Phosphomolybdate@poly(diallyldimethylammonium chloride)-reduced graphene oxide modified electrode for highly efficient electrocatalytic reduction of bromate

Estimation of the electrochemical active site density of a metal-free carbon-based catalyst using phosphomolybdate (PMo12) as an adsorbate

A method to estimate the electrochemical active site density (SD) of carbon (C) and nitrogen-doped carbon (N/C-900) using phosphomolybdate (PMo12) as a probe molecule is proposed. The complete coverage of the active sites by the probe molecules is established irrespective of the adsorbate concentration (1, 5, or 10 mM), potential cycling (1 or 10 cycles) and cleaning time (2, 5, or 10 min). A conversion factor derived from a smooth and polished glassy carbon disk of known geometrical area is used to estimate the electrochemical active surface area (ECSA) of the carbon catalyst from the SD. The relatively higher SD values estimated from DC voltammetry than from large-amplitude Fourier-transform alternating-current voltammetry (FTacV) is indicative of the contribution of capacitive charge in the former. Adsorbed probe molecules (PMo12) can readily be desorbed from the catalyst surface by cycling the electrode to lower potentials. The active site density of N/C-900 (∼0.36 × 1019 sites g-1) is higher than that of C (∼0.17 × 1019 sites g-1).

A tetrahedron-shaped polyoxoantimotungstate encapsulating a hexanuclear octahedral lanthanide-oxo cluster for an amperometric bromate sensor

An inorganic hexalanthanide-oxo-cluster-encapsulated antimotungstate, K2Na3H43[Nd6(OH)6(H2O)6(B-α-SbW9O33)4]2·67H2O (1), has been successfully synthesized by a facile one-step hydrothermal reaction method. The tetrahedron-shaped two-shell {Nd6(OH)6(H2O)6(B-α-SbW9O33)4}(1a) polyanion is composed of a novel pure lanthanide-oxo {Nd6(μ3-OH)6(H2O)6} octahedron and {(B-α-SbW9O33)4} tetrahedron. After being effectively loaded onto a glassy carbon electrode (GCE) by electrostatic adsorption using polydiallyldimethyl ammonium chloride (PDDA)-functionalized multi-walled carbon nanotubes (MWCNTs), compound 1 exhibits electrochemical activity for the reduction of bromate ions with good selectivity, a high sensitivity of 186 μA mM-1 and a detection limit that has reached 1.9 μM. To the best of our knowledge, this is the first example of an amperometric bromate sensor based on Ln-containing antimotungstates, which will provide new materials for electrochemical sensors.

Electrochemical Biosensor Based on Horseradish Peroxidase and Black Phosphorene Quantum Dot Modified Electrode

Black phosphorene quantum dots (BPQDs) were prepared by ultrasonic-assisted liquid-phase exfoliation and centrifugation with morphologies proved by TEM results. Furthermore, an electrochemical enzyme sensor was prepared by co-modification of BPQDs with horseradish peroxidase (HRP) on the surface of a carbon ionic liquid electrode (CILE) for the first time. The direct electrochemical behavior of HRP was studied with a pair of well-shaped voltammetric peaks that appeared, indicating that the existence of BPQDs was beneficial to accelerate the electron transfer rate between HRP and the electrode surface. This was due to the excellent properties of BPQDs, such as small particle size, high interfacial reaction activity, fast conductivity, and good biocompatibility. The presence of BPQDs on the electrode surface provided a fast channel for direct electron transfer of HRP. Therefore, the constructed electrochemical HRP biosensor was firstly used to investigate the electrocatalytic behavior of trichloroacetic acid (TCA) and potassium bromate (KBrO3), and the wide linear detection ranges of TCA and KBrO3 were 4.0-600.0 mmol/L and 2.0-57.0 mmol/L, respectively. The modified electrode was applied to the actual samples detection with satisfactory results.

Electrochemical sensing of nitrofurazone on Ru(bpy)32+ functionalized polyoxometalate combined with graphene modified electrode

Nitrofurazone is forbidden to be used in aquaculture, but it is often used illegally because of its good bactericidal effect, and its content in animals is extremely low and difficult to detect directly. Hence, a functionalized polyoxometalate combined with graphene modified electrodes through layer-by-layer assembly has achieved a sensitive detection of nitrofurazone in a pH = 6 Na₂HPO₄-citrate buffer solution and its detection limit as low as 0.08952 μM. Nitrofurazone has accelerated its electron transfer through [Ru-PMo₁₂/PDDA-GO]₃ modified electrode, thus realizing its direct detection at low levels through actual samples. This study provides a new perspective for the direct detection of nitrofurazone by electrochemical methods, which is of great significance for the supervision of nitrofurazone and the improvement of the quality and safety of aquatic products.

Electrochemical Sensors for Determination of Bromate in Water and Food Samples-Review

The application of potassium bromate in the baking industry is used in most parts of the world to avert the human health compromise that characterizes bromates carcinogenic effect. Herein, various methods of its analysis, especially the electrochemical methods of bromate detection, were extensively discussed. Amperometry (AP), cyclic voltammetry (CV), square wave voltammetry (SWV), electrochemiluminescence (ECL), differential pulse voltammetry and electrochemical impedance spectroscopy (EIS) are the techniques that have been deployed for bromate detection in the last two decades, with 50%, 23%, 7.7%, 7.7%, 7.7% and 3.9% application, respectively. Despite the unique electrocatalytic activity of metal phthalocyanine (MP) and carbon quantum dots (CQDs), only few sensors based on MP and CQDs are available compared to the conducting polymers, carbon nanotubes (CNTs), metal (oxide) and graphene-based sensors. This review emboldens the underutilization of CQDs and metal phthalocyanines as sensing materials and briefly discusses the future perspective on MP and CQDs application in bromate detection via EIS.

