小尺寸金石墨纳米颗粒的合成与表征
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摘要
在表面增强拉曼光谱(SERS)的研究领域中,基于局域表面等离子体共振效应的等离子体SERS基底的制备成为过去几十年的研究热点。然而,通常开发的等离子体金属基底具有较差的稳定性和重现性。对于SERS而言,石墨烯类材料具有拉曼化学增强效应,除此之外,还具有分子富集、强的稳定性与荧光猝灭能力等优点,因此基于石墨金属复合纳米材料的SERS基底受到了研究人员的重视。我们利用化学气相沉积(CVD)法制备了小尺寸的金石墨核壳纳米颗粒(Au@G),其粒径约为17 nm。我们通过在Au NP上包覆介孔二氧化硅来控制Au@G的尺寸,同时还研究了包覆二氧化硅过程中,正硅酸乙酯(TEOS)的浓度对于石墨壳层形成的影响。结果表明当TEOS在一定浓度范围内,其浓度的降低有利于得到石墨化程度高的Au@G。进一步利用Au@G对结晶紫分子进行拉曼检测,也表明了Au@G具有较好的拉曼增强效果。这种小尺寸的Au@G在分子检测与细胞成像分析领域中具有广泛的应用潜力。
The preparation of plasmonic metal-based substrates has been a hot research topic during the past decades in the area of surfaceenhanced Raman spectroscopy(SERS). The localized surface plasmon resonance effect of plasmonic metal nanostructures enhances the electromagnetic field for SERS analysis, thereby making SERS an extremely sensitive detection technique. However, commonly developed plasmonic metal substrates exhibit poor stability and reproducibility.Since the separation of graphene from graphite, graphene has been widely used in various fields because of its unique physical, chemical, electronic, and optical properties. In the field of SERS, graphene has been used for graphene-enhanced Raman scattering, which makes use of the chemical enhancement mechanism in SERS. In addition, it has capabilities of surface molecular enrichment, quenching fluorescence, surface homogenization, and has strong chemical stability. Due to these characteristics of graphene, SERS substrates based on graphene-metal nanocapsules have attracted the attention of researchers. In this work, a small size gold-graphitic nanocapsules(Au@G) was prepared by chemical vapor deposition(CVD). The material exhibits a core-shell structure consisting of a graphitized carbon layer coated on Au nanoparticles(Au NPs). The Au NP core of the Au@G provides a major enhancement factor for Raman analysis, and the external graphitized carbon shell ensures strong chemical stability of the material. The Au@G exhibits a uniform particle size with diameter ～17 nm. In order to control the size of the Au@G, tetraethyl orthosilicate(TEOS) and tetraethylorthotrimethylammonium bromide were used as the raw material and template, respectively, a 45 nm-thick layer of mesoporous silica was coated on the synthesized Au NPs. The presence of the mesoporous silica capping layer prevented aggregation and particle size growth of the Au NPs during high-temperature CVD. At the same time, we studied the effect of TEOS concentration on the growth of the graphitized carbon layer during CVD. The results revealed that a decrease of the TEOS concentration is conducive for obtaining a high graphitic Au@G, and the concentration of TEOS does not affect the particle size of the Au@G. Raman detection of crystal violet molecules using Au@G demonstrated the latter's good Raman enhancement effect. The Au@G prepared by high-temperature CVD exhibits a clean surface with no impurities. It is an SERS substrate with both physical and chemical enhancement. The unique Raman spectral peaks and small size of Au@G ensure its great potential for use in the fields of molecular detection and cell imaging analysis.
