Selective Detection of Chloride ions by Graphene Quantum Dots: Potential Use as a Diagnostic Tool for Cystic Fibrosis

Abstract

Direct carbonization of citric acid (CA) has proved to be a facile bottom-up technique for making graphene quantum dots (GQD). In this work, the effect of synthesizing GQD by varying carbonizing temperatures and time and exploring their optical and fluorescence (FL) properties, were investigated. The best sample chosen was characterized using ultraviolet-visible spectrometry, fluorescence spectrometry, fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), zeta potential analysis and scanning electron microscopy (SEM). GQDs considered as a good sensing probe because of its low toxicity, high photoluminescence, water solubility and excellent photochemical properties. The fluorescence spectra of GQDs were used as a property of optical sensor for chloride ions. The FTIR analysis, XRD patterns and SEM micrographs confirmed the preparation of 12-15nm GQDs, which are amorphous in nature with the peak emission peak observed at 362nm, at an excitation wavelength of 370nm. The fluorescence quenching response of GQD with the Cl- ions, displayed a linearity up to 100mM with a correlation coefficient of 0.98, and the lowest detection limit of approximately 3mM. This range is optimal to be used as low-cost chloridometer, paving the way for point-of-care diagnostic systems of cystic fibrosis (CF) and routine health monitoring to assess dehydration in athletes.