP,much like the sides of the Ag nanocubes presented in Fig.1.Due to the extended dimension of the nanowires,pitting began in a few different locations along the length of the wire.The gradual hollowing out of the wire was initiated from these pits and can be seen in Fig.5B.Once the non-alloyed Ag was removed,the product was a thin,continuous sheath or nanotube (Fig.5C).As with previously described structures,further addition of HAuCl 4at this stage resulted in pore formation (Fig.5E).Notably,despite the large size of the initial template,in the ?nal stage Au nanoparticles of small sizes were also generated,as seen with the Au nanocages in previously discussed morphologies.

Fig.3.Schematics and TEM images showing the different stages of a galvanic replacement reaction between HAuCl 4and 24-nm Ag spheres.Yellow and orange colors indicate {100}and {111}facets,respectively.Reproduced with permission from [55],Copyright 2008American Chemical Society.

C.M.Cobley,Y.Xia /Materials Science and Engineering R 70(2010)44–62

2.6.Multi-walled structures

It is also possible to use the galvanic replacement reaction to create structures with multiple walls[64].Three such structures are depicted in Fig.6:nanorattles,multi-walled nanoshells,and multi-walled nanotubes.Nanorattles are hollow shells containing a movable solid core.To synthesize these structures,a thin layer of pure Ag was coated on the surface of a Au-Ag alloyed particle via electroless plating.When the galvanic replacement was per-formed,the pure Ag was oxidized,resulting in a Au-Ag shell around the Au-Ag solid core,separated by a thin gap.The size of the spacing between the core and the shell could be adjusted by changing the amount of Ag plated.Interestingly,TEM results suggested that many of the cores were free to move around the interior of the particle.Few of the particles shown in Fig.6D had the core in the center of the particle.When TEM grids were dried at a tilting angle of708relative to the horizontal,40%of the cores were located on one side of the particle while21%were on the opposite side.Without tilting,there was almost no difference between the two(30%vs.27%).These observations suggest that gravity had an in?uence on the?nal location of the cores during the drying process.

This general strategy can also be used to prepare structures with more than two walls.Fig.6E shows a three-walled nanoshell created by alternating between galvanic replacement with HAuCl4 and electroless plating of Ag.These structures can also be referred to as nano-Matrioshka and are interesting to study for their optical properties due to interactions between the different shells.Finally, this technique can also be applied to Ag nanowires to create multi-walled nanotubes(Fig.6F).When subjected to strong sonication, some of these tubes broke into pieces,allowing the pentagonal cross-section of both layers to be seen,which was preserved from the original Ag wires(inset of Fig.6F).

2.7.Hollow Au-Ag octahedrons containing gold nanorods

Additional growth on the surface of faceted nanocrystals does not always lead to uniform coatings,especially when the thickness of the deposited metal extends beyond a few nm.The relative surface energies(g)of the common facets of an fcc metal are typically described by g{110}>g{100}>g{111}[65].As a result,these facets will have different reactivity,which can lead to uneven growth rates and a complete change in the morphology.A number of groups have taken advantage of these differences to generate both new geometries of a single metal[56,57]and a variety of bimetallic structures by carefully controlling overgrowth reactions[4,66,67].

It is possible to combine this versatile technique with galvanic replacement to generate increasingly complex structures[68]. Fig.7shows one such example,in which hollow Au-Ag octahedrons each contain a Au nanorod in their interior.The initial Au nanorods were capped by a mixture of{100}and{110} facets and are shown in Fig.7B.After Ag deposition,most of the particles transformed into Au@Ag octahedrons capped by{111}

Fig.4.TEM images(SEM insets)of different stages of the reaction between polycrystalline Ag quasi-spheres and increasing amounts of HAuCl4.Reproduced with permission from[22],Copyright2004American Chemical Society.

C.M.Cobley,Y.Xia/Materials Science and Engineering R70(2010)44–6249

facets,with a few other geometries such as decahedrons also present.A TEM image of the product at this stage is shown in Fig.7C and an SEM image is shown in Fig.7D.When this core-shell particle was titrated with HAuCl 4,the octahedral geometry was maintained,resulting in a hollow Au-Ag octahedron containing a Au nanorod (Fig.7E).As with a number of the reactions discussed so far (e.g.,nanocages and multi-walled structures),this reaction can also be performed with Pd and Pt,allowing for a combination of the interesting optical properties generated with galvanic replacement and the catalytic properties of these valuable metals [38,64,69].The details of the differences in the reaction with these two metals will be described in more detail in Section 3.

2.8.Galvanic replacement with small multiply-twinned particles in organic media

Studying the galvanic replacement reaction between HAuCl 4and small multiply-twinned Ag particles (MTPs)in chloroform has provided a number of insights into this versatile technique [70].In addition to the increased variety of surface coatings available,metal nanocrystals suspended in organic media may be more desirable for catalytic applications and creating optical coatings with spray deposition [71,72].The 11-and 14-nm MTPs used in the study were a mixture of decahedrons and icosahedrons.In the ideal case,these structures would be capped entirely by {111}facets,but slight truncation suggests that some {100}and (110}facets were present as well.Unlike the reaction with the larger,mostly single-crystal structures described above,a complete shell of Au was not formed during the replacement reaction.Instead,after the initial pitting,the particles were transformed immediately into either nanorings or nanocages.A mixture of these two morphologies was seen for both the 11-and 14-nm particles,though the relatively percentage of nanorings was higher with the 11-nm particles.TEM images and the proposed mechanisms for the reactions with icosahedrons and decahedrons are shown in Fig.8.From the locations of initial pores,it appears that pitting was initiated on the {111}facets,not the many grain boundaries and defects present in these multiply twinned structures.Though it has been demonstrated that replacement reactions should start from high-energy defect sites [45],studies of Ag catalysts have also shown that signi?cant amounts of oxygen species can be dissolved on grain boundary defects and the adjacent defect planes [73–76].Millar and co-workers suggested that the Ag in these regions would conse-quently be oxidized and develop a positive charge,forming a barrier to replacement reaction in these regions [73].However,the high number of vacancies and boundary defects in these multiply

Fig.5.TEM images of different stages of the reaction between 5-fold twinned Ag nanowires and increasing amounts of HAuCl 4.Insets:(A)TEM showing the pentagonal cross section of the wires,(C–E)SEM images of the respective products.Reproduced with permission from [22],Copyright 2004American Chemical Society.

C.M.Cobley,Y.Xia /Materials Science and Engineering R 70(2010)44–62

twinned structures likely promote rapid alloy formation,which could contribute to the ring-like structures observed in this system (in comparison with the hollow shells observed in other systems) [70,77].

The rapid evolution into nanocages and nanorings is also likely in?uenced by the small sizes of the template particles[70,77]. Studies of10-nm Cu and Au nanostructures found that alloying of these two metals occurred in less than30s[78].Studies of the galvanic replacement reaction with triangular Ag plates have also shown that dimensions of greater than20nm were required for complete shell formation,in plates thinner than this a triangular nanoring was formed instead[79].Interestingly,despite the very small?nal size of$15nm(for the14-nm Ag MTPs),it was possible to tune the LSPR wavelength to740nm,a region desirable for biomedical applications,before the particle collapsed into irregular solid particles with an LSPR peak around$520nm.

Studying this reaction in chloroform also provided useful insights about the effect of organic-phase capping ligands.The best results were obtained when the particles were conjugated with oleylamine (described above).If this ligand was replaced with oleic acid or tri-n-octylphosphine oxide(TOPO),the replacement reaction did not occur.The?nal product was a non-uniform mixture of particles with less than5%having a hollow structure.This difference was attributed to the stronger binding of these two ligands.Excess oleylamine added to the solution also played an important role. These molecules helped solubilize the AgCl that forms during the reaction through the formation of a AgCl(R-NH2)n complex.Without an excess amount of oleylamine in the reaction system,large AgCl clumps formed,disrupting the template-based reaction.

2.9.Synthesis of tadpole-like structures from Pd nanorods

So far,all the galvanic replacement reactions discussed have resulted in hollow structures.While this is the case for the majority of reactions,when Pd nanorods were reacted with HAuCl4,the?nal morphology was a solid tadpole-like structure with a Pd tail and an Au head[80].As this unusual localized deposition of Au was not observed when the same reaction was performed with Pd nanoparticles;the rod shape of the initial template is thought to be a key part of the mechanism.This attribution is further supported by the reports of other groups who observed a tadpole-like morphology when reacting Co nanorods with Au precursors [81].The small size of the Pd nanorods may also plays a role,as this system behaves very differently than the larger Ag wires in Section 2.5.

The initial Pd nanorods were capped by both{100}and{111} facets,and had dimensions of 4.0?0.3nm in width and of 17.4?2.4nm in length.A schematic of the reaction is shown in Fig.9and a TEM image of the initial Pd rods is shown in Fig.10A.As HAuCl4was gradually titrated into the suspension,Pd was dissolved from the entire surface of the rod and Au began to deposit at either end of the nanorod(Fig.10B).The selective deposition can be attributed to electron–electron repulsion forcing the electrons generated during Pd oxidation to be pushed to either end of the rod,where Au3+ions were reduced.

As the reaction continued,the appearance of Au at the tips switched from occurring on both ends to occurring on one end selectively(Fig.10C).This change can be attributed to Ostwald ripening,which would be enhanced by the conductivity of the rod. The Au heads continued to increase in size and eventually started to fall off the Pd tails(Fig.10D).At this point in the reaction,the dimensions of the Pd tails were reduced in all dimensions(to 2.9?0.4nm in width and11.6?2.5nm in length),suggesting that Pd was dissolved from all faces of the nanorod.

High-resolution TEM(HRTEM)analysis shown in Fig.10E con?rmed that the Au grew epitaxially on the surface of the Pd rod, due to the small lattice mismatch between the two metals(4%). Scanning TEM(STEM)and energy-dispersive spectroscopy(EDS) were also employed to analyze the composition of the head and the tail,shown in Fig.10F.The tail contained less than10%Au,while the head contained more than90%Au.The small amount of Au in the tail was likely in the form of a protective layer on the surface of the nanorod,as the Pd rod was not completely consumed even when an excess of HAuCl4was added.

Fig.6.Schematics illustrating the procedure for fabricating(A)nanorattles,(B)multi-walled nanoshells(i.e.,Matrioshka),and(C)multi-walled nanotubes composed of Au/Ag alloys.(D)TEM images of nanorattles that were prepared by reacting HAuCl4solution with Ag-coated Au/Ag colloids.(E)TEM image of multiple-walled nanoshells of Au/Ag alloy.Reproduced with permission from[64],Copyright2004American Chemical Society.(F)SEM image of double-walled nanotubes of Au/Ag alloy.Reproduced with permission from[130],Copyright2004Wiley-VCH.

C.M.Cobley,Y.Xia/Materials Science and Engineering R70(2010)44–6251

Later studies by Teng et al.with polycrystalline Pd nanowires of similar size also found a degree of spherical particle formation at the tips during the reaction with HAuCl 4[82].Unlike the result with the single-crystal nanorods reported here,the ?nal product consisted of a non-random alloy with an Au rich core and a Pd rich shell.This distribution of atoms was attributed to the higher rate of interdiffusion caused by a high concentration of defect sites/vacancies and the stronger binding of the alkylamine surfactant to Pd [82],demonstrating the importance of both surfactant choice and defect sites in controlling the galvanic replacement reaction.

3.Alloying and dealloying effects

To explain and control the ?nal morphology and properties of the resulting structures,it is critical to understand the alloying and dealloying processes involved in the galvanic replacement reac-tion.As ions of one metal are reduced and deposited onto the substrate of a different metal in the early stages of the reaction,interdiffusion across the interface leads to alloy formation.This process is described by Fick’s second law of diffusion,and the

relevant solution is:

C ex ;t T?0:5t0:5erf

2eDt T1=2

(

)

(4)

where D is the interdiffusion coef?cient and C is the atomic fraction of the deposited metal as a function of the distance from the interface (x )and time (t ).The interdiffusion coef?cient (D )depends strongly on temperature,and elevated temperatures increase the rate of diffusion [83].According to calculations based on Eq.(4),at 1008C (the typical temperature for the reactions presented herein),Ag diffusing into Au can create an alloy layer with up to 10%Ag after only 20s [21].Small particle sizes and the presence of defects and twin planes can also enhance the interdiffusion rate,as has been demonstrated in a number of systems [70,77,78,82].For example,studies of the rate of alloying of Au@Ag core-shell particles of different sizes have shown enhanced rates of interdiffusion for particles with cores smaller than $5nm with varying thicknesses of Ag shells (at room temperature)[77].This increased value of D was attributed to a greater number of vacancies through theoretical calculations [77].As the walls of Au-

Fig.7.Schematic (A)and different stages (B–E)of the synthesis of Au-Ag octahedral containing Au nanorods:(B)TEM of Au nanorods,(C)TEM of Au@Ag nanocrystals,(D)SEM of Au@Ag nanocrystals,(E)TEM of Au@Ag nanocrystals after the galvanic replacement reaction.Inset scale bars are 30nm.Reproduced with permission from [68],Copyright 2009Wiley-VCH.

C.M.Cobley,Y.Xia /Materials Science and Engineering R 70(2010)44–62

Ag nanoboxes(and related structures)are<10nm thick,the size dependence of alloying likely contributes to rapid alloy formation in most of the structures described above as well.

Alternately,dealloying interactions play a key role in the?nal stages of the reaction,when the component with the lower electrochemical potential is selectively removed from the alloyed walls.At this stage a large number of vacancies are generated, which coalesce into pores in the walls of the nanostructures.The dealloying process has been studied and reported in a number of publications,often for the removal of the less electrochemically active species with a separate etchant,such as nitric acid [42,43,84–90].In this section we will describe a few different ways that alloying and dealloying processes can effect the?nal morphology:post-reaction wet etching with Fe(NO3)3,using Pd and Pt precursors,and adjusting the order of addition in multi-metal titrations.

