Selective Growth of Co-electrodeposited Mn2O3-Au Spherical Composite Network Towards Enhanced Non-enzymatic Hydrogen Peroxide Sensing

Bubble-assisted microstreaming during electrode deposition of Mn2O3 energy harvesters

The deposition of energy-harvesting Mn2O3 onto the "Cu" electrode is reported using pulsed laser ablation at the manganese-water interface. Conventionally, laser-induced plasma deposition is carried out by orthogonally placing the substrate (electrodes) in the plasma expansion. Here, underwater material deposition is observed on electrodes placed parallel to the plasma expansion. The possible role played by the fluid dynamically assisted microbubbles in transporting the materials onto electrodes is investigated here. To verify the influence of microbubbles, external electric fields are employed, and implications for the electrodes are characterized. The studies reveal that the external field intensifies the flow of the microbubbles towards the walls, which assists in the deposition of Mn2O3 on the electrodes.

Gold nanoparticles plated porous silicon nanopowder for nonenzymatic voltammetric detection of hydrogen peroxide

A voltammetric approach was developed for the selective and sensitive determination of hydrogen peroxide using Au plated porous silicon (PSi) nanopowder modified glassy carbon electrode (GCE). The AuNPs-PSi hybrid structure was synthesized via stain etching procedure followed by an immersion plating method to deposit AuNPs onto PSi via a simple galvanic displacement reaction with no external reducing agent to convert Au³⁺ to Au⁰. The as-fabricated AuNPs-PSi catalyst was successfully characterized by XRD, Raman, FTIR, XPS, SEM, TEM and EDS techniques. Well crystalline nature of the as-fabricated hybrid structure with AuNPs size ranging from 5 to 40 nm was observed. The specific surface area and total pore volume for both PSi and AuNPs plated PSi were evaluated using N₂ adsorption isotherm technique. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were applied to investigate the catalytic efficiency of AuNPs-PSi modified electrode compared to pure PSi/GCE and unmodified GCE. The sensing performance of the active material modified GCE was thoroughly examined with linear sweep voltammetry (LSV) and square wave voltammetry (SWV) techniques. The AuNPs-PSi/GCE exhibited a remarkable linear dynamic range between 2.0 and 13.81 mM (for LSV) and 0.5-6.91 mM for (SWV) with high sensitivity and low detection limit of 10.65 μAmM^-1cm^-2 and 14.84 μM for LSV, whereas 10.41 μAmM^-1cm^-2 and 15.16 μM using SWV techniques, respectively. The fabricated sensor electrode showed excellent anti-interfering ability in the presence of several common biomolecules as well as demonstrated good operational stability and reproducibility with low relative standard deviation. Moreover, the modified electrode showed acceptable recovery of H₂O₂ in a real sample analysis. Thus, the developed AuNPs-PSi hybrid nanomaterial represents an excellent electrocatalyst for the efficient detection and quantification of H₂O₂ by the electrochemical approach.

Novel neuron-network-like Cu-MoO2/C composite derived from bimetallic organic framework for highly efficient detection of hydrogen peroxide

Fabrication of non-enzymatic electrochemical sensors based on metal oxides with low valence-state for nanomolar detection of H₂O₂ has been a great challenge. In this work, a novel neuron-network-like Cu-MoO₂/C hierarchical structure was simply prepared by in-situ pyrolysis of 3D bimetallic-organic framework [Cu(Mo₂O₇)L]_n [L: N-(pyridin-3-ylmethyl)pyridine-2-amine] crystals. Meanwhile, the MoO₂/C nano-aggregates were also obtained by liquid phase copper etching. Subsequently, two non-enzymatic electrochemical sensors were fabricated by simple drop-coating of the above two materials on the surface of glassy carbon electrode (GCE). Electrochemical measurements indicate that the Cu-MoO₂/C/GCE possesses highly efficient electrocatalytic H₂O₂ property during wider linear range of 0.24 μM-3.27 mM. At room temperature, the Cu-MoO₂/C composite displays higher sensitivity (233.4 μA mM^-1 cm^-2) and lower limit of detection (LOD = 85 nM), which are 1 and 2.5 times larger than those of MoO₂/C material, respectively. Such excellent ability for trace H₂O₂ detection mainly originates from the synergism of neuron-network-like structure, enhanced electrical conductivity and increased active sites caused by low valence-state MoO₂ and co-doping of Cu and carbon, and even the interaction between Cu and Mo. In addition, the H₂O₂ detection in spiked human serum and commercially real samples indicates that the Cu-MoO₂/C/GCE sensor has certain potential application in the fields of environment and biology.

Highly Sensitive As3+ Detection Using Electrodeposited Nanostructured MnOx and Phase Evolution of the Active Material during Sensing

A simple, one-step electrodeposition approach has been used to fabricate MnO_x on an indium-doped tin oxide substrate for highly sensitive As³⁺ detection. We report an experimental limit of detection of 1 ppb through anodic stripping voltammetry with selectivity to As³⁺ in the presence of 10 times higher concentrations of several metal ions. Additionally, we report the simultaneous phase evolution of active material occurring through multiple stripping cycles, wherein MnO/Mn₂O₃ eventually converts to Mn₃O₄ as a result of change in the oxidation states of manganese. This occurs with concomitant changes in morphology. Change in the electronic property (increased charge transfer resistance) of the material due to sensing results in an eventual decrease in sensitivity after multiple stripping cycles. In a nutshell, this paper reports stripping-voltammetry-induced change in morphology and phase of as-prepared Mn-based electrodes during As sensing.

A highly sensitive non-enzymatic hydrogen peroxide and hydrazine electrochemical sensor based on 3D micro-snowflake architectures of α-Fe2O3

In the present work, well crystalline 3D micro-snowflake structured α-Fe₂O₃ has been successfully synthesized on a large scale via a simple hydrothermal reaction by hydrolysis of a K₃Fe(CN)₆ precursor.

A novel δ-MnO2 with carbon nanotubes nanocomposite as an enzyme-free sensor for hydrogen peroxide electrosensing

We have reported the synthesis and application of carbon nanotubes supported δ-MnO₂ (δ-MnO₂/CNTs) nanocomposite as enzyme-free sensor for the detection of H₂O₂, where δ-MnO₂ serves as the catalytic center and CNTs as the highly conductive base.