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Water splitting is a promising reaction for storing sustainable but intermittent energies. The critical bottleneck for it is oxygen evolution reaction (OER) requiring insufficiently low overpotentials, η. Metal oxides are the group of high performance catalysts for water oxidation, so far. We report a facile synthesis of the mixed metal oxide composite (NiO/Mn-doped NiCo 2 O 4) and an easy dip-coating method to create electrocatalysts on nickel foam as electrode substrates cause significant efficiency for OER. The mixed metal oxides catalyst was characterized by using electrochemical methods, high-resolution transmission electron microscopy (HR-TEM), field emission-scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), inductively coupled plasma (ICP) and fourier-transform infrared spectroscopy (FTIR). Electrocatalysts were shown a Tafel slope of 34 mV dec−1 with overpotential η = 482 mV (for 100 mA cm−2) and at least 20 h durable OER activity. The electrochemical data demonstrate the synergistic effect of the coupling between the three metal-centres of Ni, Co, and Mn to decline the overpotential value. The current of (OER) is related to the electrolyte pH, displaying a non-proton-concerted mechanism in an approach to identifying rate-determining steps for OER. This could be concluded by the direct neighbour lattice O•– coupling to form an O–O bond. The simple and rapid fabrication method and the promising stability and high performance of the herein developed electrodes render them quite promising for technological water splitting systems. • A facile synthesis of the mixed trimetal oxide composite (NiO/Mn-doped NiCo 2 O 4) is reported. • NiO/Mn-doped NiCo 2 O 4 composite shows high electronic conductivity and electrochemical activity. • The Mn substituted in spinel structure can significantly increase electroacatalytic activity. • The overpotential of η = 482 mV (for 100 mA cm−2) with a Tafel slope of 34 mV dec−1 and at least 20 h stability in OER. [ABSTRACT FROM AUTHOR]

Incorporation of appropriate Lewis acid centers such as Cr3+ and nucleophilic ionic species such as Br- as assistants in the opening of epoxy rings, on the metal-organic frameworks can be considered an efficient catalyst in a CO 2 fixation processes. In this research work, we introduce a new catalyst by modifying the metal-organic framework and creating the ammonium salt with bromide, TEAB-MIL-101(Cr). The catalyst was characterized using several appropriate techniques and used as catalyst in the CO 2 fixation reaction of a large number of epoxides. The catalytic reaction was pushed forward under solvent and cocatalyst-free conditions at 1.5 bar of CO 2. The catalyst showed high activity in the presence of most epoxides, but the best result was related to epichlorohydrin, which showed 99 % conversion and 96 % selectivity to the respective cyclic carbonate within 3 h. The prepared catalyst was easily recovered and reused to the catalytic process for at least fifth times without any noticeable change in activity. [Display omitted] • An efficient catalyst for the CO2 fixation reaction of epoxides. • Solvent-free CO2 fixation reaction of epoxides. • Co-catalyst free CO2 fixation reaction of epoxides. • High conversion and selectivity in presence of low pressure of CO2 gas in CO2 fixation reaction of epoxides. [ABSTRACT FROM AUTHOR]

This paper describes the development of a new voltammetric pH-sensor based on glassy carbon electrode incorporating poly-dopamine thin film. The sensor was fabricated under ambient conditions from voltammetric polymerization of the dopamine at the surface of glassy carbon electrode in aqueous media. The analysis was performed based on the electro-oxidation of catechol moieties of poly-dopamine. Cyclic voltammograms recorded in various buffer solutions (pH 1.0–12.0) yielded a distinct and unambiguous oxidation process through which to ascribe the peak potential with Nernstian (−58.2 ± 0.09 mV/pH) manner ( T at 25 °C). It is based on a 2 proton, 2 electron system over the aqueous pH range 1.0–12.0. The developed system displays very promising performances in buffered and unbuffered solutions, with a reproducible Nernstian response to pH changes. The effect the composition and concentration of buffer solutions have been investigated. [ABSTRACT FROM AUTHOR]

In this work a binary photocatalyst of rGO and MnFe 2 O 4 was prepared completely using one-pot hydrothermal simple method. In this way, in a reaction vessel, graphene oxide was reduced and at the same time, MnFe 2 O 4 nanoparticles were formed on its surface. The obtained catalyst was characterized by N 2 adsorption, FT-IR, XPS, HRTEM, XRD, FESEM and VSM physicochemical techniques. The rGO/MnFe 2 O 4 -50 % exhibits high photocatalytic efficiency for reduction of nitroaromatic compounds given to corresponding amines at ambient temperature. In this study, the kinetic parameter (k) of the reduction reaction was investigated. The catalyst was especially excellent in conversion of 1, 4-dinitrobenzene (99 % in 30 min), 4-bromonitrobenzene (100 % in 60 min) and 4-chloronitrobenzene (100 % in 70 min). In addition to the photocatalytic behavior of rGO/MnFe 2 O 4 -50 %, the recyclability of MnFe 2 O 4 was exploited and the catalyst was used for a number of times in the nitrobenzene photocatalytic test without observing a significant decreasing in efficiency. • An efficient catalyst for photoreduction of various nitroaromatic compounds. • Robust catalyst in photoreduction of nitrobenzene in comparison with the literature. • Magnetically recovery of catalyst from the reaction and using it for several times without significant loss of ability. • Photoreduction of nitroaromatic compounds at ambient temperature. • Kinetic investigation on photocatalytic reduction of nitrobenzene. [ABSTRACT FROM AUTHOR]

