Synthetic Of Noble Mental Nanocubes For SERS Analysis

In the past four decades of development,surface enhanced Raman spectroscopy(SERS)has been widely used in chemical reaction monitoring,food safety testing,biological analysis and other fields due to its high sensitivity and selectivity.Substrate materials with excellent SERS activity play an extremely important role in the SERS field,which is also a prerequisite for high sensitivity analysis using SERS technology.Precious metal Ag has unique physical and chemical properties and is widely used in the fields of catalysis,bioassay and SERS sensing.In this paper,a novel noble metal Ag-based core-shell nanocube material was designed and synthesized,and its structure and morphology were characterized.The 4-Mercaptobenzoic acid(4-MBA)was used as the target molecule to study in SERS on the Ag-based core-shell nanocube materials.The specific research contents are as follows:(1)Firstly,the chloroauric acid was reduced to obtain the Au seed solution,and then the Au@Ag nanocube was successfully synthesized by the seed growth method.By changing the AgNO3 dosage,the amount of the Au seed solution,reaction temperature and the speed,influence of reaction conditions on the morphology of nucleation and particle size were investigated.Finally,by controlling the amount of AgNO3(2 mmol/L,5 mL),the amount of Au seed solution(12.5 mg/mL,0.5 mL),temperature(60?),speed(350 r/min),the synthesis of Au@Ag core-shell nanocube and study of SERS performance were performed through the adsorption 4-MBA on Au@Ag core-shell nanocube substrate.The Au@Ag nanocube was characterized by transmission electron microscopy,X-ray diffraction and ultraviolet spectroscopy.Using 4-MBA as target molecule,SERS properties of Au@Ag nanocube materials were studied,the actual detection range is 10-5 mol/L-10-10 mol/L and the detection limit of the Au@Ag nanocube for 4-MBA is 5×0-11 mol/L.Au@Ag nanocube as the SERS active materials for detection of 4-MBA showed its high sensitivity and wide linear range.(2)With ethylene glycol as solvent,silver trifluoroacetate was reduced into Ag nanocubes under 150?.Then by the deposit of Au on the surface of Ag nanocubes,Ag@Au core-shell nanocubes were prepared.By changing the HAuCl4 dosage,reaction temperature,reaction time and the speed,influence of reaction conditions on the morphology of nucleation and particle size were investigated.Finally,by controlling the amount of HAuCl4(2 mmol/L,0.8 mL),temperature(25?),the reaction time(10 min),speed(300 r/min),the synthesis of Ag@Au core-shell nanocube and study of SERS performance were performed through the adsorption 4-MBA on Ag@Au core-shell nanocube substrate.The Ag@Au nanocube was characterized by transmission electron microscopy,X-ray diffraction and ultraviolet spectroscopy.Using 4-MBA as target molecule,SERS properties of Ag@Au nanocube materials were studied,the actual detection range is 10-6mol/L-10-11 mol/L and the detection limit of the Ag@Au nanocube for 4-MBA is 2×10l-12 mol/L.Ag@Au nanocube as the SERS active materials for detection of 4-MBA showed its high sensitivity and wide linear range.(3)Firstly,a-Fe2O3 nanocubes were synthesized by simple precipitation method.With different amounts of TEOS adding,different thicknesses the SiO2 shells of were uniformly coated on the surface of a-Fe2O3 nanocube by low temperature reduction method.Then,a-Fe2O3@SiO2 nanocube was prepared.Then,a-Fe2O3@SiO2 nanocube was reduced by H2 and Fe3O4@SiO2 nanocube was obtained.Finally,silver nanoparticles were uniformly supported on the surface of Fe3O4@SiO2 nanocube by in-situ reduction method to prepare Ag/Fe3O4@SiO2 nanocubes.The materials prepared above are easy to control,magnetic,and the surface SERS hotspot distribution is uniform.The material is applied to the 4-MBA SERS detection,the detection limit is 3×10-9 mol/L,and the material can be quickly separated under the magnetic field during the detection,and the operation is simple and convenient.