Homogeneously Synchronous Degradation of Chitin into Carbon Dots and Organic Acids in Aqueous Solution

Biomass polysaccharides are natural biopolymers and are considered as energy storage structural materials and suppliers in animals and plants. Among various biomass polysaccharides, chitin is the second most important biomass resource, which can be regarded as an alternative raw material for fine chemicals, especially in its homogeneous solution. Herein, a homogeneous aqueous solution of potassium hydroxide/urea was used as the solvent to dissolve chitin at first under a low-temperature pretreatment, which was then degraded by a hydrothermal process. Both small molecular organic acids and carbon dots (CDs) can be formed simultaneously. The maximum yield of organic compounds (oxalic acid, malonic acid, formic acid, lactic acid, acetic acid, and pyrrole) is 68.45%, while the main product is acetic acid with yield of 31.02%. Synchronously, up to 6% CDs can be obtained, which showed excellent fluorescent properties and promising applications in the detection of iron ions. This work provides an overview of the homogeneous conversion of chitin into an aqueous solution, from which both CDs and organic compounds can be obtained in a simple and green method.