Corrosion-based Fabrication Of Noble Metal Nanoparticles Their SERS Effect

The shape,structure and composition of noble metal nanoparticles have an important influence on the properties,so the structures obtained by different preparation methods will exhibit different properties.Noble metal nanoparticles with complex nanostructures may have properties that are different from simple structures.As an important processing method,oxidative corrosion can effectively control the morphology,structure and composition of noble metal nano.Since the noble metal particles can be used as a substrate of Surface Enhanced Raman scattering(SERS),trace detection can be realized.The work of this thesis mainly uses the processing method of oxidative corrosion to prepare two kinds of noble metal nanostructures,and used as the substrate for SERS detection,and obtained the substrate with high SERS activity,high stability and low detection limit.The innovative results obtained are as follows:(1)Hollow nanocrystals of Au/Ag alloy with high SERS stabilityThe cubic silver particles with uniform size were prepared by polyol reduction.Then they were dispersed in an aqueous solution of cetylpyridinium chloride,and galvanic replacement was occurred with HAuCl4 solution to prepare Au/Ag alloy hollow porous nanoparticles.We studied the effect of HAuCl4 concentration and reaction time on the morphology of the samples.At the same time,as the morphology changed,the absorption peak of the sample moved from the visible region to the near-infrared region.Such gold-silver alloy hollow porous nanoparticles,especially those with relatively low ratio of gold and silver atoms,exhibit better long-term stability than pure Ag particles during the Raman test.(2)Au/Ag alloy hollow truncated cube with high-SERS activity and high stability fabricatedThe SERS stability of the samples after the introduction of gold is improved,but the activity is decreased compared to the silver particles.To solve this problem,we added ascorbic acid during the etching of silver particles by HAuCl4.On the one hand,ascorbic acid can reduce Au(?)in HAuCl4 to Au(?),and replace the 1:3 atom ratio between Au and Ag into 1:1 compared the reaction without ascorbic acid during the replacement.On the other hand,Au(?)can be reduced into Au atoms,agglomeration to form Au particles and deposited on the surface of the template to make it rougher.The Raman test results show that the structure has SERS activity superior to that of silver cubic particles.(3)Ag hollow micro/nano hierarchical structure based on in situ transformation of CU2OThe Cu2O was prepared by hydrothermal method and it was used as a template to react with a mixed solution containing sodium citrate,silver nitrate and nitric acid to obtain particles coated with silver nanosheets.We discussed the effects of various substances involved in the reaction on the morphology of the product.When the structure was used as a SERS substrate with 4-ATP as detect molecule and low detection limit was obtained.However,since the surface of the silicon substrate is smooth and the particle size is large,the particles are peeled off from the surface of the substrate during the test.(4)Silver nanosheet based micro/nanostructure array based on in situ conversionConsidering the problem of the samples in(3),the structure can be transferred to the silicon nano-cone array to obtain a micro/nano structure array assembled by Ag nanosheets,and the sample can be ensured while obtaining a low detection limit of high SERS activity,uniformity and stability.A silicon nano-cone array was prepared using the PS spheres array as a mask.With this as a template and after a series of reactions,an ordered array of micro/nano structures with high density edges and nano-gap assembled by Ag nanosheets was obtained.The SERS test was carried out with 4-ATP as a detection molecule,and high SERS activity,low detection limit and good stability was obtained.