Amine modified graphene
乙醇胺修饰的石墨烯量子点的合成及生物成像应用
乙醇胺修饰的石墨烯量子点的合成及生物成像应用曾敏翔;陈翔;谢虞清;管剑;甄杰明;朱先军;杨上峰【期刊名称】《中国材料进展》【年(卷),期】2015(034)011【摘要】作为新一代基于碳材料的量子点,乙醇胺(Ethanolamine,ETAM)修饰的石墨烯量子点(ETAM-GQDs)成功地通过一步水热法被合成出来,并通过实验显示出在生物成像应用中的潜力.以柠檬酸作为碳源、甘氨酸作为桥联剂,通过乙醇胺/去离子水共溶剂水热法,成功地实现了在石墨烯量子点表面修饰乙醇胺得到ETAM-GQDs.通过原子力显微镜(AFM)、光电子能谱(XPS)、拉曼光谱等对ETAM-GQDs进行表征,在测得ETAM-GQDs的稳态荧光光谱后,通过使用硫酸奎宁作为参比,在365 nm紫外光激发下测得的ETAM-GQDs的量子产率为38.2％.除此之外,活体细胞HL7702和ETAM-GQDs共培养后,通过荧光成像实验证实了ETAM-GQDs可以作为有效的生物成像剂.【总页数】6页(P841-846)【作者】曾敏翔;陈翔;谢虞清;管剑;甄杰明;朱先军;杨上峰【作者单位】中国科学技术大学材料科学与工程系中国科学院能量转换材料重点实验室合肥微尺度物质科学国家实验室,安徽合肥,230026;中国科学技术大学材料科学与工程系中国科学院能量转换材料重点实验室合肥微尺度物质科学国家实验室,安徽合肥,230026;中国科学技术大学材料科学与工程系中国科学院能量转换材料重点实验室合肥微尺度物质科学国家实验室,安徽合肥,230026;中国科学技术大学材料科学与工程系中国科学院能量转换材料重点实验室合肥微尺度物质科学国家实验室,安徽合肥,230026;中国科学技术大学材料科学与工程系中国科学院能量转换材料重点实验室合肥微尺度物质科学国家实验室,安徽合肥,230026;中国科学技术大学材料科学与工程系中国科学院能量转换材料重点实验室合肥微尺度物质科学国家实验室,安徽合肥,230026;中国科学技术大学材料科学与工程系中国科学院能量转换材料重点实验室合肥微尺度物质科学国家实验室,安徽合肥,230026【正文语种】中文【中图分类】O69【相关文献】1.氨基修饰石墨烯量子点的制备及应用研究 [J], 刘玉星;罗倩;孙志鹏;刘玉梅2.荧光碳点探针的合成、性质及其在生物成像中的应用 [J], 李亚丽;郭靖;宋娟;朴向民;徐晓龙;王英平3.席夫碱多功能金属离子探针的合成及在生物成像中的应用 [J], 曹亚萍;吴庆;胡庆红;余光勤;袁泽利4.氧化石墨烯量子点修饰氧掺杂多孔g-C3N4在光催化降解和抗菌中的应用 [J], 徐婧; 黄金; 王周平; 朱永法5.近红外荧光碳点的合成及其在生物成像中的应用 [J], 李利平;任晓烽;白佩蓉;刘妍;许玮月;解军;张瑞平因版权原因，仅展示原文概要，查看原文内容请购买。
butyl(丁基橡胶)-石墨烯纳米复合材料
Study on Modified Graphene/Butyl Rubber Nanocomposites.I.Preparation and CharacterizationHuiqin Lian,1,2,3Shuxin Li,1Kelong Liu,1Liangrui Xu,1Kuisheng Wang,2Wenli Guo11Department of Materials Science and Engineering,Beijing Institute of Petrochemical Technology,Beijing,China2Department of Materials Science and Engineering,Beijing University of Chemical Technology,Beijing,China 3Department of Chemical Engineering,Yanbian University,Beijing,ChinaButyl rubber,IIR nanocomposites based on modified graphene sheets,were fabricated by solution process-ing followed by compression molding.MG was pre-pared from natural graphite,NG through graphite oxide route.X-ray diffraction showed that the exfoliated MG was homogeneously dispersed in the IIR matrix with doping levels of1-10wt%as evidenced by the lack of the characteristic graphite reflection in the compo-sites.In contrast,the graphite retained its stacking order and showed the sharp characteristic peak in the NG-IIR composites.Scanning electron microscope images of the fracture surfaces of the IIR matrix showed that MG nanofillers exhibited better compati-bility than NG did.The mechanical properties of the MG-IIR nanocomposites were significantly improved due to the efficient distribution of the large surface area MG sheet.The tensile modulus of nanocomposite with doping level of MG10wt%was16times that of the pure IIR.POLYM.ENG.SCI.,00:000–000,2011.ª2011 Society of Plastics EngineersINTRODUCTIONCommercial butyl rubber(IIR)is a copolymer of isobu-tylene and a small amount of isoprene.It is employed in the inner linings of automobile tires and in other specialty application due to its characteristics of chemical inertness, impermeability to gases and weatherability.However, unsaturated bonds in IIR,due to the presence of isoprene monomer units in the backbone,can be attacked by atmos-pheric ozone leading to oxidative degradation and chain cleavage.Also in somefields,such as aerospace,aircraft and high-vacuum systems,IIR does not meet the extremely high-gas barrier as well as the high mechanical properties requirements.Therefore,there exists a continuous interest in lowering gas permeability and improving the mechanical properties of IIR by various techniques[1,2].It is well known that polymeric nanocomposites are of great interest for both scientific challenges and industrial applications due to their enhanced mechanical properties and unique material properties[3–5].Compared with con-ventional systems,nanomaterials are more effective rein-forcements because the stress transfer from the matrix to the reinforcement is more efficient in nanocomposites due to the increased surface area,assuming good adhesion at the interface.Also,the crack propagation length at the interface becomes longer,improving the strength and toughness.In addition to improving the mechanical prop-erty,nanofillers,such as layered silicate or carbon nanotubes,can provide dramatic improvement in thermal stability,dimensional stability,heat-distortion tempera-ture,and barrier property[6–11].Recently,graphite oxide (GO)has attracted increasing interest as afiller for poly-mer nanocomposites due to its high dispersive capacity, long coherence length and the barrier property[12,13]. GO with a typical pseudo-two-dimensional structure gen-erally contains hydroxyl,carboxyl and ether groups, which causes GO to absorb polar molecules easily and thus GO/polymer composites can be formed.Such struc-tural nanocomposites can provide reinforcement to the base polymer matrix.Also,GO may also have other desirable properties,such as mass diffusion coefficients, coefficients of thermal expansion,dielectric constants, thermal/chemical stability,solvent resistance,selectivity, conductivity,and resistivity to membrane fouling and poisoning.However,as a reinforcement of IIR,the hydro-philic surface of GO makes it difficult to disperse in the hydrophobic IIR matrix.Therefore,it is an importantCorrespondence to:Wenli Guo;e-mail:wlguo2008@Contract grant sponsor:Natural Science Foundation of China(NSFC);contract grant number:51063009;contract grant sponsor:BeijingNatural Science Foundation of China;contract grant number:KZ200910017001.DOI10.1002/pen.21997Published online in Wiley Online Library().V C2011Society of Plastics EngineersPOLYMER ENGINEERING AND SCIENCE—-2011Administratorissue to improve the compatibility of the GO sheet with the IIR matrix.Moreover,methods used to prepare polymeric nano-composites include in-situ polymerization [14],solution mixing [15],melting compound [16],and cocoagulating of polymeric composite solution [17].Considering the manufacture process of the IIR,slurry and solution pro-cess,the solution mixing is promising to fabricate IIR hybrids in the IIR industry.In this study,we report for the first time the fabrication of well-dispersed modified graphene in IIR composites through solution process.The MG nanosheets are homo-geneously dispersed in the IIR matrix with doping level of 1–10wt%.Compared with the pure IIR,the resulting nanocomposite membranes exhibit dramatic enhancement of mechanical properties.To the best of our knowledge,this is the first report of totally exfoliated graphite to reinforce IIR with outstanding mechanical property.The properties of vulcanization plateau,gas barrier,cure capa-bility,and rubber damping are under study and the results will be published in the near future.EXPERIMENTAL PROCEDURES MaterialsNatural graphite flakes with a partical size of 30l m were purchased from Aladdin Reagent Company (China).Cetyltrimethylammonium bromide (CTAB)was bought from Fuchen Chemical Reagents(Tianjin,China).Butyl rubber (IIR 1751)was obtained from YanShan Petrochem-ical Company of China.The other reagents (NaOH,NaNO 3,and KMnO 4)of analytical grade and 98%H 2SO 4,30%H 2O 2were purchased from Sinopharm Chemical Reagent Co.Ltd.