3.1.Selective dealloying with ferric nitrate

During a typical galvanic replacement reaction,the etching of Ag and the deposition of Au are tightly linked–one cannot occur without the other.However,by introducing a wet etchant such as ferric nitrate,it is possible to remove Ag without additional deposition of Au[84,85,91].This allows for even greater control of the wall thickness,composition,and the resulting optical properties of the alloyed nanostructures.By generating extremely thin walls,it is also possible to shift the LSPR peak of the nanocages to1200nm or longer while still maintaining a compact size of $50nm[91].

A schematic and TEM images(with SEM in the insets)of the product at different stages are presented in Fig.11.The initial Ag cubes with an edge length of50nm are shown in Fig.11A.In the ?rst step,a small amount of HAuCl4was titrated into the suspension to create a thin Au layer on the surface(Fig.11B). Next,as a small amount of Fe(NO3)3solution was added into a suspension of these early stage nanoboxes,the Ag remaining in the interior was dissolved,producing a thin-walled nanobox(Fig.11C). The walls of the nanobox at this stage were highly porous due to the large number of vacancies generated as the Ag was removed from the alloyed walls.

As increasing amounts of Fe(NO3)3were added,the morphology changed from a thin-walled nanobox to a nanoframe(Fig.11D). The inset of Fig.11D shows a458tilted SEM image,making the frame morphology more clear.This transition can be attributed to {100}facets being more susceptible to etching.As the Ag atoms on the faces are removed,the Au atoms can diffuse along the surface to the edges.This migration could be seen as increase in wall thickness when measured by TEM,despite the clear appearance of thinning and eventually empty side faces under SEM.At the?nal stage,the structure was100%Au as all the Ag had been removed.

3.2.Galvanic replacement with Pd and Pt precursors

The importance of alloying and dealloying of Au and Ag to the morphology and properties of resultant nanocages becomes increasingly clear when this system is compared with the same reaction performed with Na2PdCl4and Na2PtCl4[69].The electrochemical potentials for these species are listed in Table1. Fig.12A shows the result of titrating50-nm Ag nanocubes with Na2PtCl4.The replacement reaction occurred and a hollow structure was generated at the later stages of the reaction,but the surface was covered in bumps due to the lack of miscibility between Pt and Ag at the reaction temperature(1008C).When Na2PdCl4was used instead,the surface was smooth,but it was impossible to continue the reaction beyond the nanobox stage–pores never formed on the sides or at corners(Fig.12B)[69].The early stopping of the reaction indicates that the Na2PdCl4is unable to dealloy the Pd-Ag walls that formed in the early stage of the reaction.It has been noted in theoretical studies that Au and Pd can be stabilized when alloyed into an Ag matrix(and vice versa),and will consequently require higher potentials to be removed from the alloy than would be required to be oxidized as a pure metal [42,43].Given the small magnitude of the difference between the Pd and Ag potentials,the ability of Na2PdCl4to oxidize the pure Ag in the core but not dealloy Ag in the Pd-Ag alloy walls can reasonably be attributed to this type of stabilization.In both these systems,the range of LSPR tuning was also limited as compared to titrations of Ag cubes of the same size with HAuCl4.The Pt nanocages could be tuned to670nm(at which point they fell apart due to the polycrystalline walls)and the Pd nanocages could be tuned to730nm(when dealloying would typically begin),while Au nanocages of the same size can be tuned to900nm and beyond.

3.3.Effect of order of addition

When successive titrations with Au and Pd were performed in order to create nanocages incorporating more than two metals,the order of addition played a critical role in determining the?nal properties due to the differing dealloying abilities of the two precursors[38].If Pd was titrated before Au,large pores developed, whereas if Au was titrated before Pd the?nal product had solid walls,shown in Fig.12,C and D,respectively.The results from these titrations are summarized in a schematic in Fig.13.The effect of order of addition can be explained with a mechanism similar to that discussed for the Pd-Ag system above.The Au3+/Au pair has a much higher electrochemical potential than the Pd2+/Pd pair,and consequently even if small increases in the dissolution potential

Fig.8.Morphological evolution for Ag MTPs with(A)decahedral and(B)icosahedral

structures during the galvanic replacement reaction.(C)Proposed mechanisms to

account for the formation of hollow structures from oleylamine-capped Ag MTPs.

Scale bars in(A)and(B)are2nm.Reproduced with permission from[70],Copyright

2007American Chemical Society.

C.M.Cobley,Y.Xia/Materials Science and Engineering R70(2010)44–6253

occur due to alloying,Ag can still be removed through reaction with HAuCl 4.On the other hand,Pd is unable to remove Ag due to its weaker dealloying ability.The difference between the two systems also appeared in the composition and optical properties of the resulting materials.When Pd was titrated ?rst,the ?nal product had a higher Pd loading and a further red-shifted LSPR peak.

4.Precursor effects:the case of Au(I)

We have also investigated the reaction between AuCl 2àand Ag nanocubes to examine the effect that stoichiometric ratio plays in controlling the galvanic replacement.A schematic and SEM and TEM images of the progression of this reaction are shown in Fig.14[92,93].Due to the different oxidation states of Au,only one Ag atom is removed for every Au atom that is generated,resulting in striking differences in the ?nal morphology.

This reaction was performed in a saturated NaCl solution to solubilize the precursor,AuCl,though this had the added advantage of also solubilizing the AgCl byproduct as AgCl 2à.In the early stages of the reaction,the primary difference between the Au(I)and the Au(III)systems was the early disappearance of the pinhole,due to the larger amount of Au generated for the same amount of Ag being dissolved (Fig.1C).This means that the remaining Ag must diffuse through the walls of the nanobox in order to be oxidized.Difference in rates of diffusion between two metals at an interface has been shown previously to form voids in a process known as the Kirkendall effect [94].If the inner material diffuses out faster than the outer material diffuses inward,voids will form and coalesce into a pore.This effect has been shown to produce hollow nanostructures in a number of systems [95–99].Though it is possible this effect plays somewhat of a role in the late stages of the Au(I)reaction due to the early closing of the pinhole,the selective dissolution of the interior of the template during the early stages appears to be the primary mechanism for the formation hollow interiors in both the Au(I)and Au(III)systems.Instead of the consolidation of a number of small voids or the initial formation of a hollow layer in between the core and shell of a particle typically cited with the Kirkendall effect,a single void is observed to expand from one side of the cube to the other [92,96,99,100](see the TEM insets in Fig.1D or Fig.14C).

One of the notable features of the reaction with Au(I)is the thicker walls of the nanocages when compared to the Au(III)system,as shown in the schematic in Fig.14A.In the later stages of the reaction,these thicker walls helped support the formation of robust nanoframes,with greater mechanical stability than those reported from ferric nitrate etching.The evolution of the nanoframe morphology can be seen in Fig.14E–G.In the ?rst step,small pores formed on both the side and corner faces of the nanocage (Fig.14E).As more AuCl 2àwas added,the pores on the sides were enlarged and the pores on the corners began to close (Fig.14F);this process would continue until large pores dominated the side of each nanostructure,creating a nanoframe (Fig.14G).Small,extended regions were visible at the corner of each nanoframe,suggesting that the pores at the corner closed due to movement of Au atoms to the more stable {111}facet or possibly overgrowth of this facet due to the larger amount of Au being generated,as has been observed in the Pt system [101].

Based on these observations,it is clear that different precursors are ideal for different applications.When tuning the LSPR peak into

C.M.Cobley,Y.Xia /Materials Science and Engineering R 70(2010)44–62

the NIR region,the Au(III)precursor is ideal as thin walls are necessary for absorption in this region.For single particle studies of the effect of morphology on optical properties,Au(I)is preferable as it generates robust frames.

5.Optical properties:localized surface plasmon resonance One of the most useful features of nanostructures synthesized with a galvanic replacement reaction is the highly tunable optical properties that result from the tunable shift in the ratio between the inner and outer particle diameters (i.e.,the wall thickness)[24].The origin of these properties is a phenomenon known as LSPR [102,103].When a metal is irradiated with light,the delocalized electrons collectively oscillate relative to the lattice of positive nuclei.This coherent oscillation is known as a plasmon,a quantized quasi-particle analogous to a photon.For bulk metals extending in?nitely in all three dimensions,the plasma frequency (v p )is described by:

v p ?

Ne 2e 0e

1=2

where N is the number density of conduction electrons,e 0is the dielectric constant of a vacuum,e is the charge of an electron and m e is effective mass of an electron.When this plasmon couples with a photon,it creates a new quasi-particle known as a plasmon polariton,which can propagate along a metal-dielectric interface.The plasmons on the surface are the most relevant,as light cannot penetrate very deep into a metal surface (<50nm for Ag and Au).This interaction has been exploited to create waveguiding structures with metallic nanowires [5,7].However,for the primarily ‘‘0D’’nanoparticles discussed herein,the plasma oscillation will be highly localized and non-propagating due to the small dimensions of the particle relative to the electromagnetic ?eld.The resulting phenomenon is known as ‘‘localized surface plasmon resonance’’or LSPR,where resonance refers to the fact that the strongest plasmons occur when the plasma frequency is close to that of the incident light,creating a resonance condition due to constructive interference.A diagram for LSPR is shown in Fig.15for a generic metal nanosphere.

Incoming light at the LSPR wavelength can interact with the nanoparticle through two different processes:absorption and scattering.Absorbed light is converted into phonons,or heat,and is desirable for photothermal applications,whereas scattered light is

Fig.10.TEM images of (A)Pd nanorods and (B–D)samples that were obtained by titrating Pd nanorods with increasing volumes of HAuCl 4solution.The scale bars in the insets correspond to 20nm.(E)HRTEM image recorded along the [110]direction for the Pd-Au tadpoles shown in (C).(F)The EDS spectra for the Pd tail and the Au head.Reproduced with permission from [80],Copyright 2007American Chemical Society.

C.M.Cobley,Y.Xia /Materials Science and Engineering R 70(2010)44–6255

re-radiated at the same wavelength,useful for some imaging applications [16].The relative contributions of these two processes can be determined using theoretical calculations.For spheres,this can be calculated using exact solutions to Maxwell’s equations,as demonstrated by Mie in 1908[104].For more complex particles,the method of choice is typically the discrete dipole approximation (DDA),which approximates structures as an array of dipoles that interact with both the incoming light and each other [105].As a rough approximation,for small structures (e.g.,<50nm)the absorption cross section will be larger than the scattering cross section,while for larger structures (e.g.,>100nm),the inverse will be true.

The precise position of the LSPR peak depends on a number of factors,including the speci?c geometry of the nanoparticle and the local dielectric environment [102,106].Shape-controlled synthesis of metal nanocrystals has proven to be a versatile route to tune the LSPR peak position across the visible spectrum and into the NIR region [19,107–109].For solid particles,the aspect ratio,overall size,and sharpness of the features are the major determining factors of peak position and near-?eld distributions [106–111].For example,by simply truncating the corners of a nanocube,the wavelength will be blue-shifted by 50–150nm depending on the size of the initial cube [110].Despite these signi?cant shifts,it is still non-trivial to red-shift the LSPR of solid nanoparticles into the NIR region.Though extensive work has been performed with Au nanorods,whose LSPR can be shifted into the NIR region through careful control of the aspect ratio,more versatile methods to create nanostructures with NIR resonances are desirable due to the great interest in structures with absorption in this region for biomedical applications [25,26,109,112].

Galvanic replacement allows for straightforward tuning of the LSPR peak of nanostructures across the visible region and into the NIR due to the coupling between the surface plasmons of the inner and outer surfaces [16,20,21,24,113].This interaction is analogous to the combining of two orbitals in molecular orbital theory,and generates a symmetric (‘‘bonding’’)plasmon and an anti-symmet-ric (‘‘anti-bonding’’)plasmon [113].The symmetric plasmon with a lower energy interacts with the incident light,and determines the location of the LSPR peak.As the wall thickness of a nanostructure is decreased,the interaction between the two surface plasmons

Fig.11.(A)Schematic summarizing the synthesis of cubic Au nanoframes by ?rst titrating Ag nanocubes (B)with HAuCl 4to form Au-Ag nanoboxes (C),and then etching with ferric nitrate to form thin-walled nanoboxes (D)and eventually cubic nanoframes (E).Inset scale bars are 50nm.Reproduced with permission from [90],Copyright 2007American Chemical Society.

C.M.Cobley,Y.Xia /Materials Science and Engineering R 70(2010)44–62

increases,resulting in increased splitting between the symmetric and anti-symmetric plasmons.This lowers the energy of the symmetric plasmon,resulting in a red-shift of the LSPR.Through this mechanism,very small changes in wall thickness can have a signi?cant effect on the optical properties,allowing for facile tuning into the NIR region.Fig.16shows the LSPR properties of 50-nm cubic Ag nanocubes after different amounts of HAuCl 4solution had been added.As the volume increased,the walls became thinner (due to the removal of Ag as described in Fig.1)and the peak red-shifted through the visible and into the NIR region.6.Applications

6.1.Biomedical applications

Many types of nanostructures are being investigated for biological applications due to the broad range of properties present in this interesting size regime [114,115].In addition to being able to engineer the intrinsic properties like optical absorption and magnetism,it is possible to engineer the interaction between the nanomaterials and their biological surroundings through control of the size and surface properties [114–119].Particles in the right size regime have been shown to accumulate with higher concentrations in tumors than healthy tissue due to the enhanced permeability and retention (EPR)effect,also known as passive targeting.This effect can be enhanced by coating the surface of the nanostructure with polyethylene glycol (PEG),which retards recognition of the particles by the liver,

Fig.12.(A)TEM of Pt/Ag nanoboxes from the galvanic replacement reaction between Ag nanocubes and Na 2PtCl 4solution.(B)SEM and TEM (inset)of Pd/Ag nanoboxes from the galvanic replacement reaction between Ag nanocubes and Na 2PdCl 4solution.(C,D)SEM and TEM (inset)of Ag/Au/Pd nanocages from the galvanic replacement reaction between Ag nanocubes and (C)Na 2PdCl 4solution,followed by HAuCl 4solution,and (D)HAuCl 4solution,followed by Na 2PdCl 4solution.Inset scale bars are 40nm.Reproduced with permission from [38],Copyright 2008Wiley-VCH.

