硅片上Ag@Au核壳结构纳米颗粒的制备及其SERS性能
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摘要
为获得一种高效和具有一定化学稳定性的表面增强拉曼散射(SERS)基底,文中通过离子溅射的方法在Ag纳米颗粒表面覆盖6 nm和10 nm的Au层,形成Ag@Au核壳结构(分别命名为Ag@Au6/Si和Ag@Au10/Si)。利用场发射扫描电子显微镜观察Ag颗粒和Ag@Au颗粒的尺寸及颗粒间隙的变化;采用共聚焦显微拉曼光谱仪测试罗丹名6G(R6G)分子在不同基底上的拉曼光谱,对比三种基底在探测R6G溶液时的SERS光谱的强度差别,计算了最佳基底的增强因子;将基底浸泡在0.5 mol·L~(-1)的双氧水中1 h之后,测试其SERS光谱强度下降程度,以此评价基底的化学稳定性。研究结果表明:Ag颗粒表面溅射了Au层后,颗粒尺寸随金层厚度的增加而逐步增加,Ag@Au10基底中颗粒间隙尺寸降低到10 nm以内。三种基底之上,保持相同的R6G溶液浓度时,R6G分子的光谱强度的顺序为Ag@Au10/Si>Ag@Au6/Si>Ag/Si,即Ag@Au10/Si基底具有最佳的增强效果,其增强因子可达2.2×10~6。Ag纳米颗粒基底在双氧水中浸泡后,SERS增强性能完全消失;Ag@Au10/Si和Ag@Au6/Si的SERS光谱强度分别下降了46.2%和81.6%,说明Au层起到了保护Ag颗粒不被腐蚀的作用,且Au层越厚,耐化学侵蚀性能越佳。在SERS检测中,Ag@Au10/Si基底具有较高的灵敏度和较高的化学稳定性,此基底具有应用于SERS领域的潜在可能性。
To obtain SERS substrates with high efficiency and good chemical stability,Au films with thickness of 6 nm and 10 nm were sputtered on Ag nanoparticles to form Ag@Au6/Si and Ag@Au10/Si.Their size and gap between two nanoparticles were characterized by a field emission scanning electron microscope(FESEM).The Raman spectra of R6 G molecules on different substrates were measured by a confocal microscopy Raman spectrometer.The SERS intensity of R6 G on three substrates was compared and the enhancement factor for the optimal substrate was calculated.The SERS properties of such substrates with and without Au coating immersed in 0.5 mol·L~(-1) H_2O_2 solution were compared for characterizing their chemical stability.The results show that the size of Ag@Au core-shell nanoparticles increases with the Au shell's thickness and the gap between two adjacent nanoparticles reduces to less than 10 nm for Ag@Au10/Si.The intensity of Raman signals of R6 G molecular on Ag@Au/Si substrates and the chemical stability of Ag@Au/Si substrates simultaneously increase after Au film deposited are compared at the same conditions.The Ag@Au10/Si substrate achieves the optimal SERS properties with the enhancement factor of 2.2×10~6 and the best chemical stability with the Raman signal drop by only 46.2%.It is suggested that the Ag@Au10/Si substrate has the potential of being applied in SERS.
To obtain SERS substrates with high efficiency and good chemical stability,Au films with thickness of 6 nm and 10 nm were sputtered on Ag nanoparticles to form Ag@Au6/Si and Ag@Au10/Si.Their size and gap between two nanoparticles were characterized by a field emission scanning electron microscope(FESEM).The Raman spectra of R6 G molecules on different substrates were measured by a confocal microscopy Raman spectrometer.The SERS intensity of R6 G on three substrates was compared and the enhancement factor for the optimal substrate was calculated.The SERS properties of such substrates with and without Au coating immersed in 0.5 mol·L~(-1) H_2O_2 solution were compared for characterizing their chemical stability.The results show that the size of Ag@Au core-shell nanoparticles increases with the Au shell's thickness and the gap between two adjacent nanoparticles reduces to less than 10 nm for Ag@Au10/Si.The intensity of Raman signals of R6 G molecular on Ag@Au/Si substrates and the chemical stability of Ag@Au/Si substrates simultaneously increase after Au film deposited are compared at the same conditions.The Ag@Au10/Si substrate achieves the optimal SERS properties with the enhancement factor of 2.2×10~6 and the best chemical stability with the Raman signal drop by only 46.2%.It is suggested that the Ag@Au10/Si substrate has the potential of being applied in SERS.