(China)and were used as received with-out further purification.Ultrapure water with resistivity of 18M O was produced by a Milli-Q(Millipore,USA)and was used for solution preparation.Preparation of MG/NG-IIR Composite SheetsThe procedure used to prepare the MG-IIR nano-composite sheets was shown in Fig. 1.First,based on Hummers’method [18],the graphite was oxidized by con-centrated sulfuric acid to create polar hydrophilic groups (ÀÀCOOH,C ¼¼O,ÀÀOH)on the surface.The GO was dispersed in cetyltrimethylammonium bromide solution (20wt%)and ultrasonicated for 0.5h,followed by me-chanical stirring at 258C for 24h.During this process,the tertiary amine reacted with the carboxylic groups on the oxidized surface via an acid-base reaction or via hydrogen bonding between the surface ÀÀOH or C ¼¼O group and the amine groups.The suspension was filtrated and washed three times with water,dried at 408C in a vacuum for 24h.The resulting MG was added into the 15wt%solution of IIR in hexane by sonication for 0.5h to form a colloidal suspension.Then the mixture was stirred for 6h at 258C.The amounts of MG/NG added were 0,1,3,5,10wt%ofthe mass of rubber.The composite solution was then coa-gulated by adding methanol and the precipitated nanocom-posite was dried in a vacuum.Finally,sheet samples were prepared by vacuum compression molding using a 2mm thick spacer at 1008C under 10MPa for ing this procedure,the NG-IIR composite sheets were prepared.CHARACTERIZATION AND MEASUREMENTS The as-made membrane was characterized by X-ray diffraction (XRD,Scintag PAD X diffractometer,Cu K a source,operated at 45kV and 40mA).The samples were scanned with 58/min between 2y of 28–308.SEM observation was performed using Tecnai T12,at an acceleration voltage of 15kV with gold -posite samples were imaged by first fracturing in liquid nitrogen.TGA was performed using a TA Instrument Q500attached to an automatic programmer from ambient tem-perature to 5008C at a heating rate of 108C/min in a nitro-gen atmosphere.A TA instrument Q1000was used to record the DSC traces at a heating rate of 108C/min.Measurements of mechanical properties were con-ducted at 25628C according to relevant ISO standard (ISO 37).Tensile tests were measured on an Autograph AGS-J SHIMADZU universal testing machine at a cross-head speed of 500mm/min.The reported values were the average of five measurements.RESULTS AND DISCUSSIONThe FTIR spectra of NG,GO,and MG were shown in Fig.2.The FT-IR spectrum of NG showed no significant features.While that of GO showed quite differentFIG.1.Schematic representation for the fabrication of MG-IIR nano-composite membrane.2POLYMER ENGINEERING AND SCIENCE—-2011DOI 10.1002/pencharacter by the presence of new bands.The broad bandat3405cm21could be assigned to stretching of the ÀÀOH groups on the GO surface.The bands at1720and 1070cm21were associated with stretching of the C¼¼Oand CÀÀO stretching vibrations of carboxylic groupsrespectively.The FTIR spectrum of MG confirmed theeffective functionalization of graphene.The double bandsat2849and2919cm21were antisymmetric and symmet-ric CÀÀH stretching vibrations of theÀÀCH2ÀÀgroups from surfactant molecules[19]respectively.The bands at 1463and1127cm21were corresponding to CÀÀH bend-ing and the C-N stretching vibration respectively.The spectrum also showed a C¼¼C peak at1574cm21corre-sponding to the skeletal vibration of graphene sheets[20]. These spectral features showed that MG was successfully synthesized.The XRD patterns of the NG,GO,MG were shown inFig.3.The sharp diffraction peak around26.5o for pris-tine graphite(Fig.3a)showed that the basal spacing was0.34nm.Because of the strong Van der Waals force andstatic electric force between the sheets of graphite,thesheet was difficult to disperse.Thus a relatively strongoxidative acid was used to oxidize the graphite creatingpolar groups on the surface of graphite sheet.The surfac-tant of cetyltrimethyl ammonium bromide was used to functionalize the oxidized graphite through acid-base reaction to obtain stable exfoliated graphene sheets.As shown in Fig.3a,the GO showed two diffraction peaks at 2y of9.7o and25.3o,corresponding to a d-spacing of0.91 and0.35nm,respectively,and indicated that the GO was not fully oxidized and the additional peak at25.3o was that of unoxidized graphite.From Fig.3b,MG showed no characteristic peak indicating that the modified graphene sheet had been exfoliated completely.The XRD patterns of MG/NG-IIR nanocomposites membranes with different doping levels were presented in Fig.4.As shown in Fig.4a,the broad peak of2y around 15o appeared in IIR and NG-IIR membranes,due to the amorphous phase of IIR.Toki et al.[21]reported that the amorphous peak of IIR changed during uniaxial deforma-tion.In this case,with NG loading increase,the broad peak shifted slightly,from2y of14.7o in IIR to14.4o in 10wt%NG-IIR composite.It was deduced that NG did not influence the crystallization behavior of IIR very much.From Fig.4a,the diffraction peak at2y around 26.5o appeared in NG and NG-IIR composites because the NG retained its stacking order in the composite.XRD diffraction curves of MG-IR nanocomposites were shown in Fig.4b.The diffraction ascribed to graphite or oxidized graphite did not appear in all of the XRD patterns of composites,indicating the complete exfoliation of the MG in the IIR matrix.SEM images of the fractured surfaces of the as-made MG-IIR and NG-IIR composites were shown in Fig.5. SEM images of NG-IIR composites showed a smooth to-pography with the NG remained its stacking order in the IIR matrix(Fig.5a and b).In contrast,the MG-IIR com-posites appeared a rough surface and the MG dispersed in IIR matrix homogenously(Fig.5c and d).This is likely due to the organic modifier on the surface of MG produc-ing good compatibility with IIR matrix.These results were coincident with the XRD test.TGA under a nitrogen atmosphere was performed on NG,MG,IIR and MG-IIR composites to obtain the struc-ture of MG and composites,as well as to determine the effects of the MG on the thermal stability of the compo-sites.The resulting curves were shown in Fig.6.From FIG.2.FT-IR spectra of NG,GO andMG.FIG.3.The XRD patterns of(a)NG,GO and(b)MG.The curves are shifted vertically for clarity.DOI10.1002/pen POLYMER ENGINEERING AND SCIENCE—-20113FIG.4.The XRD patterns of composites(a)NG-IIR and(b)MG-IIR.The curves are shifted vertically forclarity.FIG.5.SEM images of fracture surface of(a,b)NG-IIR nanocomposites and(c,d)MG-IIR nanocompo-sites.4POLYMER ENGINEERING AND SCIENCE—-2011DOI10.1002/penNG curve of Fig.6a,graphite maintained its weight under the test condition.The curve of MG indicated that MG was composed of 17wt%graphene and 83wt%organicmodifiers.The functional surface contributed to the dis-persion of MG in the IIR solution as well as to the com-patibility with the IIR matrix in the composite membrane.Figure 6b indicated that the IIR began to decompose at 2698C and degraded completely at 4158C.In the case of MG/IIR composites,the weight loss below 3008C was attributed to the decomposition of the small organic molecules on the surface of graphene.Table 1listed the temperature at 5wt%loss of the TGA curve of IIR and MG-IIR composites.The pure IIR lost 5wt%at 3248C and the value was the highest of all the curvesobtained.FIG.6.