This study presents several new squarylium dyes derived from benzothiazole and benzoselenazole with several structural variations, namely the nature of the heteroaromatic ring and the length of the N,N′-dialkyl groups. Before being investigated in connection with their effect on living cells and/or tissues, these novel compounds were characterized, namely with respect to the determination of their main photophysical parameters. Therefore, a study of the ground state absorption, fluorescence emission (quantum yields and lifetimes) and singlet oxygen generation quantum yields was performed for all the compounds synthesized in order to evaluate their efficiency as photosensitizers. An increase of the alkyl chain length from ethyl to hexyl did not produce a clear change in the fluorescence quantum yields, showing no influence on the photoisomerization process. Heavy atom inclusion (Se instead of S) enhanced the singlet oxygen generation efficiency and decreased the intensity of the fluorescence emission. The external heavy atom effect (I⁻ as a counterion instead of CF₃SO₃ ⁻) produced a significant increase in the singlet oxygen formation quantum yield (about 20%). Transient absorption studies in aerated and oxygen free samples revealed that the photoisomerization process, which could compete with the triplet state formation for all dyes in solution, is a negligible pathway for the excited state deactivation, in accordance with the rigidity introduced by the squaric ring into the polymethine chain of the dye, both in chloroform and ethanol. However, in the case of the chloroform solution a new transient was detected in air equilibrated solutions, resulting from a reaction of the excited squarylium dye in the singlet state with CHCl₃˙, and assigned to the radical cation (SQ⁺˙) of the dye.

Micro/nanomotors represent a burgeoning field of research featuring small devices capable of autonomous movement in liquid environments through catalytic reactions and/or external stimuli. This review delves into recent advancements in light-driven semiconductor-based micro/nanomotors (LDSM), focusing on optimized syntheses, enhanced motion mechanisms, and emerging applications in the environmental and biomedical domains. The survey commences with a theoretical introduction to micromotors and their propulsion mechanisms, followed by an exploration of commonly studied LDSM, emphasizing their advantages. Critical properties affecting propulsion, such as surface features, morphology, and size, are presented alongside discussions on external conditions related to light sources and intensity, which are crucial for optimizing the propulsion speed. Each property is accompanied by a theoretical background and conclusions drawn up to 2018. The review further investigates recent adaptations of LDSM, uncovering underlying mechanisms and associated benefits. A brief discussion is included on potential synergistic effects between different external conditions, aiming to enhance efficiency—a relatively underexplored topic. In conclusion, the review outlines emerging applications in biomedicine and environmental monitoring/remediation resulting from recent LDSM research, highlighting the growing significance of this field. The comprehensive exploration of LDSM advancements provides valuable insights for researchers and practitioners seeking to leverage these innovative micro/nanomotors in diverse applications.

Recent advances (2020–2024) in visible light-driven motors to enhance pollutant photodegradation are reviewed. An overview of challenges and perspectives for future research is provided.