Synthesis And Optical Characteristic Studies Of Silica Nanospheres

In this article we develops the St ber process to synthesis monodisperse silicananospheres and hollow spheres, which can apply for the flourescent material,insulating material, nano light emitting devices owing to it’s excellent luminescentproperties.Silica nanoparticles are prepared in the mix solution of amino acids andtetraethyl orthosilicate (TEOS) and the size of silica is adjusted by changing thesolution concentration or hydrolysis conditions. The as-prepared silica products havea narrow particle size distribution and regular arrengement. While increasing theaccession amount of TEOS, the size of the silica nanoparticles gradually increase,increase of the accession amount of L-lysine leads to the decreases of silicananoparticles’ size. In the meanwhile, the hydrolysis temperature has a heavy influenton the particle size: they show a very strong positive correlation. On the basis ofparticle size study, we find the best synthesis technique to synthesize the silica withminimum diameter of18nm. Under this circumstance, the photoluminescence ofsilica particles were measured and we found that there is a strong emission peak atabout420nm originated from the structure defect for the not annealed silica samples.After thermal treated, the photoluminescence weakens considerately. Throughanalyzing mechanism of silica products, we suggest that L-lysine exerts an importantrole in the growth process of silica nanospheres. It can keep a constant pH value,facilitate TEOS slowly hydrolysis, and finally control the size of silica nanospheres.Stable amorphous silica hollow spheres with the outer diameter aout15~200nmand thickness of20~25nm are prepared in the mix solution of poly acrylic acid (PAA)and TEOS. The magnetic stirring rate, the concentration of soft template PAA and theamount of TEOS have been inversgated. The results indicate that increasing themagnetic stirring rate narrows the size distribution of as-prepared silica sample. Ifmagnetic stirring rate reaches1300r/min, the homogeneous size distribution of silicais prepared. The morphology of silica hollow spheres is adjusted via varyingcomposition of PAA and ammonia. When keeping the concentration of PAA at0.05g/ml, the porous structure silica is prepared. At this case, the wall thickness of hollowspheres gradually increases in the range of20to25nm with the increase of TEOSfrom1.5to2g. Different from the nano spheres, there are on main emission at about 350nm for the hollow silica spheres. This peak shifts to long wavelength directionwith the increase of magnetic stirring rate. At the same time, decreasing theconcentration of PAA, the peak shifts short wavelength direction with intensityincreasing continuously.