Utilization of doped GQDs for ultrasensitive detection of catastrophic melamine: A new SERS platform

The detection and filtration of melamine in food products has become an emergence due to its harmful effect on humans. In present work, we have investigated the binding mechanism of melamine over carboxyl group edge-functionalized graphene quantum dots doped with oxygen and sulphur atoms (O-GQD and S-GQD). In order to monitor melamine, surface enhanced Raman scattering (SERS) is adopted which is an effective vibrational spectroscopic approach. Electronic and vibrational properties were analysed by means of well adapted density functional theory (DFT). The calculated adsorption energy of melamine over O-GQD and S-GQD is -1.18 and -0.15 eV respectively. The characteristic peak of melamine at 688 cm^-1 is in good agreement with previously reported experimental work and enhances by 348.4% in SERS spectra of Mel-O-GQD and 48% in SERS spectra of Mel-S-GQD. We have calculated the chemical enhancement factor (EF) for melamine over O-GQD and S-GQD and found the enhancement of 4.51 and 1.48 which is greater than melamine‑silver complexes. Our theoretical studies on SERS of melamine over O-GQD and S-GQD suggest that oxygen is a better candidate for SERS. Our work demonstrates that the graphene quantum dots are remarkable platforms for the detection of melamine.