(a)TG curves of NG and MG;(b)TG curves of MG-IIR nano-composites and (c)DTG curves of MG-IIR nanocomposites.TABLE 1.Thermal propertiesofpureIIRandMG-IIRnanocomposites.IIR 1%MG-IIR 3%MG-IIR 5%MG-IIR 10%MG-IIRT 5wt%(8C)a 324297321256236T mrv (8C)b 372368375378383a Temperature at 5wt%loss.bTemperature at the maximum reactivevelocity.FIG.7.DSC curves of MG-IIRnanocomposites.FIG.8.Tensile stress-strain curve of (a)MG-IIR nanocomposites and (b)NG-IIR nanocomposites.DOI 10.1002/pen POLYMER ENGINEERING AND SCIENCE—-20115The temperature at5wt%loss decreased with the increas-ing MG content when the MG contents were3,5,and10wt%in composites respectively.This might be due to theamount of small molecule of organic modifier increasedwith the increasing MG content.Thefirst derivative of the TGA curve(DTA curvesshown in Fig.6c showed the variation in weight withtime(dW/dT)as a function of temperature.The DTApeaks indicated the temperature of the maximum reactivevelocity.Table1listed the temperature at the maximumreactive velocity of the DTA curve of IIR and MG-IIRcomposites.Pure rubber reached the maximum reactivevelocity at3728C.The value of1wt%MG-IIR nanocom-posite was3688C and it was lower than that of IIR.Thismight be that the amount of graphene was too low toinfluence the thermal stability of the composite,whilesmall organic molecules on the surface of graphene withlow decomposition temperature induced the thermaldecomposition.For all other composites,the temperatureat the maximum reactive velocity increased with increas-ing graphene content,and for the10wt%composite itwas increased by118C compared with pure IIR.Thisindicated that the thermal stability of IIR was improvedby the addition of graphene.A significant number ofpapers had reported increased thermal stability of variouspolymers using graphene asfiller[15,22,23].T.Kuilaet al.reported that the better thermal stability of gra-phene/polyethylene composite system was due to the highaspect ratio of the monodispersed graphene layers whichacted as a barrier and inhibited the emission of small gas-eous molecules[23].DSC for the MG/IIR nanocomposites was shown inFig.7.The glass transition(T g)temperature of IIR wasobserved at270.58C,and the MG loading increased,theT g values of composites which were269.28C,268.68C, 268.98C,and269.18C with the loading levels of1,3,5, 10wt%,respectively.All the composites showed aslightly higher T g than that of pure IIR;among them thehighest one was268.68C of3wt%MG-IIR nanocompo-site.It indicated that the effective exfoliation of the MGincreased the T g due to the interaction between MG andpared with the results of graphene/polystyrenenanocomposite[24],the incorporation of PS nanoparticleson graphene sheets resulted in an increase in T g by178C,while the exfoliated MG did not influence the T g of MG-IIR nanocomposite very much.Therefore,the properties of nano-filler influenced the phase behavior of polymer matrix.The interaction between MG and IIR is under further study.The typical stress–strain curves for the MG-IIR and NG-IIR compositesfilms were presented in Fig.8.The mechanical performance of MG/IIR and NG/IIR compos-itefilms was significantly increased compared with pure IIRfilm(Fig.8a and b).The effect of MG content on mechanical properties of the nanocomposites was shown in Table 2.Stresses at 100%,200,and300%elongation of composites increased along with the MG loading increase.Therefore,in this study,MG-IIR nanocomposites had higher mechanical properties than that of pure IIR.On the basis of these stress–strain curves of tensile tests(Fig.8a and b),Young’s moduli were taken as the linear regression of the initial linear part of stress–strain curves.Figure9a showed the representative calculated Young’s moduli of IIR,NG-IIR,and MG-IIR.The corre-sponding Young’s modulus values were shown in Fig.9b. The addition of MG grapheneflakes significantly increased the Young’s modulus.Remarkably,the Young’s modulus of10wt%MG-IIR was16times that of pure IIR.In comparison,the10wt%NG-IIR compositesTABLE 2.Mechanical properties of pure IIR and MG-IIR nanocomposites.Stress at 100%(MPa)Stress at200%(MPa)Stress at300%(MPa)IIR0.170.190.181%MG-IIR0.250.230.183%MG-IIR0.440.380.295%MG-IIR0.540.430.3110%MG-IIR0.770.590.40FIG.9.(a)Representative calculated Young’s moduli of IIR,NG-IIR,and MG-IIR based on the slope of the elastic region.(b)Dependence ofYoung’s modulus on loading offillers in MG-IIR and NG-IIR nanocom-posites.6POLYMER ENGINEERING AND SCIENCE—-2011DOI10.1002/penimproved3.5times only,as shown in Fig.9b.It might be that the NG stacks did not exfoliate or intercalate in the IIR matrix.This result coincided with the results of the XRD and SEM analysis.Therefore,from the result of mechanical properties,it was deduced that the modifier on the surface of the gra-phene sheet not only caused the sheet to disperse in the IIR matrix,but also bonded to the large rubber chain in two dimensions,which gave the nanocomposite better tensile performance.According to the reference[25],gra-phene layers in poly(vinyl chloride)matrix enhanced the mechanical properties of PVC,because of the strong interfacial adhesion.Therefore,in our case,MG-IIR nano-composites had higher mechanical properties than the pure IIR,which may be due to the homogenous distribu-tion of exfoliated MG and the good compatibility with polymer matrix.CONCLUSIONMG-IIR nanocomposites were prepared by solution processing.SEM and XRD analysis indicated that the exfoliated MG was homogeneously disperse in the IIR matrix.The addition of MG greatly improved the mechan-ical property of the nanocomposites.The nanocomposites with10wt%MG showed the highest Young’s modulus, 3.4MPa,which was about16times higher than that of pure IIR,0.21MPa.REFERENCES1.S.Takahashi,H.A.Goldberg,C.A.Feeney,D.P.Karim,M.Farrell,K.O’Leary,and R.Paul,Polymer,47,3083 (2006).2.Y.Liang,W.Cao,Z.Li,Y.Wang,Y.Wu,and L.Zhang,Polym.Test.,27,270(2008).3.N.A.Kotov,Nature,442,254(2006).4.M.A.Pulickel and M.T.James,Nature,447,1066(2007).5.E.P.Giannelis,Adv.Mater.,8,29(1996).6.Camenzinda,W.R.Caserib,and S.E.Pratsinis,Nano Today,5,48(2010).7.S.C.Tjong,Mater.Sci.Eng.,R53,73(2006).8.Suresha,B.N.Ravi Kumar,M.Venkataramareddy,and T.Jayaraju,Mater.Des.,31,1993(2010).9.H.Kim and C.W.Macosko,Polymer,50,3797(2009).10.Y.Liang,Y.Wang,Y.Wu,Y.Lu,H.Zhang,and L.Zhang,Polym.Test.,24,12(2005).11.E.Burgaz,H.Lian,R.H.Alonso,L.Estevez,and E.P.Gian-nelis,Polymer,50,2348(2009).12.Y.Lian,Y.Liu,T.Jiang,J.Shu,H.Lian,and M.Cao,J.Phys.Chem.C,114,21(2010).13.K.Kalaitzidou,H.Fukushima,and L.T.Drzal,Compos.Sci.Technol.,67,2045(2007).14.J.M.Herrera-Alonso,Z.Sedlakova,and E.Marand,J.Membr.Sci.,349,251(2010).15.S.Ansari and E.P.Giannelis,J.Polym.Sci.Part B:Polym.Phys.,47,888(2009).uki, A.Tukigase,and M.Kato,Polymer,43,2185(2002).17.L.Q.Zhang,Y.Z.Wang,Y.Q.Wang,Y.Sui,and D.S.Yu,J.Appl.Polym.Sci.,78,1873(2000).18.W.S.Hummers and R.E.Offeman,J.Am.Chem.Soc.,80,1339(1958).19.P.J.Thistlethwaite and M.S.Hook,Langmuir,16,4993(2000).20.T.Szabo,O.Berkesi,and I.Dekany,Carbon,43,3186(2005).21.S.Toki,I.Sics,B.S.Hsiao,S.Murakami,M.Tosaka,S.Poompradub,S.Kohjiya,and Y.Ikeda,J.Polym.Sci.Part B:Polym.Phys.,42,956(2004).22.Q.L.Bao,H.Zhang,J.X.Yang,S.Wang,D.Y.Tong,R.Jose,S.Ramakrishna,C.T.Lim,and K.P.Loh,Adv.Funct.Mater.,20,1(2010).23.T.Kuila,S.Bose,C.E.Hong,M.E.Uddin,P.Khanra,N.H.Kim,and J.H.Lee,Carbon,49,1033(2011).24.A.S.Patole,S.P.Patole,H.Kang,J.Yoo,T.Kim,and J.Ahn,J.Colloid Interface Sci.,350,530(2010).25.S.Vadukumpully,J.Paul,N.Mahanta,and S.Valiyaveettil,Carbon,49,198(2011).DOI10.1002/pen POLYMER ENGINEERING AND SCIENCE—-20117。
氨基化功能化碳纳米管
Department of Materials Science, Fudan University, The Key Laboratory of Molecular Engineering of Polymers, Ministry of Education, Shanghai 200433, China
However, the realization of nanotube-reinforced epoxy resin can only be achieved by solving following main problems: one is the lack of interfacial adhesion, which is critical for load transfer in composites – since the atomically smooth non-reactive surface of nanotubes built of rolled graphene sheets, lacking in interfacial bonding inhibits load transfer from the matrix to nanotubes across the nanotube/ polymer interface. Another problem is the poor dispersion of nanotubes in the epoxy matrix, which is also significant for the fabrication of reinforced composites. Because of the
光催化材料简介
贵金属沉积
沉积Ag后的TiO2光催化性能
光生电子在Ag岛上富集 ，光生空穴向TiO2晶粒 表面迁移，这样行成的 微电池促进了光生电子 和空穴的分离，提高了 光催化效率。
金属离子可捕获导带中的 电子，抑制电子和空穴的 复合，但是掺杂浓度过高 ，金属离子可能成为电子 空穴复合中心。金属离子 的掺杂浓度对TiO2光催化 效果的影响通常呈现抛物 线关系。
2.0
绝大部分只能吸
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3.0
阳光(紫外部分)!
