Optimazation Of Transition Metal Substrate Of SERS Usingcontrolable Nanoparticle

Gold nanoparticles have special physical and chemical properties and good chemical stability, so that makes gold nanoparticles widely used in biosensors, photochemical and electrochemical catalysis. However, with the particle size increase, the uniformity and dispersion are worsen, and are prone to coagulate. Therefore, the way to synthesis large size and good homogeneity gold nanoparticles is becoming the current focus attention of researchers.Transition metal has weak Surface-enhanced Raman Scattering (SERS) effect. To further improve the enhanced ability of transition metals, people have developed the transition metal enhancement technology called"borrowing strength". Author covered the thin transition metal layer on the strongest SERS substrates, inner metal long-range electromagnetic enhancement makes the Raman signals molecules adsorbed on the outer transition metal layer enhanced. At first, people deposit transition metal thin layer on the roughed and disordered gold electrode substrate; and then use the uniform gold particles as substrate, then it develops to synthesising nanoparticles that transition metal package gold nanoparticle as shell to optimize the transition metal nanoparticles have SERS empowerment. In this paper, synthesising larger size spherical gold nanoparticles is attempt to further optimize the enhanced ability of transition metals, the specific results are as follows:(1) Optimize the synthesis methods of large-size spherical gold nanoparticles. Based on the original"seed synthesis"to synthsis the uniform gold nanoparticles, author optimized the method of organizing Au nanoparticles larger than 100nm by changing the series of reactions (from two steps to three steps), changing the seeds'environment, changing the speed of adding gold chloride acid , changing the ratio of hydroxylamine hydrochloride and gold chloride acidand and changing the amount of material of Au atomic. The gold solution synthesized in our laboratory has good uniformity and unity, and place it at -4℃refrigerator for a few months still has a good uniformity.(2) Optimizate transition metal SERS enhancement capabilities using the synthesised gold nanoparticles. At first we discussed SERS enhancement of the condensed gold particles. Put the Au nanoparticles in the test tube, and centrifugal for three time (ten minutes for one time), then drop the third left lower concentration of Au nanoparticles on the glassy carbon electrode by pipette gun. Dry it in vacuum envirement and it can be seen that there is a layer of yellow golden on the electrode. If there is not enough Au on the glassy carbon electrode, repeat it. We have dropped Au nanoparticles of different size on the glassy carbon electrode (50nm, 80nm, 115nm, 130nm, 160nm). Detect SERS effect of the pyridine signal molecule adsorbed on the prepared electron. We found that 130nm have the strongest SERS effect. From 50nm to 130nm the SERS effect increase, from 130nm to 160nm the SERS effect decrease. Secondly, deposit different monolayer (ML) transition metals on the strongest SERS Au nanoparticles modifying electron by constant current deposition method. The deposited monolayer is 1.5ML, 5ML, 10ML, 20ML, 40ML. Using cyclic voltammetry method to detect the deposition of transition metal whether present needle. However, we discovered even the thinnest transition metal (1.5ML) present"no needle", so all of it presents no needle. At last, detect the SERS effect using pyridine as signal molecule which is adsorbed on different thickness monolayer. The experiment result is that with the Pd thickness increase the SERS effect decrease. 1.5ML of transition metal Pd presents the strongest SERS effect.