In this paper, a novel and highly sensitive atenolol sensor based on a poly-dopamine (PDA) is presented. PDA has been synthesized using a facile electro-deposition method. The polymer has been characterized with different techniques such as scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The glassy carbon modified with PDA has been applied for extraction and electrochemical sensing of atenolol. The extraction parameters such as pH, extraction time, and agitation rate were optimized. Differential pulse voltammetry has been used for quantitative determination of atenolol. The PDA thin film-based sensing platform exhibits high selectivity and sensitivity with a detection limit of 2.7 × 10 −8 M. Determination of atenolol in real samples has been demonstrated. The results suggested that the PDA modification of electrodes may provide a new strategy for atenolol concentration determination in physiological solutions. [ABSTRACT FROM AUTHOR]

In this approach, electro-oxidation of a mixture of uric acid and ascorbic acid at the surface of tosyl surface carbon nanoparticles/glassy carbon electrode has been performed. The electro-oxidation of these compounds at bare electrode is sluggish and there is no suitable peak separation between them. However, using functionalized carbon nanoparticles, two well-defined anodic peaks with a considerable enhancement in the peak current and a remarkable peak potential separation near 452 mV is obtained. The porous interfacial layer of the carbon nanoparticles modified electrode with a high specific surface area increases the conductive area; molecules can penetrate through the conductive porous channels onto the electrode more easily so leading to higher sensitivity and selectivity. The dynamic linear ranges of 1.0 × 10 − 5 to 3.0 × 10 − 3 M and 1.0 × 10 − 7 to 1.0 × 10 − 4 M with detection limits 1.0 × 10 − 5 M and 2.0 × 10 − 8 M (for S/N = 3) were obtained for ascorbic acid and uric acid, respectively. Analytical utility of the modified electrode has been examined successfully using human urine samples and vitamin C commercial tablets. [ABSTRACT FROM AUTHOR]

In this research, a novel carbon nanoparticles (Emperor 2000 ™ )-modified carbon paste electrode (CNP/CPE) was fabricated and employed for determination of paracetamol (PA), phenylephrine (PHE) and dextromethorphan (DX) with good selectivity and high sensitivity. The paste design is based on (i) a hydrophobic binder, (ii) hydrophobic graphite as conductive component, and (iii) a thin film of nanoparticulate with hydrophilic surface to provide sensitivity and selectivity. Paracetamol, phenylephrine and dextromethorphan are frequently associated in pharmaceutical formulations against the common cold. Then determination of these compounds in a mixture is very important in pharmaceuticals and human fluids. CNP/CPE displayed excellent electrochemical catalytic activities towards paracetamol, phenylephrine and dextromethorphan oxidation. Using differential pulse voltammetry (DPV), a trace determination of PA, PHE and DX has been explored at the surface of modified electrode in presence of each other. Peak currents of PA, PHE and DX increased linearly with their concentrations at the ranges of 1.0 × 10 −7 –1.0 × 10 −3 M, 8.0 × 10 −6 –8.0 × 10 −5 M and 8.0 × 10 −6 –8.0 × 10 −4 M, and the detection limits were estimated 1.5 × 10 −8 , 9.5 × 10 −7 and 2.9 × 10 −6 M, respectively. The modified electrode displayed strong function for resolving the overlapping voltammetric responses of PHE and DX into two well-defined voltammetric peaks. Method was applied successfully to the determination of PA, PHE and DX in real samples. [ABSTRACT FROM AUTHOR]

Abstract: In this approach, synthesis of nickel (II) incorporated aluminophosphate (NiAlPO-5) was performed by using hydrothermal method. The diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques were applied in order to characterize synthesized compounds. The NiAlPO-5 was used as a modifier in carbon paste electrode for the selective determination of thioridazine which is an antidepressant drug. This research is the first example of an aluminophosphate being employed in electroanalysis. The effective catalytic role of the modified electrode toward thioridazine oxidation can be attributed to the electrocatalytic activity of nickel (II) in the aluminaphosphate matrix. In addition, NiAlPO-5 has unique properties such as the high specific surface area which increases the electron transfer of thioridazine. The effects of varying the percentage of modifier, pH and potential sweep rate on the electrode response were investigated. Differential pulse voltammetry was used for quantitative determination as a sensitive method. A dynamic linear range was obtained in the range of 1.0×10−7–1.0×10−5 molL−1. The determination of thioridazine in real samples such as commercial tablets and human serum was demonstrated. [Copyright &y& Elsevier]