14
常见的光催化材料
photocatalyst Ebg（eV）
ZnO在水中不稳定，会在 粒子表面生成Zn(OH)2
photocatalyst Ebg（eV）
Si
1.1
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3.0
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2.7
ZnS
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SiC
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Fe2O3
在染料分子中，有效的抑制了电子与空
穴的复合，这些光敏化物质在可见光下
有较大的激发因子，使光催化反应延伸
到可见光范围。常用的光敏化物质有劳
氏紫、酞菁、玫瑰红、曙红等。
其他光催化材料
❖ 金属氧化物
❖ ZnO、WO、Fe2O3、SnO2、Bi2O3 等金属氧化物都具有明显的光催 化作用。Wang Cun 等人研究了纳米ZnO/ SnO2 复合光催化剂，发 现当ZnO/ SnO2 按2:1 比率复合时，有很高的光催化效率。并深入研 究了纳米ZnO/ SnO2 复合光催化剂影响因素和ZnO/SnO2 的催化反 应机理。
光催化材料简介
目录
为什么是光催化材料
中国
75%
煤
能源问题
la904014z Graphene Oxide as a Matrix for Enzyme Immobilization
DOI:10.1021/la904014z 6083Langmuir 2010,26(9),6083–6085Published on Web 03/18//Langmuir ©2010American Chemical SocietyGraphene Oxide as a Matrix for Enzyme ImmobilizationJiali Zhang,†,§Feng Zhang,‡,§Haijun Yang,†Xuelei Huang,‡Hui Liu,‡Jingyan Zhang,*,‡andShouwu Guo*,††National Key Laboratory of Micro/Nano Fabrication Technology,Research Institute of Micro/Nano Science and Technology,Shanghai Jiao Tong University,Shanghai,200240China,and ‡State Key Laboratory of Bioreactor Engineering,School of Pharmacy,East China University of Science &Technology,Shanghai,200237China.§These authors contributed equally to this work.Received October 16,2009.Revised Manuscript Received January 25,2010Graphene oxide (GO),having a large specific surface area and abundant functional groups,provides an ideal substrate for study enzyme immobilization.We demonstrated that the enzyme immobilization on the GO sheets could take place readily without using any cross-linking reagents and additional surface modification.The atomically flat surface enabled us to observe the immobilized enzyme in the native state directly using atomic force microscopy (AFM).Combining the AFM imaging results of the immobilized enzyme molecules and their catalytic activity,we illustrated that the conformation of the immobilized enzyme is mainly determined by interactions of enzyme molecules with the functional groups of GO.IntroductionGraphene oxide (GO),as a basic material for the preparation of individual graphene sheets in bulk-quantity,has attracted great attention in recent years.1-3In addition,the incredibly large specific surface area (two accessible sides),the abundant oxygen-containing surface functionalities,such as epoxide,hydroxyl,and carboxylic groups,and the high water solubility afford GO sheets great promise for many more applications.1,2For instance,the GO nanosheets modified with polyethylene glycol have been employed as aqueous compatible carriers for water-insoluble drug delivery.4The intrinsic oxygen-containing functional groups were used as initial sites for deposition of metal nanoparticles and organic macromolecules,such as porphyrin,on the GO sheets,which opened up a novel route to multifunctional nanometer-scaled catalytic,magnetic,and optoelectronic materials.5-7How-ever,few studies about the binding of biomacromolecules,such as enzymes,to GO have been reported to date.Since the discovery of the advantageous property of immobi-lized enzymes,the challenges in this area have been to explore new substrate materials with appropriate structures (including the morphology and surface functionality)and compositions to deepen the understanding of enzyme immobilization and thus to improve the catalytic efficiency of the immobilizedenzymes.8-11Recently,along with the development of nano-structured materials,a range of nanomaterials with different sizes and shapes have been utilized as the substrates for enzyme immobilization.12-14It has been demonstrated that the enzymes immobilized on the nanostructured materials have some advan-tages over the bulk solid substrates.8,15However,similar to bulk solid substrates,to efficiently immobilize enzymes on nanostruc-tured material surfaces,in many cases,labored work was required to modify/functionalize the substrate surface.16,17Moreover,for most of the nanostructured materials,it is hard to fully char-acterize their surfaces using conventional surface analytical tools.This limits the deep understanding of enzyme immobilization.Consequently,new nanostructured materials that not only can immobilize the enzyme enthusiastically but also can enable insight into the interactions between enzymes and the substrate are still in need of exploration.GO sheets should be an ideal substrate for the study of enzyme immobilization on nanostructured materials.As aforementioned,the individual GO sheet is enriched with oxygen-containing groups,which makes it possible to immobilize enzymes without any surface modification or any coupling reagents.The atomi-cally flat surface of GO should provide a platform to characterize the immobilized enzyme using conventional surface imaging techniques,such as atomic force microscopy (AFM),and to further study the interactions between enzyme molecules and the GO surface.We describe herein the immobilization of horse-radish peroxidase (HRP)and lysozyme,as model enzymes,on the GO.The enzyme immobilization was characterized in situ with AFM in a liquid cell,and the catalytic activity of the immobilized HRP was assayed using phenol and hydrogen peroxide as catalytic reaction substrates.*To whom correspondence should be addressed.E-mail:swguo@ (S.G.);jyzhang@ (J.Z.).(1)Li,D.;Muller,M.B.;Gilje,S.;Kaner,R.B.;Wallance,G.G.Nature Nanotechnol.2008,3,101–105.(2)Park,S.;Ruoff,R.S.Nature Nanotechnol.2009,4,217–223.(3)Tung,V.C.;Allen,M.J.;Yang,Y.;Kaner,R.B.Nature Nanotechnol.2009,4,25–29.(4)Liu,Z.;Robinson,J.T.;Sun,X.;Dai,H.J.Am.Chem.Soc.2008,130,10876–10877.(5)Lomeda,J.R.;Doyle,C.D.;Kosynkin,D.V.;Hwang,W.;Tour,J.M.J.Am.Chem.Soc.2008,130,16201–16206.(6)Muszynski,R.;Seger,B.;Kamat,P.V.J.Phys.Chem.C 2008,112,5263–5266.(7)Xu,Y.;Liu,Z.;Zhang,X.;Wang,Y.;Tian,J.;Huang,Y.;Ma,Y.;Zhang,X.;Chen,Y.Adv.Mater.2009,21,1275–1278.