Research On SERS Substrate Based On Flexible Substrate

Surface-Enhanced Raman Scattering(SERS)is a molecular detection technology for trace substances,which has the advantages of high sensitivity and molecular fingerprint peak characteristics.It has been widely used in the fields of food safety,biomedicine,environmental monitoring and public safety.However,traditional SERS substrates are made of rigid materials such as silicon wafers or glass wafers,which cannot be fully attached to the object to be tested for sampling.It requires more complex sample preprocessing steps before detection,so it is not suitable for rapid detection of trace substances on the surface of irregular objects on site.The flexible SERS substrate has good mechanical flexibility.It can fully sample conformally with the object to be tested,so it is suitable for rapid detection in the field.However,the current flexible SERS substrate has the problem that the surface microstructure is easily damaged during wiping sampling.In this thesis,a flexible SERS substrate with high sensitivity,high uniformity and good scratch resistance is designed to address the above problems.The specific research contents of this thesis are as follows:Firstly,the structure of the flexible substrate-based SERS substrate was designed.The flexible SERS substrate is composed of three parts: a flexible thin film with an arrayed nanocavity microstructure on the surface,a precious metal thin film layer and precious metal nanoparticles.The nanocavity microstructure and the densely distributed noble metal nanoparticles within it generate strong localized surface plasmon resonance and are fully coupled.This provides a huge SERS enhancement,enabling the SERS substrate to have high sensitivity.More importantly,the nanocavity structure can play an important role in protecting the noble metal nanoparticles inside,thereby achieving antiscratch properties during the actual wiping sampling process.Then two flexible substrate-based SERS substrates were fabricated by colloidal lithography and self-assembly techniques.They are a flexible SERS substrate with silica microspheres deposited on the surface and a flexible SERS substrate with gold nanoparticles deposited on the surface,respectively.The optimal structural parameters were determined by studying the influence of the particle size of the noble metal nanoparticles,the thickness of silver plating and the material of the noble metal nanoparticles on the performance of the two SERS substrates.The flexible SERS substrate with silver-coated thickness of 25 nm and gold nanoparticles with a particle size of 250 nm has the best SERS performance.A series of tests such as sensitivity,scratch experiments and absorption spectra were carried out.The test results show that the SERS substrate has high sensitivity,and the detection limit for 4-aminothiophenol(4-ATP)solution is as low as 1 f M.At the same time,the actual scratch test also proved that it has good anti-scratch performance.Finally,the prepared flexible SERS substrates are tested for practical application.The SERS substrate was tested for the detection of 6-benzylaminopurine(6-BA)residues on the surface of bean sprouts and apples by swab sampling.The test results show that it has good detection ability for 6-BA residues on the surface of apples and bean sprouts,and the detection limit is far lower than the relevant standards.This indicates that the prepared flexible SERS substrate has broad application prospects as a low-cost,ultrasensitive and rapid on-site detection tool for pesticide residues on the surface of fruits and vegetables.