Electrochemical Detection of Trace Arsenic(III) by Nanocomposite of Nanorod-Like α-MnO₂Decorated with ∼5 nm Au Nanoparticles: Considering the Change of Arsenic Speciation

Abstract

It has been reported that the majority of groundwater shows weak alkaline in which the As(III) species would be present as neutral HAsO species and ionized HAsO species. However, as most reported previously, electrochemical detection of As(III) has been operated under acidic conditions and the nonionic As(III) (HAsO) is the dominant species. Therefore, considering the change of As(III) speciation in different pH conditions, to develop a reliable method for the detection of As(III) in alkaline media might be more meaningful for practical applications. Here, combined the multilayer adsorption of nanorod-like α-MnO with the excellent electrocatalytic ability of ∼5 nm Au nanoparticles (AuNPs), an efficient and ultrahigh anti-interference electrochemical detection of As(III) with AuNPs/α-MnO nanocomposite in alkaline media (nearly real water environment) was developed. Notably, we have provided a thorough electrochemical analytical investigation to confirm the advantage of As(III) detection in alkaline media. The system was evaluated by a series of interference tests, and no obvious interference from commonly coexisting substances (referring to the groundwater, Togtoh region, Inner Mongolia, China) was observed in alkaline media. Furthermore, electrodes robust stability and excellent reproducibility were obtained. Under the optimized conditions, the limit of detection (3σ method) toward As(III) was 0.019 ppb, and the obtained sensitivity was 16.268 ± 0.242 μA ppb cm. Finally, the proposed method has been successfully employed for detection of As(III) in a real water sample.

Electrochemical Detection of As (III) on a Manganese Oxide‐Ceria (Mn2O3/CeO2) Nanocube Modified Au Electrode

“…Other metal ions co‐existing in the real samples can be deposited and stripped with As (III) during electrochemical analysis, interfering with the As (III) signal. Cu (II) is the main ion causing interference with As (III) on gold due to a similar stripping potential and the tendency to form Cu‐As intermetallic compounds . We thus performed a Cu (II) ion interference study on Mn 2 O 3 /CeO 2 /Au, which is shown in Figure c.…”

“…Scheme A indicates the spontaneous adsorption of As (III) on the Mn 2 O 3 /CeO 2 /Au electrode . It is reported that the non‐ionic arsenic (H 3 AsO 3 ) is the dominant form at pH below 7 but applying more negative potential can induce further As (III) reduction . Thus it is postulated that there is a strong relationship between electrical conductivity of the materials and arsenic adsorption, i. e., arsenic adsorption ability can be improved due to enhancing conductivity of Mn 2 O 3 /CeO 2 /Au electrode at the pre‐deposition step (Scheme B).…”

“…Thus it is postulated that there is a strong relationship between electrical conductivity of the materials and arsenic adsorption, i. e., arsenic adsorption ability can be improved due to enhancing conductivity of Mn 2 O 3 /CeO 2 /Au electrode at the pre‐deposition step (Scheme B). On the basis of the improved adsorption ability of Mn 2 O 3 /CeO 2 /Au electrode, large quantities of As (III) can be first adsorbed on the surface of Mn 2 O 3 /CeO 2 nanocubes, and diffuse to the surface of the Au substrate, where As (III) reduction to As (0) occurs . During the stripping process in Scheme C, the deposited As (0) is re‐oxidized to As (III) and stripped away into electrolyte, leading to the corresponding stripping current, allowing electrochemical analysis of As (III).…”

The Hybrid of Gold Nanoparticles and 3D Flower‐like MnO2 Nanostructure with Enhanced Activity for Detection of Hydrogen Peroxide

“…The peaks in the 2q range of 108-708 were shown in Figure 2a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 nanocrystals (JCPDS No. 04-0784) [46]. No obvious peaks from other phases can be observed, indicating the high purity of Au-MnO 2 nanocomposites obtained.…”

Nanoporous Gold Microelectrode: A Novel Sensing Platform for Highly Sensitive and Selective Determination of Arsenic (III) using Anodic Stripping Voltammetry

“…The quantification of arsenic in aqueous systems is one of the important concerns taking environmental issues into account, because such metal is a major toxic element when its concentration exceeds certain levels in water sources. According to the World Health Organization (WHO), the recommended toxicity level of arsenic in ground water is around 10 μg L −1 . However, owing to the large usage of industrial mining activities for various purposes, the contamination of arsenic has gradually increased in water sources, which causes many carcinogenic health issues to human beings .…”