Carbon dots (CDs) show extensive potential in various fields such as sensing, bioimaging, catalysis, medicine, optoelectronics, and drug delivery due to their unique properties, that is, low cytotoxicity, cytocompatibility, water-solubility, multicolor wavelength tuned emission, photo-stability, easy modification, strong chemical inertness, etc. This review article especially focuses on the recent advancement (2015–2022) in the green synthesis of CDs, their application in metal ions sensing and microbial bioimaging, detection, and viability studies as well as their applications in pathogenic control and plant growth promotion.

Azobenzene derivatives have become one of the most famous photoresponsive chromophores in the past few decades for their reversible molecular switches upon the irradiation of actinic light. To meet the ever-increasing requirements for applications in materials science, biomedicine, and light-driven devices, it is usually necessary to adjust their photochemical property from the molecular level by changing the substituents on the benzene rings of azobenzene groups. Among the diverse azobenzene derivatives, azopyridine combines the photoresponsive feature of azobenzene groups and the supramolecular function of pyridyl moieties in one molecule. This unique feature provides pH-responsiveness and hydrogen/halogen/coordination binding sites in the same chromophore, paving a new way to prepare multi-functional responsive materials through non-covalent interactions and reversible chemical reactions. This review summarizes the photochemical and photophysical properties of azopyridine derivatives in supramolecular states (e.g., hydrogen/halogen bonding, coordination interactions, and quaternization reactions) and illustrates their applications from photoresponsive liquid crystals to light-driven devices. We hope this review can highlight azopyridine as one more versatile candidate molecule for designing novel photoresponsive materials towards light-driven applications.

With the learning from living protein polymerization in nature, achieving living/controlled supramolecular assembly of biopolymers such as proteins in vitro is a longstanding challenge for material design. Herein, we provide a thiol-regulated interfacial protein aggregation (TRIPA) for unfolded protein systems with typical living polymerization features. By triggering globule proteins into the unfolded state through a reversible exchange reaction of disulfide bonds and sulfhydryl agents (R-SH), protein monomers are partially unfolded and assembled at the air–water/solid–water interface (AWI/SWI) through the entropy-driven adsorption and conformation transition. The process could be well repeated over time to form a two-dimensional (2D) nanofilm at the interface by following a pathway of monomer-oligomer-2D assembly. Similar to living polymerization, the film thickness exhibited a linear increase with the assembly conversion ratio of the monomers. With the stepwise addition of native protein into the reaction system, the thickness periodically increased in a linear manner. Such living/controlled supramolecular polymerization (LCSP) of protein at the interface leads to the synthesis of a nanofilm with well-defined flat morphology, ultrahigh modulus, and nano- to macroscale controlled thickness. The resultant protein nanofilm could then attach onto a variety of flexible and rigid material surfaces to produce a stable structural color coating. Compelling evidence in the present work thus underlines a demonstration of LCSP of biopolymers in vitro. It may hold a solid impact by opening a window for living/controlled polymerization of versatile biospecies such as proteins, saccharides, nucleic acids, and cells.