Fig.13.Schematic illustration of the morphological changes for Ag nanocubes during the re?uxing with Na 2PdCl 4,NaPt 2Cl 4,and HAuCl 4.When only Na 2PdCl 4or Na 2PtCl 4was added,a hollow nanobox was produced (though with a roughened surface for the Na 2PtCl 4).When only HAuCl 4was added,the reaction could continue further by dealloying the nanobox to produce a nanocage.If more than one precursor was added,the order of addition had a strong effect.For example,if HAuCl 4was added before Na 2PdCl 4,the morphology changes stopped at the box stage unless enough HAuCl 4was added to introduce pores before adding Na 2PdCl 4.If Na 2PdCl 4was added before HAuCl 4,the nanobox continued dealloying to form a nanocage as the ?nal product.Reproduced with permission from [38],Copyright 2008Wiley-VCH.

C.M.Cobley,Y.Xia /Materials Science and Engineering R 70(2010)44–6257

extending the circulation time so more particles have time to accumulate at the tumor site [116–118].Furthermore,if biologi-cally recognized molecules or antibodies are attached to the surface of a nanostructure (e.g.,through the gold-thiolate linkage),it is possible to bind selectively to over-expressed receptors on the surface of cancer cells,a process known as active targeting [114,115,119].The combination of these two effects has made nanomaterials a promising platform for highly targeted therapeu-tics,hopefully replacing current techniques that affect the body broadly and which lead to harsh side effects.

Gold nanostructures are particularly interesting because of the high biocompatibility of the metal,the well-known gold-thiolate

Fig.14.(A)Schematic diagram and (B–G)SEM images with TEM insets showing different stages of the galvanic replacement reaction between Ag nanocubes and different volumes of AuCl 2à.The scale bar below the images applies to all SEM images.The scale bar in the inset of (B)represents 100nm and applies to all TEM insets.Reproduced with permission from [93],Copyright 2008Wiley-VCH.

Fig.15.Schematic illustration of localized surface plasmon resonance (LSPR)showing the oscillation of delocalized electrons in the presence of an electromagnetic wave.

Fig.16.(Top panel)vials containing Au nanocages prepared by reacting 5mL of a 0.2nM Ag nanocube (edge length $40nm)suspension with different volumes of a 0.1mM HAuCl 4solution.(Lower panel)the corresponding UV-visible spectra of Ag nanocubes and Au nanocages.Reproduced with permission from [23],Copyright 2008Nature Publishing Group.

C.M.Cobley,Y.Xia /Materials Science and Engineering R 70(2010)44–62

chemistry that allows for simple,straightforward surface modi?-cation,and the strong optical properties from LSPR[120].Gold nanostructures with an LSPR peak in the NIR region,such as Au nanocages,are particularly desirable due to the low absorption from blood and water and low scattering from the tissue in this region[25,26].Gold nanocages also have the added advantages of a small size(e.g.,30–50nm like those shown in Fig.2),high absorption cross section,and a hollow interior,making them ideal for applications such as photothermal treatment and drug delivery, which will be described below[20].Gold nanocages are also promising contrast enhancers in optical imaging modalities; interested readers can?nd more information about such applica-tions in refs.[15],[27],and[121].

6.1.1.Photothermal transducers

Irradiation of gold nanocages with a NIR laser has been shown to cause strong heat generation,destroy cells in vitro,and cause a signi?cant decrease in metabolic activity and increase in cellular damage in tumors after in vivo injection[122–124].The amount of heat generated depends on three primary factors:the concentra-tion of nanocages,the laser power,and the irradiation time[124]. The effects of these variables are listed in Table2and depicted graphically in Fig.17.Panel A shows the change in temperature with time for different concentrations of nanocages after irradiation with a continuous wave(CW)diode laser at1W/ cm2.Panel B shows the same comparison,but with a laser power of0.5W/cm2.In both cases,only a small increase in temperature of2–38C was seen with the control sample of water,whereas increases of5–108C were seen with the lowest concentration of nanocages tested,109particles/mL.This temperature difference (D T)is enough to increase the temperature in an in vivo system from378C to well over428C,where denaturing of important biomolecules and cell death can begin to occur.With higher particle concentrations,such as1012particles/mL,the tempera-ture increase was even more pronounced,with a plateau

developing around a D T of448C after 2.5min for the more concentrated samples at1.0W/cm2.With a lower laser power of 0.5W/cm2,the temperature change was more gradual,and did not plateau in the10min of data collection.Though gold nanostructures can melt and lose their morphology and optical properties after irradiation with a pulsed laser due to the intense bursts of power,with this diode laser system no such loss of properties occurred.

6.1.2.Drug delivery

Gold nanocages can also be used to deliver other types of therapeutic payloads.There is great interest in creating drug delivery methods with speci?c release pro?les[114,115,125, 126].By coating with a thermosensitive polymer,it is possible to open and close the pores on an Au nanocage in a controllable manner,allowing the interior to serve as a drug delivery vessel [127].To allow for greater uniformity of the pore size,truncated nanocages like those shown in Fig.2are typically used for these studies[47].A schematic of the general process is shown in Fig.18A.

The PVP coating of as-synthesized gold nanocages was?rst exchanged with either poly(N-isopropylacrylamide)(pNIPAAm)or a related copolymer.A disul?de initiator was used in the polymerization in order to attach the polymer to the surface via the gold-thiolate linkage.This polymer has a sharp transition between an extended hydrophilic phase and a collapsed hydro-phobic phase at a speci?c temperature,the low critical solution temperature(LCST)[128].When the polymer is heated above that threshold,the collapsing of the polymer opens the pores and allows for release of the pre-loaded contents.This transition temperature can be engineered to a physiologically relevant value through the introduction of acrylamide(AAm)to generate pNIPAAm-co-pAAm copolymers.By adjusting the amount of AAm,the LCST can be tuned between32and508C[127,129]. The studies presented here used a copolymer with a LCST of398C, which is above the body temperature of378C,but below the onset of hyperthermia at428C.Importantly,the temperature change needed to induce this transition can be generated via the photothermal effect,making it possible to initiate and control treatment from a distance.The studies shown in Fig.18used a pulsed Ti:Sapphire NIR laser to generate the heat.

Initial studies were performed by loading a PEG-conjugated alizarin dye and monitoring the release pro?le with UV–vis spectroscopy(Fig.18B and C).The amount of dye released depended on both the irradiation time and the laser power.At the highest laser power shown,40mW/cm2,the nanocages began to melt.At lower laser powers,the nanocages retained their morphology and could be re-used if desired,showing the polymer remained on the surface during the different stages of loading and release.

This technique could also be used to release small molecule drugs and biologically active enzymes.Fig.18D shows the reduction in breast cell viability after the release of the

Table2

Temperature increase(D T)for aqueous suspension of Au nanocages upon irradiation by the diode laser for10min.

Power density(W/cm2)Nanocage concentration(particles/mL)

010*********

1 3.58C10.28C34.98C43.98C 0.5 2.38C 6.18C23.78C34.58C

Fig.17.Plot of temperature increase with time from the photothermal effect with different concentrations of Au nanocages at two different laser powers:(A)1.0W/ cm2and(B)0.5W/cm2.Reproduced with permission from[124],Copyright2010 Wiley-VCH.

C.M.Cobley,Y.Xia/Materials Science and Engineering R70(2010)44–6259

chemotherapeutic drug doxorubicin in vitro .Control samples with either laser irradiation in the absence of Au nanocages (C1)or laser irradiation of empty nanocages (C2)showed minimal cell death.A small reduction in viability in C2may be due to mild photothermal effects,though the laser power in this experiment is low compared to typical photothermal treatments (20mW/cm 2opposed to 1500mW/cm 2for pulsed laser experiments)[121].Conversely,when the drug-loaded nanocages were irradiated with the same laser power a signi?cant decrease in cell viability was seen,reduced to $60%.Though this system is still being further optimized,it has great potential for both temporally and spatially speci?c delivery.6.2.Catalytic applications

Gold nanocages may also ?nd use as catalysts for redox reactions.Though it has been shown by a number of groups that catalyst performance is enhanced as particle size is reduced,the oxidation and reduction half reactions in certain systems may need to occur on separate particles if the size is too small.These particles would then require electrical connection so the reaction can proceed.Gold nanocages could provide an alternative option as they have ultra thin,porous walls,but a large,electrically conductive surface area that could accommodate both half reactions easily.

To investigate this possibility more thoroughly,catalytic studies were performed for three different types of 50-nm Au-Ag alloyed nanostructures:hollow and porous nanocages;hollow nanoboxes;and partially hollow nanoboxes with signi?cant amounts of Ag still present in the interior [39].Data was also collected for 50-nm solid Au spheres and 5-nm Au spheres as a comparison.The concentration of Au nanostructures was held constant at 3.8?109particles/mL for all 50nm structures but was

increased to 1.56?1012for 5-nm particles to account for the signi?cant difference in surface area.TEM images of these different morphologies are shown in Fig.19A.

The reaction studied was the reduction of p -nitrophenol by NaBH 4(more accurately p -nitrophenolate ions due to the alkalinity of the solution).A schematic of this reaction and the spectral changes used to monitor it are shown in Fig.19B.After the injection of an Au-based catalyst,the extinction peak from p -nitrophenolate ions at 400nm gradually dropped in intensity.Fig.19C shows the resulting graphs of intensity versus time,which were used to calculate both the rate constant and the activation energy of the reactions.As expected,nanocages performed the best followed by nanoboxes,and then partially hollow nanoboxes,with rate constants of 2.83, 1.12,and 0.59min à1respectively.After taking into account the reducing power of the citrate,which was present on the surface of the solid gold nanospheres,the rate constants were 0.20and 0.95for the 50nm and 5nm particles respectively.A similar trend was seen in the activation energies for nanocages (28.04kJ/mol),nanoboxes (44.25kJ/mol),and partially hollow nanoboxes (55.44kJ/mol).

The enhanced performance of the nanocages is likely due to a combination of factors.Due to the porosity of this structure when compared with the other solid walled structures,the amount of accessible surface area is higher.Additionally,the Au/Ag ratio is higher for nanocages compared to the nanoboxes due to dealloying,so the surface will contain less Ag,which does not contribute to the catalytic ability.The wall thickness for nanocages is also the smallest,about 5nm by TEM measure-ments.In addition to studies with Au-based nanocages,Pd containing nanocages have also been investigated for hydro-genation reactions.More details about this study can be found in reference [38].

Fig.18.(A)Schematic showing the mechanism for drug release from Au nanocages coated with a smart polymer.When the polymer is heated above its LCST it collapses,exposing the pores and releasing the contents.(B–D)Controlled release from the Au nanocages covered by a smart polymer with an LCST at 398C (pNIPAAm-co-pAAm).(B)Absorption spectra of alizarin-PEG released from the copolymer-covered Au nanocages by exposure to a pulsed NIR laser at a power density of 10mW/cm 2for 1,2,4,8and 16min;and (C)by exposure to the near-infrared laser for 2min at 10,25and 40mW/cm 2.The insets show the concentrations of alizarin-PEG released from the nanocages under different conditions.(D)Release of a chemotherapeutic drug (doxorubicin)from Au nanocages to breast cancer cells in vitro ,showing signi?cant cell death:(C-1)cells irradiated with a pulsed near-infrared laser (20mW/cm 2)for 2min in the absence of Au nanocages;(C-2)cells irradiated with the laser for 2min in the presence of Dox-free Au nanocages;and (2/5min)cells irradiated with the laser for 2and 5min in the presence of Dox-loaded Au nanocages.Reproduced with permission from [127],Copyright 2009Nature Publishing Group.

C.M.Cobley,Y.Xia /Materials Science and Engineering R 70(2010)44–62

7.Conclusion

Galvanic replacement reactions are synthetically simple–they require no unstable organometallic precursors,take place in water and at moderate temperatures,and use very few reagents other than the initial template particles.Despite this initial simplicity,galvanic replacement can be used to generate a wide diversity of structures.A number of trends have emerged through studies with an array of precursors and template particles,which can be used to optimize the syntheses of future materials for speci?c applications:(i)Most fundamentally,it is important to consider the difference in electrochemical potentials of the metals being used.The metal being reduced must have a higher electrochemical potential than the one being oxidized for any replacement to take place,and the gap between them needs to be signi?cant enough to overcome any stabilization if dealloying and pore formation is to occur.(ii) Dealloying can also be controlled independently through the introduction of wet etchants,creating extremely thin-walled structures.(iii)If a smooth surface is required,the two metals being studied should be mutually dissolvable at the reaction temperature.(iv)Surfactants and trace ions can affect the?nal morphology in unexpected ways.Selective reaction on speci?c facets,solubilization of byproducts,and unusual segregation of alloy components have all been attributed to the in?uence of surfactants. (v)The presence of twin boundaries,defects,and vacancies can all in?uence the alloying rate,and even affect the?nal morphology in some cases.(vi)In general,size matters–particles less than$20nm are more likely to form rings than larger particles,as the rate of alloying can be increased.(vii)Stoichiometry also plays a role.By using precursors with different oxidation states,different numbers of vacancies will be generated,resulting in different porosities and morphologies.(viii)Finally,galvanic replacement can be performed multiple times or combined with other synthetic techniques such as overgrowth to generate increasingly complex structures.

The nanomaterials generated with this method have highly tunable LSPR properties and compositions,making them ideal for applications in biomedicine,photonics,and catalysis.Particular attention has been paid to Au nanocages.The surface of these versatile particles can be modi?ed with PEG and antibodies to create targeted photothermal transducers for cell death,or modi?ed with PNIPAAm-based smart polymers to harness the hollow interior as a drug delivery vessel for precise delivery.Future studies aim to expand and possibly combine these techniques. Additionally,the thin walls and high porosity of Au nanocages make them promising substrates for catalysis,as initially demonstrated with the reduction of p-nitrophenol with NaBH4. Upcoming research in this area is likely to illuminate new mechanisms and unexpected effects,but the studies presented herein represent a strong foundation for future work. Acknowledgements

This work was supported in part by a Director’s Pioneer Award (DP1OD000798)from NIH,a fellowship from David and Lucile Packard Foundation,a DARPA-DURINT subcontract from Harvard University,and various research grants from NSF and NIH.Y.X.is an Alfred P.Sloan Research Fellow(2000–2002)and a Camille Dreyfus Teacher Scholar(2002–2007).We thank all of our coworkers and collaborators for their invaluable contributions to this work. References

[1]J.Aiken,R.Finke,J.Mol.Catal.A:Chem.145(1999)1–44.