A label-free immunosensor for the detection of a new lung cancer biomarker, GM2 activator protein, using a phosphomolybdic acid/polyethyleneimine coated gold nanoparticle composite

A novel electrochemical immunosensor for the detection of a new lung cancer biomarker based on a polyoxometalate-adsorbed poly(ethylenimine)-coated gold nanoparticle modified electrode.

Electrochemical sensor for rutin detection based on N-doped mesoporous carbon nanospheres and graphene

A new electrochemical sensor shows great sensing performance to rutin and high selectivity towards even 13 interfering species and realizes detection of rutin in real samples such as human serum.

Rationally designed naphthyl substituted amine functionalized ionic liquid platform for covalent immobilization and direct electrochemistry of hemoglobin

Herein, we have designed and demonstrated a facile and effective platform for the covalent anchoring of a tetrameric hemoprotein, hemoglobin (Hb). The platform comprises of naphthyl substituted amine functionalized gel type hydrophobic ionic liquid (NpNH₂-IL) through which the heme protein was covalently attached over a glassy carbon electrode (Hb-NpNH₂-IL/GCE). UV-vis and FT-IR spectral results confirmed that the Hb on NpNH₂-IL retains its native structure, even after being covalently immobilized on NpNH₂-IL platform. The direct electron transfer of redox protein could be realized at Hb-NpNH₂-IL/GCE modified electrode and a well resolved redox peak with a formal potential of −0.30 V and peak separation of 65 mV was observed. This is due to the covalent attachment of highly conducting NpNH₂-IL to the Hb, which facilitates rapid shuttling of electrons between the redox site of protein and the electrode. Further, the fabricated biosensor favoured the electrochemical reduction of bromate in neutral pH with linearity ranging from 12 to 228 µM and 0.228 to 4.42 mM with a detection limit and sensitivities of 3 µM, 430.7 µA mM⁻¹ cm⁻² and 148.4 µA mM⁻¹ cm⁻² respectively. Notably, the fabricated biosensor showed good operational stability under static and dynamic conditions with high selectivity and reproducibility.

A PDDA functionalized nitrogen and sulphur doped graphene composite as the counter electrode for dye-sensitized solar cells

Poly-diallyldimethylammonium chloride (PDDA) functionalized nitrogen and sulphur doped graphene (SN-Gp) was synthesized as a Pt-free counter electrode (CE) for developing highly efficient and low cost dye sensitized solar cells (DSSCs).

Power and Time Dependent Microwave Assisted Fabrication of Silver Nanoparticles Decorated Cotton (SNDC) Fibers for Bacterial Decontamination

Plasmonic nanoparticles (NPs) such as silver and gold have fascinating optical properties due to their enhanced optical sensitivity at a wavelength corresponding to their surface plasmon resonance (SPR) absorption. Present work deals with the fabrication of silver nanoparticles decorated cotton (SNDC) fibers as a cheap and efficient point of contact disinfectant. SNDC fibers were fabricated by a simple microwave assisted route. The microwave power and irradiation time were controlled to optimize size and density of silver nanoparticles (SNPs) on textile fibers. As prepared cotton fabric was characterized for ATR-FTIR, UV-VIS diffuse reflectance, SEM and TEM investigations. Size of SNPs as well as total density of silver atoms on fabric gets increased with the increase of microwave power from 100 W to 600 W. The antibacterial efficacy of SNPs extracted from SNDC fibers was found to be more effective against Gram-negative bacteria than Gram-positive bacteria with MIC 38.5 ± 0.93 μg/mL against Salmonella typhimurium MTCC-98 and 125 ± 2.12 μg/mL against Staphylococcus aureus MTCC-737, a linear correlation coefficient with R² ranging from ∼0.928–0.935 was also observed. About >50% death cells were observed through Propidium Iodide (PI) internalization after treatment of SNPs extracted from SNDC fibers with concentration 31.25 μg/mL. Generation of ROS and free radical has also been observed which leads to cell death. Excellent Escherichia coli deactivation efficacy suggested that SNDC fibers could be used as potentially safe disinfectants for cleaning of medical equipment, hand, wound, water and preservation of food and beverages.

Signal amplification biosensor based on DNA for ultrasensitive electrochemical determination of metronidazole

The biosensor (PDDA-GN/DNA/GCE) showed remarkable signal amplification performance toward the reduction of metronidazole, and was applied to determinate metronidazole in urine and lake water samples with satisfactory results.

Sensitive and selective detection of Hg2+ based on an electrochemical platform of PDDA functionalized rGO and glutaraldehyde cross-linked chitosan composite film

In this paper, a uniform PDDA-functionalized graphene composite film (GA–CS@PDDA-rGO) was utilized for detection of trace Hg²⁺ by using glutaraldehyde cross-linked chitosan (GA–CS) as a Hg²⁺-chelating adsorbent and film-forming agent.

The first tritopic bridging ligand 1,3,5-tris(4-carboxyphenyl)-benzene (H3BTB) functionalized porous polyoxometalate-based metal–organic framework (POMOF): from design, synthesis to electrocatalytic properties

A POMOF with substantial catalytic activity towards bromate reduction was isolated through the extension of transition-metal-grafted ε-Keggin by a tripodal ligand H₃BTB.