Over recent years a biomedical application of nanomaterials based on carbon сan be considered as the emerging trend in science and technology. Due to their unique properties, materials are in the center of interest in many types of research focused on the sensor application, biomedicine, electronic materials and antibacterial materials. In this contribution, we developed the method for the design of carbon quantum dots with enhanced antibacterial activity via surface modification by 4-((triethylammonio)methyl)benzenediazonium ditosylate. The diazonium modification is a convenient and effective method for covalent attachment the required chemical group on CDs surface. Furthermore, the photodynamic properties of the CDs enhanced their bactericidal function under visible light irradiation. Therefore, the diazonium modification introduces the new considerable opportunities in the design of novel antimicrobial agents.