Colorimetric Assay Conversion to Highly Sensitive Electrochemical Assay for Bimodal Detection of Arsenate Based on Cobalt Oxyhydroxide Nanozyme via Arsenate Absorption

Abstract

This study reports a novel and convenient bimodal method for label-free and signal-off detection of arsenate in environmental samples. Cobalt oxyhydroxide (CoOOH) nanoflakes with facile preparation and intrinsic peroxidase-like activity as nanozyme can efficiently catalyze the conversion of chromogenic substrate such as 2,2′-azinobis­(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with the presence of H2O2 into green-colored oxidation products. CoOOH nanoflakes can specifically bind with arsenate via electrostatic attraction and As–O bond interaction, which gives rise to inhibition of the peroxidase-like activity of CoOOH. Thus, through arsenate specific inhibition of CoOOH nanozyme toward ABTS catalysis, a simple colorimetric method was developed for arsenate detection with a detection limit of 3.72 ppb. Based on the system of CoOOH nanozyme and ABTS substrate, this colorimetric method can be converted into an electrochemical sensor for arsenate assay by the utilization of CoOOH nanoflake-modified electrode. The electrochemical measurement can be realized by chronoamperometry, which showed more sensitive and a lower limit of detection as low as 56.1 ppt. The applicability of this bimodal method was demonstrated by measuring arsenate and total arsenic in different real samples such as natural waters and soil extracted solutions, and the results are of satisfactory accuracy as confirmed by inductively coupled plasma mass spectrometry analysis. The bimodal strategy offers obvious advantages including a label-free step, convenient operation, on-site assay, low cost, and high sensitivity, which is promising for reliable detection of arsenate and total arsenic in environmental samples.

Enhanced Thermometric Sensor for Arsenate Analysis Based on Dual Temperature Readout Signaling Strategy

“…First, the morphologies of the obtained CoOOH nanoflakes were demonstrated by TEM. As shown in Figure a, the obtained uniform two-dimensional CoOOH nanoflakes are hexagonal ultrathin nanosheets with an average thickness of ∼7.5 nm and an average size of ∼120 nm, which is very similar to that in the previous reports . DLS (SI Figure S3) shows that the size distributions of the obtained CoOOH nanoflakes have good monodispersion and that the diameter agreed with the size measured from TEM.…”

Recent Advances in Colorimetric Detection of Arsenic Using Metal-Based Nanoparticles

“…Cobalt oxyhydroxide (CoOOH) nanoflakes showed significant arsenic detection efficiency in addition to iron oxide [ 78 ]. CoOOH nanoflakes show peroxidase-like activity, which produces a green-colored oxidation product in the presence of H 2 O 2 and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS).…”

“…Interestingly, the green color was not observed in the presence of arsenic, as arsenic binds with CoOOH through electrostatic attraction and forms an As–O bond to inhibit peroxidase-like activity. Therefore, it can effectively detect arsenic in water using the colorimetric method with a LOD of 3.72 ppb [ 78 ].…”

Hexagonal CoOOH Nanoflakes Synthesized From Three-Dimensional Cellulose Membrane Matrix With Enhanced Detection of Ascorbic Acid

“…For CoCl 2 solution, it had a maximum absorption peak at 510 nm, while the CoOOH nano akes had a maximum absorption peak at 413 nm. (Wen et al 2019) The color of CoCl 2 solution also changed from pink to brown during the conversion of CoCl 2 to CoOOH nano akes.…”