[2]C.Burda,X.Chen,R.Narayanan,M.A.El-Sayed,Chem.Rev.105(2005)1025–

1102.

[3]R.Narayanan,M.El-Sayed,J.Phys.Chem.B109(2005)12663–12676.

[4]B.Lim,M.Jiang,P.H.C.Camargo,E.C.Cho,J.Tao,X.Lu,Y.Zhu,Y.Xia,Science324

(2009)1302–1305.

[5]E.Ozbay,Science311(2006)189–193.

[6]Y.Lu,Y.Yin,Z.Li,Y.Xia,Nano Lett.2(2002)785–788.

[7]A.L.Pyayt,B.Wiley,Y.Xia,A.Chen,L.Dalton,Nature Nanotech.3(2008)660–

665.

[8]A.Shipway,E.Katz,I.Willner,Chem.Phys.Chem.1(2000)18–52.

[9]J.Camden,J.Dieringer,J.Zhao,R.V.Duyne,Acc.Chem.Res.41(2008)1653–1661.

[10]N.L.Rosi,C.A.Mirkin,Chem.Rev.105(2005)1547–1562.

Fig.19.(A)Representative TEM images of the Au nanocages,nanoboxes,and nanoparticles used in the catalytic studies.(B)UV–vis spectra showing the disappearance of the 400nm peak of p-nitrophenol due to the reduction of–NO2group into–NH2group.(C)Plots ofàln I ext against time for Au-based nanocages,nanoboxes,and partially hollow nanoboxes.These plots were used to determine the reaction rate constant and activation energy.Reproduced with permission from[39],Copyright2009American Chemical Society.

C.M.Cobley,Y.Xia/Materials Science and Engineering R70(2010)44–6261

[11]A.P.Alivisatos,Nat.Biotechnol.22(2004)47–52.

[12]K.Kneipp,H.Kneipp,I.Itzkan,R.Dasari,M.Feld,Chem.Rev.99(1999)2957–

2975.

[13]S.Nie,S.Emory,Science275(1997)1102–1106.

[14]M.Hu,J.Chen,Z.-Y.Li,L.Au,G.V.Hartland,X.Li,M.Marquez,Y.Xia,Chem.Soc.

Rev.35(2006)1084–1094.

[15]S.E.Skrabalak,J.Chen,L.Au,X.Lu,X.Li,Y.Xia,Adv.Mater.19(2007)3177–3184.

[16]https://www.360docs.net/doc/6c1184671.html,l,S.E.Clare,N.J.Halas,Acc.Chem.Res.41(2008)1842–1851.

[17]X.Huang,I.H.El-Sayed,W.Qian,M.A.El-Sayed,J.Am.Chem.Soc.128(2006)

2115–2120.

[18]C.J.Murphy,A.M.Gole,J.W.Stone,P.N.Sisco,A.M.Alkilany,E.C.Goldsmith,S.C.

Baxter,Acc.Chem.Res.41(2008)1721–1730.

[19]Y.Xia,Y.Xiong,B.Lim,S.E.Skrabalak,Angew.Chem.Int.Ed.48(2009)60–103.

[20]S.E.Skrabalak,J.Chen,Y.Sun,X.Lu,L.Au,C.M.Cobley,Y.Xia,Acc.Chem.Res.41

(2008)1587–1595.

[21]X.Lu,J.Chen,S.E.Skrabalak,Y.Xia,Proc.Inst.Mech.Eng.N.221(2008)1–16.

[22]Y.Sun,Y.Xia,J.Am.Chem.Soc.126(2004)3892–3901.

[23]S.E.Skrabalak,L.Au,X.Li,Y.Xia,Nature Protoc.2(2007)2182–2190.

[24]N.J.Halas,MRS Bull.30(2005)362–367.

[25]V.Ntziachristos,C.Bremer,R.Weissleder,Eur.Rad.13(2003)195–208.

[26]R.Weissleder,Nat.Biotechnol.19(2001)316–317.

[27]K.H.Song,C.Kim,C.M.Cobley,Y.Xia,L.V.Wang,Nano Lett.9(2009)183–188.

[28]E.Fu,S.Ramsey,J.Chen,T.Chinowsky,B.J.Wiley,Y.Xia,P.Yager,Sens.Actuators

B123(2007)606–613.

[29]Y.Sun,Y.Xia,Anal.Chem.74(2002)5297–5305.

[30]S.Oldenburg,R.Averitt,S.Westcott,N.J.Halas,Chem.Phys.Lett.288(1998)243–

247.

[31]L.R.Hirsch,A.M.Gobin,A.R.Lowery,F.Tam,R.A.Drezek,N.J.Halas,J.L.West,Ann.

Biomed.Eng.34(2006)15–22.

[32]C.Graf,A.V.Blaaderen,Langmuir18(2002)524–534.

[33]J.C.Bauer,X.Chen,Q.Liu,T.-H.Phan,R.E.Schaak,J.Mater.Chem.18(2008)275–

282.

[34]M.Chen,D.Kumar,C.Yi,D.Goodman,Science310(2005)291–293.

[35]M.Nutt,J.Hughes,M.Wong,Environ.Sci.Technol.39(2005)1346–1353.

[36]A.Venezia,V.L.Parola,G.Deganello,B.Pawelec,J.Fierro,J.Catal.215(2003)317–

325.

[37]V.Bansal,H.Jani,J.Du Plessis,P.Coloe,S.Bhargava,Adv.Mater.20(2008)717–

723.

[38]C.M.Cobley,D.Campbell,Y.Xia,Adv.Mater.20(2008)748–752.

[39]J.Zeng,Q.Zhang,J.Chen,Y.Xia,Nano Lett.(2009),ASAP.

[40]S.Kim,M.Kim,W.Lee,T.Hyeon,J.Am.Chem.Soc.124(2002)7642–7643.

[41]H.M.Chen,R.-S.Liu,M.-Y.Lo,S.-C.Chang,L.-D.Tsai,Y.-M.Peng,J.-F.Lee,J.Phys.

Chem.C112(2008)7522–7526.

[42]A.Dursun,D.Pugh,S.Corcoran,J.Electrochem.Soc.150(2003)B355–B360.

[43]J.Greeley,J.Norskov,Electrochim.Acta52(2007)5829–5836.

[44]Y.Sun,B.Mayers,Y.Xia,Nano Lett.2(2002)481–485.

[45]Z.Wang,T.Ahmad,M.El-Sayed,Surf.Sci.380(1997)302–310.

[46]M.Batzill,B.Koel,Surf.Sci.553(2004)50–60.

[47]J.Chen,J.McLellan,A.Siekkinen,Y.Xiong,Z.-Y.Li,Y.Xia,J.Am.Chem.Soc.128

(2006)14776–14777.

[48]Q.Zhang,C.Cobley,L.Au,M.Mckiernan,A.Schwartz,L.-P.Wen,J.Chen,Y.Xia,

ACS Appl.Mater.Interfaces1(2009)2044–2048.

[49]J.McLellan,A.R.Siekkinen,J.Chen,Y.Xia,Chem.Phys.Lett.427(2006)122–126.

[50]Y.Sun,B.Mayers,T.Herricks,Y.Xia,Nano Lett.3(2003)955–960.

[51]B.J.Wiley,T.Herricks,Y.Sun,Y.Xia,Nano Lett.4(2004)1733–1739.

[52]B.J.Wiley,Y.Xiong,Z.-Y.Li,Y.Yin,Y.Xia,Nano Lett.6(2006)765–768.

[53]S.H.Im,Y.T.Lee,B.J.Wiley,Y.Xia,Angew.Chem.Int.Ed.44(2005)2154–2157.

[54]A.R.Siekkinen,J.McLellan,J.Chen,Y.Xia,Chem.Phys.Lett.432(2006)491–496.

[55]M.H.Kim,X.Lu,B.J.Wiley,E.P.Lee,Y.Xia,J.Phys.Chem.C112(2008)7872–

7876.

[56]A.Tao,P.Sinsermsuksakul,P.Yang,Angew.Chem.Int.Ed.45(2006)4597–4601.

[57]D.Seo,C.Yoo,J.Park,S.Park,S.Ryu,H.Song,Angew.Chem.Int.Ed.47(2008)

763–767.

[58]Y.Yin,C.Erdonmez,S.Aloni,A.P.Alivisatos,J.Am.Chem.Soc.128(2006)12671–

12673.

[59]Y.Sun,Y.Xia,Nano Lett.3(2003)1569–1572.

[60]Y.Yin,Z.-Y.Li,Z.Zhong,B.Gates,Y.Xia,S.Venkateswaran,J.Mater.Chem.12

(2002)522–527.

[61]Y.Sun,Y.Xia,Analyst128(2003)686–691.

[62]A.Pyatenko,M.Yamaguchi,M.Suzuki,J.Phys.Chem.C111(2007)7910–7917.

[63]Y.Sun,Z.Tao,J.Chen,T.Herricks,Y.Xia,J.Am.Chem.Soc.126(2004)5940–5941.

[64]Y.Sun,B.Wiley,Z.-Y.Li,Y.Xia,J.Am.Chem.Soc.126(2004)9399–9406.

[65]L.Vitos,A.Ruban,H.Skriver,J.Kollar,Surf.Sci.411(1998)186–202.

[66]F.-R.Fan,D.-Y.Liu,Y.-F.Wu,S.Duan,Z.-X.Xie,Z.-Y.Jiang,Z.-Q.Tian,J.Am.Chem.

Soc.130(2008)6949–6951.

[67]S.E.Habas,H.Lee,V.Radmilovic,G.A.Somorjai,P.Yang,Nat.Mater.6(2007)

692–697.

[68]E.C.Cho,P.H.C.Camargo,Y.Xia,Adv.Mater.(2009),ASAP.

[69]J.Chen,B.J.Wiley,J.McLellan,Y.Xiong,Z.-Y.Li,Y.Xia,Nano Lett.5(2005)2058–

2062.

[70]X.Lu,H.-Y.Tuan,J.Chen,Z.-Y.Li,B.A.Korgel,Y.Xia,J.Am.Chem.Soc.129(2007)

1733–1742.

[71]H.Liang,H.Zhang,J.Hu,Y.Guo,L.Wan,C.Bai,Angew.Chem.Int.Ed.43(2004)

1540–1543.

[72]P.Selvakannan,M.Sastry,https://www.360docs.net/doc/6c1184671.html,m.(2005)1684–1686.

[73]https://www.360docs.net/doc/6c1184671.html,lar,J.Metson,G.Bowmaker,R.Cooney,J.Catal.147(1994)404–416.

[74]G.Meima,L.Knijff,R.Vis,A.Van,J.Chem.Soc.Faraday Trans.85(1989)269–277.

[75]K.Wu,D.Wang,X.Wei,Y.Cao,X.Guo,J.Catal.140(1993)370–383.

[76]L.Lefferts,J.Vanommen,J.Ross,Appl.Catal.31(1987)291–308.

[77]T.Shibata,B.A.Bunker,Z.Zhang,D.Meisel,C.F.Vardeman,J.D.Gezelter,J.Am.

Chem.Soc.124(2002)11989–11996.

[78]H.Mori,M.Komatsu,K.Takeda,H.Fujita,Phil.Mag.Lett.63(1991)173–178.

[79]Y.Sun,B.Mayers,Y.Xia,Adv.Mater.15(2003)641–646.

[80]P.H.C.Camargo,Y.Xiong,L.Ji,J.M.Zuo,Y.Xia,J.Am.Chem.Soc.129(2007)

15452–15453.

[81]F.Wetz,K.Soulantica,A.Falqui,Angew.Chem.119(2007)7209–7211.

[82]X.Teng,Q.Wang,P.Liu,W.Han,A.I.Frenkel,N.Wen,J.C.Marinkovic,J.A.Hanson,

Rodriguez,J.Am.Chem.Soc.130(2008)1093–1101.

[83]S.Wonnell,J.Delaye,M.Bibole,Y.Limoge,J.Appl.Phys.72(1992)5195–5205.

[84]R.Newman,K.Sieradzki,Science263(1994)1708–1709.

[85]L.Martinez,M.Segarra,M.Fernandez,F.Espiell,Metall.Trans.B24(1993)827–

837.

[86]K.Sieradzki,J.Electrochem.Soc.140(1993)2868–2872.

[87]K.Sieradzki,N.Dimitrov,D.Movrin,C.McCall,N.Vasiljevic,J.Erlebacher,J.

Electrochem.Soc.149(2002)B370–B377.

[88]J.Erlebacher,J.Electrochem.Soc.151(2004)C614–C626.

[89]J.Erlebacher,M.J.Aziz,A.Karma,N.Dimitrov,K.Sieradzki,Nature410(2001)

450–453.

[90]A.Dursun,D.Pugh,S.Corcoran,J.Electrochem.Soc.152(2005)B65–B72.

[91]X.Lu,L.Au,J.McLellan,Z.-Y.Li,M.Marquez,Y.Xia,Nano Lett.7(2007)1764–

1769.

[92]L.Au,X.Lu,Y.Xia,Adv.Mater.20(2008)2517–2522.

[93]L.Au,Y.Chen,F.Zhou,P.H.C.Camargo,B.Lim,Z.-Y.Li,D.S.Ginger,Y.Xia,Nano

Res.1(2008)441–449.

[94]E.O.Kirkendall,Aime Trans.147(1942)104–109.

[95]Y.Yin,R.M.Rioux,C.K.Erdonmez,S.Hughes,G.A.Somorjai,A.P.Alivisatos,

Science304(2004)711–714.

[96]Y.Yin,C.Erdonmez,A.Cabot,S.Hughes,A.P.Alivisatos,Adv.Funct.Mater.16

(2006)1389–1399.

