CuO nanoleaf and ß-cyclodextrin functionalized reduced graphene oxide: a highly selective and sensitive electrochemical sensor for the simultaneous detection of 2-chlorophenol and 2, 4-dichlorophenol.

Chlorophenols are considered priority pollutants and are harmful to humans and the environment; consequently, sensitive, and selective detection of chlorophenols is very significant. In the present article, a glassy carbon electrode was modified by copper oxide nanoleaves, ß-cyclodextrin, and reduced graphene oxide through an electrostatic self-assembly method (CuO NLs-ß-CD-rGO-GCE) and successfully utilized for the selective and sensitive detection of 2-chlorophenol (2-CP) and 2,4-dichlorophenol (2,4-DCP). The modified electrodes were characterized by using SEM, EDX, ATR-FTIR, CV, and EIS. The electrochemical behaviour of 2-CP and 2,4 DCP on different modified electrodes was investigated by cyclic voltammetry whereas differential pulse voltammetry was used for the quantitative determination of chlorophenols. Under the optimized conditions, the anodic peak current displayed a good linear relationship to concentration in the range of 5 to 50 µM for 2-CP and 5 to 30 µM for 2,4-DCP, with detection limits of 0.22 nM and 0.52 nM, respectively. Moreover the proposed sensor exhibited good reproducibility, high sensitivity, and long term stability. To further study the practical applicability of the newly developed sensor, the modified electrode was successfully used to determine 2-CP and 2,4-DCP in a water sample with good recovery.

Novel SnO2@ZIF-8/gC3N4 nanohybrids for excellent electrochemical performance towards sensing of p-nitrophenol.

Herein, a novel synthetic strategy has been proposed to prepare engineered SnO2@ZIF-8/gC3N4 nanohybrids for electrochemical sensing of p-nitrophenol (p-NP). The electrochemical properties were investigated using cyclic voltammetry (CV), chronoamperometry (CA), and differential pulse voltammetry (DPV). The developed nanohybrid sensor displayed an excellent electrochemical performance towards sensing of p-NP with a detection limit of 0.565 µM. The sensitivity of the prepared nanohybrid was found to be 2.63 µAcm-2µM-1. Moreover, the newly fabricated sensor exhibited remarkable selectivity (over tenfold excess) in the presence of common interferents. The simultaneous detection of isomers of nitrophenol is difficult using the developed sensor. However, other common interferents, such as phenol and aminophenol have negligible effects on the sensitivity of SnO2@ZIF-8/gC3N4 towards the detection of p-nitrophenol. Further, the newly developed sensor showed consistency of sensing response up to 30 days. Thus, implementation of SnO2@ZIF-8/gC3N4 nanohybrids as a p-NP electrochemical sensor offers the advantages of simplicity, selectivity, and stability.

Synthesis of ultrasmall and monodisperse sulfur nanoparticle intercalated CoAl layered double hydroxide and its electro-catalytic water oxidation reaction at neutral pH.

Ultrasmall and monodisperse sulfur nanoparticle (S-NP) intercalated CoAl-layered double hydroxide (CoAl-LDH) electrocatalyst exhibits an excellent electrocatalytic activity towards water oxidation with a low overpotential of 250 mV at a high current density of 7.9 mA cm-2 and a Tafel slope of 61 mV dec-1 at the neutral pH condition. The fabrication strategy to achieve a high-performance, robust and durable electrocatalyst is a scale-up in next generation renewable energy fields.

Electrocatalytic oxidation of water by the immobilized [CuII(l-ala)(Phen)(H2O)]+ complex on a self-assembled NCS- modified gold electrode.

Copper(ii) complex [CuII(l-ala)(Phen)(H2O)]+ (l-ala = l-phenylalanine, phen = phenanthroline) was immobilized over a self-assembled NCS- modified gold electrode for the electrocatalytic oxidation of water. This surface anchored molecular complex can catalyze water oxidation reaction at a remarkably low overpotential of 327 mV with a current density of 0.5 mA cm-2 at neutral pH.

Electrocatalytic oxidation of water at a polyoxometalate nanoparticle modified gold electrode.

Spherical polyoxometalate nanoparticles, [HPMo]NPs, were synthesized from a very well known Keggin-type polyoxometalate [H3PMo12O40] in the presence of sodium dodecyl sulphate (SDS) and polyvinyl pyrrolidine (PVP) in aqueous medium and characterized by UV-Vis spectroscopy and Transmission Electron Microscopy (TEM). The [HPMo]NPs were used to modify a gold working electrode and they were characterized by SEM, EDX, elemental mapping, cyclic voltammetry and electrochemical impedance spectroscopy and applied for the electrocatalytic oxidation of water in a phosphate buffer solution at neutral pH. The modified electrode showed excellent electrocatalytic activity towards oxidation of water at an impressively low overpotential ∼350 mV with a high current density of around 1.7 mA cm-2, good stability under exhaustive electrolysis conditions and also showed long term stability.

MnO doped SnO2 nanocatalysts: Activation of wide band gap semiconducting nanomaterials towards visible light induced photoelectrocatalytic water oxidation.

Semiconducting nanomaterials are very important by means of their stability and wide band gap tunability. Visible light induced photoelectrocatalytic water oxidation based on these material are challenging as they have large band gap energies. Herein, we report that MnO doping can activate wide band gap semiconductors like SnO2 towards visible light induced water oxidation. Rutile SnO2 nanoparticles (band gap 3.6eV), usually absorbing at UV region, was capable of harvesting visible light when doped with MnO thereby minimizing the energy requirement for photoelctrocatalytic water splitting. The system was characterized using UV-Vis, TEM and XPS. Photoelectrocatalytic activity was examined by LSV and CPE. The highly stable catalyst showed very good photoelectrocatalytic activity for the oxidation of water under alkaline condition with low overpotential of ∼370mV at 1.0mAcm-2.

Cerium(III) Complex Modified Gold Electrode: An Efficient Electrocatalyst for the Oxygen Evolution Reaction.

Exploring efficient and inexpensive electrocatalysts for the oxidation of water is of great importance for various electrochemical energy storage and conversion technologies. In the present study, a new water-soluble [Ce(III)(DMF) (HSO4)3] complex was synthesized and characterized by UV-vis, photoluminescence, and high-resolution X-ray photoelectron spectroscopy techniques. Owing to classic 5d → 4f transitions, an intense photoluminescence in the UV region was observed from the water-soluble [Ce(III)(DMF) (HSO4)3] complex. A stacking electrode was designed where self-assembled l-cysteine monolayer modified gold was immobilized with the synthesized cerium complex and was characterized by scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The resulting electrode, i.e., [Ce(III)(DMF) (HSO4)3]-l-cysteine-Au stacks shows high electrocatalytic water oxidation behavior at an overpotential of η ≈ 0.34 V under neutral pH conditions. We also demonstrated a way where the overpotential is possible to decrease upon irradiation of UV light.

Photocatalytic hydrogen production from water in self-assembled supramolecular iridium-cobalt systems.

Supramolecular photosynthetic systems made up of the [Ir(ppy)(2)(bpy)](+) and [Co(bpy)(3)](2+) cores (ppy = 2-phenylpyridinate, bpy = 2,2'-bipyridine) are in situ self-assembled in aqueous media to generate H(2) upon visible light irradiation, where one of them recorded a relatively high turnover number of 20.