Characteristic UV luminescence from sol-gel silica coatings

Photoluminescence (PL) from silica coatings prepared via sol-gel under different conditions and using different precursors are investigated. Upon excitation with 3.85 eV (322 nm) light, the coatings prepared in air show a PL spectrum dominated by a peak at 3.35 eV (370 nm) with a shoulder at about 2.95 eV (similar to 420 nm). After heat treatments under reducing conditions or when the coatings are prepared in an oxygen-controlled atmosphere, the PL spectrum at 3.35 eV exhibits a significant decrease in intensity. Results are discussed on the basis of silanol groups at superficial regions, oxygen-rich defects and the presence of residual organic matter in the coatings. (C) 2000 Elsevier Science B.V. All rights reserved.