One-step synthesis of size-tunable gold nanoparticles immobilized on chitin nanofibrils via green pathway and their potential applications

Chitin is the second most abundant natural biopolymer on earth after cellulose with vast application potential. In the present work, the chitin nanofibrils (CNFs) fabricated through a simple physical method were validated, for the first time, to be capable of simultaneously generating and immobilizing gold nanoparticles (AuNPs) via a one-step synthesis. In our findings, CNFs acted as both reductant for the in-situ synthesis of AuNPs and stabilizer for the generated AuNPs, due to the reducibility and chelation capacity of the amino groups on chitin. When the CNFs concentration varied from 2.0 to 7.1 mg/mL, well dispersed AuNPs with controllable diameters (7–30 nm) were synthesized and immobilized along the chitin nanofibrils, showing high stability for at least three months. This new pathway was an environmentally friendly process, and even generated small AuNPs with diameters of less than 10 nm. Moreover, the CNF-AuNPs displayed peroxidase mimic behavior and catalyzed the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to produce a blue solution. When combined with glucose oxidase, the CNF-AuNPs could sensitively detect glucose with a limit of 94.5 nM, which was highly specific, safe, cheap, and visible with low contamination. This work has put forward a facile "green" pathway for the heterogeneous synthesis of the size controllable and stable AuNPs immobilized on the biocompatible chitin nanofibrils and their potential in biosensing were evaluated.