One-step preparation of N-doped grapheme quantum dots with high quantum yield for bioimaging and highly sensitive electrochemical detection of isoniazid.

Conventional techniques for synthesizing GQDs have a poor quantum yield (QY) that restricts their biological applications. Herein, we present a rapid, cost-effective and high quantum yield synthesis of nitrogen-doped graphene quantum dots (N-GQDs) through a scientific microwave reactor. The reaction parameters like microwave irradiation time, temperature, precursor concentration and pressure were optimized for achieving high quantum yield. The prepared N-GQDs exhibit bright blue fluorescence and excitation independent emission property with a quantum yield of 42.81%. In-vivo investigations on C. elegans revealed that the as-prepared N-GQDs are exceptionally biocompatible and maintain the normal physiological functioning of the primary and secondary targeted organs in nematodes. The synergetic effect of intestinal barrier and defecation behavior mitigates N-GQDs translocation into reproductive organs of nematode. In addition, the N-GQDs modified GCE was tested for electrochemical sensing characteristics towards the anti-tuberculosis drug isoniazid (INZ). The N-GQDs showed appreciable electrocatalytic performance towards INZ with high sensitivity (3.76 μA μM cm). The differential pulse voltammetry (DPV) analysis of N-GQDs exhibit a lower detection limit of 10.91 nM for INZ. The N-GQDs modified sensor exhibits good reproducibility, excellent anti-interference ability and excellent analytical performance for INZ in real samples like human blood serum and urine samples.