Highlights: [•] The covalently modification of carbon nanoparticles with cysteine functional group (CNP-Cys) is demonstrated. [•] Cysteine acts as a receptor for dopamine at the surface of carbon nanoparticles. [•] Enhanced voltammetric responses are observed for pre-adsorbed dopamine at the surface of GC/CNP-Cys electrode. [•] High sensitivity with low levels of DA is achieved due to the interaction between DA and cysteine. [•] This specific surface immobilized receptor groups could be developed to allow disease bio-marker detections. [Copyright &y& Elsevier]

[Display omitted] Polymers of intrinsic microporosity (PIMs) provide high surface area materials (typically 1000 m2 g−1 apparent BET surface area) that are processable from organic solvents to give glassy films or composite coatings. Multi-functionality for sensing with these materials is achieved (i) based on the polymer backbone itself being fluorescent or chemically active or (ii) based on guest species (chromophores, nano-catalysts, nano-photo-catalysts, etc.) that are readily embedded into PIMs and accessible through micropores in the polymer host. The ease of forming uniform microporous films or composite films is linked to molecular rigidity and highlighted here for sensing/electroanalytical applications. [ABSTRACT FROM AUTHOR]

In the present paper, carbon cloth (CC) as a flexible substrate was modified by molybdenum carbide nanospheres (Mo 2 C NSs @CC) by the drop-coating method to develop a sensitive electrochemical platform for detecting caffeic acid. The uniform Mo 2 C NSs were prepared via an easy route followed by pyrolyzing the precursor of the Mo-polydopamine (Mo-PDA) NSs. The Mo 2 C NSs were characterized and analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDS), Raman spectroscopy (RS), and electrochemical methods. CC not only gave a flexible feature to the sensor but also provided a larger surface area for Mo 2 C NSs. Meanwhile, the excellent conductivity and large electroactive specific surface area of Mo 2 C NSs exhibited excellent electrocatalytic performance for caffeic acid determination. The developed sensor showed high sensitivity and selectivity, good reproducibility, and long-term stability with a limit of detection (LOD) and a wide linear range of 0.001 μM (S/N = 3) and 0.01–50 μM, respectively. In addition, the Mo 2 C NSs @CC sensor showed a promising application prospect for the detection of caffeic acid in green and black tea samples, indicating its importance in food safety and the food industry. [Display omitted] • A new flexible electrochemical sensor was fabricated based on Mo 2 C NSs @CC. • Mo 2 C NSs @CC exhibited outstanding electrocatalytic activity toward the detection of caffeic acid (CA). • The Mo 2 C NSs @CC was applied to the detection of CA in green and black tea samples. [ABSTRACT FROM AUTHOR]

Abstract: We review the state-of-the-art application of nanoparticles (NPs) in electrochemical analysis of environmental pollutants. We summarize methods for preparing NPs and modifying electrode surfaces with NPs. We describe several examples of applications in environmental electrochemical sensors and performance in terms of sensitivity and selectivity for both metal and metal-oxide NPs. We present recent trends in the beneficial use of NPs in constructing electrochemical sensors for environmental monitoring and discuss future challenges. NPs have promising potential to increase competitiveness of electrochemical sensors in environmental monitoring, though research has focused mainly on development of methodology for fabricating new sensors, and the number of studies for optimizing the performance of sensors and the applicability to real samples is still limited. [Copyright &y& Elsevier]

Integration of aluminum-terephthalate metal-organic frameworks, MIL-53 (Al) with reduced graphene oxide (rGO) leads to the formation of MIL-53 (Al)@rGO hybrid materials with superior charge storage properties. This work reports the synthesis of MIL-53 (Al)@rGO nanocomposites through solvothermal method and study of their electrochemical charge storage properties. The optimized composite of MIL-53 (Al) and rGO (coded as C-10) exhibits a specific capacitance of 280 F g−1 at 0.5 A g−1. Furthermore, electrochemical measurements, carried out in a symmetric two-electrode configuration, revealed that the hybrid composite C-10 reached an energy density of 6.66 Wh kg−1 and a power density of 3655 W kg−1. It displayed a capacitance retention of 50% after 5,000 charge/discharge cycles. Integration of MIL-53(Al) and rGO leads to the creation of alternate pathways for ion-diffusion, hierarchical pore features, greater exposure of MIL-53 (Al) clusters as redox active sites attributed to their uniform distribution on rGO sheets, resulting in better charge storage performance. Hybrid composite of aluminum terephthalate MIL-53 (Al) with reduced graphene oxide synthesized though solvothermal approach exhibits enhanced electrochemical charge storage properties. The hybrid composite sees better pore features and modified morphology with lesser agglomeration. The hybrid composite also exhibits better charge conductivity. Image 1 • MIL-53 (Al) was synthesized solvothermally and integrated with reduced graphene oxide. • Reduced graphene oxide increases the surface area and porosity in the composite. • The synthesized composites are applied as electrodes for supercapacitors. • Established synergy enhances charge storage property in the synthesized composites. [ABSTRACT FROM AUTHOR]