Visible-Light-Activated Bactericidal Functions of Carbon “Quantum” Dots

Abstract

Carbon dots, generally defined as small carbon nanoparticles with various surface passivation schemes, have emerged as a new class of quantum-dot-like nanomaterials, with their optical properties and photocatalytic functions resembling those typically found in conventional nanoscale semiconductors. In this work, carbon dots were evaluated for their photoinduced bactericidal functions, with the results suggesting that the dots were highly effective in bacteria-killing with visible-light illumination. In fact, the inhibition effect could be observed even simply under ambient room lighting conditions. Mechanistic implications of the results are discussed and so are opportunities in the further development of carbon dots into a new class of effective visible/natural light-responsible bactericidal agents for a variety of bacteria control applications.

Photoexcited state properties of carbon dots from thermally induced functionalization of carbon nanoparticles

“…Nevertheless, the visible light activation obviously made the PEI-carbon dots orders of magnitude more effective in the inhibition of B. subtilis . The bacteria inhibition may be attributed to photodynamic effect, 42 similar to what has been reported on the use of conventional semiconductor nanomaterials. 46–49 …”

“…From a somewhat different angle, the photoexcited state properties of carbon dots have been investigated by examining their photodynamic effects, 4 including for example the use of carbon dots for photoinduced killing of cancer cells 39–41 and also more recently for the visible light-driven bactericidal functions of the EDA-carbon dots. 42 Thus, the PEI-carbon dots obtained from the thermally induced functionalization were also evaluated for their ability with visible light activation to inhibit bacterial growth.…”

“…The results are generally consistent with those from similar studies in which carbon dots from other syntheses were used. 42 However, the apparently somewhat significant antibacterial effect of the PEI-carbon dots even in the absence of light activation is puzzling. In addition to experimental factors such as the high sensitivity of the bactericidal function of carbon dots to even minimal ambient light exposure, 42 the carbon nanoparticle-bound PEI species might have some surfactant-like properties, slightly inhibitive to the bacterial cell growth in the dark controls.…”

“…42 However, the apparently somewhat significant antibacterial effect of the PEI-carbon dots even in the absence of light activation is puzzling. In addition to experimental factors such as the high sensitivity of the bactericidal function of carbon dots to even minimal ambient light exposure, 42 the carbon nanoparticle-bound PEI species might have some surfactant-like properties, slightly inhibitive to the bacterial cell growth in the dark controls. Nevertheless, the visible light activation obviously made the PEI-carbon dots orders of magnitude more effective in the inhibition of B. subtilis .…”

Modified facile synthesis for quantitatively fluorescent carbon dots

“…3–10 A wide variety of potential technological applications of CDots have been pursued, including bioimaging and sensing, 11–14 drug and gene delivery, 15,16 photodynamic therapy, 17 bactericidal functions, 18 photocatalytic energy conversion, 8,19 and others. 20–23 Most of these targeted applications mimic, compete, and/or go beyond those already derived from conventional semiconductor quantum dots (QDs).…”