Marine waste to blue economy innovation: synthesis and applications of crab-derived chitosan quantum dots for sustainable aquaculture

This study aimed to develop a sustainable method for synthesizing quantum dots (QDs) from crab-derived chitosan waste and evaluate their potential applications in marine environmental monitoring and aquaculture. We employed a microwave-assisted green synthesis protocol where chitosan extracted from local crab processing waste was dissolved in 1% acetic acid, subjected to microwave digestion (180 degrees C, 20 min), neutralized to pH 7, and purified through centrifugation, filtration, dialysis, and lyophilization at - 68 degrees C. Comprehensive characterization using multiple analytical techniques (AFM, FTIR, XRD, UV-Vis, photoluminescence) revealed QDs with uniform size distribution (2-4 nm), crystalline structure (62% crystallinity index), high quantum yield (46 +/- 3%), and exceptional stability in marine environments (87% fluorescence retention in 3.5% NaCl). The QDs demonstrated excellent shelf-life (> 90% activity after 6 months at 4 degrees C) and photostability (8% reduction after 6 h of continuous UV exposure). Performance testing confirmed their effectiveness for water quality monitoring (detection limits 0.5 mu M for Hg-2(+), 0.8 mu M for Pb-2(+)), antifouling applications (78% biofilm reduction), and pollutant remediation (adsorption capacities 187 mg/g for methylene blue, 142 mg/g for Cu-2(+)). We conclude that crab-derived chitosan QDs represent a viable circular economy approach to transform seafood industry waste into high-value nanomaterials with significant applications in sustainable aquaculture and marine environmental protection, supporting blue economy innovation through waste valorization while reducing environmental impact.