Bacterial deactivation by using graphene quantum dot as an effective photodynamic therapy agent*

Antibiotics are commonly used in bacterial infection. However, the widespread use of antibiotics has resulted in the emergence of multidrug-resistant or pathogenic bacterial strains. Consequently, the need for developing new bactericidal materials and techniques arose. Photodynamic therapy (PDT) is proposed as an alternative approach. In PDT, light interacts with certain materials and chemicals to induce damage to bacteria. Graphene quantum dots (GQD) are one of the most promising antimicrobial agents since they possess high germicidal activity against a broad range of microbes. In our project, we aim to investigate an effective, inexpensive and available compound which will hold even higher antimicrobial activity and lower toxicity toward human blood. For this purposes, we used GQD and methylene blue (MB). GQDs were grown by focusing nanosecond laser pulses into benzene and were later combined with MB. The Gram-negative bacteria, Escherichia coli, and Gram-positive bacteria, Micrococcus luteus, were deactivated by GQD/MB. Detailed characterization was performed with transmission electron microscopy (TEM), scanning electron microscopy (SEM),UV-Visible (UV-Vis), and photoluminescence (PL) spectra.