Porous Silver Substrate Of Solid Phase Microextraction Coupled With Surface Enhanced Raman Spectroscopy For Rapid Detection

Surface enhanced Raman spectroscopy(SERS)is a high sensitive molecule vibration spectrum,which can enhance the Raman scattering of molecules adsorbed on the surfaces of metal nanostructures(usually silver and gold).SERS can provide the information of vibrational mode and a unique spectral fingerprint.Both electromagnetic and chemical enhancing contributed to this effect according to the mechanism of surface plasmon resonance and charge-transfer,respectively.SERS have been widely used in rapid and nondestructive analysis,such as pollutants,explosives,food safetyand and preservation of cultural property.The preparation techniques of nanostructure substrate play an essential role in the application of SERS.A clean,stable and uniform substrate can give the sensitive and accurate SERS response for complex matrix.The samples can be probed on-situ using a portable Raman spectrometer,disregarding the need to transport them to the laboratory.SPME is a speed and efficient equilibrium-extraction method,which has been proved as a powerful pre-concentration procedure.SPME is based on the equilibrium of the distribution between the analyses and stationary phase on a metallic or fused silica supporting substrate.The stationary phase was usually composed of a thin coating layer of sorbent material，which plays a crucial role in the extraction and desorption process.On other hand,the properties of the coating materials will determine the scope of their applications.1 In this section,the nanoporous Ag layer was in situ electrochemical synthesized and served as the SERS-active substrate for absorption-type SPME coating.The SERS response of organotin compounds(OTCs)were investigated on this nanostrucute surface,the extraction capacity for these OTCs were subsequently evaluated and the extraction parameters were optimized.A fast and on-situ analysis methods for OTCs was established through SPME-SERS by a portable Raman spectrometer.The proposed methods was successfully applied to the determination of OTCs in textile sample,and the results were validated by ICP-MS.2 The ultrathin Au layer was depositionin on porous Ag surface by galvanic-free displacement reaction.The redox potential of Au+ decrease when the complexation occur between Au+ with I’ in solution.Then Au3+ was reduced by ascorbic acid,which form the uniform film on Ag surface.The porous Ag@Au substrate was characterized by SEM,EDS,XPS and AFM methods.The stability under laser and heating were investigated by SERS using 4-aminothiophenol as the probe.The SERS response of nitrofurazone and semicarbazide were performed on this substract.A fast and on-situ analysis methods for illegal additives was established through SPME-SERS hyphenated methods,the limit of detection was low to ppb level.3 Finally,the opposite surface oxidation states were obtained by self-assembly of 4-aminothiophenol and 4-nitrobenzenethiol on porous Ag@Au,respectively.The role of oxidation state in interaction between nanoparticles and blood proteins was investigation.Gold nanparticles was synthesized and modified model the surface oxidation state in solution.Then,the complex of particles-protein was separated by capillary electrophoresis quantitatively,giving the dissociation constants(KD)and cooperativeness coefficients(n)according to the Hill equation.Further,the binding sites and force were evaluated by molecular docking.Results demonstrate that the surface oxidation state can affect the intensity and mode of protein conjugation.