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.
