| Surface-Enhanced Raman Scattering?SERS?is a high sensitivity detection technology that provides various information of vibrational fingerprint and is widely used in ana-lytical chemistry,environmental monitoring,and food safety.Because of the quality of the spectral line is affected by the microstructure of the surface of the SERS substrate,so it is necessary to find a suitable method to prepare an excellent substrate.According to the form of the SERS substrate,it can be roughly subdivided into a metal colloids substrate and a solid substrate.The metal colloids has a simple preparation process and a good Raman enhancement effect,but it is easy to self-aggregate,not conducive to long-term preservation,and difficult to ensure stability.The solid could overcomes these factors such as aggregation of metal colloids particles and signal instability,and it can be stored for a long time.At present,solid substrates are prepared by physically or chemically transferring metal nanoparticles onto a substrate or directly preparing metal nanoparticles on a substrate.Monocrystalline silicon semiconductor materials were a unique optical and electrical properties,and wide application prospects in solar cells,biosensing,nano materials,etc.In this work,the two kinds of SERS substrates with different enhancement characteristics were prepared by physical and chemical methods using monocrystalline silicon as the solid substrate.The Experimental re-search content was as follows:?1?Pyramid microstructures were prepared by anisotropic etching of the<100>surface of single crystal silicon by chemical etching.Pyramid morphology was ana-lyzed at 90?by changing potassium phosphate concentration,potassium silicate con-centration and reaction time.The surface morphology optical properties of the sample was characterized by scanning electron microscopy?SEM?and UV-Vis spectropho-tometer.The results show that the optimal etch conditions are potassium phosphate concentration 15wt%,potassium silicate concentration 3wt%,etch time 36min,under these conditions,pyramid microstructure formed on the surface of monocrystalline sil-icon have high coverage rate 99.9%with average size 1.89?m,maximum size 2.94?m,which provide a low reflectivity and good regularity.?2?Using physical method,a certain thickness of gold nanoparticles is sputtered on the surface of the pyramid microstructure which was prepared by the best etch con-dition in?1?.By using methylene blue?MB?as a probe molecule to detect the SERS characteristics the relationship between Raman enhancement activity and different sputtering time was analyzed.The results show that the substrate has the maximum Raman-enhancing activity when the sputtering time is 5 min.The SERS spectrum with a concentration of 1×10-55 mol/L MB was detected to be more effective than the con-ventional Raman spectroscopy.At the same time,a melamine solution with a concen-tration of 1×10-3 mol/L was detected,and all Raman peaks were observed.The results above shows this substrate has a good Raman enhancement effect,and has potential application value in detection of low concentration detection and food safety.?3?A new method was proposed to preparation monolayer silica@gold core-shell nanoparticles?SiO2@Au NPs?that combines spin-coating,nanoscale masking and in situ reduction techniques.The surface morphology,optical properties and crystallinity of the samples were characterized by scanning electron microscopy,transmission elec-tron microscopye,ultraviolet-visible spectrophotometry,X-ray diffraction,and energy-dispersive X-ray spectroscopy.The Raman enhancement activity of SiO2@Au NPs substrate was studied by selecting different concentrations of crystal violet?CV?as the probe molecules,the lowest detectable concentration was determined to be 1×10-8mol/L,and the spectrum remained unchanged after three weeks.The Raman enhance-ment factor of the substrate was calculated to be 1.4×107,and the relative standard deviation?RSD?at the characteristic peak of 1178 cm-11 was 14.07%.By using this new method,we propose a way to fabricate monolayer core-shell nanostructure,which are easy to transport,store and use,as a promising viable alternative to existing SERS substrates. |
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