Biomass-derived carbon quantum dots via continuous hydrothermal flow synthesis for nano-sensing applications Kiem Nguyen, Ioan-Alexandru Baragau, Tariq Sajjad, Suela Kellici London South Bank University, UK Carbon quantum dots (CQDs) derived from biomass, which is considered to be a green approach for nanomaterial synthesis, [1] often exhibit poor optical characteristics, and have low photoluminescence quantum yield (PLQY). This research utilised an eco-friendly, cost-effective, continuous hydrothermal flow synthesis (CHFS) process to produce efficient nitrogen-doped carbon quantum dots (N-CQDs) from biomass precursors (glucose and ammonia). Notably, the CHFS allows engineering of nanoparticles and their properties for specific functions. [2-4] The optical properties of CHFS derived CQDs were optimised by varying the concentrations of nitrogen dopant precursor (ammonia). To investigate the source of the optical enhancement, a variety of characterisation techniques were employed. Our optimised N-CQDs demonstrated significant enhancement in optical properties with a PLQY of 9.6% when compared to undoped glucose-CQDs which has PLQY of <1%. The N-CQDs were applied as a nano-sensor for highly toxic chromium (VI) ions and efficient photoluminescence (PL) quenching was observed. Hence, our results (supported by a variety of characterisation techniques), revealed that the N-doping process has changed the overall electronic structure of N-CQDs. This leads to enhancement of their optical properties and their overall performance as a nano-sensor. References 1. Hu, B., Wang, K., Wu, L., Yu, S.H., Antonietti, M. and Titirici, M.M., 2010. Engineering carbon materials from the hydrothermal carbonization process of biomass. Advanced Materials , 22 (7), pp.813-828 2. Kellici, S., Acord, J., Moore, K.E., Power, N.P., Middelkoop, V., Morgan, D.J., Heil, T., Coppo, P., Baragau, I.A. and Raston, C.L., 2018. Continuous hydrothermal flow synthesis of graphene quantum dots. Reaction Chemistry & Engineering , 3 (6), pp.949-958. 3. Baragau, I.A., Lu, Z., Power, N.P., Morgan, D.J., Bowen, J., Diaz, P. and Kellici, S., 2021. Continuous hydrothermal flow synthesis of S-functionalised carbon quantum dots for enhanced oil recovery. Chemical Engineering Journal , 405 , pp.126631. 4. Baragau, I.A., Power, N.P., Morgan, D.J., Heil, T., Lobo, R.A., Roberts, C.S., Titirici, M.M., Dunn, S. and Kellici, S., 2020. Continuous hydrothermal flow synthesis of blue-luminescent, excitation-independent nitrogen-doped carbon quantum dots as nanosensors. Journal of Materials Chemistry A , 8 (6), pp.3270-3279.
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