Preparation Of Silver Nanomaterials And Its SERS Studies

Surface-enhanced Raman Spectroscopy(SERS)is a high-sensitivity modern analytical detection technology that enables molecular qualitative and quantitative analysis and provides information on the structure of molecules.SERS has the advantages of simplicity,speed and high sensitivity,and is widely used in biomedicine*food safety,medicals and health applications.How to obtain a SERS substrate with excellent sensitivity and reproducibility is a major challenge for SERS detection technology.Compared with other precious metal nanomaterials,silver nanomaterials are easy to be controlled in the structure and surface morphology.Moreover,silver nanomaterials have strong enhancement factors.Therefore,silver nanomaterials have wide application in the field of SERS.However,since the optical coupling phenomenon of smooth silver nanowires is confined to the ends and intersections of the silver nanowires,the "hot spots" distribution of the SERS substrate is greatly reduced.Therefore,it is very important to obtain more uniform "hot spots" on the surface of silver nanowires by physical or chemical methods,and to obtain SERS substrates with good reproducibility and signal stability.Silver nanowires with high aspect ratio and high yield were prepared by the polyol method.Meanwhile,the effects of reaction temperature of silver nanowires,molar ratio of PVP and AgNO3,molar ratio of CuCl2·2H2O and AgNO3,and reaction time on the morphology of silver nanowires were investigated.Silver nanowires prepared by polyol method were characterized by scanning electron microscopy(SEM),atomic force microscopy(AFM),ultraviolet-visible spectrometer(UV-vis)and X-ray powder diffraction(XRD).The silver nanowires prepared by the parameter optimized polyol method have a length of about 20-30 μm and a diameter of about 70-80 nm with high aspect ratio.In order to further increase the activity of the silver nanowire SERS substrate,the surface of the smooth one-dimensional silver nanowire was chemically etched by a mild etchant Fe(NO3)3 at room temperature to add more "hot spots".Corrugated silver nanowires with uniformly etched surface were obtained by adjusting the amount of the etchant Fe(NO3)3.By analyzing the SERS results of the Rhodamine B probe molecule,the Raman signal intensity of the corrugated silver nanowire SERS substrate is 3-5 times higher than that of the smooth silver nanowire SERS substrate.Therefore,corrugated silver nanowires prepared by chemical etching can be used as an effective SERS activity substrate.The dendritic silver nanomaterial has a multi-level layered structure,and more micro-nano voids can be formed between each other,and the surface plasma can be effectively excited by the incident light,and the intensity of the Raman signal can be further improved.Preparation of dendritic silver nanostructures by redox reaction using zinc powder as reducing agent to reduce silver nitrate.It can be observed that the dendritic silver nanostructures have a three-level layered structure.By analyzing the SERS results of the Rhodamine B probe molecule,the dendritic silver nanostructure SERS substrate has a significantly improved Raman signal intensity compared to the smooth silver nanowire SERS substrate.In order to investigate the sensitivity of dendritic silver nanostructures,the detection of Rhodamine B probe molecules can reach 10-10M,which can realize the trace and rapid detection of Rhodamine B molecules.