Electrochemical sensing of ascorbic acid, hydrogen peroxide and glucose by bimetallic (Fe, Ni)-CNTs composite modified electrode

In this research, bimetallic supported CNT modified electrode (Fe,Ni/CNTs/GCE) has been developed for sensitive, stable and highly elctroactive sensing of glucose, ascorbic acid and hydrogen peroxide. Transition metals such as Iron (Fe) and Nickel (Ni) offer high electrical and thermal conductance, high active surface‐to‐volume ratio and presence of d‐band electrons gives enhanced electrocatalytic behavior. While, CNTs provide high surface area, stability and excellent conductivity. Synthesized material is characterized by SEM, EDS, XRD and FTIR to access morphology, elemental composition and structure. This unique combination is employed for the electrochemical sensing of ascorbic acid, glucose and hydrogen peroxide and different experimental parameters are optimized. Fe,Ni/CNTs/GCE shows good sensing efficiency at pH 7.4 which is ideally suitable for variety of analytes. The modified electrode also show good reproducibility and sensitivity under optimized conditions and can be reused upto 30 cycles without compromising the efficiency. With good linearity, reproducibility and limit of detection, this material possess significant potential as non‐enzymatic biosensor for variety of analytes

Synthesis of the highly efficient catalysts CdZnS@MIL-53(Fe) and ZnS@MIL-53(Fe) and their thermally decomposed derivative for electrochemical OER activity and photodegradation of Rhodamine B dye

The development of a highly efficient catalyst for water splitting and photodegradation of organic dyes has become the focus of a considerable number of research groups. In the work described here CdZnS@MIL-53(Fe) and ZnS@MIL-53(Fe) were synthesized by the solvothermal method and subjected to thermal degradation at 520 °C in an oxidative environment to obtain CdZnS/Fe₂O₃ and ZnS/Fe₂O₃, respectively. Electrocatalytic activity for the oxygen evolution reaction is analyzed via cyclic voltammetry and linear sweep voltammetry. It was found that CdZnS@MIL-53(Fe) shows maximum catalytic activity for the oxygen evolution reaction and delivers 10 mAcm⁻² current density at 95 mV overpotential as compared to MIL-53(Fe)/NF (210 mV) and ZnS@MIL-53(Fe)/NF (112 mV). Similarly, the derivative of it, CdZnS/Fe₂O₃, shows maximum catalytic activity for the oxygen evolution reaction and delivers 10 mAcm⁻² current density at 90 mV overpotential as compared to Fe₂O₃ (204 mV) and ZnS/Fe₂O₃ (115 mV). Based on these results, it is evident that these materials are highly efficient for OER activity compared with other materials in literature. Similarly, CdZnS/Fe₂O₃ shows maximum photocatalytic activity for the photodegradation of Rhodamine B, up to 75% compared to CdZnS@MIL-53(Fe), which degrades up to 51% of the dye. The synthesized materials were characterized by powdered X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. Based on these results the aim is to develop more MOF-based materials and their derivatives by simple heat treatment and to implement them in different catalytic applications.ISSN:1879-3487ISSN:0360-319

Structural, electrical, dielectric and magnetic properties of Mn-Nd substituted CoFeO3 nano sized multiferroics

A series of MnxCo1−xFe1−yNdyO3 (where x=0.0–1.0 & y=0.0–0.1) multiferroic nanocrystals was synthesized via sol-gel auto-combustion technique. The structure was confirmed by X-ray diffraction (XRD) while morphology was investigated by scanning electron microscopy (SEM). The electrical resistivity was observed to increase from 2.14×107 to 8.77×109 Ω-cm and activation energy was found to increase from 0.64 to 0.75 eV, while the drift mobility decreased from 4.75×10−13 to 1.27×10−15 cm2 V−1 S−1 by the substitution of Mn and Nd contents. The dielectric constant, dielectric loss and dielectric loss factor decrease with frequency and Mn-Nd contents. The saturation magnetization was increased from 34 to 70 emu g−1 while the coercivity decreased from 705 to 262 Oe with the increase of substituents. The increase in electrical resistivity and saturation magnetization while decrease in dielectric parameters and coercivity make these nanomaterials suitable for applications in microwave devices and longitudinal magnetic recording media

Incorporation of MnO2 nanoparticles into MOF-5 for efficient oxygen evolution reaction

