Enhancing Persistent Luminescence of Cellulose by Dehydration for Label-Free Time-Resolved Imaging

Organic persistent luminescence is usually emitted from synthesized materials containing π units (aromatic rings, double bonds, etc.). It is challenging but desirable to develop organic materials from renewable resources with tunable persistent luminescence to reduce environmental impact. Herein, we proposed an effective method to enhance the luminescence of cellulose, the most abundant natural renewable material free of π units. It was found that removing the crystal water in cellulose would increase the compactness of molecular packing and stabilize the hydroxyl clusters of polysaccharide chains, consequently leading to significant enhancement of phosphorescence with lifetime up to subseconds. This dehydration induced luminescence enhancement was found in not only purified cellulose but also cellulose-contained substances such as papers, cottons, and many other plant tissues. This indicated easier access to cellulose-based luminescence materials without chemical purification. In addition, label-free time-resolved luminescence imaging of plant tissues was achieved on a smartphone-based apparatus, since endogenous cellulose is distributed extensively in plants. Compared with synthetical luminophores, cellulose is a renewable and biodegradable source abundant in nature, not only readily available but also environmentally friendly. We believe this method may be used to develop other sustainable organic luminescence materials with a lack of π units for various optical applications.