Preparation And Sensing Properties Of Self-cleaning SERS Devices

The growing issues of food safety and environmental pollution have a crying need for Ultra-sensitive detection of target molecules.Surface-enhanced Raman scattering（SERS）technology is one of the popular means for efficient and rapid molecular-level detection.However,the preparation of recycled SERS substrate with high activity and stability have become the bottleneck for its development.Based on this,the paper will combine SERS technology with semiconductor materials with excellent photocatalytic degradation capabilities to construct a series of semiconductor,precious metal and graphene multilayer composite structures through reasonable design.What’s more,in this paper,the SERS property and photocatalytic Self-cleaning property of the prepared substrates will be further studied.Last but not least,this paper bears critical research significance and application value to provide a practical approach for obtaining a SERS active substrate with balanced coexistence of high sensitivity,stability,repeatability and recyclability.The specific research contents are as follows:（1）A simple,efficient,high uniformity and high stability new type of self-cleaning SERS substrate was proposed,which was composed of wet transfer graphene（G）film,magnetron sputtering silver（Ag）and titanium dioxide（TiO₂）multilayer composite.The chemical enhancement of graphene and the plasmon resonance coupling effect between silver nanoparticles greatly enhanced the Raman signal of the substrate,and the detection limit of Rhodamine 6G（R6G）was as low as 10^-11mol/L（enhancement factor is 3.75×10⁶）.There was a good linear correlation between the Raman peak intensity and R6G concentration,and the fitting curve R²=0.98.It is proved that the prepared substrate has the potential for quantitative analysis of probe molecular concentration of unknown concentration.The graphene layer effectively isolated the precious metal layer from the probe molecules to avoid directly contacting between the precious metal layer and air,and the composite base still maintained good SERS signal stability after 30 days of placement.The uniform deposition of TiO₂and Ag by magnetron sputtering made the composite substrate show good signal uniformity,and the relative standard deviation of characteristic peak intensity at 20 different locations in the random region was less than 9%.The photocatalytic degradation function of TiO₂enabled the SERS base to still have excellent SERS activity after five cycles of use.（2）A kind of Au/G/Ag@ZnO multilayer composite substrate using graphene film as nanospace layer was proposed.The multiple plasmon resonance coupling effect of precious metal particles within and between layers combined with the photocatalytic degradation performance of ZnO made the SERS substrate exhibit excellent high sensitivity,signal uniformity and reusability.FDTD simulation was used to study the mechanism of plasmon resonance coupling enhancement between precious metal layers regulated by different graphene layers thickness,and the optimal SERS structure was obtained.The results show that monolayer graphene has the best interlayer regulation effect,and the detection limit of R6G on composite substrate is as low as 10^-13mol/L（enhancement factor is 5.68×10⁷）.Due to the excellent molecular enrichment ability of graphene and the unique homogeneity of SERS device structure,the SERS base had good signal reproducibility,with the relative standard deviation（RSDS）<15%.Due to the excellent photocatalytic performance of low-cost wide-band gap semiconductor ZnO,SERS devices have excellent reusability,which can be reused for 5 times.