Facile Access to Solid-State Carbon Dots with High Luminescence Efficiency and Excellent Formability via Cellulose Derivative Coatings

Carbon dots (CDs), which are one kind of novel fluorescent materials, exhibit benign biocompatibility, high photobleaching resistance, and easy processing; thus, they have attracted a lot of attention. However, the intrinsic self-aggregation of nanoscale-sized CDs leads to fluorescence quenching, thereby limiting their application in the solid state. In this work, we demonstrate an effective and universal method to obtain solid-state CDs with high luminescence efficiency and excellent formability. Taking advantage of the charged surfaces of most CDs, we utilize two types of eco-friendly cellulose derivatives with positive or negative charges to surround the CDs via electrostatic attractions. As a result, the particles of CDs have been isolated and their aggregation-induced quenching phenomenon has been inhibited. The obtained CDs@cellulose derivative powders show bright fluorescence and have a high fluorescence quantum yield (QY); for example, the QY of blue-emitting powder reaches up to 71.5%. Such a simple strategy is available for various CDs. More significantly, the excellent processability and formability of cellulose derivatives enable CDs@cellulose derivatives to be easily processed into films, coatings, and printing inks, providing a huge potential in eco-friendly solid-emitting devices and light-stable anticounterfeiting labels.