[97]H.J.Fan,M.Knez,R.Scholz,K.Nielsch,E.Pippel,D.Hesse,M.Zacharias,U.Gosele,

Nat.Mater.5(2006)627–631.

[98]B.Liu,H.C.Zeng,J.Am.Chem.Soc.126(2004)16744–16746.

[99]H.J.Fan,U.G P sele,M.Zacharias,Small3(2007)1660–1671.

[100]A.Cabot,R.K.Smith,Y.Yin,H.Zheng,B.M.Reinhard,H.Liu,A.P.Alivisatos,ACS Nano2(2008)1452–1458.

[101]J.Chen,B.Lim,E.Lee,Y.Xia,Nano Today4(2009)81–95.

[102]U.Kreibig,M.Vollmer,Optical Properties of Metal Clusters,Springer,New York, 1995.

[103]S.Maier,Plasmonics:Fundamentals and Applications,Springer,New York,2007 .

[104]G.Mie,Anal.Phys.23(1908)377–445.

[105]B.Draine,P.Flatau,J.Opt.Soc.Am.B11(1994)1491–1499.

[106]K.Kelly,E.Coronado,L.Zhao,G.C.Schatz,J.Phys.Chem.B107(2003)668–677. [107]X.Lu,M.Rycenga,S.E.Skrabalak,B.J.Wiley,Y.Xia,Ann.Rev.Phys.Chem.60 (2009)167–192.

[108]B.J.Wiley,S.H.Im,Z.-Y.Li,J.McLellan,A.R.Siekkinen,Y.Xia,J.Phys.Chem.B110 (2006)15666–15675.

[109]C.J.Murphy,T.K.Sau,A.M.Gole,C.J.Orendorff,J.Gao,L.Gou,S.E.Hunyadi,T.Li,J.

Phys.Chem.B109(2005)13857–13870.

[110]C.M.Cobley,M.Rycenga,F.Zhou,Z.-Y.Li,Y.Xia,J.Phys.Chem.C113(2009) 16975–16982.

[111]J.McLellan,Z.-Y.Li,A.R.Siekkinen,Y.Xia,Nano Lett.7(2007)1013–1017. [112]P.K.Jain,X.Huang,I.H.El-Sayed,M.A.El-Sayed,Acc.Chem.Res.41(2008)1578–1586.

[113]E.Prodan,C.Radloff,N.J.Halas,P.Nordlander,Science302(2003)419–422. [114]D.Peer,J.M.Karp,S.Hong,O.C.Farokhzad,R.Margalit,https://www.360docs.net/doc/6c1184671.html,nger,Nature Nanotech.2(2007)751–760.

[115]J.R.Heath,M.E.Davis,Annu.Rev.Med.59(2008)251–265.

[116]H.Lu,C.Campbell,D.Castner,Langmuir16(2000)1711–1718.

[117]J.M.Harris,N.E.Martin,M.Modi,Clin.Pharmacokinet.40(2001)539–551. [118]S.M.Moghimi,A.C.Hunter,J.C.Murray,Pharmacol.Rev.53(2001)283–318. [119]L.Au,Q.Zhang,C.Cobley,M.Gidding,A.Schwartz,J.Chen,Y.Xia,ACS Nano (2009),ASAP.

[120]M.-C.Daniel,D.Astruc,Chem.Rev.104(2004)293–346.

[121]J.Chen,F.Saeki,B.J.Wiley,H.Cang,M.J.Cobb,Z.-Y.Li,L.Au,H.Zhang,M.B.

Kimmey,X.Li,Y.Xia,Nano Lett.5(2005)473–477.

[122]J.Chen,D.Wang,J.Xi,L.Au,A.Siekkinen,A.Warsen,Z.-Y.Li,H.Zhang,Y.Xia,X.

Li,Nano Lett.7(2007)1318–1322.

[123]L.Au,D.Zheng,F.Zhou,Z.-Y.Li,X.Li,Y.Xia,ACS Nano(2008)1645–1652. [124]J.Chen,C.Glaus,https://www.360docs.net/doc/6c1184671.html,forest,Q.Zhang,M.Yang,M.Gidding,M.J.Welch,Y.Xia, Small6(2010)811–817.

[125]G.Mayer,A.Heckel,A.Angew.Chem.Int.Ed.45(2006)4900–4921.

[126]E.Gullotti,Y.Yeo,Mol.Pharm.6(2009)1041–1051.

[127]M.S.Yavuz,Y.Cheng,J.Chen,C.M.Cobley,Q.Zhang,M.Rycenga,J.Xie,C.Kim, K.H.Song,A.G.Schwartz,L.V.Wang,Y.Xia,Nature Mater.12(2009)935–939. [128]A.S.Hoffman,Adv.Drug Deliv.Rev.43(2002)3–12.

[129]C.M.Schilli,M.Zhang,E.Rizzardo,S.H.Thang,Y.K.Chong,K.Edwards,G.

Karlsson,A.H.E.Mu¨ller,Macromolecules37(2004)7861–7866.

[130]Y.Sun,Y.Xia,Adv.Mater.16(2004)264–268.

C.M.Cobley,Y.Xia/Materials Science and Engineering R70(2010)44–62 62

高二《甜美纯净的女声独唱》教案

高二《甜美纯净的女声独唱》教案一、基本说明教学内容 1）教学内容所属模块：歌唱 2）年级：高二 3）所用教材出版单位：湖南文艺出版社 4）所属的章节：第三单元第一节 5）学时数： 45 分钟二、教学设计 1、教学目标： ①、在欣赏互动中感受女声的音域及演唱风格，体验女声的音色特点。 ②、在欣赏互动中，掌握美声、民族、通俗三种唱法的特点，体验其魅力。 ③、让学生能够尝试用不同演唱风格表现同一首歌。 ④、通过学唱歌曲培养学生热爱祖国、热爱生活的激情。 2、教学重点： ①、掌握女高音、女中音的音域和演唱特点。 ②、掌握美声、民族、通俗三种方法演唱风格。 3、教学难点： ①、学生归纳不同唱法的特点与风格。

②、学生尝试用不同演唱风格表现同一首歌。 3、设计思路《普通高中音乐课程标准》指出：“音乐课的教学过程就是音乐的艺术实践过程。”《甜美纯净的女声独唱》作为《魅力四射的独唱舞台》单元的第一课，是让学生在丰富多彩的歌唱艺术形式中感受出女声独唱以其优美纯净的声音特点而散发出独特的魅力。为此，本课从身边熟悉的人物和情景入手，激发学生学习兴趣，把教学重心放在艺术实践中，让学生在欣赏、学习不同的歌唱风格中，培养自己的综合欣赏能力及歌唱水平。在教学过程中让学生体会不同风格的甜美纯净女声的内涵，感知优美纯净的声音特点而散发出的独特魅力，学会多听、多唱，掌握一定的歌唱技巧，提高自己的演唱水平。为实现以上目标，本人将新课标“过程与方法”中的“体验、比较、探究、合作”四个具体目标贯穿全课，注重学生的个人感受和独特见解，鼓励学生的自我意识与创新精神，强调探究、强调实践，将教学过程变为整合、转化间接经验为学生直接经验的过程，让学生亲身去感悟、去演唱，并力求改变现在高中学生普遍只关注流行歌曲的现状，让学生自己确定最适合自己演唱的方法，自我发现、自我欣赏，充分展示自己的的声音魅力。三、教学过程教学环节及时间教师活动学生活动设计意图

尊重的素材

尊重的素材（为人处世）思路人与人之间只有互相尊重才能友好相处要让别人尊重自己，首先自己得尊重自己尊重能减少人与人之间的摩擦尊重需要理解和宽容尊重也应坚持原则尊重能促进社会成员之间的沟通尊重别人的劳动成果尊重能巩固友谊尊重会使合作更愉快和谐的社会需要彼此间的尊重名言施与人，但不要使对方有受施的感觉。帮助人，但给予对方最高的尊重。这是助人的艺术，也是仁爱的情操。—刘墉卑己而尊人是不好的，尊己而卑人也是不好的。———徐特立知道他自己尊严的人，他就完全不能尊重别人的尊严。———席勒真正伟大的人是不压制人也不受人压制的。———纪伯伦草木是靠着上天的雨露滋长的，但是它们也敢仰望穹苍。———莎士比亚尊重别人，才能让人尊敬。———笛卡尔谁自尊，谁就会得到尊重。———巴尔扎克人应尊敬他自己，并应自视能配得上最高尚的东西。———黑格尔对人不尊敬，首先就是对自己的不尊敬。———惠特曼

每当人们不尊重我们时，我们总被深深激怒。然而在内心深处，没有一个人十分尊重自己。———马克·吐温忍辱偷生的人，绝不会受人尊重。———高乃依敬人者，人恒敬之。———《孟子》人必自敬，然后人敬之；人必自侮，然后人侮之。———扬雄不知自爱反是自害。———郑善夫仁者必敬人。———《荀子》君子贵人而贱己，先人而后己。———《礼记》尊严是人类灵魂中不可糟蹋的东西。———古斯曼对一个人的尊重要达到他所希望的程度，那是困难的。———沃夫格纳经典素材 1元和200元（尊重劳动成果）香港大富豪李嘉诚在下车时不慎将一元钱掉入车下，随即屈身去拾，旁边一服务生看到了，上前帮他拾起了一元钱。李嘉诚收起一元钱后，给了服务生200元酬金。这里面其实包含了钱以外的价值观念。李嘉诚虽然巨富，但生活俭朴，从不挥霍浪费。他深知亿万资产，都是一元一元挣来的。钱币在他眼中已抽象为一种劳动，而劳动已成为他最重要的生存方式，他的所有财富，都是靠每天20小时以上的劳动堆积起来的。200元酬金，实际上是对劳动的尊重和报答，是不能用金钱衡量的。富兰克林借书解怨（尊重别人赢得朋友）

那一刻我感受到了幸福_初中作文

那一刻我感受到了幸福本文是关于初中作文的那一刻我感受到了幸福，感谢您的阅读！每个人民的心中都有一粒幸福的种子，当它拥有了雨水的滋润和阳光的沐浴，它就会绽放出最美丽的姿态。那一刻，我们都能够闻到幸福的芬芳，我们都能够感受到幸福的存在。在寒假期间，我偶然在授索电视频道，发现(百家讲坛)栏目中大学教授正在解密幸福，顿然引起我的好奇心，我放下了手中的遥控器，静静地坐在电视前，注视着频道上的每一个字，甚至用笔急速记在了笔记本上。我还记得，那位大学教授讲到了一个故事：一位母亲被公司升职到外国工作，这位母亲虽然十分高兴，但却又十分无奈，因为她的儿子马上要面临中考了，她不能撇下儿子迎接中考的挑战，于是她决定拒绝这了份高薪的工作，当有人问她为什么放弃这么好的机会时，她却毫无遗憾地说，纵然我能给予儿子最贵的礼物，优异的生活环境，但我却无当给予他关键时刻的那份呵护与关爱，或许以后的一切会证明我的选择是正确的。听完这样一段故事，我心中有种说不出的感觉，刹那间，我仿拂感觉那身边正在包饺子的妈妈，屋里正在睡觉的爸爸，桌前正在看小说的妹妹给我带来了一种温馨，幸福感觉。正如教授所说的那种解密幸福。就要选择一个明确的目标，确定自已追求的是什么，或许那时我还不能完全诠释幸福。当幸福悄悄向我走来时，我已慢慢明白，懂得珍惜了。那一天的那一刻对我来说太重要了，原本以为出差在外的父母早已忘了我的生日，只有妹妹整日算着日子。我在耳边唠叨个不停，没想到当日我失落地回到家中时，以为心中并不在乎生日，可是眼前的一切，让我心中涌现的喜悦，脸上露出的微笑证明我是在乎的。

爸爸唱的英文生日快乐歌虽然不是很动听，但爸爸对我的那份爱我听得很清楚，妈妈为我做的长寿面，我细细的品尝，吃出了爱的味道。妹妹急忙让我许下三个愿望，嘴里不停的唠叨：我知道你的三个愿望是什么?我问：为什么呀!我们是一家人，心连心呀!她高兴的说。那一刻我才真正解开幸福的密码，感受到了真正的幸福，以前我无法理解幸福，即使身边有够多的幸福也不懂得欣赏，不懂得珍惜，只想拥有更好更贵的，其实幸福比物质更珍贵。那一刻的幸福就是爱的升华，许多时候能让我们感悟幸福不是名利，物质。而是在血管里涌动着的，漫过心底的爱。也许每一个人生的那一刻，就是我们幸运的降临在一个温馨的家庭中，而不是降临在孤独的角落里。家的感觉就是幸福的感觉，幸福一直都存在于我们的身边!