A composite MnO2@MOF-5 is prepared by in situ incorporation of pre-synthesized MnO2 nanoparticles into metal organic framework, MOF-5, during synthesis. The product is characterized by powder X-ray diffraction analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and elemental mapping, which support the formation of proposed composite materials. The oxygen evolution reaction activity of MnO2@MOF-5 composite is evaluated by cyclic voltammetry, linear sweep voltammetry, and chronoamperometric measurement under visible light. It is found that MnO2@MOF-5/NF has better durability and ability to produce a current density of 10 mAcm−2 at only 324 mV overpotential with lower 71 mVdec−1 Tafel slope as compared to some of previously reported Mn-based catalysts for oxygen evolution reaction (OER). The stability of these electrodes is evaluated by chronoamperometric studies for 6000 s in the presence of visible light, and they showed constant current density. Furthermore, the stability studied by continuous CV sweeps in 1.0 M NaOH at a scan rate of 100 mVs−1 shows that these materials are stable up to 100 cycles, which confirms the stability and durability of the electrodes

Recent Progress on Adsorption Materials for Phosphate Removal

International audienceBACKGROUND:High concentration of phosphate has been threatening human health and the ecosystem. Adsorption is one of high-efficiency and low-cost techniques to reduce the concentration of phosphate. This mini review aims to summarize the recent development of adsorption materials for phosphate removal.METHOD:We conducted a detailed search of "adsorption of phosphate" in the published papers and the public patents on the adsorbents for phosphate based on Web of Science database in the period from January 1 2012 to December 31 2017. The corresponding literature was carefully evaluated and analyzed.RESULTS:One hundred and forty one papers and twenty two recent patents were included in this review. An increased trend in scientific contributions was observed in the development of adsorption materials for phosphate removal. Three kinds of promising adsorbents: layered double hydroxides, natural materials, and metal oxides were paid special attention including removal mechanism, performance as well as the relationship between adsorption performance and structure. Both the chemical composition and the morphology play a key role in the removal capacity and rate.CONCLUSION:The findings of this review confirm the importance of phosphate removal, show the development trend of high-performance and low-cost adsorption materials for phosphate removal, and provide a helpful guide to design and fabricate high-efficiency adsorbents

A Novel Electrochemical Sensing Platform for the Detection of the Antidepressant Drug, Venlafaxine, in Water and Biological Specimens

A stable bimetallic catalyst composed of Co–Pd@Al2O3 was synthesized using a wet impregnation method, followed by calcination and H2 reduction. The synthesized catalyst was thoroughly characterized using XRD, BET, SEM, EDX, and TPR techniques. The catalyst was then drop-casted on a glassy carbon electrode (Co–Pd@Al2O3/GCE) and applied for the sensitive and selective electrochemical determination of a common antidepressant drug, venlafaxine (VEN). The proposed sensor (Co–Pd@Al2O3/GCE) demonstrated a remarkable catalytic activity for the electro-oxidation of VEN, with a decent repeatability and reproducibility. The pH dependent responsiveness of the electro-oxidation of VEN helped in proposing the redox mechanism. A linear relationship between the peak current and concentration of VEN was observed in the range of 1.95 nM to 0.5 µM, with LOD and LOQ of 1.86 pM and 6.20 pM, respectively. The designed sensor demonstrated an adequate selectivity and significant stability. Moreover, the sensor was found to be quite promising for determining the VEN in biological specimens

A Novel Electrochemical Sensing Platform for the Sensitive Detection and Degradation Monitoring of Methylene Blue

Methylene blue is a toxic dye that is extensively used as a colorant in textile industries. Industrial effluent containing methylene blue, when drained into water bodies without proper treatment, poses a serious threat to aquatic and human lives. In order to protect the biocycle, various methods have been established to detect and remove hazardous dyes from aqueous systems. Electrochemical methods are preferred, owing to their characteristic features of simplicity, portability, potential selectivity, cost effectiveness, and rapid responsiveness. Based on these considerations, an electrochemical sensor consisting of amino-group-functionalized, multi-walled carbon nanotubes (NH2-fMWCNTs) immobilized on a glassy carbon electrode (GCE) was developed for the sensitive detection of methylene blue in aqueous solutions. The performance of the designed sensor was analyzed by electrochemical impedance spectroscopy, cyclic voltammetry, and square wave voltammetry. The developed sensing tool demonstrated promising features of sensitivity, selectivity, stability, fast responsiveness, and the ability to work with a very small volume of the analyte, i.e., in microliters, for analysis. Amino groups rich in electrons provide a negative charge to multi-walled carbon nanotubes, which significantly enhances the electrocatalytic activity of NH2-fMWCNTs for cationic dyes such as methylene blue. Using the designed sensing platform, a linear calibration plot with a limit of detection of 0.21 nM was obtained for methylene blue under optimized conditions. The designed sensor was also employed to monitor the extent and kinetics of the degradation of methylene blue. Titania nanoparticles were used for photocatalytic degradation, and the kinetics of degradation was monitored by both UV-Visible spectroscopic and electrochemical methods. The results revealed more than 95% removal of methylene blue in a time span of just 30 min

