Study Of Surface-enhanced Raman Spectroscopy Based On Polymethacrylate Porous Material

As a sensitive analytical technique, surface-enhanced Raman scattering (SERS) has attracted more and more concern in trace detection. Based on poly(glycidyl methacrylate-ethylene dimethacrylate (GMA-EDMA) porous material combining with silver nanoparticles, several kinds of enhancement substrates were developed for ultrasensitive SERS detection.A novel ultrasensitive SERS detection method was established based on the GMA-EDMA porous material in rod shape. The topography of this porous material could supply gaps and/or pores which were beneficial for the generation of "hot spots" that were essential to enhancement effect. This method was so sensitive that SERS signals of probe molecules of Rhodamine6G (R6G) and p-aminothiophenol (PATP) at concentrations as low as10-18mol/L and10"16mol/L could be detected. Biology samples and pesticides were successfully detected by this method. The ultrasensitive SERS based on porous material method showed promising features in on-site detection.An investigation of rapid SERS detection method was developed by using porous material in powder shape, the shape of porous material was changed from rod to powder. Meanwhile, a set of device was developed by using this powder-shape porous material, which fitted the rapid detection of micro-sample volume. The feature of ultrasensitivity was retained, furthermore, the detection time and the required sample volume were also significantly reduced with this device. By this method, R6G at concentration of10"18mol/L was detected. Meanwhile, the precision of the method was improved. Four pesticides (thiabendazole, tricyclazole, paraquat and diquat) were also detected at the concentrations of0.27mg/L,5×10-3mg/L,0.05mg/L and1×10-3mg/L. This rapid and sensitive detection method was meaningful in practical sample detection.Although metal colloid showed good performances in SERS enhancement, the aggragation of this kind of colloid led to uncontrollable distances between nanoparticles which result in poor signal-reproducibility. In order to achieve a uniform substrate, the GMA-EDMA porous material was modified with ammonia. With this modification, the silver nanoparticles could self-assemble onto the porous material surface. With this procedure, a uniform substrate was attained, and correspondingly the signal-reproducibility was improved. The Ag-self-assemble GMA-EDMA porous material in powder shape showed advantages like good enhancement performances, miniaturization, low price and good reproducibility. By this substrate, the mixing of colloid and hydrophobic pesticides could be avoided, which was normally difficult in operation. The procedure of the experiment was simplified (SERS spectrum could be collected after the addition of sample onto the substrate). This made the substrate suitable in on-site SERS detection. Dimethoate and carbendazim at concentrations of0.1mg/L and0.625mg/L were detected using this substrate, and the reproducibility was improved dramatically. With a portable storeage, the substrate showed a long-term stability for one month. Combining with a portable Raman instrument, excellent performances of this substrate have shown attractive potential in on-site detection of low concentration samples.