Pulsed Laser Fragmentation Synthesis of Carbon Quantum Dots (Cqds) as Fluorescent Probes in Non-Enzymatic Glucose Detection

Pulsed laser fragmentation in liquid (PLFL) is one of the synthesis routes for producing high-purity carbon quantum dots (CQDs) with less toxic by-products in a straightforward system. However, there is only limited literature regarding the impact of laser-synthesized CQDs in biomedical applications. Herein, we explored their relevance by exploiting them as fluorescent probes in glucose sensing. The design of a fluorescent-based non-enzymatic glucose sensor was achieved by implementing CQDs as fluorescent probes and 3-aminophenylboronic acid (APBA) as glucose receptors. The CQDs were fabricated by PLFL through an Nd:YAG nanosecond laser, starting from the carbon black powder dispersion in ethanol. Then, a laser-assisted post-modification process with oxidizing acid was implemented to produce CQDs with excellent surface functionality and water dispersibility for easy functionalization. Owing to this further modification, this work also provides a novel method for producing water-soluble CQDs, which is difficult to achieve with this technique. Functionalizing these CQDs with APBA (CQDs-APBA) tunes their optical properties, resulting in a blue-shifted emission wavelength with a quantum yield of 35% and high photostability. The CQDs-APBA exhibited a turn-off response with the addition of glucose at increasing concentrations. The method has good sensitivity with a linear detection range of glucose with a concentration of 0.1 to 8mM and a low detection limit of 165 M. The applicability of the sensor to real analytes such as saliva obtained a satisfactory result with good reproducibility. This shows that CQDs synthesized from PLFL can also be an alternative fluorescent probe for fluorescent-based sensing applications.