(8)Bornscheuer,U.T.Angew.Chem.,Int.Ed.2003,42,3336–3337.(9)Betancor,L.;Luckarift,H.R.Trends Biotechnol.2008,26,566–572.(10)Badalo,A.;Gomez,J.L.;Gomez,E.;Bastida,J.;Maximo,M.F.Chemo-sphere 2006,63,626–632.(11)Chen,B.;Pernodet,N.;Rafailovich,M.H.;Bakhtina,A.;Gross,ngmuir 2008,24,13457–13464.(12)Kim,J.;Grate,J.W.;Wang,P.Chem.Eng.Sci.2006,61,1017–1026.(13)Zhi,C.;Bando,Y.;Tang,C.;Golberg,D.J.Am.Chem.Soc.2005,127,17144–17145.(14)Tsang,S.C.;Yu,C.H.;Gao,X.;Tam,K.J.Phys.Chem.B 2006,110,16914–16922.(15)Takahashi,H.;Li,B.;Sasaki,T.;Miyazaki,C.;Kajino,T.;Inagaki,S.Chem.Mater.2000,12,3301–3305.(16)Lee,Y.M.;Kwon,O.Y.;Yoon,Y.J.;Ryu,K.Biotechnol.Lett.2006,28,39–43.(17)Lin,Y.;Lu,F.;Tu,Y.;Ren,Z.Nano Lett.2004,4,191–195.Letter Zhang et al.Experimental SectionGO was prepared using natural graphite powder through amodified Hummers method.18,19The as-obtained yellow-brownaqueous suspension of GO was stored at RT on a lab bench,and used for characterizations and enzyme immobilization.Thesamples for Fourier transform infrared(FT-IR)measurementwere prepared by grinding the dried powder of graphene oxidewith KBr together and then compressing the mixture into thinpellets(EQUINOX55,Bruker,Germany).The specimens oftransmission electron microscopy(TEM)(JEM-2010)were pre-pared by placing the aqueous suspension(∼0.02mg/mL)ofgraphene oxide on the carbon-coated copper grids,and blottedafter30s.AFM images of graphene oxide were taken on aMultiMode Nanoscope V scanning probe microscopy system(Veeco).The samples for AFM were prepared by dropping theaqueous suspension(∼0.02mg/mL)of GO on a freshly cleavedmica surface.AFM images of the GO-bound enzymes wereacquired in a liquid cell using tapping mode.To acquire in situAFM images for enzyme immobilization,the liquid cell wascirculated with the fresh enzyme solution during imaging.20Enzyme immobilization was carried out by adding the desiredamount of GO to0.1M phosphate buffer that contained theenzymes to be immobilized.21The mixture was incubated for30min on ice with shaking and then centrifuged.The supernatantwas used to determine the enzyme loading.The immobilized enzy-mes were washed three times with the same buffer to remove physi-cal adsorbed enzymes.The resulting immobilized enzymes werethen subjected to activity assay.A colorimetric assay was employedto evaluate HRP activity.22The initial reaction rates were obtainedvia a linear fit of the curve of the product absorbance at510nmversus the reaction time(Supporting Information Figure S2).23Results and DiscussionThe morphology of as-prepared GO was characterized firstusing AFM(Figure1a).The height of the flat GO sheet is∼1nm(Figure1b),demonstrating a single atomic layer thicknessstructure feature.The thin nanoplate motif of the GO sheetswas also confirmed by TEM(Figure1c).The functional groups (Figure1d)existing on the GO surface were verified by FT-IR spectroscopy(Supporting Information Figure S1).The enzyme immobilization was carried out by incubating the GO(0.5to 1mg/mL aqueous dispersions)with the enzymes in phosphate buffer solution at4°C.We found that HRP can be spontaneously immobilized on GO.Presumably,the amine groups of HRP may form amide bonds with the carboxylic groups of GO;however, without any coupling reagents,this covalent interaction usually happens very slowly.24Therefore,the covalent bonding may not contribute to HRP-GO interaction.To elucidate the contribu-tion of other interactions,the phosphate buffers with pH from4.8 to8.8,were tested.As shown in Figure2,the loading of HRP on the GO decreases with increasing pH.HRP(pI=7.2)has a net positive charge at pH below7.2and a net negative charge at pH above7.2.The GO sheets are negatively charged in the aqueous solution with a pH range from4to11(see Supporting Informa-tion Figure S3).1-3Thus,in the buffer solutions with a pH range from4.8to7.2,the positively charged HRP interacts with the negatively charged GO by electrostatic interaction,while in the buffer solutions from pH7.2to8.8,HRP and GO both are negatively charged,and will repel each other.Therefore,less HRP was loaded.Only an∼30%enzyme loading decrease was observed when the pH of the buffer solutions increased from 4.8to8.8(Figure2),suggesting that other interactions,such as hydrogen bonding between the oxygen-containing functionalities of GO and surface amino acid residues of HRP,may contribute to GO-HRP interaction,too.Owing to the strong electrostatic interactions and hydrogen bonding,the maximum loading of HRP on GO at pH7.0is about100μg/mg of GO,which is much higher than the loadings on many reported materials.25-27To further illustrate the electrostatic interaction between the enzymes and GO,we examined the immobilization of lysozyme,an enzyme with pI=10.3(positively charged at pH7.0).The lysozyme can be spontaneously immobilized on GO,too,with the maximum loading of about700μg/mg of GO at pH7.0.The positively charged surface of lysozyme apparently is favorable for its interaction with GO.The loading difference between HRP and lysozyme indicates that the interactions of substrate-enzymes are determined by the surface charges of the specified enzymes and the substrate.The high enzyme loadings reveal the exceptional potential of GO as a solid substrate for enzyme immobilization. The enzyme immobilization was monitored in situ using AFM. Figure3a and b shows typical AFM images of the GO in a liquid Figure1.(a)Tapping mode AFM image of graphene oxide(GO) on a mica surface,(b)height profile of the AFM image,(c)TEM image of the GO,and(d)schematic model of GO.Figure2.pH influence on HRP loading.Conditions:50μg GO and2μg/mL HRP.(18)Hummers,W.S.;Offerman,R.E.J.Am.Chem.Soc.1958,80,1339–1339.(19)He,H.;Klinowski,J.;Forster,M.;Lerf,A.Chem.Phys.Lett.1998,287,53–56.(20)Guo,S.;Ward,M.D.;Wesson,ngmuir2002,18,4284–4291.(21)Cheng,J.;Ming,Yu,S.;Zuo,P.Water Res.2006,40,283–290.