Spectroscopic investigation of chemically doped metal cations in sol-gel glass.

摘要

The sol-gel process has been intensively investigated as a new and a promising method of silica glass synthesis. Unlike the conventional melting methods of glass production, the sol-gel process allows preparation of metal oxide-mixture silica glass at low temperatures with the precursor components mixed on the molecular level.; The work contained in this thesis focused on the use of sol-gel glass as a means to encapsulate organic and inorganic molecules to prepare novel materials that are utilized at the xerogel stage and are used for a variety of diagnostic applications.; The level of metal cation detection and the response time required for forming colored {dollar}rm Msp{lcub}n+{rcub}/EDTA{dollar} complexes in sol-gel matrix are at least an order of magnitude better than those in solution.; In sol-gel systems, not only by thermochemical means but also by dopants, a massive concentration of electron-hole carriers can be created at low temperatures. We utilized these electron-hole pairs for the reduction of (i) Eu{dollar}sp{lcub}3+{rcub}{dollar} to Eu{dollar}sp{lcub}2+{rcub}{dollar}, (ii) Cy{dollar}sp{lcub}6+{rcub}{dollar} to Cy{dollar}sp{lcub}3+{rcub}{dollar}. The electron-hole carrier emission in the Eu{dollar}sp{lcub}3+{rcub}{dollar} doped sol-gel-derived silica glass is observed. The sol-gel process is shown to be an effective surface to reduce Cr (VI) to Cr (III) by the e{dollar}sp{lcub}-{dollar}-h{dollar}sp{lcub}+{rcub}{dollar} carriers; a 90% conversion of Cr (VI) to Cr(III) was calculated.; Energy transfer between Ce{dollar}sp{lcub}3+{rcub}{dollar} and Tb{dollar}sp{lcub}3+{rcub}{dollar} in sol-gel glass at the xerogel stage is investigated using luminescence spectroscopy. The change in the emission intensity and the decay times of Tb{dollar}sp{lcub}3+{rcub}{dollar} ions behaving as donors caused by the coexistence of Ce{dollar}sp{lcub}3+{rcub}{dollar} behaving as acceptor is investigated.; In summary, the sol-gel glass serves as a solid support for reactive materials in which the dopant molecules are capable of responding chemically to the environment through the pore space. The defect sites generated during hydrolysis and condensation of silicon alkoxides could be utilized to reduce high-oxidation-state heavy metal ions to a stable low oxidation state that could be adapted to a variety of technologies. The optical transparency along with the homogeneity the sol-gel offers make it a proper host to investigate energy transfer between rare earth ions.