Study Of Multidimensional Coupling High-performance SERS Biochemical Detection Chip

Surface-enhanced Raman Spectroscopy（SERS）technology has great potential for the rapid and accurate analysis of biochemical samples as it is non-destructive,non-contact,and can provide rich chemical fingerprint information.However,the complex composition and small Raman scattering cross-sections of biochemical samples result in lower detection sensitivity.At the same time,the performance of SERS chips requires further improvement,especially the sensitivity and uniformity.In this study,a new multi-dimensional coupling SERS chip has been proposed,which integrates a high-enhancement SERS substrate and micro-optical elements for Raman scattering signal collection.The study includes the simulation of local electric field distribution of nanostructures,the design of SERS chip,the self-assembly of nanoparticle,the design and preparation of signal collection microstructures,as well as verification using biochemical samples.The main works of the thesis are summarized as follows:（1）The effects of nanoparticle material,particle size,number of layers,and support material on the local field enhancement were investigated.The local electric field distribution of multilayer silver nanoparticles（AgNPs）on different supports was analyzed.Finally,an optimized design of the multi-dimensional coupling high-performance SERS substrate was achieved.The simulation results showed that the maximum local field enhancement of four-layer AgNPs films on glass was increased approximately 162 times,and that of two-layer AgNPs films on gold film was increased approximately 408 times.（2）Two signal collection microstructures based on an inverted pyramid micro-reflecting cavity and PDMS microlens,respectively,were proposed.Parameters,including bottom side length,height,and the material and thickness of the reflective film of the micro-reflecting cavity,as well as the radius,height,and curvature of the PDMS microlens,were optimized.The optimized micro-reflecting cavity and microlens could increase the signal intensity approximately 2.23 times and 5.91 times,respectively.（3）The liquid-liquid interface self-assembly processes of AgNPs were studied.The process parameters were optimized,and two SERS substrates,"4-AgNPs@glass"and"2-AgNPs@Au film",were successfully fabricated.The SERS enhancement factor of the"4-AgNPs@glass"SERS substrate was about 6.23×10⁶,with a limit of detection（LOD）for R6G of 1×10^-10 mol/L and a relative standard deviation（RSD）of the signal in the SERS mapping test of about 22.3%;The SERS enhancement factor of the"2-AgNPs@Au film"SERS substrate was 2.5×10¹⁰ with a LOD for R6G of 1×10^-15 mol/L and an RSD about 11.0%.（4）The manufacturing processes of the micro-reflecting cavity and microlens were investigated.The micro-reflecting cavity was fabricated successfully using anisotropic wet etching and magnetron sputtering and the microlens was fabricated using isotropic wet etching and reverse molding.Experimental results showed that the RSD of the microlens size was as low as 0.37%and that the micro-reflecting cavity and microlens could increase the SERS signal intensity by about 50%and 5.03 times,respectively.（5）SERS detection experiments on biochemical samples were carried out.The experimental results showed that Escherichia coli and Staphylococcus aureus were rapidly detected by the SERS chip.Measurement of creatinine concentrations in aqueous solution and serum were carried out at Chongqing Cancer Hospital.The results showed that the LOD of the creatinine aqueous solution was 1×10^-7 mol/L,while the detection resolution of serum creatinine was better than 10μmol/L,with an accuracy of blind detection of serum samples reaching 90%.In conclusion,the SERS chip developed in this study was characterized by its high enhancement factor,good signal uniformity,and good repeatability,making it particularly suitable for the rapid and accurate analysis of biochemical samples.