(22)Nicell,J.A.;Wright,H.Enzyme Microb.Technol.1997,21,302–310.(23)Buchanan,I.D.;Nicell,J.A.Biotechnol.Bioeng.1997,54,251–261.(24)Cao,Y.;Kyratzis,I.Bioconjugate Chem.2008,19,1945–1950.(25)Pundir,C.S.;Malik,V.;Bhargava,A.K.;Thakur,M.;Kaliam,V.;Singh, S.;Kuchhal,N.K.J.Plant Biochem.Biotechnol.1999,8,123–126.(26)Azevedo,A.M.;Vojinovic,V.;Cabral,J.M.S.;Gibson,T.D.;Fonseca, L.P.J.Mol.Catal.B:Enzym.2004,28,121–128.(27)G o mez,J.L.;B o dalo,A.;G o mez,E.;Bastida,J.;Hidalgo,A.M.;G o mez, M.Enzyme Microb.Technol.2006,39,1016–1022.6084DOI:10.1021/la904014z Langmuir2010,26(9),6083–6085DOI:10.1021/la904014z6085Langmuir 2010,26(9),6083–6085Zhang et al.Lettercell after being incubated together with HRP in phosphate buffer for 30min.With a lower enzyme loading (HRP/GO =3:500,in weight),the particles (bright spots,presumably the immobilized enzyme molecules)on the GO surface were observed (Figure 3a).The average diameter and height of the particles on the GO surfaceare about 140and 15A,respectively.The dimension size of the immobilized HRP molecule,140Â140Â15A,is roughly con-sistent with the dimension size of free HRP,30Â65Â75A3.28This is the first picture of the native immobilized enzyme.The larger average diameter and shorter height of the immobilized HRP molecules revealed that immobilization induced some conforma-tional changes of the HRP molecules.With a higher enzyme loading (HRP/GO =3:50,in weight),the enzyme molecules tethered densely over all of the GO surface in the AFM image (Figure 3b).The distribution of HRP on the GO surface should be determined by the intrinsic sites of the oxygen functionalities.Except for the carboxylic groups,which are located at the periphery,others,such as hydroxyl and epoxide groups,distributed randomly over the GO surface.19The mole ratio of C/O of the GO used in the work is about 4,and thus,HRP may densely bind on the GO surface.This is in agreement with the AFM image (Figure 3b)where we observed the increased surface coverage with higher enzyme loading.The catalytic property of the HRP immobilized on GO was investigated using phenol as a reducing substrate.We found that the initial catalytic reaction rates of the immobilized HRP were linear to the HRP loading under an excess and constant substrate concentration (Figure 3d),though they are relatively lower than that of free HRP.29This result suggested that the voids presented between the immobilized HRP molecules are enough for the free diffusion of substrate and product into and out of the HRP active sites,though the immobilized enzymes seem crowded on the GO surface (see Figure 3b).Given the single atomic layer feature ofthe GO sheet,the total surface area is about 7.05Â1022A2/g,and assuming the average transverse area of one molecule HRP isabout 3000A2,the HRP molecules cover less than 50%of the surface area of GO even with the higher enzyme loading.The catalytic activities of the HRP immobilized on GO with the lower and higher enzyme loadings were further characterized by turnover number (K cat )and enzyme efficiency (K cat /K m ).K m and K cat values were obtained according to the Lineweaver -Burk equation as described in the Supporting Information (Figure S2).The values of the kinetic parameters K m and K cat are summarized in Table 1.The similar K m values for the GO immobilized HRP with the lower and higher enzyme loadings,and free HRP indicated that they all have a similar affinity to the reducing substrate.However,K cat /K m values of the immobilized HRP are lower than those of free HRP.Noticeably,the comparable K cat /K m values for the HRP immobilized on GO with the higher and lower enzyme loadings confirmed that increasing enzyme loading does not affect the enzyme efficiency.The catalytic reactions of the immobilized HRP (with the higher and lower enzyme loadings)with a bulky reducing substrate,2,4,6-trimethylphenol,exhibited similar activity,further supporting this result.Thus,combined with the AFM imaging results,we believe that the observed lower enzymatic activity for the immobilized HRP is mainly due to the HRP conformational changes induced by its binding to GO.According to the number of oxygen containing groups on the GO surface and the transverse area of one HRP molecule,there should be at least an average of two oxygen containing groups of the GO surface interacting with one HRP molecule (Figure 3c).Multiple interactions between the substrate and the enzyme molecule could change the enzyme conforma-tion.11Thus,to maintain the conformation and catalytic cap-ability of the immobilized enzyme,the distribution,number,and property of the functional groups on the substrate surface must be optimized to match the surface of the enzyme being immobilized.ConclusionIn summary,we have demonstrated that individual GO sheets could be used as substrates to study enzyme immobilization.Pronouncedly,the rich surface functional groups of GO make the immobilization of the enzymes happen quickly through electro-static interaction without using any cross-linking reagents;the unique flat surface of GO made it possible to observe the native immobilized enzyme in situ using AFM.We found that the catalytic performance of the immobilized enzymes is determined by the interaction of enzyme molecules with the surface functional groups of the substrate,but the enzyme specific activity is not influenced by the enzyme loading as far as the substrate surface was not fully covered by the enzyme.Based on the AFM images and enzyme activity assay,we conclude that full retention of the conformation of immobilized enzyme should be the key to improve its catalytic performance.Acknowledgment.This work was supported by the National “973Program”(Nos.2007CB936000and 2010CB933900)and the NSFC of China (Nos.20774029and 20671034).Supporting Information Available:FT-IR spectrum of GO and catalytic data of the immobilized HRP.This material is available free of charge via the Internet at .Figure 3.Tapping mode AFM images of the GO-bound HRPwith (a)lower and (b)higher enzyme loadings acquired in a liquid cell.(c)Schematic model of the GO-bound HRP.(d)Initial reaction rates of GO-bound HRP versus HRP concentration.Table 1sampleK m (mM)K cat (s -1)K cat /K m (mM -1s -1)Free HRP2.27161.7(34.1071.2GO Immobilized HRP (lower loading)1.96(0.2133.6(1.2017.1(1.22GO immobilized HRP (higher loading)1.76(0.1036.6(2.9020.8(0.52(28)Henriksen,A.;Schuller,D.J.;Meno,K.;Smith,A.T.;Gajhede,M.Biochemistry 1998,37,8504–8060.(29)Cooper,V.A.;Nicell,J.A.Water Res.1996,30,954–964.。
