Facile Synthesis of High-Loading Cu Single-Atom Nanozyme for Total Antioxidant Capacity Sensing

Abstract

Single-atom catalysts (SACs) with atomically dispersed active sites and maximum atomic utilization efficiency provide new opportunities to develop high-performance nanozymes. However, the preparation of SACs with a high metal content still faces serious challenges. Herein, we report a pyrolysis method for achieving a Cu single-atom catalyst (Cu-SAC) on nitrogen-doped carbon with a Cu loading of 7.98 wt %. Isolated Cu atoms with Cu–N3–C coordination were confirmed by spherical aberration-corrected transmission electron microscopy and X-ray absorption spectroscopy. The synthesized Cu-SAC displayed outstanding peroxidase-like activity by effectively catalyzing the reaction between 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2 to show a blue color. Based on the inhibition effect on the oxidation of TMB by ascorbic acid (AA), a colorimetric assay for AA was established with a limit of detection (LOD) of 0.63 μM. Furthermore, the total antioxidant capacities (TACs) of practical samples including vitamin C tablets, commercial beverages, and fresh fruit were successfully detected by the proposed colorimetric assay. This study provided a facile method for the preparation of high-metal-loading SACs, which exhibited high enzymatic properties with promising applications in food and drug safety.

Visual Sensor Array for Multiple Aromatic Amines via Specific Ascorbic Acid Oxidase Mimic Triggered Schiff-Base Chemistry

“…The high-resolution spectrum of O 1s showed a new peak at 530.9 eV, which was attributed to the Cu–O bond (Figure E) . Similarly, the high-resolution spectrum of N 1s at 400.6 eV was attributed to the Cu–N bond (Figure F) . The results indicated that the Cu 2+ bonded with Trp through Cu–O and Cu–N bonds .…”

Gold Nanobipyramid-Based Photothermal Sensors for the Portable Evaluation of Total Antioxidant Capacity

“…Because of their simplicity and portability, colorimetric sensors offer a more appealing alternative, enabling target analysis through observable color changes. However, colorimetric approaches only provide the qualitative or semiquantitative analysis of target concentrations perceptible to the naked eye, with quantitative analyses still reliant on ultraviolet–visible (UV–vis) absorption spectrometry. − Because of increasing demand for on-site quantitative analysis, the conversion of TAC information into easily measurable signals has emerged as an important research focus.…”

MnOx In Situ Growth-Induced Luminescence and Oxidase-Like Feature Bimodulation of CePO4:Tb Nanorods: Toward Ascorbic Acid-Related Bioanalysis in a “One-Stone-Two-Birds” Manner

“…Nanozymes, that is, nanomaterials with intrinsic enzyme-like catalytic activity, attract widespread attention for their merits over natural enzymes, such as tunable activity, environmental tolerance, and easy synthesis and storage. − Given these advantages, nanozymes have been implemented in several fields. Especially in the bioanalytical field, nanozymes with oxidoreductase-like activity are gradually replacing natural enzymes (like horseradish peroxidase) in the development of optical analytical methods. , Among these nanozyme-based optical sensors, colorimetric detection depending on the nanozyme-catalyzed oxidation of chromogenic substrates is widely studied due to its inherent virtues of simplicity, rapidness, and low cost. − However, most colorimetric sensors are based on a single colorimetric or fluorescent signal output, susceptible to outside interference (redox substances, color distractors etc.…”