Fig. 40. (A) Fluorescence spectra of N-doped GQDs decorated with V₂O₅ nanosheets (N-GQD@V₂O₅) of cysteine in the concentration range of 0–125 μM. (B) The change of fluorescence intensity as a function of cysteine concentration in the range of 0–125 μM. The inset shows a linear relationship in the 0–15 μM concentration range. (C) Selectivity of the N-GQD@V₂O₅ biosensors in the presence of 22 common interfering electrolytes and biological analytes, including metal ions, inorganic salts, amino acids, sugar, reducing agents, proteins, and glucose oxidase (GOx). Reprinted with permission from ref. 750, A. B. Ganganboina, A. D. Chowdhury and R.-A. Doong, N-Doped Graphene Quantum Dots-Decorated V₂O₅ Nanosheet for Fluorescence Turn Off–On Detection of Cysteine, ACS Appl. Mater. Interfaces, 2017, 10, 614–624. Copyright© 2018 American Chemical Society.