Structural and dielectric properties of doped ferrite nanomaterials suitable for microwave and biomedical applications

The sol–gel auto-combustion method was adopted to synthesize nanomaterials of single-phase X-type hexagonal ferrites with the composition of Sr2−xGdxNi2Fe28−yCdyO46 (x=0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and y=0, 0.1, 0.2, 0.3, 0.4, 0.5). The structural properties were carried out by XRD analysis and the lattice parameters show variation with the doping of Gd–Cd. The average particle size measured by TEM was in the range of 8–10 nm which is beneficial in obtaining suitable signal-to-noise ratio in recording media and biomedical applications. The room temperature resistivity enhanced with the increase of the dopant concentration. The increase in resistivity indicates that the synthesized materials can be considered good for the formation of the multilayer chip inductors (MLCIs) as well as for the reduction of eddy current losses. The dielectric constant decreased with the increase in the frequency which is the general reported trend of the hexagonal ferrites and can be explained on the basis of Koop׳s theory and Maxwell–Wagner polarization-model. The abnormal dielectric behavior indicates the formation of small polarons in the material. The maximum value of tangent loss at low frequencies reflects the application of these materials in medium frequency devices (MF)

Facile synthesis of NiMn2O4/ZnMn2O4 heterostructure nanocomposite for visible-light-driven degradation of methylene blue dye

Nowadays, waste discharge and contaminants in drinking water have emerged as a significant global problem. Therefore, it is necessary to remove these pollutants from the water and photocatalysis is the best technique for this purpose. The co-precipitation technique was employed to produce NiMn2O4 and ZnMn2O4 and a photocatalyst containing NiMn2O4/ZnMn2O4 heterostructure nanocomposite. Various analytical techniques have been ascribed to examine the physical, morphological and optical features of the fabricated catalysts. XRD diffraction peak patterns were utilized to confirm the presence of cubic NiMn2O4, tetragonal ZnMn2O4 and NiMn2O4/ZnMn2O4 phases in a nanocomposite. In photodegradation tests, the nanocomposite catalyst outperformed the individual catalysts. After 60 minutes of visible light exposure, this nanocomposite catalyst eliminated the methylene blue (MB) dye, attaining substantially higher degradation rates than pure NiMn2O4 (66%) and ZnMn2O4 (77%). The nanocomposite catalyst was highly effective against methylene blue (MB) dye with a degradation efficiency of 92%

Preparation and characterization of doubly substituted microwave absorbing material by sol-gel technique for super high frequency applications

Rare earth Dy3+ and divalent Mn2+ elements substituting W-type hexagonal ferrites Ba1−xDyxZn2Fe16−yMnyO27 (x = 0, 0.02, 0.06, 0.1 and y = 0, 0.1, 0.3, 0.5) were prepared by sol-gel method. The thermo- gravimetric analysis (TGA) and differential scanning calorimetry (DSC) was carried out to find the temperature at which single phase can be obtained. XRD patterns indicate the presence of the single phase for all the synthesized samples with the absence of any extra peak due to unreacted material and secondary phases. The occurrence of absorption bands at low wave numbers (563 and 446 cm−1), can be assigned to the stretching vibration of metal and oxygen ions in FTIR spectra, which also confirms the single hexagonal phase for prepared material. The grains are of platelet like structure, which enhances the microwave absorption properties of hexagonal ferrites. The synthesized material exhibits the minimum reflection loss of −20.9 dB at 11.8 GHz frequency, which reflects the applications of this material in super high frequency devices. The microwave conductivity of the material increases with frequency. Keywords: Sol-Gel synthesis, XRD, Microwave absorption properties, Microwave conductivit