临沂市第十三届自然科学优秀学术成果奖评选结果公示
临沂市第十三届自然科学优秀学术成果奖评选结果公示
根据《临沂市自然科学优秀学术成果奖评审与管理办法》，中共临沂市委组织部，临沂市人力资源和社会保障局，临沂市财政局，临沂市科协组织开展了临沂市第十三届自然科学优秀学术成果奖评选。
评选范围是2012年1月至2014年3月期间在正式学术刊物上发表或在学术会议上交流的学术成果，考察论证或调研报告，科技建议和正式出版的学术专著等。
按照评选标准和优中选优并兼顾学科分布的原则，经推荐单位初评，领导小组办公室初审，临沂市第十三届自然科学优秀学术成果奖评审委员会评审，评出一等奖88篇，二等奖118篇，三等奖232篇。
现予以公示，详情请登录临沂市科协网站（）查看。
如有异议，请于刊登之日起7日（8月5日—11日）内将意见反馈市自然科学优秀学术成果评选领导小组办公室（地址：临沂市科协，联系人：韩成峰，联系电话：8727781，邮政编码：276001）。
临沂市自然科学优秀学术成果奖
评选领导小组办公室
2014年8月5日
临沂市第十三届自然科学优秀学术成果奖
一等奖（88项）
二等奖（118项）
Bis[2--pyridyl)–4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide- 2O,N]tris(nitrato-
三等奖（232项）
21。
光催化材料简介
常见半导体材料的能带结构
SiC ZrO2 SrTiO3 TiO 2
0.0
ZnS
-1.0
Ta2O5 Nb2O5 SnO ZnO 2
)/eV
3.0
WO3 3.6
CdS
H+/H2 (E=0 eV)
2.4
Evs.SHE(pH=
1 4
0
1.0
3.2 eV
3.2 4.6 5.0 3.4
3.8 3.2
O2/H2O (E=1.23eV)
I
COOH
Cl
rose bengal
rhdamine B
环保方面的应用有机物催化剂光源光解产物烃tio2紫外co2h2o卤代烃tio2紫外hclco2h2o羧酸tio2紫外氙灯coh2烷烃醇酮酸表面活性剂tio2日光灯co2so32染料tio2紫外co2h2o无机离子中间物含氮有机物tio2紫外co32no3nh4po43f等有机磷杀虫剂tio2紫外太阳光crpo43co2无机污染物的光催化氧化还原光催化能够解决cr6hg2pd2等重金属离子的污染还可分解转化其它无机污染物如cnno2h2sso2nox等有机化合物的光催化降解纳米tio2光催化绿色涂料对室内氨气等的降解光催化材料的应用灭杀细菌和病毒可以用于生活用水的的杀菌消毒
光催化技术的发展历史
1972年，Fujishima （藤岛）在N-型半导 体TiO2电极上发现了水的光催化分解作用， 从而开辟了半导体光催化这一新的领域。 1977年，Yokota （横田）T等发现了光照 条件下，TiO2对环丙烯环氧化具有光催化活 性，从而拓宽了光催化反应的应用范围，为 有机物的氧化反应提供了一条新思路。 近年来，光催化技术在环保、卫生保健、 自洁净等方面的应用研究发展迅速，半导体 光催化成为国际上最活跃的研究领域之一。
超支化水性聚氨酯的合成与性能研究
超支化水性聚氨酯的合成与性能研究韩文松【摘要】以季戊四醇为"核",N,N-二羟乙基-3-胺基丙酸甲酯为支化单体,用逐步聚合的方法合成第三代超支化聚酯;将其引入到水性聚氨酯中,合成超支化水性聚氨酯;对其结构和性能用红外光谱、激光粒度分析仪、动态力学分析、X射线衍射、热重分析等进行表征.结果表明:超支化水性聚氨酯的粒径分布较水性聚氨酯的粒径分布宽;超支化水性聚氨酯和水性聚氨酯都为无定型结构;超支化水性聚氨酯的玻璃化温度在35℃左右,稍高于水性聚氨酯的玻璃化温度;超支化水性聚氨酯的热稳定性和力学性能优于水性聚氨酯.【期刊名称】《山东轻工业学院学报（自然科学版）》【年(卷),期】2016(030)005【总页数】6页(P14-19)【关键词】水性聚氨酯;超支化水性聚氨酯;超支化聚酯;合成【作者】韩文松【作者单位】齐鲁工业大学化学与制药工程学院,山东济南250353【正文语种】中文【中图分类】TQ323.4水性聚氨酯是利用多异氰酸酯(含-NCO基团)或其加成物与含活泼氢(主要是羟基中的活泼氢)的聚多元醇和亲水扩链剂等的加成反应制备的[1-2]。
水性聚氨酯的合成可分为：外乳化法和自乳化法。
目前,水性聚氨酯的合成多以自乳化法为主，即在聚氨酯大分子中引入-COOH、-SO3、-OH、-O-等亲水基团。
由于这些亲水基团的存在及聚氨酯树脂本身的一些不足之处，使水性聚氨酯产品在耐水、耐溶剂、耐候等方面表现较差，因此人门采用了各种方法对水性聚氨酯树脂进行改性[3-5]。
超支化聚合物是最近几十年发展起来的一种新型高分子材料，它具有高度支化的分子结构，分子间具有较少的链缠结，含有大量的末端官能团，具有粘度低、活性高、溶解性好等优点。
超支化聚合物已经被广泛应用于涂料、塑料加工、光电材料、纳米材料等许多领域[6-8]。
本文将超支化聚合物应用于水性聚氨酯，首先合成第三代超支化聚酯，将其在乳化过程中引入到水性聚氨酯中，得到超支化的水性聚氨酯；对其结构和性能用红外光谱、激光粒度分析、动态力学热分析、热重分析等进行了表征，并与未改性的水性聚氨酯在性能上进行了比较。
季铵盐改性氧化石墨烯的制备及其性能研究
惠昱 晨 马 晓 燕 ， １ 陈智 群 ２ 张 皋 ｚ 宋 颖 １ 侯 秀璋
ｆ 西北 工业 大学理 学院 ． 空 间应 用物理 与化 学教 育部 重点 实验 室 和 陕 西省 高分 子科 学与技 术 重点 实验 室， 西安 ７ １ ０ １ ２ ９ ）
（ ２ 西安近代 化 学研 究所 ， 西安 ７ １ ０ ０ ６ ５ ）
Ａ ｂ ｓ ｔ ｒ ａ ｃ ｔ ：Ｇ ｒ ａ ｐ ｈ ｅ ｎ ｅ ｏ ｘ ｉ ｄ ｅ（ Ｇ Ｏ ）ｗ ａ ｓ ｐ ｒ ｅ ｐ ａ ｒ ｅ ｄ ｂ ｙ ｔ ｈ ｅ ｍｏ ｄ ｉ ｉ ｆ ｅ ｄ Ｈ ｕ ｍ ｍｅ ｒ ｓ ｍｅ ｔ ｈ ｏ ｄ ， ａ ｎ ｄ ｍ ｏ ｄ ｉ ｉ ｆ ｅ ｄ ｂ ｙ ｄ ｏ ｄ ｅ ｃ ｙ ｌ ｄ ｉ ｍｅ ｔ ｈ ｙ ｌ ｂ ｅ ｎ ｚ ｙ ｌ ａ ｍｍ ｏ ｎ ｉ ｕ ｍ ｃ ｈ ｌ ｏ ｉ ｒ ｄ ｅ （ １ ２ ２ ７ ） ｔ ｏ ｐ ｒ ｏ ｄ ｕ ｃ ｅ １ ２ ２ ７ ｎ ｏ ｎ — ｃ ｏ ｖ ａ ｌ ｅ ｎ ｔ ｍｏ ｄ ｉ ｉ ｆ ｅ ｄ ｇ ｒ ａ ｐ ｈ ｅ ｎ ｅ ｏ ｘ ｉ ｄ ｅ （ Ｇ Ｏ － １ ２ ２ ７ ） ．
对苯二胺功能化还原氧化石墨烯的结构和官能团变化
对苯二胺功能化还原氧化石墨烯的结构和官能团变化赵小龙;孙红娟;彭同江【摘要】采用一步水热回流法,选取对苯二胺(PPD)对氧化石墨烯(GO)进行还原与改性处理,制备了功能化还原氧化石墨烯(GOP-X).采用傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)及X射线衍射(XRD)等研究了PPD与GO的反应作用类型及结构变化.结果表明,随着PPD与GO质量比的增加,GOP-X层间距(d值)先增大后减小,GOP-X共轭结构逐渐恢复,与溶剂分子作用时,层间距增幅呈减小趋势,并最终趋于恒定.PPD单体与GO反应时存在3种键合类型:(1)GO含氧官能团和PPD分子之间的氢键作用(C—OH…H2N—X);(2)质子化PPD与弱酸性GO带负电位置之间的离子键作用(—COO-H3+N—X);(3)PPD中氨基(NH2)与GO含氧官能团之间形成的共价键作用.与GO中羧基(COOH)的酰胺化反应将先于与环氧基(C—O—C)的亲核取代反应.提出了相应的作用机理.%The p-phenylene diamine( PPD ) were selected as reducion and modification agent to prepare functionalized and reduced graphene ( GOP-X ) by one-step simple refluxing method. Infrared spectrum ( FTIR) , X-ray photoelectron spectroscopy( XPS) , X-ray diffraction( XRD) and UV-Vis absorption spectrum were used to investigate the reaction types and structure changes between PPD and graphene oxide( GO) . The results show that the d-spacing of GOP-X layers increases firstly and then decreases with the increase of X( the mass ratio of PPD and GO ) , and the conjugated structure gradually restored; when the solvent molecular interaction, the amplification of the d-spacing decrease to a steady figure. Three types of bonds between PPD and GO were proposed:(Ⅰ) hydrogen-bondinginteraction between the oxygen-containing functional groups of GO and the PPD molecules ( C—OH…H2 N—X ); (Ⅱ) ion ic bonding in protonating amine by the weakly acidic sites of the GO layers(—COO-H3+N—X); (Ⅲ) covalent bonding from amidation and nucleophilic addition reactions between the amie in PPD ( NH2 ) and the oxygen containing groups of GO. Furthermore, the NH2 prefers to react first with the carboxyl group( COOH) and then with the epoxide group( C—O—C) , and the relative action mechanisms were also described.【期刊名称】《高等学校化学学报》【年(卷),期】2016(037)004【总页数】8页(P728-735)【关键词】对苯二胺;功能化还原氧化石墨烯;质子化;层间距;反应次序【作者】赵小龙;孙红娟;彭同江【作者单位】西南科技大学理学院,绵阳621010;固体废物处理与资源化利用教育部重点实验室,绵阳621010;矿物材料及应用研究所,绵阳621010;矿物材料及应用研究所,绵阳621010;分析测试中心,绵阳621010【正文语种】中文【中图分类】O641;O613.71石墨烯因其独特的sp2杂化轨道碳原子以蜂巢晶格排列构成的二维单原子层结构[1], 使其拥有优良的力学[2]、热学[3]和电学性能[4], 在场效应管[5]、透明电极[6]、传感器[7]及超级电容器[8]等领域具有广阔的应用前景. 目前, 化学氧化还原法被看作最有可能实现大规模制备石墨烯的方法之一[9～11], 但由于该制备过程中作为石墨烯前驱体的氧化石墨烯(GO)结构中引入了大量含氧官能团[12～14], 严重破坏了石墨烯材料本身优异的物理性能, 因此, 需要对GO进行还原或修复, 或是通过特定化学反应对其进行功能化改性, 将多种活性官能团引入石墨烯结构中, 从而调控石墨烯结构, 改变其光、电、磁等性能.目前, 肼[15]、羟胺[16]及吡咯[17]等含氮化合物被用于还原氧化石墨烯, 但得到的石墨烯分散性较差, 易于团聚, 且具体反应机理不明确. 通过密度泛函理论计算可知, 氧化石墨烯经化学或热还原后, 羟基不能被完全消除[18,19]. 