Protein-Rich Marine Spirulina for Synthesizing Biocompatible Carbon Dots with High Quantum Yield for Fluorescent yarns

Abstract

Carbon dots (CDs) are fluorescent carbon nanomaterials that can be widely used in multiple areas as an optical functional material. Compared to commercial chemicals used to synthesize CDs, biomass offers environmental friendliness and biocompatibility, especially for biomedical or human-contact applications. However, biomass-derived CDs often suffer from low quantum yields (QY) and inconsistent quality due to compositional complexity. In this study, we demonstrate a new strategy utilizing Spirulina, a marine microalga which obtains high content phycocyanin as the sustainable nitrogen-rich precursor for high-performance CDs production. By refining spirulina to extract high-purity phycocyanin and incorporating urea doping, we achieved nitrogen-enriched CDs (PU-CDs) with a QY of 20.4%, which was 1.3-fold and 2.4-fold higher than those from purified phycocyanin and raw spirulina, respectively; the QY remained stable in 6 time repliacate experiments with the standard deviation value is 1.14. Meanwhile, the PU-CDs have excellent biocompatibility and low cytotoxicity (93% cell viability at 500 μg/mL), which are suitable for bio-applications. As a proof-of-concept, the as-prepared PU-CDs were successfully integrated into nylon fibers via dyeing or electrospinning approach. PU-CDs in yarns demonstrating strong fluorescence under UV light and exceptional photostability (retaining 92.4% intensity after 20 h). This work highlights a reproducible , eco-friendly approach to synthesizing biomass-based CDs for advanced anti-counterfeiting textiles, addressing key challenges in precursor purity and performance.