Preparation Of Anisotropic Micro-Nano Particles As Sensitive Sers Substrates And Studies On Its Properties

Surface enhanced Raman scattering（SERS）,as a molecular detection technique,is widely used in the fields of environmental safety,life science,medical care,because of its convenient and rapid detection and high sensitivity.However,the preparation of SERS substrate with high SERS effect,good homogeneity and recyclability is the focus and challenge of human exploration.Hierarchical noble metal nanoparticles,which possess abundant hot spot,could generate intense enhancement of Raman signals.However,the traditional noble metal substrates suffer from the lack of reproducibility and recyclability Therefore,the combination of noble metal with semiconductor nanostructures or carbonaceous materials such as carbon nanotubes,activated carbon,and graphene could make up the deficiency and improve SERS performance.In this paper,we successfully fabricated a series of hierarchically anisotropic silver nanoparticles.The effects of the carbon chain length,functional groups of organic acids on the morphologies were systematically investigated.The preparation methods of Au/flower like titanium dioxide composite and graphene/Au/flower like titanium dioxide composite were studied.The SERS properties and photocatalytic degradation properties were studied.The specific research contents and conclusions are as follows:（1）The hierarchical silver nanoparticles were prepared by the solution reduction method,with different small molecular organic acids（oxalic acid,malonic acid,succinic acid,malic acid,tartaric acid）.It is found that the different structure of small organic acids and dosage will affect the morphology of silver nanoparticles.As the carbon chain of organic acid grows,the morphology of the synthesized silver nanoparticles is staggered from layer to layer and then to Walnut shape,and its particle size is gradually smaller.This is because the carbon chain becomes longer,the space hindrance becomes larger and the self-assembly of silver nanoparticles becomes slow,which makes the silver nanoparticles less anisotropic and thus the particle size changes.Small。However,the number of hydroxyl groups in organic acids affects the morphology of silver nanoparticles mainly in the change of lamellar structure.The Raman detection of these morphologies of silver nanoparticles showed that the enhanced effect of oxalic acid induced silver nanoparticles on R6G was 2-3 times that of malonic acid and succinic acid.（2）The flower like TiO₂ particles were prepared by solvothermal method and Au/flower like titanium dioxide composites were prepared by in situ reduction method.It was found that the effect of the reaction time and the amount of chloroauric acid on the particle size and loading density of the synthesized Au/flower like titanium dioxide composite were influenced by the change of the reaction time and the amount of chloroauric acid.Based on the results,when the reaction time is 5 h and the amount of chloroauric acid is 2 mL,the obtained Au/flower like titanium dioxide composite materials have better performance.The uniformity of the substrate is good.The average deviation of the Raman peak of 20 points is less than 10%.The detection limit is 10^-10 M,and the sensitivity is excellent.The base is reused.It was found that catalytic degradation of R6G after 6 times,the degradation rate of the substrate decreased by 37%,and its SERS performance weakened.The peak intensity of R6G Raman signal at1514 cm^-1 decreased to 40%,indicating that the duplication performance of the substrate was better.（3）rGO/Au/flower like titanium dioxide composite was prepared by hydrothermal method.It was found that by changing the content of graphene oxide,rGO/Au/flower titanium dioxide composites with different thickness and transparency were obtained.The Raman test was carried out using R6G as a probe.It has been demonstrated that when the content of graphene oxide was 1.2 mg,the SERS properties of the composite substrates were the best.The catalytic performance of R6G is excellent,which can completely degrade the R6G molecule.This indicates that the addition of graphene enhances the photocatalytic activity of TiO₂,and plays a synergistic role with Au nanoparticles.