Preparation And SERS Perfor Mance Study Of Ag Nanoparti Cles/Multi-morphology TiO₂

Surface enhanced Raman scattering technology（SERS）has the advantages of ultra-high sensitive and non-invasive detection,it has been widely used in materials science,analytical science,biological science and other fields,the most important is the development of SERS substrates.Traditional SERS substrates mainly focus on noble metal,due to high cost and low stability,which limits its wide application,Recently,Semiconductors have been paid more and more attention in the application of SERS by virtue of their advantages,such as low cost,rich variety,structure stabilization and high biocompatibility.However,the single semiconductor SERS substrate has low enhancement effect.Therefore,This paper focus on the development of novel SERS substrates with noble metal composite semiconductor that synergetic the strong SERS effect of noble metals and the advantages of semiconductors.Morphology has an important influence on SERS effect,TiO₂ with different morphologies are combined with high SERS activity of Ag NPs,Three SERS substrates of Ag/TiO₂ are prepared.Their SERS properties are investigated and explored its application in the field of food safety and pesticide testing.The SERS mechanism of Ag/TiO₂ structure is also explored.The main work of this paper is as follows:（1）The Flower-like TiO₂ material is successfully synthesized,then Ag NPs are modified to its surface by electron beam evaporation to obtain Flower-like Ag/TiO₂SERS substrate.The detection limit of CV in SERS performance is up to 10^-16 M,the Enhancement Factor（EF）is 10¹⁰,the signal uniformity is less than 13%.The detection limit of Flower-like Ag/TiO₂ substrate for melamine can reach 7.41×10^-10 M,it is 4orders of magnitude higher than the national standard,which indicates that Flower-like Ag/TiO₂ substrate has application value in food safety.The cycling test shows that it has the ability to be recycled,it also has good performances in the complex environment,the above results indicate that Flower-like Ag/TiO₂ substrate has excellent SERS properties.（2）The deformable flexible PDMS-Ag/TiO₂ Nanobelts substrate is prepared,Its SERS performance show that the detection limit of CV can reach 10^-14 M,EF is 10⁸,the signal uniformity is less than 11%.it indicates that PDMS-Ag/TiO₂ Nanobelts substrate gets high SERS properties.By utilizing the flexible capabilities of PDMS,thiram is extracted from orange surface and its detection limit is 8.51×10^-10 M,it’s far below the minimum standards of states,which indicates PDMS-Ag/TiO₂ Nanobelts substrate has the ability to extract detection molecules on rough,curved surfaces and rapid detection ability,it has practical application value in pesticide detection.（3）Ag/TiO₂ Array substrate is prepared by a bottom-up approach.The detection limit of CV can reach 10^-13 M,EF is 10⁸,the signal uniformity is less than 8%,it shows the advantage of array substrates in signal uniformity is demonstrated.The detection limit is 3.31×10^-10 M when the thiram solution is mixed with tea,It indicates Ag/TiO₂Array substrate has prospects in complex environment and well anti-interference ability.（4）The structure of Ag/TiO₂ was analyzed by electromagnetic field simulation and first principles method,the synergistic mechanism of electromagnetic field enhancement based on surface Ag NPs and PICT enhancement based on TiO₂ is proposed（EM-PICT mechanism）.The reason for the SERS enhancement of Ag/TiO₂is revealed.These studies not only provide great help for the development and mechanism research of new SERS nano-base materials,but also provide new ideas for the application of semiconductor substrate SERS nano-materials in food safety and pesticide testing.