初中语文古文赏析曹操《短歌行》赏析(林庚)

教育资料《短歌行》《短歌行》赏析(林庚) 曹操这一首《短歌行》是建安时代杰出的名作，它代表着人生的两面，一方面是人生的忧患，一方面是人生的欢乐。而所谓两面也就是人生的全面。整个的人生中自然含有一个生活的态度，这就具体地表现在成为《楚辞》与《诗经》传统的产儿。它一方面不失为《楚辞》中永恒的追求，一方面不失为一个平实的生活表现，因而也就为建安诗坛铺平了道路。这首诗从“对酒当歌，人生几何”到“但为君故，沉吟至今”，充分表现着《楚辞》里的哀怨。一方面是人生的无常，一方面是永恒的渴望。而“呦呦鹿鸣”以下四句却是尽情的欢乐。你不晓得何以由哀怨这一端忽然会走到欢乐那一端去，转折得天衣无缝，仿佛本来就该是这么一回事似的。这才是真正的人生的感受。这一段如是，下一段也如是。“明明如月，何时可掇?忧从中来，不可断绝。越陌度阡，枉用相存。契阔谈宴，心念旧恩。月明星稀，乌鹊南飞。绕树三匝，何枝可依。”缠绵的情调，把你又带回更深的哀怨中去。但“山不厌高，海不厌深”，终于走入“周公吐哺，天下归心”的结论。上下两段是一个章法，但是你并不觉得重复，你只觉得卷在悲哀与欢乐的旋涡中，不知道什么时候悲哀没有了，变成欢乐，也不知道什么时候欢乐没有了，又变成悲哀，这岂不是一个整个的人生吗?把整个的人生表现在一个刹那的感觉上，又都归于一个最实在的生活上。“我有嘉宾，鼓瑟吹笙”，不正是当时的情景吗?“周公吐哺，天下归心”，不正是当时的信心吗? “青青子衿”到“鼓瑟吹笙”两段连贯之妙，古今无二。《诗经》中现成的句法一变而有了《楚辞》的精神，全在“沉吟至今”的点窜，那是“青青子衿”的更深的解释，《诗经》与《楚辞》因此才有了更深的默契，从《楚辞》又回到《诗经》，这样与《鹿鸣》之诗乃打成一片，这是一个完满的行程，也便是人生旅程的意义。“月明星稀”何以会变成“山不厌高，海不厌深”?几乎更不可解。莫非由于“明月出天山”，“海上生明月”吗?古辞说：“枯桑知天风，海水知天寒”，枯桑何以知天风，因为它高；海水何以知天寒，因为它深。唐人诗“一叶落知天下秋”，我们对于宇宙万有正应该有一个“知”字。然则既然是山，岂可不高?既然是海，岂可不深呢?“并刀如水，吴盐胜雪”，既是刀，就应该雪亮；既是盐，就应该雪白，那么就不必问山与海了。山海之情，成为漫漫旅程的归宿，这不但是乌鹊南飞，且成为人生的思慕。山既尽其高，海既尽其深。人在其中乃有一颗赤子的心。孟子主尽性，因此养成他浩然之气。天下所以归心，我们乃不觉得是一个夸张。 .

适合女生KTV唱的100首好听的歌

适合女生KTV唱的100首好听的歌别吝色你的嗓音很好学 1、偏爱----张芸京 2、阴天----莫文蔚 3、眼泪----范晓萱 4、我要我们在一起---=范晓萱 5、无底洞----蔡健雅 6、呼吸----蔡健雅 7、原点----蔡健雅&孙燕姿 8、我怀念的----孙燕姿 9、不是真的爱我----孙燕姿 10、我也很想他----孙燕姿 11、一直很安静----阿桑 12、让我爱----阿桑 13、错过----梁咏琪 14、爱得起----梁咏琪 15、蓝天----张惠妹 16、记得----张惠妹 17、简爱----张惠妹 18、趁早----张惠妹 19、一念之间----戴佩妮 20、两难----戴佩妮 21、怎样----戴佩妮 22、一颗心的距离----范玮琪 23、我们的纪念日----范玮琪 24、启程----范玮琪 25、最初的梦想----范玮琪 26、是非题----范玮琪 27、你是答案----范玮琪 28、没那么爱他----范玮琪 29、可不可以不勇敢----范玮琪 30、一个像夏天一个像秋天----范玮琪 31、听，是谁在唱歌----刘若英 32、城里的月光----许美静 33、女人何苦为难女人----辛晓琪 34、他不爱我----莫文蔚 35、你是爱我的----张惠妹 36、同类----孙燕姿 37、漩涡----孙燕姿 38、爱上你等于爱上寂寞----那英 39、梦醒了----那英 40、出卖----那英 41、梦一场----那英 42、愿赌服输----那英

43、蔷薇----萧亚轩 44、你是我心中一句惊叹----萧亚轩 45、突然想起你----萧亚轩 46、类似爱情----萧亚轩 47、Honey----萧亚轩 48、他和他的故事----萧亚轩 49、一个人的精彩----萧亚轩 50、最熟悉的陌生人----萧亚轩 51、想你零点零一分----张靓颖 52、如果爱下去----张靓颖 53、我想我是你的女人----尚雯婕 54、爱恨恢恢----周迅 55、不在乎他----张惠妹 56、雪地----张惠妹 57、喜欢两个人----彭佳慧 58、相见恨晚----彭佳慧 59、囚鸟----彭羚 60、听说爱情回来过----彭佳慧 61、我也不想这样----王菲 62、打错了----王菲 63、催眠----王菲 64、执迷不悔----王菲 65、阳宝----王菲 66、我爱你----王菲 67、闷----王菲 68、蝴蝶----王菲 69、其实很爱你----张韶涵 70、爱情旅程----张韶涵 71、舍得----郑秀文 72、值得----郑秀文 73、如果云知道----许茹芸 74、爱我的人和我爱的人----裘海正 75、谢谢你让我这么爱你----柯以敏 76、陪我看日出----蔡淳佳 77、那年夏天----许飞 78、我真的受伤了----王菀之 79、值得一辈子去爱----纪如璟 80、太委屈----陶晶莹 81、那年的情书----江美琪 82、梦醒时分----陈淑桦 83、我很快乐----刘惜君 84、留爱给最相爱的人----倪睿思 85、下一个天亮----郭静 86、心墙----郭静

关于我的幸福作文八篇汇总

关于我的幸福作文八篇汇总幸福在每个人的心中都不一样。在饥饿者的心中，幸福就是一碗香喷喷的米饭；在果农的心中，幸福就是望着果实慢慢成熟；在旅行者的心中，幸福就是游遍世界上的好山好水。而在我的心中，幸福就是每天快快乐乐，无忧无虑；幸福就是朋友之间互相帮助，互相关心；幸福就是在我生病时，母亲彻夜细心的照顾我。幸福在世间上的每个角落都可以发现，只是需要你用心去感受而已。记得有一次，我早上出门走得太匆忙了，忘记带昨天晚上准备好的钢笔。老师说了：“今天有写字课，必须要用钢笔写字，不能用水笔。”我只好到学校向同学借了。当我来到学校向我同桌借时，他却说：“我已经借别人了，你向别人借吧！”我又向后面的同学借，可他们总是找各种借口说：“我只带了一枝。”问了三四个人，都没有借到，而且还碰了一鼻子灰。正当我急的像热锅上的蚂蚁团团转时，她递给了我一枝钢笔，微笑的对我说：“拿去用吧！”我顿时感到自己是多么幸福！在我最困难的时候，当别人都不愿意帮助我的时候，她向我伸出了援手。幸福也是无时无刻都在身旁。当我生病的时候，高烧持续不退时，是妈妈在旁边细心

的照顾我，喂我吃药，甚至一夜寸步不离的守在我的床边，直到我苏醒。当我看见妈妈的眼睛布满血丝时，我的眼眶在不知不觉地湿润了。这时我便明白我有一个最疼爱我的妈妈，我是幸福的！幸福就是如此简单！不过，我们还是要珍惜眼前的幸福，还要给别人带来幸福，留心观察幸福。不要等幸福悄悄溜走了才发现，那就真的是后悔莫及了！这就是我拥有的幸福，你呢？悠扬的琴声从房间里飘出来，原来这是我在弹钢琴。优美的旋律加上我很强的音乐表现力让一旁姥爷听得如醉如痴。姥爷说我是幸福的，读了《建设幸福中国》我更加体会到了这一点。儿时的姥爷很喜欢读书，但当时家里穷，据姥爷讲那时上学可不像现在。有点三天打鱼两天晒网，等地里农活忙了太姥爷就说：“别去念书了，干地里的活吧。”干活时都是牛马拉车，也没机器，效率特别低。还要给牲口拔草，喂草，拾柴火，看书都是抽空看。等农闲时才能背书包去学校，衣服更是老大穿了，打补丁老二再接着穿，只有盼到过年时才有能换上件粗布的新衣服。写字都是用石板，用一次擦一次，那时还没有电灯，爱学习的姥爷在昏暗的煤油灯下经常被灯火不是烧了眉毛就是燎了头发。没有电灯更没有电视，没有电视更没有见过钢琴，只知道钢琴是贵族家用的。

高中语文文言文曹操《短歌行(对酒当歌)》原文、翻译、赏析

曹操《短歌行【对酒当歌】》原文、翻译、赏析译文原文面对美酒应该高歌，人生短促日月如梭。对酒当歌，人生几何？好比晨露转瞬即逝，失去的时日实在太多！譬如朝露，去日苦多。席上歌声激昂慷慨，忧郁长久填满心窝。慨当以慷，忧思难忘。靠什么来排解忧闷？唯有狂饮方可解脱。何以解忧？唯有杜康。那穿着青领（周代学士的服装）的学子哟，你们令我朝夕思慕。青青子衿，悠悠我心。正是因为你们的缘故，我一直低唱着《子衿》歌。但为君故，沉吟至今。阳光下鹿群呦呦欢鸣，悠然自得啃食在绿坡。呦呦鹿鸣，食野之苹。一旦四方贤才光临舍下，我将奏瑟吹笙宴请宾客。我有嘉宾，鼓瑟吹笙。当空悬挂的皓月哟，你运转着，永不停止；明明如月，何时可掇？我久蓄于怀的忧愤哟，突然喷涌而出汇成长河。忧从中来，不可断绝。远方宾客踏着田间小路，一个个屈驾前来探望我。越陌度阡，枉用相存。彼此久别重逢谈心宴饮，争着将往日的情谊诉说。契阔谈讌，心念旧恩。明月升起，星星闪烁，一群寻巢乌鹊向南飞去。月明星稀，乌鹊南飞。绕树飞了三周却没敛绕树三匝，何枝

翅，哪里才有它们栖身之所？可依？高山不辞土石才见巍峨，大海不弃涓流才见壮阔。（比喻用人要“唯才是举”，多多益善。）山不厌高，水不厌深。只有像周公那样礼待贤才（周公见到贤才，吐出口中正在咀嚼的食物，马上接待。《史记》载周公自谓： “一沐三握发，一饭三吐哺，犹恐失天下之贤。”），才能使天下人心都归向我。周公吐哺，天赏析曹操是汉末杰出的政治家、军事家和文学家，他雅好诗章，好作乐府歌辞，今存诗22首，全是乐府诗。曹操的乐府诗多描写他本人的政治主张和统一天下的雄心壮志。如他的《短歌行》，充分表达了诗人求贤若渴以及统一天下的壮志。《短歌行》是政治性很强的诗作，主要是为曹操当时所实行的政治路线和政策策略服务的，但是作者将政治内容和意义完全熔铸在浓郁的抒情意境之中，全诗充分发挥了诗歌创作的特长，准确而巧妙地运用了比兴手法，寓理于情，以情感人。诗歌无论在思想内容还是在艺术上都取得了极高的成就，语言质朴，立意深远，气势充沛。这首带有建安时代"志深比长""梗概多气"的时代特色的《短歌行》，读后不觉思接千载，荡气回肠，受到强烈的感染。对酒当歌，人生几何？譬如朝露，去日苦多。慨当以慷，幽思难忘。何以解忧，唯有杜康。青青子衿，悠悠我心。但为君故，沈吟至今。呦呦鹿鸣，食野之苹。我有嘉宾，鼓瑟吹笙。明明如月，何时可掇？忧从中来，不可断绝。越陌度阡，枉用相存。契阔谈，心念旧恩。月明星稀，乌鹊南飞，绕树三匝，何枝可依？山不厌高，海不厌深，周公吐哺，天下归心。《短歌行》是汉乐府的旧题，属于《相和歌?平调曲》。这就是说它本来是一个乐曲的名称，这种乐曲怎么唱法，现在当然是不知道了。但乐府《相和歌?平调曲》中除了《短歌行》还有《长歌行》，唐代吴兢《乐府古题要解》引证古诗“长歌正激烈”，魏文帝曹丕《燕歌行》“短歌微吟不能长”和晋代傅玄《艳歌行》“咄来长歌续短歌”等句，认为“长歌”、“短

小学生作文《感悟幸福》范文五篇汇总

小学生作文《感悟幸福》范文五篇小草说,幸福就是大地增添一份绿意;阳光说,幸福就是撒向人间的温暖;甘露说,幸福就是滋润每一个生命。下面是为大家带来的有关幸福650字优秀范文，希望大家喜欢。感悟幸福650字1 生活就像一部壮丽的交响曲，它是由一篇一篇的乐章组成的，有喜、有怒、有哀、有乐。每一个人都有自己丰富多彩的生活，我也有自己的生活。我原本以为，吃可口的牛排，打电脑游戏，和朋友开心玩乐就是幸福。可是，我错了，幸福并不仅仅如此。记得有一次，我放学回到家里放下书包就拿起一包饼干来吃。吃着吃着，突然我觉得牙齿痛了起来，而且越来越痛，痛得我连饼干也咬不动了。我放下饼干，连忙去拿了一面镜子来看。原来这又是那一颗虫牙在“作怪”。“哎哟哟，哎哟哟，痛死我了……”我不停地说着。渐渐地，那牙疼得越来越厉害，疼得我坐立不安，直打滚。后来在妈妈的陪伴下去了医院，治好了那颗虫牙。跨出医院大门时，我觉得心情出奇的好，天空格外的蓝，路边的樟树特别的绿，看什么都顺眼，才猛然一悟，幸福是简单而平凡的，身体健康就是一种幸福! 这学期我发现我的英语退步了，我决定要把这门功课学好，于是，我每天回

家做完作业后，都抽出半小时时间复习英语，在课上也听得特别认真，一遇到不懂的题目主动请教老师。经过一段时间的努力，终于，在上次考试的时候，我考了97分。妈妈表扬了我，我心里美滋滋的。我明白了经过自己的努力享受到成功的喜悦，这也是一种幸福。 …… 每个人都无一例外的渴望幸福。不同的人有不同的感受，其实，幸福就是那种能在平凡中寻找欢乐、能在困境中找到自信的一种心境。同学们，幸福其实很简单，就在我们的身边，触手可及。用心去认真地品味吧，它一直未曾离开我们身边! 感悟幸福650字2 有的人认为幸福就是腰缠万贯，有的人认为幸福就是找到意中人，“采菊东篱下，悠然见南山”是陶渊明对邪恶幸福，“从明天起做一个幸福人，喂马、劈柴、周游世界。从明天起，关心蔬菜和粮食，我有一所房子，面朝大海，春暖花开。”这是海子的幸福。一千种人就有一千种对幸福的理解。我对幸福的理解就是幸福使简单而平凡的，是无处不在的! 我的牙疼得奇怪而顽强不是这颗牙疼就是那颗牙疼;不是吃冷的疼就是吃热

