Designing of biomass-derived carbon quantum dots@polyvinyl alcohol film with excellent fluorescent performance and pH-responsiveness for intelligent detection

Carbon quantum dots (CQDs) have attracted extensive attentions because of their unique luminescent properties and promising prospects in intelligent sensing and detection. However, the increasing environmental pollution caused by chemical substances for synthesizing illuminants limits their expansion in practical applications. Herein, we employed a facile and green synthesis strategy to extract biomass-derived CQDs from natural lignocellulose. The obtained CQD nanoparticles not only showed excellent fluorescent performance, but also posed desirable environmental-friendly characteristic. Moreover, to relieve the fluorescence quenching induced by CQDs aggregation, the well-dispersed CQDs@polyvinyl alcohol (CQDs@PVA) composite film with strong hydrogen-bond interaction was successfully fabricated. The resultant film exhibited high transparency (transmittance of 88%), excellent mechanical flexibility (tensile strength of 39.7 MPa and elongation at break of 453%), and exceptional fluorescence performance. The high concentrated emitting centered in 502 nm emission wavelength was realized in a wide excitation range of 350 ~ 420 nm with high-stability turquoise fluorescence. More impressively, this fluorescent film demonstrated a sensitive pH-responsiveness, i.e., the fluorescent intensity varied upon pH stimulation. As a proof-of-concept, an intelligent pH-detector based on this fluorescent film was rationally designed for real-time sensing and detection of pH variation in human sweat during movement processing. From fundamental materials to desired applications, this study not only enriches the synthetic strategy of illuminants in an environment-friendly manner, but also paves the way for further applications in wearable, real-time health monitoring.

Automated summary

This study developed an environmentally-friendly method to extract biomass-derived carbon quantum dots (CQDs) from natural lignocellulose and successfully fabricated CQDs@PVA composite film with excellent fluorescent performance and desirable environmental-friendly characteristic. The film showed high transparency, mechanical flexibility, and stable fluorescence. It also exhibited sensitive pH-responsiveness, making it suitable for real-time sensing and detection of pH variation in human sweat during movement processing.