Optical properties of TiO2 and disperse red-19 composite

• DR-19 and TiO2 composite was fabricated with two step synthesis.
• The absorption band of the composite shifted toward red.
• All the PL peaks of the composite were shifted toward red compared with those of pure materials.
• Relatively large emission peak shift of the ICPDRTiO2 could be due to the FRET.

Characteristic absorption and photoluminescence (PL) of TiO2 and disperse red-19 (DR-19) composite have been investigated. Two step synthetic processes were employed to incorporate the DR-19 to the TiO2 sol–gel. Firstly, urethane bonds between the DR-19 (OH) and 3-isocyanatopropyl triethoxysilane (ICPTES, NCO) were fabricated (ICPDR) prior incorporation to the TiO2 sol–gel. Secondary, hydrolysis of the ethoxy group from the ICPDR and condensation reaction between silanol groups from ICPDR and TiO2 sol–gel were performed by adding ICPDR to the TiO2 sol–gel and aged for several days at room temperature (ICPDRTiO2). There was no absorption peak shift with increasing the DR-19 concentration in methanol. However, UV–visible absorption band was shifted toward red approximately 0.09 eV for the ICPDRTiO2 film, which indicated the formation of dimmer or more aggregates. The PL peaks of ICPDRTiO2 were red-shifted compared with DR-19 in methanol (0.12 eV) and ICPDR film (0.09 eV). The relatively large emission peak shift toward red could be due to the fluorescence resonance energy transfer (FRET) between DR-19 and TiO2 in ICPDRTiO2 matrix.