SiO_2干凝胶光致发光性质的研究

Photoluminescence of SiO_2 Xerogels

以硅酸酯Si(OC2 H5) 4 (TEOS)和H2 N(CH2 ) 3 Si(OC2 H5) 3 (APS)为主要原料 ,在不同的条件下 (催化剂、热处理、高分子添加剂 )通过溶胶 凝胶法制备了一系列不同组成的SiO2 干凝胶 ,并通过发光光谱对所得的干凝胶进行了表征。在长波 36 5nm紫外光激发下 ,干凝胶样品都显示出较强的蓝光发射 ,但其发光波长和发光强度随着组成和处理条件的不同而有明显的差异。APS与有机酸 (醋酸 )和无机酸 (盐酸、硝酸、硫酸 )所得SiO2 干凝胶的结果为IHAc(λmax =4 32nm ) >IHNO3(λmax=4 4 1nm )≈IH2 SO4 (λmax =4 2 6nm ) IHCl(λmax =4 4 2nm) ,并且在APS与HCl作用所得的干凝胶样品中 ,明显存在两种发光中心 (其发射峰值波长分别位于4 4 2nm和 4 87nm ,相应的激发波长分别位于 36 5nm和 2 73nm)。一定量的TEOS与APS相混合并与HAc作用不仅有利于干凝胶样品的迅速形成 ,而且有利于提高其发光强度 :当R(APS/TEOS +TEOS摩尔比 ) =0 5～ 0 7时 ,样品发光较强 ;在 0 .5摩尔APS +0 5摩尔TEOS与 3摩尔HAc的反应过程中加入高分子添加剂聚乙二醇 (PEG5 0 0 0、PE10 0 0 0 ) ,所得样品的发光强度先随着PEG的加入量的增加而变强 ,然后随着PEG的加入量的增加而变弱 ,PEG5 0 0 0和PEG10 0 0 0的最佳掺杂量分别为 0 8g和

The sol gel process, which is mainly based on an inorganic polymerization reaction, is a chemical synthesis method initially used for the preparation of inorganic materials such as glasses and ceramics. The mild characteristics offered by the sol gel process allow the introduction of organic molecules inside an inorganic network. Inorganic and organic components can then be mixed at the nanometric scale, in virtually any ratio leading to so called hybrid organic inorganic nanocomposites. These hybrids are extremely versatile in their composition, processing and the related optical and mechanical properties. Sol gel derived silica gel(aerosol or serogel) is of great importance based on its wide applications in optics,catalysts,sensors and solar energy collectors.Organic dyes and rare earth ions have been incorporated into the microporous silica gel,which is generally considered to possess an optically inert framework. However ,the sol gel derived silica gel is not optically inert,but optically active,i.e.,it shows lminescence usder UV excitation.Of particular interest and importance is that, a new class of stable and efficient white photoluminescent silicate materials has been obtained from an alkoxysilane and a carboxylic acid through sol gel route.Other related report is the sol gel derived undoped usea cross linked organic inorgels which display strong blue light emission. In this paper,undoped SiO\-2 xerogels were prepared by the sol gel method under various preparation conditions and compositions by using tetracthoxysilane(TEOS)and (3 aminopropyl) triethoxysilane(APS),orgaic acid (CH 3COOH)and in orgagic acids (HCl,HNO 3,H 2SO 4) as the main precursor.Luminescence spectra were used to characterize the resulted SiO 2 xerogels.Under the excitation of 365nm all the xerogels exhibit strong luminescence in the blue region,but the emission intensity and position depend on the starting precureor compositions to a large extent.Suitable amount of polyethylene glycol(PEG500 and PEG10000)in the SiO 2 xerogels can enhance the emssion intensity.Additionally,the emission intensity of the hybrid xerogels in creases with heat treatment temperature in the range of ambient to 200℃, and vacuum condition is also able to enhance the emission intensity.