Study Of Novel Hybrid SERS Substrate Au-SiO₂ And Synthesis Of Pd-Au/GC Material For Catalytic Reaction

Gold nanoparticles,as one of the various metal colloids,exhibit very special physical and chemical properties such as optical properties,electrochemical properties,and excellent catalytic activity,et al.It is a vital type of basic material for many research areas because of it’s good performance,and can be widely used in photoelectric science,analytical science,biomedical study and catalysis field,which often make it draws great attention from scientists.One of its applications is in surface enhanced Raman spectroscopy,an efficient spectrum detection technology.Advanced SERS detection technology relies on effective preparation of SERS active substrate.So far,there are plenty of methods for substrate preparation,but high production cost,complicated and time-consuming experiment steps remain serious problems.On the other hand,efficiency of direct methanol fuel cell(DMFC)are severely restrained by kinetics of reaction,therefore catalysts are introduced to improve this situation.Traditional Pt-based catalysts are high activity,but its rare resource and high cost make it greatly necessary to search for non-Pt catalyst.Thus,in this paper,we use gold nanocolloid to prepare SERS substrate with a extremely simple method.In addition,we also synthesis Pd-Au/GC catalytic materials based on gold nanoparticles,which are applied to catalytic oxidation process of methanol later.Main study contents and results are summarized as below:(1)Gold nanoparticles and silica nanocolloids with 55 nm and 60 nm size are synthesized respectively.Form hybrid nanoparticles via mixing concentrated gold nanoparticles with different amounts of silica colloids by ultrasonic operation.Drop hybrid nanoparticles to glassy carbon electrode and dried in vacuum condition.Then we obtain the Au-SiO2 composite substrates.(2)Characterize series of Au-SiO2 composite substrates prepared above with SERS method.When it comes to a ratio of particle numbers N(Au):N(SiO2)= 10:3.5,substrate exhibits 2 fold enhancement than pure gold colloids.And other composite substrates get fairly SERS signal with pure gold colloids.Conclusions can be drawn that certain amount of silica addition improves performance of SERS substrate.Further,this can save amounts of noble metal materials and reduce the cost.(3)First,55 nm gold nanoparticles are physically absorb onto the glassy carbon electrode to make Au/GC.Then a slow controlled-rate deposition of different thickness palladium(from sub-monolayer to multilayer)are realized by employing constant cathodic currents.(4)Cyclic voltammetry are performed to test catalytic properties of Pd-Au/GC with different palladium thickness in alkaline methanol solution.When palladium thickness is 10 ML,the current density 6.94 mA·cm-2 of CH3OH comes to be the largest on Pd-Au/GC and it has the most excellent catalytic activity.As palladium thickness increasing,Pd-Au/GC develop from ease poisoned inefficient catalyst to high intermediate tolerant performance methanol catalyst,this provide to direct methanol fuel cell another novel catalyst.