因此, 选取具有还原及功能化改性作用的物质将显得十分重要. Chen等[20]利用对苯二胺(PPD)作为还原剂与稳定剂和氧化石墨烯反应, 结果发现, 残余吸附的PPD包含质子化—N+, 阻止了石墨烯片的π-π 相互作用与堆叠, 使其易于分散在乙醇和乙二醇等溶剂中, 得到的石墨烯薄膜电导率可达15000 S/m. Ryu等[21]则利用不同链长烷基胺改性氧化石墨烯, 表明存在2种反应: 一种是胺与GO边缘羧基的酰胺化反应; 另一种是胺与GO表面环氧基的亲核取代反应, 并发现烷基胺链长可以影响表面能及粗燥程度, 并由此得到超疏水石墨烯薄膜. Kumar等[22]利用甲基丙氨酸和甘氨酸作为还原剂与改性剂制备了功能化还原氧化石墨烯, 发现由于二者等电点不同, 导致在酸性与碱性条件下的还原时间不同, 反应过程中甲基丙氨酸中胺基(NH2)与羧基负离子(COO-)对氧化石墨烯环氧和羟基进行亲核攻击, 并通过脱羧反应形成氮掺杂石墨烯. 相比大多数还原或改性试剂, 利用具有还原与改性作用的含氮有机分子得到还原、功能化及氮掺杂石墨烯具有明显优势. 但现有研究工作对于芳香胺改性氧化石墨烯的作用机理仍未明确, 反应过程中物理吸附胺对结构影响规律的探讨不足. 本文选取具有共轭结构芳香胺PPD还原并改性氧化石墨烯, 通过改变PPD与GO用量比获得不同还原与功能化程度的石墨烯. 采用FTIR, XPS, XRD及SEM等测试手段对其表面官能团、结构及形貌进行了研究, 旨在进一步揭示芳香胺与氧化石墨烯的作用机理及物理吸附胺对功能化还原氧化石墨烯结构的影响规律.1.1 试剂与仪器天然鳞片石墨(含碳量≥90%, 过200目筛, 产地内蒙古兴和县唐僧沟); 高锰酸钾和浓硫酸(国药试剂集团); 5%H2O2溶液和0.05 mol/L的HCl溶液(成都金山化学试剂公司); 对苯二胺(PPD)、氮氮二甲基甲酰胺(DMF)(≥99.5%)、甲醇(≥99.5%)、丙酮(≥99.7%)购于成都市科龙化工试剂厂; 所有试剂均为分析纯, 实验用水均为去离子水(>10 MΩ·cm).DF-101S型恒温水浴电磁搅拌器(巩义予华仪器有限公司); 202-1型恒温干燥箱(上海圣欣科学仪器有限公司); UPT-Ⅱ-10T型超纯水系统(成都超纯科技有限公司); JT2003型电子天平(上海舜宇仪器有限公司); Nicolet-5700型红外光谱仪(FTIR, 美国尼高力仪器公司), 扫描范围: 4000～500 cm-1, KBr压片法制样; XSAM800型多功能表面分析电子能谱仪(XPS, 英国Kratos公司), Al靶(1486.6 eV), X光功率12 kV×15 mA, 采用FAT方式, 数据采用污染碳C1s(284.8 eV)校正; X’pert MPD Pro型X射线衍射仪(XRD, 荷兰帕纳科公司), Cu靶, DS:(1/2)°, SS: 0.04 rad, AAS:5.5 mm, 扫描范围5°～45°; UV-3150 型紫外可见近红外光谱仪(UV-Vis, 日本岛津公司), 以超纯水为参比, 测试范围200～500 nm.1.2 样品的制备1.2.1 氧化石墨烯(GO)的制备通过改进的Hummers法[23], 利用天然石墨粉末合成GO.1.2.2 功能化还原氧化石墨烯(GOP-X)的制备将0.2 g氧化石墨粉末加入到250 mL二甲基甲酰胺(DMF) 中超声分散120 min形成0.8 mg/mL 的GO分散液; 再向GO 分散液中加入0.4 g PPD超声10 min混匀; 然后, 将上述混合液在500 mL 三口烧瓶中于90 ℃条件下水浴磁力搅拌回流反应24 h, 利用平均孔径为0.2 μm 的聚丙烯(PP)薄膜过滤, 并用乙醇和去离子水洗涤5次; 最后, 将薄膜于80 ℃下干燥24 h, 即获得样品. 重复上述操作, 通过改变PPD用量分别为0.8, 1.2和1.6 g, 制得不同PPD与GO质量比的对苯二胺功能化还原氧化石墨烯样品, 分别记为GOP-X(X代表PPD与GO质量比, X=2, 4, 6, 8), 各取部分样品分别在甲醇和丙酮中浸泡24 h, 编号为GOPJ-X.2.1 表面官能团分析图1为GO和GOP-X的FTIR谱图. 可以看出, GO结构中存在较多含氧官能团, 其中在3422, 1713, 1630, 1396, 1186和1060 cm-1处的吸收峰可分别对应于水分子(H2O)、羰基(CO)、芳香性骨架碳环(CC)、羧基(CO)、环氧基(C—O)和烷氧基(C—O)的伸缩振动峰, 而GOP-X在819, 1585和1173 cm-1处观察到3个新的吸收峰, 可分别对应于N—H的伸缩振动峰、弯曲振动峰和C—N的伸缩振动峰[24,25]. 与GO相比, GOP-X中羧基(COOH)和环氧(C—O—C) 的吸收峰峰强减弱, 含量减少.为进一步研究样品官能团变化情况, 对GO和GOPJ-X(X=2, 4, 6, 8)进行XPS表征. 从图2(A)可以看出, GO片层不含氮, 只在289和535 eV处存在2个特征峰, 可分别对应C1s和O1s谱图[24,26]. 而GOPJ-X在400 eV处出现1个新的N1s谱峰, 说明PPD接枝在GO结构中[22]. 就C/O含量比而言, GO及GOPJ-X(X=2, 4, 6, 8)分别为2.32, 4.80, 5.30, 6.58和4.55. 可知, 随着X值增大, GOPJ-X的C/O含量比逐渐升高后减小, 这是由于反应消耗其中的氧(O), 同时, PPD吸电子芳香环结构促进了对氨基对GO含氧基团的还原作用[27].对样品的N1s及C1s谱图进行分峰拟合处理, 结果如图2(B)及图3(A)～(D)所示. 由图3(A)可知, GO的C1s谱由4个拟合峰组成, 结合能284.6, 286.7, 288.2和289.4 eV分别对应C—C/CC, C—O—C/C—O, CO, O—CO的特征峰[28,29]. 而由图3(B)～(D)可以看出, 在GOPJ-X结构中O—CO峰消失, C—O—C/C—O峰强度明显减弱, 285.6 eV处又出现1个新的特征峰, 这可归属为C—N的特征峰[29,30].2.2 结构变化分析图4为 GO及GOP-X在干燥和湿润状态下的XRD谱图. 将干燥与湿润状态下样品层间距值随质量比X变化作图, 结果如图5(A)所示.在干燥状态下[图4(A)], GO特征衍射峰2θ值在10.1°处对应层间距d值为0.88 nm, 而GOP-X系列样品的衍射峰相对GO发生了偏移. 由图5可知, 随着X值增大, 样品GOP-X对应的d值分别为1.08, 1.14, 0.99, 0.87 nm. 与GO相比, d值先增大后减小, 基本呈抛物线状分布. 结合FTIR结果可知, GOP-X中应存在物理吸附的PPD, 随着GOP-X层间PPD分子增加, 通过GO与PPD交联及层间PPD分子物理堆叠致使层间距逐渐增大, 而后相应层间距达到最大, 当X值进一步增大时, PPD与GO之间改性交联作用减弱, 而PPD对GO含氧官能团的还原消除作用不断增强, GOP-X层间距不断减小, 最终使GOP-X层间距小于GO的层间距.为了进一步验证功能化前后是否有物理吸附PPD及对GOP-X层间距的影响, 将样品浸入质量分数为90%的乙醇-水混合液中, 测量在湿润状态下不同样品的XRD谱图, 结果如图4(B)所示. 与干燥状态相比, GO层间距d值从0.88 nm转变为1.14 nm, 而GOP-X片层d值变化较小, 在湿润状态下, d值分别为1.29, 1.36, 1.11和0.99 nm . 可知, 与干燥状态相比, 湿润状态下GO层间距增加29.5%, 而GOP-X 层间距分别增加19.4%, 19.3%, 12.1% 和13.8%.由图5(B)可以看出, 层间距d值的不同变化, 主要是由于在湿润状态下, 溶剂分子进入GO层间, 导致GO片层间氢键及π-π相互作用被破坏, GO层间负电荷排斥作用增强, 层间距增大[31], 而GOP-X片层之间由于存在C—N共价键, 抑制这一现象的发生. 同时, 随着X值增大, 拟制效应呈增强趋势, 说明反应后存在物理吸附及裸露在GO表面的胺. 在湿润状态下, 随着X值增大, 物理吸附胺及接枝在GO表面的胺质子化作用加强, 与GO含氧官能团间氢键及带负电GO层离子键作用增强,因此, 拟制作用逐渐增强, 直到GO结构中含氧官能团大部分被消除, 层间负电荷排斥作用与干燥状态下达到一致.2.3 形貌特征图6为 GO和GOP-X(X=2, 4 , 6)的SEM照片. 由图6可知, GO与GOP-X片层之间最显著的差异是表面粗糙程度, 相比功能化改性GOP-X片层, GO片层表面非常光滑, GOP-X表面更加粗糙, 并随着PPD用量增加, 粗燥程度增加, 这主要是由于具有刚性结构的PPD单体在与GO反应后, 在石墨烯层间充当纳米空间阻隔片的作用, 拟制了石墨烯片层的堆叠, 导致石墨烯片层层间位错随机不规整排列, 当PPD用量增加时, 阻隔作用更强, 同时, 由于含氧官能团的大量消除, 石墨烯层结构缺陷增多, 从而表面更加粗糙.2.4 共轭结构变化图7为GO及GOP-X的UV-Vis谱图. GO显示出2个主要特征峰: 234 nm处的谱峰由芳香环CC发生π→π* 跃迁而引起, 位于302 nm处的1个吸收肩峰则是CO的n→π* 跃迁引起[27]. 而在GO与PPD单体发生反应后, GOP-2吸收峰转变为257 nm, 且随着X值增大, 吸收峰轻微增加, 这是因为具有孤电子对的—NH2与π键相连, 发生p-π共轭效应, 电子活动范围增大, 容易激发, π→π*跃迁吸收带向长波方向移动, 表明GO的还原及在GOP-X片层内共轭结构的形成, 此外, 由于PPD与GO含氧官能团发生反应消除CO, 使302 nm处吸收肩峰消失, 这与XPS 分析结果一致.结合FTIR, XPS及XRD分析结果, PPD 单体与 GO 之间存在的键合类型如下: (Ⅰ) GO含氧官能团和PPD分子之间的氢键作用(C—OH…H2N—X); (Ⅱ) 质子化PPD 与弱酸性GO带负电位置之间的离子键作用(—COO-H3+N—X); (Ⅲ) PPD胺基与GO含氧官能团之间通过酰胺化反应和亲核取代反应形成的共价键. 反应过程及共价作用机理如图8所示.上述(Ⅰ)和(Ⅱ)2种反应类型, PPD单体仅是通过物理吸附作用存在于GO上, 类型(Ⅲ)中, PPD单体与GO通过共价键键合. 而GOPJ-X已消除物理吸附, 仅保留化学键的连接, 所以将(Ⅰ), (Ⅱ)2种情况排除, 结合FTIR与XPS C1s结果可知, 反应时O—CO首先消失, 而后C—O—C逐渐消失, 并由图2(A)和(B)可知, GOPJ-X(X=2, 4, 6)中N的百分含量依次为11.34%, 10.48%, 9.39%和8.32%, 呈逐渐减少趋势; GOPJ-X结构中N配置类型也不同, 在X≤4 时, GOPJ-X结构中N元素以3种不同形式存在, 在结合能为398.8, 399.8 和 400.9 eV处分别对应于吡啶氮、吡咯氮和石墨骨架氮[32,33]; 当X>4 时, 吡啶氮消失. 因此, PPD中NH2与COOH及C—O—C均发生反应, 但对苯二胺芳香环及其胺基孤对电子有很高的共振稳定性, 降低了氨基反应活性, 且PPD芳香环有很高的位阻[24,34], 就其本身而言, 它既不攻击GO片层上的C, 也不与C—O—C发生开环取代反应. 因此, NH2不太可能先与C—O—C发生开环反应, 而是先与COOH发生酰胺化反应, 当COOH消耗完后, PPD中胺基(NH2) 再与C—O—C发生开环反应. 而由图2(B)可知, 由GOPJ-2到GOPJ-8, 石墨氮与吡咯氮结合能先向低能侧偏移, 后向高能侧偏移, 这是因为随着质量比X增加, 导致价电子密度发生变化, 而核外电荷分布的变化都可从原子内层电子结合能偏移反映出来, 反应时存在还原与氮化作用, 在X较小时, 由于“—CN”及“—NH”基团的形成和增加, 使N1s结合能减小; 当X较大时, “—CN”及“—NH”基团向“—NOx”基团转化, 从而N1s结合能向高能方向偏移[35,36]. 结合文献[20,22,37], 我们认为, 反应时C—O—C被打开, 形成碳正离子(C+)和氧负离子(O-), 伴随质子转移氧负离子夺取 PPD 分子NH2中的H形成羟基, 丢失胺基氢的 PPD 分子与碳正离子(C+) 相结合, 同时通过分子内缩合反应脱去水分子, 形成以C—N键键合中间产物, 然后又快速转换为共轭结构乙烯基, 以不稳定态氮氧化合物分子和水分子释放出去. 因此, X较小时, 胺基(NH2)先与COOH 反应以C—N键键合, 结构中N保留较多, N含量比较高, 而当X较大时, COOH已完全消耗, PPD胺基与GO环氧基发生开环反应后, 将以不稳定态氮氧分子释放更多的N, 使GOPJ-X结构中N含量减少.对苯二胺与氧化石墨烯反应时, 随着质量比X增加, GOP-X层间距(d值)基本呈抛物线状分布, 即先增大后减小, 功能化还原氧化石墨烯共轭结构逐渐恢复; 当受溶剂分子作用时, 物理吸附胺质子化, 而受含氧官能团变化及质子化胺影响, 层间距增幅呈减小趋势, 并最终趋于恒定; PPD与GO反应过程中存在非共价的氢键(C—OH…H2N—X)与离子键(—COO-H3+N—X) 以及C—N共价键作用, 且PPD中氨基(NH2) 与COOH之间的酰胺化反应先于与C—O—C之间的亲核取代反应. 为选择性功能化还原氧化石墨烯的制备提供依据.† Supported by the National Natural Science Foundation ofChina(No.41272051) and the Doctor Foundation of Southwest University of Science and Technology, China(No.11ZX7135).【相关文献】[1] Novoselov K. 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