Fabircation Of SERS Substrates With Special Morphologies And Studies Of Their Performance

Surface-enhanced Raman scattering (SERS) is a nondestructive analytical technology,which can provide characteristic vibrational information of target molecules with highsensitivity. SERS can amplifies the normal Raman scattering intensity by106orders ofmagnitude or more, even can realize single molecular detection, and exhibits great potentialfor ultrasensitive molecular sensing. However, the lack of low-cost, high-throughput andreproducible methods for fabrication of SERS substrates has limited the widespreadapplication of SERS as a general technique for qualitative and quantitatice analysis. Designand fabrication of SERS substrates with high sensitivity, reproducibility and stability stillremains a big challenge, and high-quality SERS substrate plays an important role in SERSfurther development and application. To explore how to prepare high-quality SERS substrateswith low-cost and high throughput, three kinds of SERS substrates with differentmorphologies were prepared by different methods, and their SERS performance wasinvestigated by utilizing benzenethiol as a Raman probe. The main contents and experimentalresults are summarized as follows.(1) Monodispersed silica nanospheres were synthesized by the St ber method, then usingthe mixture of silica and polymeric monomer SR454HP with different volume ratio (RS-P) asprecursor, silica-polymer composite templates were fabricated by programmed spin-coatingand in situ UV polymerization. A non-close-packed colloidal SiO2array was embedded in thepolymer matrix, and the spheres of the top layer protrude out of the film, forming a periodicsurface. After the first layer of SiO2being etched by HF solution, leaving behind a highlyperiodic hexagonal array of polymer nanovoids. By subsequent deposition of Au layer, ahighly periodic array of nanovoids has been fabricated, and could be used as SERS-activesubstrates. SERS performance of the nanovoids array was investigated by using benzenethoilas the Raman probe. The results show that the enhancement factor (EF) can be in the order of108and the relative standard deviation (RSD) of the EF is less than8%, which indicates thegood enhancement ability and reproducibility of the nanovoids array substrates.(2) Monodispersed rhombic dodecahedral (RD) Au NPs were synthesized by theseed-mediated growth method, using cetyltrimethylammonium chloride (CTAC) as thestabilizer. Through the intraparticle ripening induced by chlorine ions, the shape evolutionfrom RD to spherical Au NPs was achieced. Then the Au NPs can self-assemble onto thethio-functional ion exchange resin beads by forming Au-S chemical bond between the Au NPsand sulfhydryl group. The resulting Au NPs-Resin microspheres can be used as SERS-activesubstrates, which can be prepared with high throughput and easy-to-use. The SERSperformance of the Au NPs-Resin microspheres was investigated by using benzenethoil as theRaman probe. The results show that the EF of the substrates can be in the order of1011~1012and the RSD of the EF is less than15%, which indicates the excellent enhancement abilityand good reproducibility of the substrates. The trace detection of paraquat (PQ), by using RDAu NPs-Resin as the SERS substrate, has also been studied, and the PQ detection limit canreach10-9mol/L. (3) Copper grid-based Au NPs (CGAu) and blade-like Au array (CGHAu and CGBAu),for SERS-active substrates, have been fabricated by the galvanic replacement reactionbetweem copper grid and HAuCl4aqueous solution. By using benzenethoil as the Ramanprobe, the SERS performance of CGAu, CGHAu and CGBAu was studied in detail. The SERSresults show that the EF of these substrates can be107~108orders of magnitude and the RSDof the EF is less than28%. The SERS detection of methylene blue (MB), by using CGBAu asthe SERS substrate, has also been studied, and the MB detection limit can reach10-10mol/L.Furthermore, the as-prepared CGBAu could be used as immobilized nanogold catalyst for thereduction of p-nitrophenol (4-NP) to p-aminophenol (4-AP) with an excess amount of NaBH4.The catalyst efficiency was evaluated on the basis of turnover frequency (TOF) andrecyclability. The average TOF of the CGBAu catalyst was3.23×10-3mol·gAu-1·h-1with arelative standard deviation of3.84%in10-cycle reuse.