The Preparation And Application Of Recyclable SERS Substrates

As a kind of high sensitive detection technology,surface enhancement Raman scattering?SERS?is getting more extensive attention,especially using in trace organic molecule detection with the detection limit as low as 10^-77 M.Unlike infrared spectroscopy,water has no influence on Raman spectroscopy.Thus,the Raman measurements can be taken in aqueous solution.Of benefits the extremely sensitivity of SERS,we can obtain the key fingerprint information of molecules by Raman spectroscopy.In the paper,we mainly focus on the preparation of new type multifunctional SERS substrates,applying the SERS substrates in recycling detection trace organic dye molecules,and recording the transformation of molecules on the surface of substrates.The main research contents are as follows:1.The CoFe₂O₄ nanorods were synthesized by a micro emulsion method.A layer of TiO₂ nanoparticles was deposited on CoFe₂O₄ nanorods surface by hydrothermal method using?NH₄?TiF₆ as Ti source.At last,Ag nanoparticles were decorated on CoFe₂O₄/TiO₂nanorodsurfacebysilvermirrorreaction,tofabricate CoFe₂O₄/TiO₂/Ag nanorod arrays as the SERS substrate.The samples was characterized a series of means such as TEM,XRD,UV-vis diffuse reflectance spectroscopy and magnetic hysteresis studies.Subsequently,we compared the photocatalytic properties of samples of CoFe₂O₄/TiO₂ and CoFe₂O₄/TiO₂/Ag??-??.The results show that the as-obtained CoFe₂O₄/TiO₂/Ag samples exhibit incrementing UV-vis photocatalysis activities when the deposition of Ag nanoparticles increased.Using Rhodamine 6G?R6G?as a target molecule,we examined SERS detection performance of the as-synthesized CoFe₂O₄/TiO₂/Ag nanorods.The experimental results showed that the Raman signals were enhanced as the deposition Ag nanoparticles increased.The CoFe₂O₄/TiO₂/Ag???exhibits the best SERS enhancement with the detect limitation up to 10^-1010 M for R6G solution.Furthermore,the as-obtained samples exhibited stable recycling properties.2.The reduction process of 4-Nitrobenzenethiol?4-NTP?molecules on the surface of CoFe₂O₄/TiO₂/Ag???was studied by in-situ SERS monitoring.The 4-NTP molecules were adsorbed on the surface of CoFe₂O₄/TiO₂/Ag???substrate,and the transformation of 4-NTP molecules was reduced under NaBH₄ solution,532 nm laser,and UV light,respectively.The experimental results show that reduction of the 4-NTP under different conditions gives different final products.In the presence of NaBH₄,4-NTP is eventually reduced to 4-Aminobenzenethiol?4-ATP?,while 4-NTP was reduced under visible light?532 nm?and UV light irradiation,the final products were trans-DMAB and cis-DMAB,respectively.This is mainly due to the trans-DMAB and cis-DMAB will interconvert under different light irradiation.We also successfully in-situ monitored the interconversion between trans-DMAB and cis-DMAB under UV and visible light conditions by Raman spectroscopy.3.In chapter 4,we designed and constructed a hierarchical suprastructure composed of cellulose microfiber?CMF?-supported TiO₂@Ag nanocomposite particles?TiO₂@Ag/CMFs?,which serves as a dual-functional platform for both high-erformance heterogeneous photocatalysis and in situ reaction monitoring using SERS as an ultrasensitive,in situ monitoring spectroscopic tool.We chose the photocatalytic degradation of 4-Chlorophenol?4-CP?on TiO₂@Ag/CMFs as a model reaction system,and demonstrated that the interfacial chemical transformations on the photocatalyst surfaces can be tracked in real time with detailed molecular structural information using SERS as a time-resolving and molecular fingerprinting spectroscopic tool.Through time-resolved SERS measurements,we have been able to track the temporal evolution of several important aromatic intermediates during the photocatalytic degradation of 4-CP.A key insight gained form our SERS results is that the quinhydrone complex rather than the monomeric HQ,BQ,or their hydroxylated derivatives,such as HHQ and HBQ,serves as the final aromatic intermediates before the mineralization upon aromatic ring cleavage.This work not only highlights the value of SERS as an ultrasensitive spectroscopic tool for in situ reaction monitoring but also provides important design principles that guide us to deliberately construct dual-functional materials systems integrating superior photocatalytic performances and in situ molecular sensing functions.