曹操《短歌行》其二翻译及赏析

曹操《短歌行》其二翻译及赏析引导语：曹操(155—220)，字孟德，小名阿瞒，《短歌行二首》是曹操以乐府古题创作的两首诗，第一首诗表达了作者求贤若渴的心态，第二首诗主要是曹操向内外臣僚及天下表明心迹。短歌行其二曹操周西伯昌，怀此圣德。三分天下，而有其二。修奉贡献，臣节不隆。崇侯谗之，是以拘系。后见赦原，赐之斧钺，得使征伐。为仲尼所称，达及德行，犹奉事殷，论叙其美。齐桓之功，为霸之首。九合诸侯，一匡天下。一匡天下，不以兵车。正而不谲，其德传称。孔子所叹，并称夷吾，民受其恩。赐与庙胙，命无下拜。小白不敢尔，天威在颜咫尺。晋文亦霸，躬奉天王。受赐圭瓒，钜鬯彤弓，卢弓矢千，虎贲三百人。威服诸侯，师之所尊。八方闻之，名亚齐桓。翻译姬昌受封为西伯，具有神智和美德。殷朝土地为三份，他有其中两分。整治贡品来进奉，不失臣子的职责。只因为崇侯进谗言，而受冤拘禁。后因为送礼而赦免，受赐斧钺征伐的权利。他被孔丘称赞，品德高尚地位显。始终臣服殷朝帝王，美名后世流传遍。齐桓公拥周建立功业，存亡继绝为霸首。

聚合诸侯捍卫中原，匡正天下功业千秋。号令诸侯以匡周室，主要靠的不是武力。行为磊落不欺诈，美德流传于身后。孔子赞美齐桓公，也称赞管仲。百姓深受恩惠，天子赐肉与桓公，命其无拜来接受。桓公称小白不敢，天子威严就在咫尺前。晋文公继承来称霸，亲身尊奉周天王。周天子赏赐丰厚，仪式隆重。接受玉器和美酒，弓矢武士三百名。晋文公声望镇诸侯，从其风者受尊重。威名八方全传遍，名声仅次于齐桓公。佯称周王巡狩，招其天子到河阳，因此大众议论纷纷。赏析《短歌行》 (“周西伯昌”)主要是曹操向内外臣僚及天下表明心迹，当他翦灭群凶之际，功高震主之时，正所谓“君子终日乾乾，夕惕若厉”者，但东吴孙权却瞅准时机竟上表大说天命而称臣，意在促曹操代汉而使其失去“挟天子以令诸侯”之号召，故曹操机敏地认识到“ 是儿欲据吾著炉上郁!”故曹操运筹谋略而赋此《短歌行 ·周西伯昌》。西伯姬昌在纣朝三分天下有其二的大好形势下，犹能奉事殷纣，故孔子盛称 “周之德，其可谓至德也已矣。 ”但纣王亲信崇侯虎仍不免在纣王前还要谗毁文王，并拘系于羑里。曹操举此史实，意在表明自己正在克心效法先圣西伯姬昌，并肯定他的所作所为，谨慎惕惧，向来无愧于献帝之所赏。并大谈西伯姬昌、齐桓公、晋文公皆曾受命“专使征伐”。而当今天下时势与当年的西伯、齐桓、晋文之际颇相类似，天子如命他“专使征伐”以讨不臣，乃英明之举。但他亦效西伯之德，重齐桓之功，戒晋文之诈。然故作谦恭之辞耳，又谁知岂无更讨封赏之意乎 ?不然建安十八年(公元 213 年)五月献帝下诏曰《册魏公九锡文》，其文曰“朕闻先王并建明德，胙之以土，分之以民，崇其宠章，备其礼物，所以藩卫王室、左右厥世也。其在周成，管、蔡不静，惩难念功，乃使邵康公赐齐太公履，东至于海，西至于河，南至于穆陵，北至于无棣，五侯九伯，实得征之。世祚太师，以表东海。爰及襄王，亦有楚人不供王职，又命晋文登为侯伯，锡以二辂、虎贲、斧钺、禾巨鬯、弓矢，大启南阳，世作盟主。故周室之不坏，系二国是赖。”又“今以冀州之河东、河内、魏郡、赵国、中山、常山，巨鹿、安平、甘陵、平原凡十郡，封君为魏公。锡君玄土，苴以白茅，爰契尔龟。”又“加君九锡，其敬听朕命。” 观汉献帝下诏《册魏公九锡文》全篇，尽叙其功，以为其功高于伊、周，而其奖却低于齐、晋，故赐爵赐土，又加九锡，奖励空前。但曹操被奖愈高，心内愈忧。故曹操在曾早在五十六岁写的《让县自明本志令》中谓“或者人见孤强盛，又性不信天命之事，恐私心相评，言有不逊之志，妄相忖度，每用耿耿。

2019-2020年高一音乐甜美纯净的女声独唱教案

2019-2020年高一音乐甜美纯净的女声独唱教案一、教学目标 1、认知目标：初步了解民族唱法、美声唱法、通俗唱法三种唱法的风格。 2、能力目标：通过欣赏部分女声独唱作品，学生能归纳总结出她们的演唱风格和特点，并同时用三种不同风格演唱同一首歌曲。 3、情感目标：通过欣赏比较，对独唱舞台有更多元化的审美意识。二、教学重点：学生能用三种不同风格演唱形式演唱同一首歌。三、教学难点：通过欣赏部分女声独唱作品，学生能归纳总结出她们的演唱风格和特点。四、教学过程：（一）导入 1、播放第十三界全国青年歌手大奖赛预告片（师）问：同学们对预告片中的歌手认识吗（生）答：（师）问：在预告片中提出了几种唱法？（生）答：有民族、美声、通俗以及原生态四种唱法，今天以女声独唱歌曲重点欣赏民族、美声、通俗唱法，希望通过欣赏同学们能总结出三种唱法的风格和特点。（二）、音乐欣赏

1、通俗唱法 ①(师)问：同学们平常最喜欢唱那些女歌手的歌呢？能唱唱吗？（可让学生演唱几句喜欢的歌，并鼓励） ②欣赏几首通俗音乐视频一：毛阿敏《绿叶对根的情谊》片段、谭晶《在那东山顶上》片段、韩红《天路》片段、刘若英《后来》片段视频二：超女《想唱就唱唱得响亮》 ①由学生总结出通俗音乐的特点 ②师总结并板书通俗音乐的特点：通俗唱法是在演唱通俗歌曲的基础上发展起来的，又称“流行唱法”。通俗歌曲是以通俗易懂、易唱易记、娱乐性强、便于流行而见长，它没有统一的规格和演唱技法的要求，比较强调歌唱者本人的自然嗓音和情绪的渲染，重视歌曲感情的表达。演唱上要求吐字清晰，音调流畅，表情真挚，带有口语化。 ③指出通俗音乐尚未形成系统的发声训练体系。其中用沙哑、干枯的音色“狂唱”和用娇柔、做作的姿态“嗲唱”，不属于声乐艺术的正道之物，应予以摒弃。 2、民族唱法 ①俗话说民族的才是世界的那么民族唱法的特点是什么呢？ ②欣赏彭丽媛《万里春色满人间》片段鉴赏提示：这首歌是剧种女主角田玉梅即将走上刑场时的一段难度较大的咏叹调。

关于以幸福为话题的作文800字记叙文5篇

关于以幸福为话题的作文800字记叙文5篇 ----WORD文档，下载后可编辑修改---- 下面是作者为各位家长学生收集整理的作文（日记、观后感等）范本，欢迎借鉴参考阅读，您的努力学习和创新是为了更美好的未来，欢迎下载！以幸福为话题的作文800字记叙文1：那是我生病后的第三天，妈妈从早上五点就起来为我准备早点。她蹑手蹑脚地走着“针步”，下楼煮早点，“啪”的一声，妈妈打开了煤气。在拿肉丝，打鸡蛋的她全然不知我正躲在楼梯口“监视”着她的一举一动。不一会儿，蛋炒好了。她开始切肉丝，一不小心，妈妈的手指切破皮了，鲜血正一滴一滴地流下来，为了不影响我的睡眠，她把手指放在嘴里吸了一下，坚持把剩下的肉丝切完。此时的我，心中犹如打翻了五味瓶，眼里的泪像断了线的珍珠般掉了下来，我再也忍不住了，一个劲地冲到妈妈面前，她赶紧把手背了过去，生怕让我知道了什么。她吃惊地问我：“妈妈太吵了，吵到你了?”“不，不，没有”她见我这么早起来就让我再回去补个觉。我关心地问：“妈，你的手没事吧?”她吱唔着说：“没事，擦破点皮，不碍事!”我仔细地帮她清洗了伤口，贴了一片创可贴。吃饭时，妈妈一直地往我碗里夹肉，“孩子，病刚好，多吃点!”可是我见她始终都没吃一块肉。我也夹了两块放在她的碗里。“儿子懂事了，你自己快点吃吧!补身体要紧!”我冲她点点头笑了笑，“嗯。” 这就是幸福，一份简简单单的幸福!我祈祷这幸福能伴我成长。以幸福为话题的作文800字记叙文2：在我眼中，成长就是记录我们长大过程中一点一滴的小事情的，而幸福就在这点点滴滴中。在我的成长记忆中，永不磨灭的是2017年11月的一天。妈妈要去云南，妈妈早上四点半要到指定地点集合，这么早，妈妈要两三点就起来，可是最近我咳嗽比较严重，所以天天给我煮萝卜汤喝。 “叮铃铃，叮铃铃”闹钟叫了起来，把我从睡梦中吵醒，一醒来，去找妈妈，

尊重议论文

谈如何尊重人尊重他人，我们赢得友谊；尊重他人，我们收获真诚；尊重他人，我们自己也获得尊重；相互尊重，我们的社会才会更加和谐. ——题记尊重是对他人的肯定，是对对方的友好与宽容。它是友谊的润滑剂，它是和谐的调节器，它是我们须臾不可脱离的清新空气。“主席敬酒，岂敢岂敢？”“尊老敬贤，应该应该！”共和国领袖对自己老师虚怀若谷，这是尊重；面对许光平女士，共和国总理大方的叫了一声“婶婶”，这种和蔼可亲也是尊重。尊重不仅会让人心情愉悦呼吸平顺，还可以改变陌生或尖锐的关系，廉颇和蔺相如便是如此。将相和故事千古流芳:廉颇对蔺相如不满，处处使难，但蔺相如心怀大局，对廉颇相当的尊重，最后也赢得了廉颇的真诚心，两人结为好友，共辅赵王，令强秦拿赵国一点办法也没有。蔺相如与廉颇的互相尊重，令得将相和的故事千百年令无数后人膜拜。现在，给大家举几个例子。在美国，一个颇有名望的富商在散步时，遇到一个瘦弱的摆地摊卖旧书的年轻人，他缩着身子在寒风中啃着发霉的面包。富商怜悯地将8美元塞到年轻人手中，头也不回地走了。没走多远，富商忽又返回，从地摊上捡了两本旧书，并说：“对不起，我忘了取书。其实，您和我一样也是商人！”两年后，富商应邀参加一个慈善募捐会时，一位年轻书商紧握着他的手，感激地说：“我一直以为我这一生只有摆摊乞讨的命运，直到你亲口对我说，我和你一样都是商人，这才使我树立了自尊和自信，从而创造了今天的业绩??”不难想像，没有那一句尊重鼓励的话，这位富商当初即使给年轻人再多钱，年轻人也断不会出现人生的巨变，这就是尊重的力量啊可见尊重的量是多吗大。大家是不是觉得一个故事不精彩，不够明确尊重的力量，那再来看下一个故事吧！一家国际知名的大企业，在中国进行招聘，招聘的职位是该公司在中国的首席代表。经过了异常激烈的竞争后，有五名年轻人，从几千名应聘者中脱颖而出。最后的胜出者，将是这五个人中的一位。最后的考试是一场面试，考官们都作文话题素材之为人处世篇：尊重思路人与人之间只有互相尊重才能友好相处要让别人尊重自己，首先自己得尊重自己尊重能减少人与人之间的摩擦尊重需要理解和宽容尊重也应坚持原则尊重能促进社会成员之间的沟通尊重别人的劳动成果尊重能巩固友谊尊重会使合作更愉快和谐的社会需要彼此间的尊重名言施与人，但不要使对方有受施的感觉。帮助人，但给予对方最高的尊重。这是助人的艺术，也是仁爱的情操。———刘墉卑己而尊人是不好的，尊己而卑人也是不好的。———徐特立知道他自己尊严的人，他就完全不能尊重别人的尊严。———席勒真正伟大的人是不压制人也不受人压制的。———纪伯伦草木是靠着上天的雨露滋长的，但是它们也敢仰望穹苍。———莎士比亚

短歌行赏析介绍

短歌行赏析介绍说道曹操，大家一定就联想到三国那些烽火狼烟岁月吧。但是曹操其实也是一位文学大家，今天就来分享《短歌行》赏析。《短歌行》短歌行》是汉乐府旧题，属于《相和歌辞·平调曲》。这就是说它本来是一个乐曲名称。最初古辞已经失传。乐府里收集同名诗有 24 首，最早是曹操这首。这种乐曲怎么唱法，现在当然是不知道。但乐府《相和歌·平调曲》中除《短歌行》还有《长歌行》，唐代吴兢《乐府古题要解》引证古诗 “长歌正激烈”，魏文帝曹丕《燕歌行》 “短歌微吟不能长”和晋代傅玄《艳歌行》 “咄来长歌续短歌”等句，认为“长歌”、 “短歌”是指“歌声有长短”。我们现在也就只能根据这一点点材料来理解《短歌行》音乐特点。《短歌行》这个乐曲，原来当然也有相应歌辞，就是“乐府古辞”，但这古辞已经失传。现在所能见到最早《短歌行》就是曹操所作拟乐府《短歌行》。所谓“拟乐府”就是运用乐府旧曲来补作新词，曹操传世《短歌行》共有两首，这里要介绍是其中第一首。这首《短歌行》主题非常明确，就是作者希望有大量人才来为自己所用。曹操在其政治活动中，为扩大他在庶族地主中统治基础，打击反动世袭豪强势力，曾大力强调“唯才是举”，为此而先后发布“求贤令”、“举士令”、“求逸才令”等;而《短歌行》实际上就是一曲“求贤歌”、又正因为运用诗歌形式，含有丰富抒情成分，所以就能起到独特感染作用，有力地宣传他所坚持主张，配合他所颁发政令。《短歌行》原来有“六解”(即六个乐段)，按照诗意分为四节来读。 “对酒当歌，人生几何?譬如朝露，去日苦多。慨当以慷，忧思难忘。何以解忧，唯有杜康。” 在这八句中，作者强调他非常发愁，愁得不得。那么愁是什么呢?原来他是苦于得不到众多“贤才”来同他合作，一道抓紧时间建功立业。试想连曹操这样位高权重人居然在那里为“求贤”而发愁，那该有多大宣传作用。假如庶族地主中真有“贤才”话，看这些话就不能不大受感动和鼓舞。他们正苦于找不到出路

