Preparation Of Hollow Cubic Metal SERS Substrate And Its Application In In Situ Catalysis/Monitoring

Surface-enhanced Raman technology is widely used because of its high sensitivity,simple operation and strong signal specificity.Hollow metal nanocubes are often used as high-quality SERS active substrates due to their large specific surface area,low density,and angular structure that can generate a large number of hot spots.Ag and Cu not only have excellent SERS performance,but also have considerable catalytic performance.Integrating the two functions to develop multifunctional SERS substrates capable of in-situ detection and in-situ catalysis is the current research hotspot.Based on the development of a multifunctional active substrate for SERS-in situ catalysis/detection,the following works are carried out:（1）In this paper,the chemical reduction method is adopted,using Na Cl cubes as templates,in situ loading Ag⁺to form Ag Cl shells and in situ reduction,and after removing the templates,Ag hollow cubic structures with uniform size,good monodispersity and smooth surface are obtained.By adjusting the PVP concentration of the reaction solution,the recrystallization time of Na Cl cubes,and the loading time of Ag⁺on the surface of the Na Cl template during the preparation process,the optimal process of Ag hollow cubes was obtained.The prepared Ag hollow cubes have certain catalytic activity and can be used as catalysts to catalyze the degradation of 4-NP;It has good SERS performance.When used as a SERS active substrate to detect crystal violet probe molecules,the enhancement factor（EF）can reach 10⁴.However,its SERS performance and catalytic performance are unstable,due to the large size of Ag hollow cubes and poor structural stability,resulting in a decrease in SERS performance and catalytic performance.（2）On the basis of the above experiments,in order to improve the stability of the material,a SERS substrate with excellent SERS performance and catalytic performance,which can be recycled and reused,is obtained.In this paper,SiO₂was first loaded on the surface of Na Cl as a carrier,and then Ag nanoparticles were in situ supported on SiO₂by seed growth method to obtain SiO₂@Ag hollow cubes.In order to optimize the preparation process of SiO₂@Ag hollow cubes,the following work is done in this paper:1.The morphology of SiO₂hollow cubes was optimized by adjusting the amount of TEOS.2.Use different Ag loading methods to find the best process.3.To explore the effect of PVP with different molecular weights on the Ag loading process.4.To explore the effect of SiO^-bonds on the surface of SiO₂cubes on the Ag loading process.The prepared SiO₂@Ag hollow cubes have the following characteristics:1.Excellent catalytic performance.In the4-NP catalytic experiment,the reaction constant can reach K₁=0.01936 s^-1,which is much higher than other types of materials.2.The morphology and structure are stable and can be recycled and reused.After 10 repeated tests of catalytic degradation of 4-NP,the conversion rate of 4-NP can still reach 97%.3.It has good SERS performance.When used as a SERS active substrate to detect crystal violet probe molecules,the enhancement factor（EF）can reach 10⁵.4.The photocatalytic performance is remarkable and has great potential in the field of photocatalysis.When used as SERS active substrate and photocatalytic medium at the same time in 4-NTP in situ synchronous photocatalysis/detection reaction,the maximum in situ photocatalytic reaction constant can reach K₃=0.09376 s^-1,which is much higher than other materials of the same type.（3）In order to further improve the catalytic activity of SiO₂@Ag hollow cubes and make them applicable to more complex catalytic reaction systems,in this chapter,Cu nanoparticles were in situ supported on the surface of SiO₂@Ag hollow cubes by chemical reduction method.At the same time,different reducing agents were used to conduct exploratory experiments on the preparation of SiO₂@Ag/Cu bimetallic hollow cubes,and the loading of metal Cu on SiO₂@Ag hollow cubes under different reducing agents was explored.And SiO₂@Ag/Cu bimetallic hollow cubes were successfully prepared using ascorbic acid as reducing agent.