Extinction of photo-induced Ti3+ centres in titanium oxide gels and gel-based oxo-PHEMA hybrids

Extinction of photo-induced Ti3+ centres has been measured in titanium oxide gels and gel-based organic-inorganic hybrids by simultaneous absorption and EPR experiments. Despite of expected heterogeneous origin of the absorption band, the electronic traps population is found pure statistical: it can be characterised by effective extinction coefficients ε¯=780cm-1M-1 (gel) and ε¯=340cm-1M-1 (hybrid) in the maximum of the absorption continua, respectively, at 600 nm and 640 nm. Using these values, an extremely high concentration of long-lived trapped electron exceeding 1020 cm−3 has been evidenced in these materials.