SiO_2包覆对ZnS纳米材料发光的增强机制

Mechanism of the enhanced fluorescence of SiO_2-coated ZnS nanoparticles

为了明确团聚现象及表面性质对Zn S纳米材料发光性质的影响,采用Si O2对Zn S材料进行了表面修饰,并对Zn S及Zn S/Si O2复合材料的光学性质进行对比研究。采用吸收光谱分析了包覆前后光吸收性质的差异,发现Si O2包覆后Zn S纳米材料的带边由333 nm红移至360 nm。为了研究Zn S纳米材料与Zn S/Si O2纳米复合材料的光发射性质,分别对含纳米材料的水溶液样品及粉末样品的发光光谱进行了采集。对比研究的结果表明,Si O2包覆后Zn S纳米材料在蓝紫光区的发光得到了明显增强。以氙灯作为激发光源所获得荧光光谱显示Zn S/Si O2粉末样品发光的积分强度增大为原来的17.5倍,但相同条件下针对溶液样品的测试结果显示其发光强度只增大了1.1倍,这种增强可用Si O2的存在抑制了Zn S纳米粒子间的团聚来解释,且这一推断由325 nm紫外激光激发下获得的光致发光数据进行了验证。

In order to investigate the influence of aggregation and surface effect on the optical properties of ZnS nanoparticles, SiO2 is used to modify the surface of ZnS nanopartieles. The optical properties of the synthe- sized ZnS and ZnS/SiO2 nanopartieles are both studied for making a comparison. According to the absorption spectra recorded by an ultraviolet-visible spectrophotometer, the band gap edge red-shifts from 333 nm to 360 nm. To analyze the emission properties, the fluorescence spectra of the solution and the powders contai- ning the ZnS or ZnS/SiO2 nanoparticles are both collected. It is found that the light emission of the ZnS nanop- articles in the violet to blue region is enhanced obviously when SiO2 is introduced. When the samples are exci- tated by a xenon lamp, the integrated fluorescence intensity of the ZnS/SiO2 nanoparticles is enhanced by 17.5 times. However, a much smaller enhancement is found in the measurement for the solution samples. The fluorescence is only 1.1 times higher after coating ZnS nanoparticles by SiO2. The inhibition of the aggregation between the ZnS nanoparticles by the SiO2 coated layer is supposed to be responsible for the enhancement, which is confirmed by the photoluminescence data where a 325 nm He-Cd laser is used as the excitation source.