CoO Nanotubes Loaded on Graphene and Modified with Porphyrin Moieties for Colorimetric Sensing of Dopamine

Abstract

In this paper, CoO nanotubes loaded on the surface of graphene oxide (GO) have been first modified by 5,10,15,20tetrakis(4-carboxyl phenyl)porphyrin (Por) by a hydrothermal method. Por/CoO/GO exhibits excellent peroxidase-like activity, which is evaluated by virtue of the chromogenic substrate 3,3,5,5tetramethylbenzidine (TMB). In the presence of H 2 O 2 , Por/CoO/ GO nanoperoxidase can rapidly catalyze colorless TMB to be oxidized into blue oxTMB, which is distinguished visually in 1 min. The experimental data including fluorescence and electrochemistry data and radical scavengers confirm that the catalytic mechanism of Por/CoO/GO is ascribed to electron transfer between substrates, as well as produced active species (h + and • O 2 − ). Based on Por/ CoO/GO nanoperoxidase, a fast colorimetric sensor for H 2 O 2 has been established for a wide range of concentrations (0.1−3 mM) with a lower limit of detection (LOD = 0.2942 mM). Notably, the blue color of oxTMB can be gradually faded in the presence of dopamine (DA) with various concentrations. Thus, a fast, cheap, and convenient colorimetric sensor has been designed to monitor DA in a wide range (0.2−10 μM) with a much lower LOD (0.1391 μM). The Por/CoO/GO-based colorimetric platform has been validated by determining DA in real serum samples.

Novel Thermal Decomposition Method for the Synthesis of Iron‐doped SnS2 Nanoparticles and Studies on their Peroxidase‐like Activity

“…Under strong acidic conditions, the amino groups of TMB get protonated and they are not able to donate their lone pair of electrons to the catalyst. [73,74] Thus, the catalytic activity of the catalyst is decreased. When pH > 5, number of OH À ions in the solution increases which leads to decomposition of H 2 O 2 .…”

“…When pH > 5, number of OH À ions in the solution increases which leads to decomposition of H 2 O 2 . [73] The generation of hydroxyl radicals decreases beyond pH = 5 and the catalytic activity is thus decreased. leaching on the peroxidase-like activity of Sn 1-x Fe x S 2 nanoparticles (SF-0.20).…”

“…It is proposed in the present study that hydroxyl radicals and superoxide radicals act as active species during the peroxidase-like activity of iron doped SnS 2 nanoparticles. [73] Isopropyl alcohol (IPA) and p-benzoquinone (PBQ) were used as the radical scavengers to understand the role of hydroxyl radicals and superoxide radicals, respectively. [73] For this, 300 μL of 6 mM TMB solution, 30 μL of H 2 O 2 (100 mM), 30 μL of catalyst dispersion (2 mg SF-0.20 in 1 mL water followed by sonication) and 0.5 mL of scavenger (10 mM) were added to 3.0 mL of actetic acid-acetate buffer (0.1 M, pH = 5) taken in a cuvette.…”

CoO Nanozymes with Multiple Catalytic Activities Regulate Atopic Dermatitis

“…However, in previous studies, CoO nanoparticles have often been doped with other substances as part of the catalyst. Few studies have used CoO nanoparticles alone as catalysts to participate in the reaction, and most of the related enzyme-like catalytic activities were peroxidase-like or oxidase-like [53][54][55][56]. In this paper, we prepared CoO nanoparticles with a "cluster" morphology, and the morphology of CoO nanoparticles can be changed by changing the reaction temperature.…”

“…Co 3 O 4 nanozymes are widely used in cancer therapy, antiviral, magnetic resonance imaging (MRI), and targeted drug delivery [49][50][51]. At present, many studies have reported that CoO nanozymes with POD-like activity prepared by a variety of synthetic methods have extremely high application value in biosensing [52][53][54][55]; CoO nanostructures have the advantages of high stability, large specific surface area, and easy redox [56,57]. However, pure CoO nanoparticles show poor electrical conductivity and tend to self-aggregate to cover active sites.…”