The preparation of plasmonic metal-based substrates has been a hot research topic during the past decades in the area of surfaceenhanced Raman spectroscopy(SERS). The localized surface plasmon resonance effect of plasmonic metal nanostructures enhances the electromagnetic field for SERS analysis, thereby making SERS an extremely sensitive detection technique. However, commonly developed plasmonic metal substrates exhibit poor stability and reproducibility.Since the separation of graphene from graphite, graphene has been widely used in various fields because of its unique physical, chemical, electronic, and optical properties. In the field of SERS, graphene has been used for graphene-enhanced Raman scattering, which makes use of the chemical enhancement mechanism in SERS. In addition, it has capabilities of surface molecular enrichment, quenching fluorescence, surface homogenization, and has strong chemical stability. Due to these characteristics of graphene, SERS substrates based on graphene-metal nanocapsules have attracted the attention of researchers. In this work, a small size gold-graphitic nanocapsules(Au@G) was prepared by chemical vapor deposition(CVD). The material exhibits a core-shell structure consisting of a graphitized carbon layer coated on Au nanoparticles(Au NPs). The Au NP core of the Au@G provides a major enhancement factor for Raman analysis, and the external graphitized carbon shell ensures strong chemical stability of the material. The Au@G exhibits a uniform particle size with diameter ～17 nm. In order to control the size of the Au@G, tetraethyl orthosilicate(TEOS) and tetraethylorthotrimethylammonium bromide were used as the raw material and template, respectively, a 45 nm-thick layer of mesoporous silica was coated on the synthesized Au NPs. The presence of the mesoporous silica capping layer prevented aggregation and particle size growth of the Au NPs during high-temperature CVD. At the same time, we studied the effect of TEOS concentration on the growth of the graphitized carbon layer during CVD. The results revealed that a decrease of the TEOS concentration is conducive for obtaining a high graphitic Au@G, and the concentration of TEOS does not affect the particle size of the Au@G. Raman detection of crystal violet molecules using Au@G demonstrated the latter's good Raman enhancement effect. The Au@G prepared by high-temperature CVD exhibits a clean surface with no impurities. It is an SERS substrate with both physical and chemical enhancement. The unique Raman spectral peaks and small size of Au@G ensure its great potential for use in the fields of molecular detection and cell imaging analysis.
引文
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(3)Hudson,S.D.;Chumanov,G.Anal.Bioanal.Chem.2009,394,679.doi:10.1007/s00216-009-2756-2
(4)Tripp,R.A.;Dluhy,R.A.;Zhao,Y.Nano Today 2008,3,31.doi:10.1016/S1748-0132(08)70042-2
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(6)Golightly,R.S.;Doering,W.E.;Natan,M.J.ACS Nano 2009,3(10),2859.doi:10.1021/nn9013593
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(16)Novoselov,K.S.;Geim,A.K.;Morozov,S.V.;Jiang,D.;Zhang,Y.;Dubonos,S.V.;Grigorieva,I.V.Science 2004,306,666.doi:10.1126/science.1102896
(17)Somani,P.R.;Somani,S.P.;Umeno,M.P.Chem.Phys.Lett.2006,430,56.doi:10.1016/j.cplett.2006.06.081
(18)Liu,Z.F.Acta.Phys.-Chim.Sin.2016,32(4),810.[刘忠范.物理化学学报,2016,32(4),810.]doi:10.3866/PKU.WHXB201603012
(19)Allen,M.J.;Tung,V.C.;Kaner,R.B.Chem.Rev.2010,110,132.doi:10.1021/cr900070d
(20)Dreyer,D.R.;Todd,A.D.;Bielawski,C.W.Chem.Soc.Rev.2014,43,5288.doi:10.1039/C4CS00060A
(21)Ling,X.;Xie,L.;Fang,Y.;Xu,H.;Zhang,H.;Kong,J.;Mildred,S.;Dresselhaus,M.S.;Zhang,J.;Liu,Z.Nano Lett.2010,10,553.doi:10.1021/nl903414x
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(24)Gong,T.;Zhu,Y.;Zhang,J.;Ren,W.;Quan,J.;Wang,N.Carbon2015,87,385.doi:10.1016/j.carbon.2015.02.055
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