Fabrications And Applications Of Flexible SERS Substrate And Shell Isolated SERS Active Microfluidic Channel

Surface enhanced Raman scattering（SERS）technology has high sensitivity,and provide abundant molecular vibration and rotation information.It has great application potential in biomedicine,surface science,food safety,environmental monitoring and other fields.The preparation of high performance SERS substrate is an important step in the application of SERS.The substrate needs to have good convenience,uniformity and sensitivity.However,the actual detection environment will put forward different requirements for SERS substrate,so it is very important to prepare suitable SERS substrate for different application situation.To meet the above requirements,three types of SERS substrates were developed to achieve efficient and convenient SERS detection,the main research contents are as follows:（1）Gold nanoparticles with size of 18 nm,50 nm and 60 nm were prepared by reducing chloroauric acid with sodium citrate.Two kinds of flexible SERS substrates were prepared based on 50 nm gold nanoparticles.The first flexible SERS substrate is ultra-thin PDMS based flexible SERS substrate with a thickness of 15μm,the detection limit of R6G is 5×10^-7M,the average RSD was 15.7%.The in situ SERS detection of malachite green on the surface of samples was realized by using this substrate.The second kind of flexible substrate is high-density adhesive tape flexible SERS substrate.The density of substrate is greatly increased by transferring single layer Au nano-film by adhesive tape for many times,and form dense multilayer structure.The detection limit of R6G was 5×10^-8M,which is an order of magnitude higher than the ultra-thin PDMS based flexible SERS substrate.（2）Au@Si O₂nanoparticles was synthesized by hydrolysis of sodium silicate on the surface of Au nanoparticles,the size of Au core is about 50 nm and the thickness of Si O₂shell is about 4 nm.Au@Si O₂nanoparticles can easily obtain the molecular information on the surface,so the effect of oxygen plasma treatment on the surface adsorption capacity of PDMS was successfully detected by using Au@Si O₂nanoparticles.Finally,the nanoparticles were assembled on PDMS to form a shell isolated SERS active substrate through layer by layer self-assembly method.（3）The shell isolated SERS active microfluidic channel were prepared.A layer of Au nanoparticles was assembled in the microfluidic channel through layer by layer self-assembly method.Finally,silica layer was prepared on the surface of Au nanoparticles by sodium silicate hydrolysis method.This method can increase the assembly density of nanoparticles and the sensitivity of SERS detection.Using 1,4-BDT as the analyte and sodium borohydride as the cleaning agent,the cyclic detection ability of the shell isolated SERS active microfluidic channel was explored.After four times of cleaning,the microfluidic channel still maintained SERS activity,the shell isolated SERS active microfluidic channel also has a good ability to detect the mixture（R6G and 1,4-BDT）.Finally,the common water pollutant malachite green was detected in the shell isolated SERS active microfluidic channel,the results show that the peak intensity at 1616 cm^-1increases linearly with the increase of malachite green concentration from 10^-6M to 10^-4M,and the detection limit can reach 10^-7M.These results above indicate that the shell isolated SERS active microfluidic channel have good potential in practical applications.