Currently, controlled release formulations (CRFs) of pesticides in response to biotic and/or abiotic stimuli have shown great potential for providing “on-demand” smart release of loaded active ingredients. In this study, amphiphilic biopolymers were prepared by introducing hydrophobic (7-diethylaminocoumarin-4-yl)methyl succinate (DEACMS) onto the main chain of hydrophilic carboxymethylchitosan (CMCS) via the formation of amide bonds which were able to self-assemble into spherical micelles in aqueous media and were utilized as light-responsive nanocarriers for the controlled release of pesticides. FTIR and NMR characterizations confirmed the successful synthesis of the CMCS-DEACMS conjugate. The critical micelle concentration (CMC) decreased with the increase in the substitution of DEACMS on CMCS, which ranged from 0.013 to 0.042 mg/mL. Upon irradiation under simulated sunlight, the hydrodynamic diameter, morphology, photophysical properties and photolysis were researched by means of dynamic light scattering (DLS), transmission electron microscopy (TEM), UV-vis absorption spectroscopy and fluorescence spectroscopy. Moreover, 2,4-dichlorophenoxyacetic acid (2,4-D) was used as a model pesticide and encapsulated into the CMCS-DEACMS micelles. In these micelle formulations, the release of 2,4-D was promoted upon simulated sunlight irradiation, during which the coumarin moieties were cleaved from the CMCS backbone, resulting in a shift of the hydrophilic–hydrophobic balance and destabilization of the micelles. Additionally, bioassay studies suggested that this 2,4-D contained which micelles showed good bioactivity on the target plant without harming the nontarget plant. Thereby, the light-responsive CMCS-DEACMS micelles bearing photocleavable coumarin moieties provide a smart delivery platform for agrochemicals.
The chemoselectivity of visible-light-induced coupling reactions of bromoalkynes with alcohols can be controlled by simple changes to the reaction atmosphere.
A convenient and practical synthetic route to α-ketoamides from bromoalkynes and anilines through phototriggered organic transformations via a C-N cross-coupling and an oxidation of C≡C was developed. The reaction could be furnished without an external photocatalyst at ambient conditions, and a wide range of α-ketoamides were obtained in good yields.
Chitin and chitosan are renewable biomass resources with macromolecular structures. Due to the strong intra-and inter-molecular hydrogen bonds, chitin and chitosan cannot be dissolved in water or traditional organic solvents, which tremendously limit their applications in many fields. Ionic liquid, as a novel green solvent, provides excellent solubility to chitin and chitosan. In this paper, the research progress on dissolution performance and dissolution mechanism of chitin and chitosan in ionic liquids is reviewed. Materials including fibers, films and gels created from the homogeneous solutions are summarized; meanwhile, the chemical derivatization of chitin and chitosan in ionic liquids are also discussed. Finally, the challenges and future development of ionic liquids in chitin and chitosan chemistry are proposed.
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