Green Synthesis of Multifunctional Carbon Dots with Antibacterial Activities

Abstract

Carbon dots (CDs) were obtained from medicinal turmeric leaves (<i>Curcuma longa</i>) by a facile one-step hydrothermal method and evaluated for their bactericidal activities against two gram-negative; <i>Escherichia coli</i>, <i>Klebsiella pneumoniae</i>, and two gram-positive counterparts; <i>Staphylococcus aureus</i>, <i>S. epidermidis</i>. The CDs exhibited spherical shapes with a mean size of 2.6 nm. The fluorescence spectra of CDs revealed intense fluorescence at λ_ex/_em = 362/429 nm with a bright blue color in an aqueous solution. The CDs showed strong photostability under various environmental conditions (pH, salt, and UV-radiation). The complete bactericidal potency of CDs was 0.25 mg/mL for <i>E.coli</i> and <i>S. aureus</i> after 8 h of exposure, while for <i>K. pneumoniae</i>, and <i>S. epidermidis</i>, the CDs at 0.5 mg/mL good antibacterial effect within 8 h and complete eradication after 24 h of exposure is observed. The release of reactive oxygen species played a crucial role in the death of the bacterial cell. The present study provides a strategy for the preparation of CDs from a medicinal plant and their potential antibacterial activities against four common contagious pathogens.