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The Synthese of Silver Self-assemblies Assisted by Amino Acids and Their Sers Properties

Author: KangLeiLei
Tutor: QiangLiangSheng
School: Harbin Institute of Technology
Course: Inorganic Chemistry
Keywords: Silver self-assembly Amino acids Enhancement factor Surface-enhanced Raman spectroscopy (SERS)
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Type: Master's thesis
Year: 2012
Downloads: 17
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Abstract


Since the surface-enhanced Raman scattering phenomenon was found, due to itshigh sensitivity, simple operation, free from water interference, has been widely usedin surface science, analytical science, biological sciences and other fields. With therapid development of computer science, nanoscience and nanotechnology, theoreticalstudies of surface-enhanced Raman spectroscopy（SERS） and substrate preparationhave been a new breakthrough in recent years. Surface-enhanced Ramanspectroscopy, however, has long way to be further used in quantitative analysis, traceanalysis, availability of single molecule detection, which is still restricted by SERSsubstrate associated with poor enhanced performance.we choose ascorbic acid as reducing agent, adding small amino acid moleculesassisted preparation of a micron silver nanoparticles by self-assembly in theconventional aqueous solution. Amino acids which relate to different surfacemorphology of the assemblies play a vital role on the guiding of the silvernanoparticles into complex with defined nanostructures. As-prepared silverassemblies with the different surface morphology was prepared by self-assembly forthe SERS substrates which enhanced performance would be tested. Theconcentration of reactants, amino acids, reductants, and other experimentalconditions were considered as influencing factors on surface morphology and SERSperformance of silver self-assembly. The silver self-assembly surface morphology,lattice type and SERS enhancement were characterized and disscussed through themethods of SEM, XRD, EDS, and Raman spectroscopy. Studies have shown that theparticle size, surface morphology of silver self-assemblies are not closely relatedwith classification of the amino acids. The length and functional groups of the Rwhich is branched chain of amino acid, have great impact on the silver particles sizedistribution and surface morphology. Five kinds of silver particles with definednanostructure were selected as SERS substrate to further detection of4-mercaptobenzoic acid （MBA） in order to calculate the enhancement factor. To detectthe minimum detection limit, selection of exquisite silver particles with higherenhancement factor were used as SERS substrate. The experiment result show thatas-prepared SERS substrate can detect as low as10-8mol/L MBA solution.By tuning the concentration of AgNO3, the surface morphology of the silverassemblies have a great change. When AgNO3solution concentration is low, silverself-assembly surface is smooth and particle size is small. With increasing concentration of AgNO3solution, silver particles gradually increase the size, andthese nanostructures of particle surface continue to grow to form nano-sheet structure,leading to increasing the roughness of silver micro assemblies. Process ofconstruction of silver self-assembly with uniform particle size, rough surface anddifferent patterns, by adding small amino acids, can be a general plateform tofabricate well-defined micro particles. It has a very important guiding significance toother directing agent assisted synthesis of SERS substrate.

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