Microwave-assisted synthesis of multifunctional fluorescent carbon quantum dots from A4/B2 polyamidation monomer sets

Carbon quantum dots (CQDs) are becoming a desirable alternative to metal-based QDs due to their high biocompatibility, low toxicity, ease of preparation, and unique photophysical properties. In the present study, a simple microwave-assisted synthesis using a domestic oven has been adopted to produce multifunctional CQDs from the ethlyenediaminetetraacetic acid (EDTA) and 4, 7, 10-trioxa-1, 13-tridecanediamine (TTDDA) monomers. The molecular surface of the prepared CQDs is composed of hyperbranched polyamides obtained from the polymerization reaction of both EDTA and TTDDA. The controlled functionalities and chemical structures of the molecular surface of CQDs are attained by varying the initial feed ratio of EDTA and TTDDA from 1:1 to 1:2, 1:3, 1:4, 1:5, and 3:1. The T-richCD3 (EDTA: TTDDA = 1:4) with highest mass yield of 25 wt% exhibited five-folds higher photoluminescence quantum yield (PLQY) (53.3%) compared to E-richCD1 (EDTA: TTDDA = 3:1). All synthesized CQDs revealed good sensitivity and selectivity to a Cu2+ ion that is prone to cause different neurodegenerative diseases and obstruct many biological activities, while the sensitivity increased with the decrease in EDTA to TTDDA ratio. The zebrafish model has been used to demonstrate the toxicity, adverse effects, transport, and biocompatibility of CQDs. At higher concentrations (1.0 mg/mL), the T-richCDs exhibited superior cell viability than the E-richCDs for Madin-Darby Canine Kidney (MDCK) and human breast cancer MDA-MB-231 (MDAMB) cells. Because of the excellent down conversion fluorescence ability, T-richCD3 were employed as luminescent down-shifting (LDS) layer in CuInSe 2 solar cell to enhance its performance.