Deciphering a Nanocarbon‐Based Artificial Peroxidase: Chemical Identification of the Catalytically Active and Substrate‐Binding Sites on Graphene Quantum Dots

Abstract

The design and construction of efficient artificial enzymes is highly desirable. Recent studies have demonstrated that a series of carbon nanomaterials possess intrinsic peroxidase activity. Among them, graphene quantum dots (GQDs) have a high enzymatic activity. However, the catalytic mechanism remains unclear. Therefore, in this report, we chose to decipher their peroxidase activity. By selectively deactivating the ketonic carbonyl, carboxylic, or hydroxy groups and investigating the catalytic activities of these GQD derivatives, we obtained evidence that the -C=O groups were the catalytically active sites, whereas the O=C-O- groups acted as substrate-binding sites, and -C-OH groups can inhibit the activity. These results were corroborated by theoretical studies. This work should not only enhance our understanding of nanocarbon-based artificial enzymes, but also facilitate the design and construction of other types of target-specific artificial enzymes.

Low-Cost Nanocarbon-Based Peroxidases from Graphite and Carbon Fibers

“…As shown in Figure 5a,c,e, the absorbance keep increasing with the increase of H 2 O 2 concentration and the color reaction is obvious, which may be observed by naked eyes. As can be seen in Figure 5b It has been reported that the presence of functional group could affect peroxidase-like activity of carbon nanomaterials [30]. The ketonic carbonyl groups act as the catalytically active sites and the carboxylic groups serve as the substrate-binding sites.…”

“…According to the deconvoluted XPS spectra of C 1s in Figure 3, there were C−C, C−O and −COOH on Carbon nanomaterials-1 surface, and C=O on Carbon nanomaterials-2 and Carbon nanomaterials-3 surface. The carbonyl group can act as substrate binding sites [30], which are beneficial to peroxidase like catalytic reaction. This can prove that the catalytic activity of Carbon nanomaterials-2 and Carbon nanomaterials-3 is better than that of Carbon nanomaterials-1.…”

“…The possible reason is that the surface of the Carbon nanomaterials-2 contains more ketonic carbonyl groups and carboxylic groups than that of Carbon nanomaterials-1 (Figure 3). It has been reported that the presence of functional group could affect peroxidase-like activity of carbon nanomaterials [30]. The ketonic carbonyl groups act as the catalytically active sites and the carboxylic groups serve as the substrate-binding sites.…”

Unveiling the active sites of graphene-catalyzed peroxymonosulfate activation

“…In addition to defective sites and edges, the versatile oxygen functional groups on graphene were also well demonstrated to serve as the active sites in heterogeneous catalysis [13,15,39]. In preliminary studies, we discovered that graphene oxide with a high oxygen-doping level (over 35 at.%) can hardly activate PMS, whereas the activity was significantly improved after eliminating the excess oxygen functional groups through thermal (or hydrothermal) reduction process [22,23].…”

“…Loh's group performed in situ Fourier transform infrared (FTIR) and electron spin resonance (ESR) spectroscopies to elucidate that the boundary defects (edges and vacancies) of base-treated graphene oxide (ba-GO) can effectively activate oxygen molecules to generate superoxide radicals, whereas the carboxylic groups M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 4 functionalized at the edging defects are capable of synergistically trapping the reactants via the localized unpaired electrons [13]. Besides, chemical titration was adopted as a fantastic strategy to selectively block either ketonic carbonyl (C=O), hydroxyl (-OH), or carboxylic groups (-COOH) on the carbon catalysts to probe the effect of the functional groups on catalytic reactions, and kenotic groups were discovered to account for the intrinsic activity of decomposition of H 2 O 2 and oxidative dehydrogenation (ODH) reactions [14][15][16]. Deng et al…”