The photochemistry section covers a wide range of interests on excited state processes. Photophysical methodologies, such as excited state decays, are being used to study conformational relaxation in conjugated oligomers and polymers, and also to learn how to control photochemical behaviour of photoiniators and photochromics. Full photophysical characterization has been made of various photoswitches. Insights have been obtained on how to modify photoisomer stability in photochromic benzopyrans. Acrylate copolymers have been developed for light-sensitive contact lenses. Optoelectronic properties of cyano-terminated oligothiophenes have been determined. Optical sensors have been developed in collaboration with other groups within the Coimbra Chemistry Centre. Systems include chlorins for oxygen sensing, metalloporphyrin triads for amine sensing, chemosensors for metal detection, conjugated polymers for explosives sensing and block copolymers for DNA assay. Combined NMR, ab initio, DFT and photophysical methods have provided information on metal ion sensors with fluorescent organic ligands. In turn, electric properties were also calculated for hyperpolarizability "record-breaking" molecules by electronic structure methods. Direct and catalysed photrodegradation of pollutants, such as pesticides and pharmaceuticals are being studied in terms of both reaction mechanisms and development of novel methods for mineralization. These photochemically active materials are being incorporated into mesoporous matrices for enhanced stability. Microalgal photofixation of industrial carbon dioxide emissions is being studied as a route to novel value added materials. Photophysical studies are being used to unveil the secrets of Molecules with Colour and History.