Synthesis, Silica Coating And Catalytic Properties Of Multi-scale Gold Nanoparticles

Recently, metal nanopartic les represented by go ld nanopartic les become ahotspot, due to excelle nt phys ical, che mical properties and considerab leprospects in catalys is, sensing, bio logical probes, vivo ima ging and other fie lds.By us ing a variety of a nalys is techniques suc h as a transmiss ion e lectronmicroscope (TEM), UV-vis ib le absorptio n spectra (UV-vis), atomic forcemicroscopy (AFM), fluorescence spectroscopy methods, we study the synthesisof different scales of oil-solub le and water-solub le go ld nanopartic les, coatedwith silica and its catalytic performance.As the gold nanopartic les have typ ical size effect, its catalytic perfor manceis c losely re lated to partic le size. We synthesize oil-solub le and water solub legold na noparticles by Stucky method and Frens method respective ly, andsystematic study the effect of synthes is conditio n, such as temperature, solventratio for oil-solub le na noparticles and the growth steps for the water-solub lenanopartic les, on the shape, size, monodispersity and the corresponding opticalproperties by refine the reaction conditions.The results indicate that the size of the as-prepared oil-solub le go ldnanopartic les are located in the quantum scale. The dia meter of the go ldnanopartic les could be increased from3nm to7nm by tuning the temperature.Increasing temperature will not only increase the size of the resulting go ldnanopartic les, but also increase uniformity. Increasing polarity of the solvent canreduce the size of the as-prepared gold nanoparticles, ultimate ly achieve thetransition to gold nanoclusters with photoluminescence property. The size of thewater-solub le gold nanopartic les increases with an increase in growth steps. Thesize of the gold nanoparticles is controllable fro m a few nanometers to severaltens of nanometers or greater.In order to increase stability and controllability of go ld nanopartic les duringthe catalytic reaction, the various types of go ld nanoparticles are coated withSiO2by St ber method. We achieve the regulation of the shell thickness and thenumbers of the partic les in the she ll, and reveal the effect of the amount ofammonia and TEOS on the formed core-shell structure. In order to achieve theuniform silica coating of single gold nanopartic le, the amo unt of ammonia andTEOS should be optimized simulta neously. The thickness of s ilica shell does notreduce monotonically reduce the amount of TEOS while mainta ining the thickness of coating is not uniform.Reaction of the reductio n of p-nitrophenol by sodium borohydride ischoosed as the detection foundation. We study the catalytic properties of go ldnanopartic les of before and after silica coating in the rea ction, revea l the effectof a number of factors on the cata lytic rate， such as orders of additives,amounts of gold partic les sol, dia meter of go ld nanopartic les and so on. Theresults ind icate that catalytic reaction rate will be significantly accelerate byimproving the d ispersib ility of gold nanoparticles, increasing the dosage of go ldand selecting the appropriate dia meter of gold core. Compared to the pre-coatedgold nanopartic les, the solution stability, dispersion and controllab ility aresignificantly improved by silica coating.