Recent theoretical studies on geometric and chemical modification strategies, band engineering, and charge carrier dynamics of TiO₂nanoparticles are discussed.

An indole conjugated coumarin 1 for KCN chemodosimeter has been prepared and displayed considerable dual changes in both absorption (blue-shift) and emission (turn-on) bands exclusively for KCN. DFT/TDDFT calculations support that the fluorescence enhancement of 1-KCN is mainly due to blocking of the ICT process.

A rationally designed, coumarin-based fluorescent sensor imino-coumarin (IC) displays high selectivity for Cu²⁺ over a variety of competing metal ions in aqueous solution with a significant fluorescence increase. DFT/TDDFT calculations support that the fluorescence ‘turn-on’ of IC originates from blocking the electron transfer of the nitrogen lone pair upon complexation with Cu²⁺. IC was successfully applied to microscopic imaging for detection of Cu²⁺ in LLC-MK2 cells (in vitro) and several living organs (in vivo).