Microwave-assisted green synthesis of monodispersed carbon micro-spheres and their antibacterial activity

[Display omitted] •Rapid green synthesis of carbon spheres (CSs) from ascorbic acid (AA).•Synthesized CSs exhibit uniform morphology with abundant oxygen functional groups.•Effects of the AA concentration, reaction time, and temperature on the CSs were studied.•Dimensions of the formed CSs were tunable by altering the experimental conditions.•The formed microspheres show strong biocidal activity against E. coli and S. aureus. Well-dispersed mono-carbon microspheres were synthesized via the hydrothermal carbonization of ascorbic acid (AA) using a microwave reactor without adding any catalyst. The synthesized materials were characterized by various microscopic and spectroscopic techniques (e.g., SEM, TEM, XRD, Raman, XPS, EDX, and FTIR spectroscopy), showing that the formed carbon spheres (CSs) exhibited uniform morphology and surface structure with abundant oxygen functional groups. The dimension of the formed CSs could be easily tuned by altering the AA concentration, reaction time, and temperature. A mechanism for the formation of the CSs was proposed, and their antibacterial activities were also investigated against two bacterial strains, showing the inhibition rate of 94% for E. coli and 100% for S. aureus. This biocidal activity was achieved with the pure CSs produced from the inexpensive AA (Vitamin C) via a rapid green process without any further surface modification or doping, thus promising for myriad surface coating, medical and environmental applications.