Characterization of Carbon Quantum Dots Synthesized from Vinasse and Date Seeds as Agro-industrial Wastes

Multifunctional carbon quantum dots (CQDs) were synthesized hydrothermally from vinasse (CQD-V) and date seeds (CQD-P) as wastes of bioethanol and date fruit processing industries, respectively. The particle size, morphological and structural characteristics, fluorescence properties, antioxidant and antimicrobial activity, and cytotoxicity of CQDs were investigated. Both CQDs had a narrow size distribution plot with an average particle size of 2.37 and 6.82 nm in CQD-P and CQD-V, respectively. The CQDs emitted intense green fluorescence under the excitation of UV light (380 nm). The quantum yield of CQD-V (20.64%) was higher than that of CQD-P (5.16%). However, transmission electron microscopy approved the formation of uniform spherical-shaped nanoparticles. The ATR-FTIR and EDX analyses confirmed the synthesis of naturally occurring N and P-doped CQDs from both precursors. The antioxidant power of CQDs-P (IC50 = 3.6 mg/mL) was stronger than that of CQDs-V (IC50 = 4.5 mg/mL). In addition, CQD-P represented antimicrobial performance on all microbial strains (Listeria monocytogenes, Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli) compared to CQD-V, with high activity on P. aeruginosa. The cytotoxicity of the synthesized CQDs on L929 cell lines was quite low, and they could be considered potentially non-toxic nanomaterials. This study demonstrated that the agro-industrial waste of vinasse and date seeds are excellent candidates for the synthesis of CQDs with high fluorescence activity and antioxidant potential, which could be suggested for a wide range of applications.