Construction Of Several Molecules Assemblies On Surfaces Of Gold,Silver And Semiconductor Substrates And The Detection Application In Surface-enhanced Raman Spectroscopy

Raman spectroscopy is an important characterization method in the field of detection.SERS substrates have a major influence on chemical detection.Therefore,different substrates were prepared using different methods,including silver sol,porous gold nanoparticles,silver/porous gold composite substrate,and AZO substrate.The differences in these substrates were characterized and their advantages and disadvantages were compared.Different molecules were detected using these substrates.(1)A new type of surface-enhanced Raman scattering(SERS)substrate was fabricated through the layer-by-layer self-assembly of silver nanoparticles(Ag NPs,av.45 nm in diameter)and porous gold nanoclusters/nanoparticles(Au NPs,av.143 nm in diameter).The development of the porosity of the Au NPs was investigated,and successful SERS applications of the porous Au NPs were also examined.As compared with Ag NP films,the enhancement factor of Ag-Au compound substrates is increased 6 times at the concentration of 10-6 M.This additional enhancement contributes to the trace-amount-detection of target molecules enormously.The contribution is generated through the increase of the usable surface area arising from the nanoscale pores distributed three-dimensionally in the porous Au NPs,which enrich the adsorption sites and hot spots for the adsorption of probe molecules,making the developed nanofilms highly sensitive SERS substrates.The substrates were used for the detection of a physiological metabolite of urea molecules.The results reached to a very low concentration of 1 m M and exhibited good quantitative character over the physiological concentration range(1 ~ 20 m M)under mimicking biophysical conditions.These results show that the prepared substrate has great potential in the ultrasensitive SERS-based detection and in SERS-based biosensors.(2)Here we investigated the detection of MS molecules based on surface-enhanced Raman scattering(SERS)in a novel molecule/assistant/metal system constructed with MS,4,4?-(hexafluoroisopropylidene)bis(benzoic acid)and Ag nanoparticles(Ag NPs).To explore the function of assisted reagent,we also referred another system without assistant molecules.The result demonstrates that SERS signals were not acquired,which proves that the assistant molecules are critical for the capture of MS molecules.Two possible mechanisms of MS/assistant/Ag NPs system were speculated through two patterns of hydrogen bonds.The linker molecules acted as the role of the bridge between metallic substrates and target molecules through the molecular recognition.This strategy is very beneficial to the expanding of MS detection techniques and other hydrogen bond based coupling detections with SERS.(3)Aluminium-doped zinc oxide nanocrystals(AZONs)with controllable morphology were successfully prepared via a solvothermal method by using four surfactants of poly(diallyldimethylammonium chloride)(PDDA),polyvinyl pyrrolidone(PVP),polyetherimide(PEI),sodium dodecyl sulfate(SDS)as capping agents.The different surfactants had different effects on the morphology of the obtained AZONs.For examples,the PDDA has the effect to induce an anisotropic growth;the PVP promotes the crystal growth rate;PEI has no obvious effect;and the SDS is to inhibit the crystallization.All these AZONs were synthesized at a doping ratio of 3% aluminium content for the sake to their high charge carrier density,which potentially contributes to the surface-enhanced Raman scattering(SERS).In a comparison the AZONs synthesized without surfactants were used as references.Along with it,the AZONs obtained by different surfactants were used as SERS substrates.The influence on the spectral enhancement was studied.Compared with the reference,the enhancement factor of AZONs capped with PVP is increased 6 times.But the AZONs capped with other surfactants(PEI,SDS and PDDA)have no obvious enhancement or similar enhancement to the reference.These results demonstrate that the morphology,also with special chemical surfaces,play an important role in the SERS enhancement.The extending synthesis methods for new AZONs expand the research scope of AZO materials and applications.