Preparation of Flower-like NiMnO₃ as Oxidase Mimetics for Colorimetric Detection of Hydroquinone

Abstract

Hierarchical flower-like NiMnO3 composites were facilely prepared by template-free hydrothermal treatment and calcined under mild conditions. Due to the strong ability to absorb oxygen, the as-prepared NiMnO3 composites were endowed with oxidase-like activity to catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue product without H2O2. Investigations on the mechanism indicate that oxidase-like activity of NiMnO3 composites originates from superoxide radical generation. The oxidase-like activity of the NiMnO3 composites was selectively inhibited by hydroquinone (HQ), which could reduce oxTMB to colorless TMB and could result in significant blue color fading. With increasing HQ concentration, the absorbance at 652 nm decreased gradually. A colorimetric method based on the NiMnO3 composite was established for the detection of the concentration of HQ in water and practical samples. This assay was simple, rapid, sensitive, and selective for detecting HQ with a low detection limit of 0.68 μM and an excellent linear range of 1–85 μM. This colorimetric sensor could be effectively applied for the detection of HQ in real water samples with RSD < 3.89% (n = 3) and Er < 2.17% (n = 3). The above results illustrated that the NiMnO3 composites have outstanding potential for application in environmental chemistry.

Au3+‐Functionalized UiO‐67 Metal‐Organic Framework Nanoparticles: O2•− and •OH Generating Nanozymes and Their Antibacterial Functions

“…•− and aerobic conditions, Equation (1) or of •OH upon reduction of H 2 O 2 , Equation ( 2). Accordingly, potential mechanistic cycles leading to the oxidation of TMB to TMB OX [40,85] by the respective ROS species summarized in Scheme 2, panels I,II, respectively. We note, however, that these mechanistic cycles are, at present suggested only by the inferred ROS intermediates generated by the catalyst, and further mechanistic evaluation of the processes is required.…”

Photoenhanced Oxidase–Peroxidase-like NiCo2O4@MnO2 Nanozymes for Colorimetric Detection of Hydroquinone

“…Based on the above results, the mechanism of the photoenhanced oxidase–peroxidase-like activity of NiCo 2 O 4 @MnO 2 microcubes can be elaborated as follows. Under dark conditions, like the classic ferric oxides, the Ni 3+ –Ni 2+ and Co 3+ –Co 2+ redox pairs act as electron mediators between the oxidizing agents (O 2 for oxidase mimics or H 2 O 2 for peroxidase mimics) and the reducing agent (TMB). , Namely, first O 2 (for oxidase, eq ) or H 2 O 2 (for peroxidase, eq ) oxidizes Ni 2+ and Co 2+ into Ni 3+ and Co 3+ , respectively, and simultaneously produce O 2 • – or •OH. In addition, under an acidic environment, O 2 • – can combine with H + to produce H 2 O 2 , generating more free radicals (eq ).…”

“…Bimetallic oxides had been extensively studied in the field of catalysis because of their tunable band gap and favorable electron-transfer performance. − Among them, NiCo 2 O 4 as a p-type semiconductor has significant advantages in promoting redox reactions due to the ion pairs of Ni 3+ /Ni 2+ and Co 3+ /Co 2+ , thus is known as a promising photocatalyst . NiCo 2 O 4 can be excited under visible light with a narrow band gap of ∼1.77 eV .…”

Motion-based phenol detection and degradation using 3D hierarchical AA-NiMn-CLDHs@HNTs-Ag nanomotors

“…The main redox pair Ni 2+ /Ni 3+ and Mn 3+ /Mn 4+ in AA-NiMn-CLDHs@HNTs-Ag nanomotors could catalyze H 2 O 2 to produce ˙OH in acidic medium (eqn ( 12)-( 14)). 56 Then phenol underwent the attack of ˙OH to form a series of intermediates, including dihydroxybenzoic acid, hydroxyquinone and hydroquinone. Next, these intermediates could further transform to succinic acid and muconic acid by capturing electrophilic ˙OH, and were finally mineralized into CO 2 and H 2 O (eqn ( 15)).…”