感受幸福作文(15篇)

感受幸福作文(15篇) 感受幸福作文第1篇：幸福是什么？这是许多同学要问的问题。很小的时候，我就明白钱能够买来一大盒巧克力；钱能够买来玩具汽车；钱能够买许多的美丽的洋娃娃；钱能够买来一个大楼…… 我以为有钱就是幸福。倡我错了，钱虽然能够买来一屋子巧克力，但买了甜蜜，钱虽然能买到房子，可是却买来家庭幸福；钱虽然能买来药，可是却买来健康，钱虽然能买来闹钟，可是买来时间……那时，我又明白了有钱必须幸福。以前，我总是为了一条连衣裙而朝思暮想，盼望有一天能够穿上裙子，去放风筝。那时候，我以为拥有就是幸福。最终有一天，妈妈给我买了这条连衣裙，我高兴的一宿都没有睡觉。可是几天的新鲜劲没有了，穿上裙子后，我并没有什么改变，依然是一个黄毛丫头。于是把它扔到箱子里。几个月后，我又把它翻出来，可是已经小了，穿下了。我又明白了，虽然裙子很美，但都是暂时的，完美的时光总是转瞬消失。 “幸福是什么？”我依然没有感受到。几年后，我在街上看到了一对耄耋老人，他们虽然履蹒跚，可是互相搀扶，有时抬头看看天上的云卷云舒，有时望望西天如血的残阳，她们脸上洋溢着的是满足和幸福。噢，我明白幸福就是真情。虽然他们很穷，可是他们很

相爱。他们彼此珍惜，从感叹世界对他们的公平。往往有的有钱人，他们虽然很有钱，可是他们并幸福，因为他们的心总是被金钱和权势所占据了，根本享受了这天伦之乐。幸福其实很简单，就是和爸爸、妈妈吃一顿饭，和他在一齐聊聊天。感受幸福作文第2篇：夜，悄悄地打开了黑暗，散布着一如既往的宁静，天上的繁星披上了闪装，正对着我的眼，似乎害怕我听到它们之间的悄悄话。知何时，甘寂寞的虫儿起劲地奏起了动听的乐曲，清凉的微风夹杂着泥土的芳香悄悄地将白天的烦闷与喧嚣赶跑。夜，显得更加宁静而诗意了。静静的，左思，右想，就这样静静地坐在楼顶上，感受着夜馈赠我的美妙。就连天上偶尔飘过的云朵，也像是怕惊动了夜的宁静，如绒毛在平静水面滑过般，显得那么轻柔而迷人。今夜独处在空旷的夜空下，感受着夜带给我的美妙，幸福惬意溢满于心。原先自我一向以来苦苦追寻的幸福其实就在自我的身边。以往，有人努力打拼，渴望生活富裕来获得幸福，可一辈子的艰辛拼搏使自我逐渐沦为金钱的奴隶，苦苦追寻的幸福也越寻越远，最终留给自我的是岁月无情地染白的头发。其实，幸福并非是追寻能得到的，幸福是一种感受，仅有用心感受身边的一切，你就能发现，幸福无处在，譬如，管贫

短歌行赏析

短歌行赏析《短歌行》对酒当歌，人生几何？譬如朝露，去日苦多。概当以慷，忧思难忘。何以解忧？唯有杜康。青青子衿，悠悠我心。但为君故，沈吟至今。呦呦鹿鸣，食野之苹。我有嘉宾，鼓瑟吹笙。明明如月，何时可掇？忧从中来，不可断绝。越陌度阡，枉用相存。契阔谈咽，心念旧恩。月明星稀，乌鹊南飞。绕树三匝，何枝可依。山不厌高，海不厌深，周公吐哺，天下归心。 “短歌行”是汉乐府一个曲调的名称，是用于宴会场合的歌辞。曹操集子里现存《短歌行》两首，课文选的是第一首。作为一位政治家兼军事家的诗人曹操，十分重视人才，这首诗抒发了他渴望招纳贤才、建功立业的宏图大愿。全诗三十二句，分四节，每八句一节。第一节抒写诗人人生苦短的忧叹。“对酒当歌，人生几何？譬如朝露，去日苦多。”“当”，对着。“去日”，指逝去的岁月。这四句意思是：在边喝着酒，边唱着歌时，忽然感叹道：人生能有多久呢？人生啊，就好比早晨的露水，一会儿就干了，又苦于过去的日子太多了。“慨当以慷，忧思难忘。何以解忧？唯有杜康。”“慨当以慷”是“慷慨”的间隔用法，“当以”，没有实在意义，即指宴会上歌声慷慨激昂。“杜康”相传是发明酿酒的人，这里作酒的代称。这四句意思是：即使宴会上歌声慷慨激昂，诗人内心的忧愁还是难以消除。用什么来消除胸中的忧愁呢？只有借酒浇愁。我们如何理解诗人这种人生苦短的忧叹呢？诗人生逢乱世，

目睹百姓颠沛流离，肝肠寸断，渴望建功立业而不得，因而发出人生苦短的忧叹。这个点我们可从他的另一首诗《蒿里行》中得到佐证：“白骨露于野，千里无鸡鸣。生民百遗一，念之断人肠。” 第二节抒写诗人对贤才的渴求。“青青子衿，悠悠我心”，是引用《诗经?郑风?子衿》中的成句。“青衿”，周代读书人的服装，这里指代有学问的人。“悠悠”，长久的样子，形容思念之情。这两句意思是：你的衣领青青啊，总是让我如此挂念。原诗后两句是：“纵我不往，子宁不嗣音？”意思是：虽然我不能去找你，你为什么不主动给我音信？曹操因为事实上不可能一个一个地去找那些贤才，所以他使用这种含蓄的话来提醒他们，希望贤才主动来归。“但为君故，沉吟至今。”“沉吟”，低声叨念，表示渴念。这两句意思是：只因为你的缘故，让我渴念到如今。“青青子衿，悠悠我心。但为君故，沉吟至今。”四句以女子对心爱的男子的思念比喻自己对贤才的渴求。“呦呦鹿鸣，食野之苹。我有嘉宾，鼓瑟吹笙。”这四句引自《诗经?小雅?鹿鸣》，《鹿鸣》是一首描写贵族盛宴热情款待尊贵客人的的诗歌。前两句起兴，意思是：野鹿呦呦呦呦地叫，欢快地吃着野地里的艾蒿。以下各句描写宾客欢宴的场面，这里引用的两句意思是：我有很多尊贵的客人，席间弹起琴瑟，吹起笙乐。诗人引用这几句诗，表示自己对贤才的热情。第三节抒写诗人对贤才难得的忧思和既得贤才的欣喜。“明明如月，何时可掇？”“明月”，比喻人才。“掇”，拾取，摘取。意思是：贤才有如天上的明月，我什么时候才能摘取呢？“忧从中来，不可断绝。”因为求才不得，内心不禁产生忧愁，这种忧愁无法排解。“越陌度阡，枉用相存。契阔谈讌，心念旧恩。”“陌”、“阡”，都是指田间小路，东西向叫“陌”，南北向叫“阡”。“枉”，枉驾，屈驾。“用”，以。“存”，探问，问候。“契阔”，久别重逢。

女生唱的歌曲欢快甜美

女生唱的歌曲欢快甜美美妙的歌曲能令我们陶醉其中而无法自拨，最激烈的歌曲能令我们的身体不由自主的跟着手舞足蹈起来，下面是小编整理的欢快甜美的歌曲的内容，希望能够帮到您。欢快甜美的歌曲 1. Talking - 2. 羽毛- 劲歌金曲 3. 为你- 黑龙 4. 我的小时候- 罗艺达 5. 听说爱情回来过 6. 那个男人 7. 夫妻观灯_韩再芬、李迎春- 中国民歌宝典二 8. 往生- 镀飞爱在阳光空气中- 区瑞强- 音乐合辑 9. 说中国- 班- 华语群星 10. 第十八封信- Kent王健 11. 那一夜你喝了酒- 傅薇 12. 最近比较烦- 周华健/李宗盛/品冠- 滚石群星 13. 告白- 张娜拉 14. Talking VIII - 15. my love - 网友精选曲 16. 音乐人民- 音乐合辑 17. 深深深深- 徐誉滕 18. Honkytonk U - Toby Keith 19. 征服- 阿强 20. 我总会感动你- 沙宝亮欢快甜美的歌曲 1. 一千步的距离- 高桐 2. fleeing star - 音乐合辑 3. My Life - 李威杰 4. 小妹听我说- 金久哲 5. 上海滩- 梁玉嵘- 华语群星 6. 爱我多爱一些- 黎姿 7. 恋人未满- 8. 玛奇朵飘浮- 音乐听吧 9. 風- 音乐听吧 10. 七月- 小鸣 11. 滚滚红尘- 罗大佑 12. 张震岳—想要- 华语群星 13. 有梦有朋友- 14. 童年- 拜尔娜 15. 洪湖水，浪打浪- 宋祖英 16. 只爱到一半- 魏晨 17. 风雨人生路- 何静 18. 居家男人- 回音哥如果当时- 许嵩 19. 那个男人的谎言Tae In - 非主流音乐

尊重他人的写作素材

尊重他人的写作素材导读：——学生最需要礼貌著名数学家陈景润回厦门大学参加 60 周年校庆，向欢迎的人们说的第一句话是：“我非常高兴回到母校，我常常怀念老师。”被人誉为“懂得人的价值”的著名经济学家、厦门大学老校长王亚南，曾经给予陈景润无微不至的关心和帮助。陈景润重返母校，首先拜访这位老校长。校庆的第三天，陈景润又出现在向“哥德巴赫猜想”进军的启蒙老师李文清教授家中，陈景润非常尊重和感激他。他还把最新发表的数学论文敬送李教授审阅，并在论文扉页上工工整整写了以下的字：“非常感谢老师的长期指导和培养——您的学生陈景润。”陈景润还拜访了方德植教授，方教授望着成就斐然而有礼貌的学生，心里暖暖的。 ——最需要尊重的人是老师周恩来少年时在沈阳东关模范学校读书期间 , 受到进步教师高盘之的较大影响。他常用的笔名“翔宇”就是高先生为他取的。周恩来参加革命后不忘师恩 , 曾在延安答外国记者问时说：“少年时代我在沈阳读书 , 得山东高盘之先生教诲与鼓励 , 对我是个很大的促进。” 停奏抗议的反思 ——没有礼仪就没有尊重孔祥东是著名的钢琴演奏家。 1998 年 6 月 6 日晚，他在汕头

举办个人钢琴独奏音乐会。演出之前，节目主持人再三强调，场内观众不要随意走动，关掉 BP 机、手提电话。然而，演出的过程中，这种令人遗憾的场面却屡屡发生：场内观众随意走动， BP 机、手提电话响声不绝，致使孔祥东情绪大受干扰。这种情况，在演奏舒曼作品时更甚。孔祥东只好停止演奏，静等剧场安静。然而，观众还误以为孔祥东是在渴望掌声，便报以雷鸣般的掌声。这件事，令孔祥东啼笑皆非。演出结束后，孔祥东说：有个 BP 机至少响了 8 次，观众在第一排来回走动，所以他只得以停奏抗议。 “礼遇”的动力 ——尊重可以让人奋发日本的东芝公司是一家著名的大型企业，创业已经有 90 多年的历史，拥有员工 8 万多人。不过，东芝公司也曾一度陷入困境，土光敏夫就是在这个时候出任董事长的。他决心振兴企业，而秘密武器之一就是“礼遇”部属。身为偌大一个公司的董事长，他毫无架子，经常不带秘书，一个人步行到工厂车间与工人聊天，听取他们的意见。更妙的是，他常常提着酒瓶去慰劳职工，与他们共饮。对此，员工们开始都感到很吃惊，不知所措。渐渐地，员工们都愿意和他亲近，他赢得了公司上下的好评。他们认为，土光董事长和蔼可亲，有人情味，我们更应该努力，竭力效忠。因此，土光上任不久，公司的效益就大力提高，两年内就把亏损严重、日暮途穷的公司重新支撑起来，使东芝成为日本最优秀的公司之一。可见，礼，不仅是调节领导层之间关

Engineering the properties of metal nanostructures via galvanic replacement reactions

高二《甜美纯净的女声独唱》教案

尊重的素材

那一刻我感受到了幸福_初中作文

初中语文古文赏析曹操《短歌行》赏析(林庚)

适合女生KTV唱的100首好听的歌

关于我的幸福作文八篇汇总

高中语文文言文曹操《短歌行(对酒当歌)》原文、翻译、赏析

小学生作文《感悟幸福》范文五篇汇总

曹操《短歌行》其二翻译及赏析

2019-2020年高一音乐 甜美纯净的女声独唱教案

关于以幸福为话题的作文800字记叙文5篇

尊重议论文

最新整理高中关于幸福的议论文800字范文3篇

短歌行赏析介绍

感受幸福作文(15篇)

短歌行赏析

女生唱的歌曲欢快甜美

尊重他人的写作素材

2019-2020年高一音乐甜美纯净的女声独唱教案