The Institute of chemistry, Chinese Academy of Sciences has made a series of progress in solid-state fluorescent materials based on cellulose and their applications

Cellulose is the natural polymer with the largest reserves in nature It has the advantages of wide sources, huge reserves, renewable, complete biodegradation and good biocompatibility It is considered as the "inexhaustible and inexhaustible" energy and chemical raw materials to meet the future sustainable development of human society There are abundant hydroxyl groups on the cellulose polymer chain periodically, which have excellent chemical modifiability Through the homogeneous reaction of cellulose, different functional groups can be introduced into the cellulose chain, thus giving cellulose new properties It is an effective way to realize the high value utilization of cellulose (mater Chem Front., 2017, 1, 1273) With the support of NSFC, the Ministry of science and technology and the Chinese Academy of Sciences, the research group of Zhang Jun, researcher of the Institute of chemistry of the Chinese Academy of Sciences, has carried out in-depth research on homogeneous chemical reaction of cellulose and design and synthesis of new functional materials of cellulose in recent years The common fluorescent molecules with aggregation induced quenching (ACQ) effect are linked to the main chain of cellulose by chemical bonding using the hydroxyl groups which are easy to modify on cellulose Through the "anchoring" and "dilution" effects of polymer chains and the synergistic effect of electrostatic repulsion between groups, the ACQ effect of fluorescent molecules is effectively overcome, and the cellulose based solid fluorescent materials containing ACQ fluorescent molecules are obtained (adv optical mater., 2016, 4, 2044) Based on the above strategies, the research group has synthesized three kinds of cellulose based solid-state fluorescent materials, respectively Combining the fluorescence resonance energy transfer effect and the principle of three primary colors, a new type of dynamic full-color solid-state fluorescent material that is easy to print is obtained by simply mixing and controlling the proportion (adv funct Mater., 2018, 28, 1703548) By linking the fluorescent groups with responsive properties to the cellulose polymer chain, the research team can also significantly enhance its molecular recognition ability, so as to obtain a new type of fluorescent probe and portable test paper that are super sensitive to metal ions and acid-base (acspappl Mater Interfaces, 2018, 10, 2114; Analytical Chemistry, 2019, 91, 3085) In recent years, Zhang Jun's research team and Wang Shu's research team, the Key Laboratory of organic solid state institute, have cooperated to carry out the application research of cellulose based optical functional materials in the biomedical field, and made a series of progress For example, using several reactive hydroxyl groups on cellulose to chemically bond porphyrin and quaternary ammonium salt groups on cellulose molecular chain at the same time, a cellulose based antibacterial coating material (adv health mater., 2019, 8, e1801591) which is white light driven, highly effective in killing resistant bacteria and non-toxic is obtained Recently, they designed and synthesized a novel ratio type amine responsive cellulose based fluorescent material, and based on this, they proposed a visual method to monitor the freshness of seafood The fluorescein isothiocyanate (FITC) as indicator and protoporphyrin (PpIX) as internal standard are respectively covalently bonded to cellulose acetate (CA) molecular chain In this paper, CA FITC and Ca PpIX are simply mixed in proportion, and the solid-state fluorescent materials with tunable initial fluorescence are obtained The fluorescence emission intensity ratio of the material is linear with the logarithm of amine concentration (5-25000 ppm) At the same time, the fluorescence of the material changes from red to green, realizing the purpose of rapid, accurate and real-time visual monitoring of amine concentration in the environment This new cellulose based fluorescent material is simple to prepare, has good stability, reversible response, biodegradability and processing performance, and can be prepared into a variety of material forms, such as ink, coating, transparent flexible film and nanofiber film The nanofiber film of the ratio type amine response cellulose based fluorescent material was used as an indicator label to successfully realize the in-situ visual monitoring of freshness of seafood (such as shrimp) The research results were recently published in nature communications (nature communications, 2019, 10, 795).