Polyoxometalate Nanostructures Decorated with CuO Nanoparticles for Sensing Ascorbic Acid and Fe²⁺ Ions

Abstract

Nanozymes are considered as ideal substitutes for nature enzymes; however, the enzyme activity and the relevant detection sensitivity in actual samples still need to be further improved. Here, a nanomaterial of CuO NP-POM composed of polyoxometalate (POM) decorated with copper oxide nanoparticles (CuO NPs), which possessed tetraenzyme mimetic activities including oxidase (OXD)-, peroxidase (POD)-, catalase (CAT)-, and glutathione peroxidase (GPx)-like activities was developed. The corresponding catalytic performances, mechanisms, and kinetics were systematically investigated. Based on the POD-like activity of a CuO NP-POM nanocomposite, a colorimetric sensing platform for ascorbic acid (AA) was built with the detection limit of 15 nM, depending on the fact that AA can efficiently react with the oxidation product of TMB, which was catalyzed by CuO NP-POM on the basis of the POD-like activity. A simple fluorometric sensor for Fe 2+ was developed on the basis of the GPx-like activity of CuO NP-POM with the detection limit of 8.0 nM. CuO NP-POM can weaken the fluorescence of the isoindole derivative derived from GSH and o-phthalaldehyde (OPA) due to the excellent GPx-like activity, which can accelerate the catalysis of GSH into GSSG in the presence of H 2 O 2 . However, in the presence of Fe 2+ , the fluorescence was recovered owing to the fact that the Fenton reaction between Fe 2+ and H 2 O 2 could reduce GSSG into GSH. The proposed colorimetric and fluorometric sensors have been successfully applied in detecting AA and Fe 2+ in several food and biological samples. This work not only developed a nanocomposite with enhanced multinanozyme activity but also offered rapidly detection methods for the analysis of specific targets via the special nanozyme activities.

Porous, Oxygen Vacancy Enhanced CeO2–x Microspheres with Efficient Enzyme-Mimetic and Photothermal Properties

“…Here, K m and − r m values of HRP and catalase are also included. As seen here, the maximum substrate consumption rates determined for oxidase-, peroxidase-, and catalase-like activities of g-CeO 2– x microspheres are much higher with respect to those of previously synthesized nanozymes. ,,,,− Owing to the maximum substrate consumption rates obtained with g-CeO 2– x microspheres are too high, as expected, K m values of g-CeO 2– x microspheres are also higher. It should be noted that the maximum substrate consumption rates obtained for the oxidase-, peroxidase-, and catalase-like activities of g-CeO 2– x microspheres are higher with respect to those of plain CeO 2 microspheres (Table ).…”

Multi-Mimic Activities of Co3O4 Nanopolyhedrons and Application in Regulating the Content of Intracellular Hydrogen Peroxide/Oxygen

“…and then react with aminobenzene sulfonic acid and naphthalamine to produce a pink azo dye, the characteristic peak of UV at 530 nm (A 530nm ) was used for identification. 48 As shown in Figure S4A, in the presence of Co S3A), a strong absorption peak at 652 nm can be observed. Also, O 2 had little influence on the POD-like enzyme activity (Figure S3B).…”

“…To confirm the intermediates produced during the OXD-like catalytic process, a typical colorimetric reaction was applied. Because O 2 ·– can react with hydroxylamine to produce NO 2 – and then react with aminobenzene sulfonic acid and naphthalamine to produce a pink azo dye, the characteristic peak of UV at 530 nm ( A 530nm ) was used for identification . As shown in Figure S4A, in the presence of Co 3 O 4 nanopolyhedrons, A 530nm appeared, which suggested that O 2 ·– was produced in the reaction process.…”

Titania (TiO2)/silica (SiO2) nanospheres or NSs amalgamated on a pencil graphite electrode to sensel-ascorbic acid electrochemically and augmented NSs for antimicrobial behaviour

“…2–6 Further, the inadequate or high concentration of ascorbic acid can cause various diseases, mainly digestive and gastric issues, anemia, mental disorder, cancers, AIDS, infertility, common cold and respiratory infections. 5,7–10 Further, AA detection is very difficult due to its low stability and rapidly oxidizes to dehydroascorbic acid. 3 Therefore, the proper detection and quantification of ascorbic acid in food industry and pharmaceutical compounds is necessary to maintain normal AA concentration (∼11.4 to 28.4 μM) in human serum.…”