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 photo-bleaching 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.