Fluorescent Aerogels Based on Chemical Crosslinking between Nanocellulose and Carbon Dots for Optical Sensor

Generally produced by solvent sublimation via freeze-drying or critical point drying treatment, nanocellulose-based aerogels have attracted considerable interest in offering the features such as sustainability, available surface reactivity, lightweight, high porosity, and specific surface area. This study presents a novel strategy for the preparation of fluorescent aerogels based on covalent linkage between the natural skeleton of a cellulose nanofibril (CNF) and a fluorescent carbon dot (CD). The maximum CD grafting content on the CNF-based aerogel was 113 mg g^-1, providing bright blue fluorescence under ultraviolet radiation with a high fluorescence quantum yield of 26.2%. Besides improved mechanical properties with a 360% increase in compression strength, the covalently bonded CD nanoparticle further serves as a structural stabilizer to endow the characteristic of shape recovery in water for the fabricated fluorescent aerogel. Finally, this aerogel displays high sensitivity and selection on the recognition of NO _x and aldehyde species, which is studied for the detection of glutaraldehyde at ultralow concentrations (ppm) in water. Using the innovation of an organic solvent-free route and avoiding the toxic crosslinking reagents or fluorescent sources, the CNF/CD-based fluorescent aerogel developed in this study is a promising functional material for potential optical sensing application.