引文
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[2] SCHLüCKER S.Surface-Enhanced Raman Spectroscopy:Concepts and Chemical Application[J].Angewangte Chemie International Edition,2014,53(19):4756.
[3] JAIN P K,EL-SAYED M A.Plasmonic Coupling in Noble Metal Nanostructures[J].Chemical Physics Letters,2010,487(4/6):153.
[4] LIU F,LU Y H,YU W H,et al.Tunable Surface-Enhanced Raman Spectroscopy via Plasmonic Coupling Between Nanodot-Arrayed Ag Film and Ag Nanocube[J].Plasmonics,2013,8(2):1279.
[5] WU C F,ZHOU X,WEI J.Localized Surface Plasmon Resonance of Silver Nanotriangles Synthesized by a Versatile Solution Reaction[J].Nanoscale Research Letters,2015,10:354.
[6] YANG Y,LIU J,FU Z,et al.Galvanic Replacement-free Deposition of Au on Ag for Core-Shell Nanocubes with Enhanced Chemical Stability and SERS Activity[J].Journal of the American Chemical Society,2014,136(23):8153.
[7] MURSHID N,GOUREVICH I,COOMBS N,et al.Gold Plating of Silver Nanoparticles for Superior Stability and Preserved Plasmonic and Sensing Properties[J].Chemical Communications,2013,49(97):11355.
[8] WANG R,XU Y,WANG R J,et al.A Microfluidic Chip Based on an ITO Support Modified with Ag-Au Nanocomposites for SERS Based Determination of Melamine[J].Microchim Acta,2017,184(1):279.
[9] WANG X T,MA G S,LI A R,et al.Composition-adjustable Ag-Au Substitutional Alloy Microcages Enabling Tunable Plasmon Resonance for Ultrasensitive SERS[J].Chemical Science,2018,9:4009.
[10] YING Z,YANG C L,XUE B,et al.Highly Effective and Chemically Stable Surface Enhanced Raman Scattering Substrates with Flower-like 3D Ag-Au Hetero-nanostructures[J].Scientific Reports,2018,8:898.
[11] PUSTOVIT V N,SHAHBAZYAN T V.Quantum-size Effects in SERS from Noble-metal Nanoparticles[J].Microelectronics Journal,2005,36(3/6):559.
[12] KLEINMAN S L,FRONTIERA R R,HENRY A I,et al.Creating,Characterizing,and Controlling Chemistry with SERS Hot Spots[J].Physical Chemistry Chemical Physics,2013,15(1):21.
[13] MIAO P,WANG B D,YIN J,et al.Electrochemical Tracking Hydrogen Peroxide Secretion in Live Cells Based on Autocatalytic Oxidation Reaction of Silver Nanoparticles[J].Electrochemistry Communications,2015,53:37.
[14] PARNKLANG T,LAMLUA B,GATEMALA H,et al.Shape Transformation of Silver Nanospheres to Silver Nanoplates Induced by Redox Reaction of Hydrogen Peroxide[J].Materials Chemistry and Physics,2015,153:127.
[15] RIVERO P J,IBA?EZ E,GOICOECHEA J,et al.A Self-referenced Optical Colorimetric Sensor Based on Silver and Gold Nanoparticles for Quantitative Determination of Hydrogen Peroxide[J].Sensors and Actuators B:Chemical,2017,251:624.