Sustainable fabrication of fluorescent carbon quantum dots as an optical amplifier in modern agriculture, anti-counterfeiting, food packing and intelligent pH detection

Abstract

Carbon quantum dots (CQDs) have received a great deal of attention due to their distinctive luminescent features and exciting potential applications in the fields of agronomy, enhanced anti-counterfeiting, drug tracking and intelligent sensing and detection. The focus of the current effort is on easily transforming toxic, non-biodegradable waste expanded polystyrene foam (WEPS) into extremely luminescent CQDs and investigating their various applications. As a nano-priming agent for Cajanus cajan (L.), the green pigeon pea (GPP), WEPS derived CQDs are used. The outcomes showed that seed priming had beneficial effects at all CQDs concentrations (100–900 mg/L), including accelerated seed germination rate, increased shoot and root length, augmented root vigour, higher chlorophyll content and biomass accumulation in comparison to the control groups. The most crucial data coding can be protected under 365 nm UV light using the optimized CQDs concentration (700 mg/L) blue fluorescent ink. In addition, a straightforward sensing platform with high sensitivity and selectivity is needed for the detection of dual metal ions, as well as one with a "turn-on and turn-off" fluorescence (FL) response. Additionally, a composite film containing well-dispersed CQDs (700 mg/L) in polyvinyl alcohol and strong hydrogen-bond interaction is successfully developed to alleviate the FL quenching caused by CQD aggregation. The resulting film had extraordinary FL performance, good mechanical flexibility and high transparency (transmittance of 90 %). Even more remarkably, this luminescent film showed sensitive pH responsiveness, signifying that when pH is stimulated, the FL intensity changed. A smart pH-detector based on this luminescent film is logically created as a proof-of-concept for real-time sensing and detection of pH changes in human sweat. These results show that WEPS derived CQDs have enormous potential as nano-priming agents for seed germination, seedling development, anti-counterfeiting ink, food packaging and intelligent pH-detector in wearable, real-time health monitoring.