Self-assembly Array Of Au NPs And The SERS Performance

Surface-enhanced Raman scattering （SERS） is a powerful tool for the analysis ofvibration information of analyte molecules with nondestructive analysis of the sample, and ithas a sufficient sensitivity to achieve single molecule detection. Based on the long-rangeelectromagnetic and short-range chemical mechanisms for enhancement, the weak Ramansignal can be amplified108times or even more by a SERS active substrate with Au or Agnanostructure. Recently, orderly array of Au or Ag nanostructure as SERS substrate hasbecome the hot spot in this field. In order to prepare high quanlity SERS substrate with lowcost and high yield, two kinds of core-shell nanostructure SERS substrates have beendesigned and synthesized, SERS performance were studied as well. The main results andconclusions are summerized as follows.（1） Self-assembled Au NPs with different size on resin and the SERS performance.Monodisperse Au NPs with7different diameters were synthesized by the method of seedgrowth and the range of the diameter is from25nm to200nm. SH type resins were preparedby the reaction of thioglycolic acid and OH type resin. Au NPs can easily self-assemble ontothe SH type resin at room temperature. So a kind of core-shell architecture （Au NPs-Resin） isdeveloped, in which the densely packed Au NPs monolayer and the resin bead are the outershell and the inner core, respectively. The resulting Au-Resin microspheres are demonstratedto be excellent, easy-to-use SERS active substrates with high SERS enhancing capacity （TheSERS enhanced factor is in the range of109-1010orders of magnitude）. Systematicmeasurements and statistical analysis show that the substrates exhibit high SERSreproducibility with less than18%relative standard deviation from point-to-point andsample-to-sample. The SERS enhancing capacity could be tuned by Au NPs size variation.The trace detection of paraquat aqueous solution by Au NPs-Resin SERS substrate has beenexplored as well, and the results show that the substrates exhibit high SERS enhancingcapacity for paraquat and the limit of detection is10^-9mol·L^-1.（2） The synchronous construction of Au microposts and array on resin and the SERSperformance. By the reduction reaction of AuCl4^--Resin by ascorbic acid in aqueoussolutions, raspberry-like Au-Resin microspheres were prepared, in which the anion exchangeresin microsphere as the inner core and the monolayer array of micro-sized Au posts as theouter shell. The formation of Au micro-sized posts and the corresponding array aresimultaneously obtained in a single step. The performance of SERS for the raspberry-likeAu-Resin microspheres is explored using benzenethiol as the probe. The SERS enhancedfactor is in the range of10⁸-10⁹orders of magnitude, the relative standard deviation of bothRaman intensity and EF is about35±5%. The detection of aromatic carboxylic acid by Au-Resin SERS substrate has been explored. The recyclable catalytic performance ofAu-Resin microspheres is demonstrated in converting4-nitrophenol to4-aminophenol.Amino-functionalized Au-Resin can be used as efficient separate supporters for volatileorganic acid from fermentation broth as well.