Ultrafine nitrogen-doped graphene quantum dot structure and antibacterial activities against Bacillus subtilis 3610

The potential of green synthesis of quantum dots (QDs) has been proficiently examined for future design and clinical applications. This research reported that GQDs and N-doped GQDs were synthesized and tested for their antibacterial activity toward Bacillus subtilis (B. subtilis) 3610. The GQDs were prepared by a pyrolysis method as nitrogen-free GQDs (N0) and considered as a green way to synthesize QDs. N-doped GQDs were synthesized at the different ratios of urea noted as N1, N2, N3, and N4-doped GQDs respectively via hydrothermal method. The particle size of the as-synthesized materials was found to change from 2 nm (N0, N1, and N2-doped GQDs) to 1.5 nm (N3 and N4-doped GQDs). The crystalline structures of N1 to N4 from XRD patterns reveal the carbogenic core. The optical properties of N-doped GQDs at 260 nm (C--C) and 340 nm (C--O) were observed in the UV/vis spectra. The amines and amides were confirmed for nitrogen-bonding functionalities of N-doped GQDs by FTIR and XPS measurements. The lowest concentration of the antibacterial of N-doped GQDs was spotted on the N2 and N3 to have inhibitory effects at 100 and 200 ppm. The minimum inhibitory concentration (MIC) of the antibacterial of N-doped GQDs was spotted on the N2 and N3 to have inhibitory effects at 100 and 200 ppm and N4 was found to show the lowest bacterial cell growth. Moreover, this work demonstrates a cost-effective way of producing N-doped GQDs by hydrothermal method for antibacterial activity of surface chemistry (pyrroles).