Synthesis And Fabrication Of Substrates For Surface-enhanced Raman Spectroscopy (SERS) Quantitative Analysis

Surface-enhanced Raman spectroscopy(SERS)is a highly sensitive technique that could provide the fingerprint vibrational information of surface species,and the sensitivity of SERS up to single molecule level in some special conditions.With the development of SERS,SERS have been widely used in the field of chemical analysis,bioimaging,environmental detection and food safety.The strength of the SERS depends not only on the nature of the metals but also closely related to the size,shape,and spacing of nanostructures.Coinage metals(e.g.,Ag,Au and Cu etc.)with nanoscale rough surface or their nanostructures can provide high SERS enhancement.SERS mostly used to qualitative detection due to the poor uniform or reproducibility of substrates.With emphasis on methodology,the uniformity and reproducibility of SERS intensity caused by substrate and surface morphology were discussed.We rationally designed and synthesized two kinds of nanoparticles,Au-IS@Ag cuboids and Au octahedrons,with the seeds-mediated method.With the two kinds of nanoparticles,we assembled them into 2D or 3D substrates for SERS quantitative detection.The main content researched and conclusion are listed as follows:(1)Synthesis and SERS study of Au-IS@Ag core-shell cuboid nanoparticles.We synthesized monodisperse and size uniform Au-IS@Ag core-shell cuboids nanoparticles with seeds-mediated method.The average length and width of the cuboids are 92 nm and 43 nm,respectively.The internal standard(IS)molecules should be adsorbed to the surface of the core and assistant the growth of the silver shell.Here we embeded two kinds of ISs,4-aminobenzoic acid(pMBA)and 4-aminothiophenol(pATP),without desdroyed the structure of the cuboid.Au-IS-Ag shell cuboids can be used to calibrate the SERS detection and SERS enhancement due to their sharp edges and corners.An excellent linearity was attained when used Au-IS@Ag shell cuboids solution as SERS substrate without adding any salt to aggragate and Rhodamine 6G(R6G)as target molecule.In addition,2D SERS solid substrate was assembled with the air-water interface assistant.R6G as targets again,Although the sensitivity of the quantitatie detection was not strong,the ability of calibration quantitative was significant with the solid substrate.(2)Au octahedron nanoparticles synthesis and SERS study.Au NRs were also used as seeds to synthesize different sizes of Au octahedral nanoparticles with monodisperse.Uniform and large area 3D substrates were fabricated through air-water assistant with layer by layer.All the average SERS intensity RSD of 3D Au octahedron substrates were less than 10%,the optimize substrate down to 3%,demonstrating that the 3D Au octahedron substrates were uniform and reproducible.Two kinds of biomolecules,animos and urea,were quantitatively detected,with a good linearity and sensitivity.