Solvent‐Free Synthesis of S,N‐Doped Carbon Dots for Extended Visible‐Light‐Induced Oxidase‐Mimicking Activities and Antimicrobial Applications

Abstract

Photo-oxidase nanozymes are emerging enzyme-mimicking materials that produce reactive oxygen species (ROS) upon light illumination and subsequently catalyze the oxidation of the substrate. Carbon dots are promising photo-oxidase nanozymes due to their biocompatibility and straightforward synthesis. Carbon dot-based photo-oxidase nanozymes become active for ROS generation under UV or blue light illumination. In this work, sulfur and nitrogen doped carbon dots (S,N-CDs) were synthesized by solvent-free, microwave assisted technique. We demonstrated that sulfur, nitrogen doping of carbon dots (band gap of 2.11 eV) has enabled photo-oxidation of 3,3,5,5'tetramethylbenzidine (TMB) with extended visible light (up to 525 nm) excitation at pH 4. The photo-oxidase activities by S,N-CDs produce Michaelis-Menten constant (K m ) of 1.18 mM and the maximum initial velocity (V max ) as 4.66 × 10 À 8 Ms À 1 , under 525 nm illumination. Furthermore, visible light illumination can also induce bactericidal activities with growth inhibition of Escherichia coli (E. coli). These results demonstrate that S,N-CDs can increase intracellular ROS in the presence of LED light illumination.

Rapid Pathogen Purge by Photosensitive Arginine–Riboflavin Carbon Dots without Toxicity

“…Arg CDs were synthesized using arginine (Arg) as a nitrogen source and citric acid as a carbon source based on our earlier report [16,17]. Following our previous work, Arg and citric acid solution at a 3:1 weight ratio was mixed and placed in a microwave for 3 min to prepare Arg CDs.…”

“…The great fluorescence intensity of CDs makes them excellent antimicrobial materials under light treatment with their light-activated reactive oxygen species (ROS) production property inducing toxicity against pathogenic organisms. The produced ROS species by photosensitive CDs oxidize some significant biomacromolecules, including proteins, nucleic acids, and lipids, engendering cytotoxicity and cell wall damage to pathogenic organisms [15][16][17][18].…”

Recent advances in photo‐responsive carbon dots for tumor therapy

“…However, CDs with photocatalytic properties require more in‐depth research and application in the field of tumor treatment. Many CDs exhibit excellent photocatalytic properties, but they are only used in fields such as organic dye degradation or in vitro cell research, and their application in vivo tumor treatment has not been well developed [52,120–126] In addition to their photothermal, photodynamic, and photocatalytic properties, CDs often exhibit other beneficial properties for tumor therapy, such as active/passive tumor targeting, easy surface modification, etc.…”

“…However, CDs with photocatalytic properties require more in‐depth research and application in the field of tumor treatment. Many CDs exhibit excellent photocatalytic properties, but they are only used in fields such as organic dye degradation or in vitro cell research, and their application in vivo tumor treatment has not been well developed [52,120–126] …”

A novel GO hoisted SnO2–BiOBr bifunctional catalyst for the remediation of organic dyes under illumination by visible light and electrocatalytic water splitting

“…28 The limited surface area of SnO 2 –BiOBr can be a drawback as it provides fewer active sites for photocatalytic and electrocatalytic reactions. 67 As a result, doping GO into semiconductors like SnO 2 and BiOBr may get over their inherent constraints and increase their photocatalytic performance and water splitting in concerted ways. 19,29…”