• Fereshteh Chekin

      Articles written in Bulletin of Materials Science

    • Silver nanoparticles prepared in presence of ascorbic acid and gelatin, and their electrocatalytic application

      Fereshteh Chekin Somayeh Ghasemi

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      In this paper, we reported a simple and low-cost procedure to synthesize silver nanoparticles (AgNPs) by using ascorbic acid as reducing agent and gelatin as stabilizer. The synthesized AgNPs were characterized by various means such as transmission electron microscope (TEM), powder X-ray diffraction (XRD) and energy-dispersive X-ray (EDX). TEM observations and XRD analysis demonstrated that the size of AgNPs is about 20 nm. Silver nanoparticles modified with carbon-paste electrode (AgNPs–CPE) displayed excellent electrochemical catalytic activities towards hydrogen peroxide (H2O2). The reduction overpotential of H2O2 was decreased significantly compared with those obtained at the bare CPE. The sensor responded linearly to hydrogen peroxide (H2O2) in the concentration of 10–350 𝜇M, with detection limit of 5.6 𝜇M at 3𝜎 using amperometry. The studied sensor exhibited good reproducibility and long-term stability.

    • Cobalt oxide nanoparticle-modified carbon nanotubes as an electrocatalysts for electrocatalytic evolution of oxygen gas

      Jahan Bakhsh Raoof Fereshteh Chekin Vahid Ehsani

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      A simple procedure was developed to prepare cobalt oxide nanoparticles (nano-CoO𝑥) on multiwall carbon nanotube-modified glassy carbon electrode (MWNT/GCE). Scanning electron microscopy revealed the electrodeposition of nano-CoO𝑥 with an average particle size of 25 nm onto MWNT/GCE. Also, the presence of nano-CoO𝑥 was revealed by energy dispersive X-ray spectra. The electrocatalytic activity of nano-CoO𝑥 and MWNT composite-modified GCE (CoO𝑥–MWNT/GCE) has been examined towards the oxygen evolution reaction (OER) by linear sweep voltammetry. The OER is significantly enhanced at CoO𝑥–MWNT/GCE, as demonstrated by a negative shift in the polarization curves at the CoO𝑥–MWNT/GCE compared with that obtained at the CoO𝑥–GCE and GCE. Optimization of the operating experimental conditions (i.e., solution pH and loading level of nano-CoO𝑥) has been achieved to maximize the electrocatalytic activity of CoO𝑥–MWNT/GCE. The maximum electrocatalytic activity towards the OER was obtained in alkaline media (pH = 13). The electrocatalytic activity of CoO𝑥–MWNT/GCE increased with the number of potential cycles employed for the CoO𝑥 deposition till a certain loading (20 cycles) beyond which an adverse effect is observed. The fabricated CoO𝑥–MWNT/GCE exhibited a good stability and durability. The value of energy saving per gram of oxygen gas at a current density of 10 mA cm-2 is 19.3 kWh kg-1.

    • Synthesis and spectroscopic characterization of palladium-doped titanium dioxide catalyst

      Fereshteh Chekin Samira Bagheri Sharifah Bee Abd Hamid

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      In this work, we reported synthesis of palladium (Pd)-doped titanium dioxide (TiO2)(Pd-TiO2) nanoparticles by the sol–gel-assisted method. The synthesized Pd-doped TiO2 nanoparticles were characterized using X-ray diffraction, transmission electronic microscopy, energy-dispersive spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and voltammetry techniques. The analysis showed that particles are spherical in shape and pure anatase form with average size about 10 nm. To investigate the catalytic efficiency of Pd-TiO2 nanoparticles, the hydrogen evolution reaction using the deposited film of Pd-TiO2 nanoparticles on glassy carbon electrode (Pd-TiO2/GCE) was studied in 0.1 M H2SO4 solution using linear scanning voltammetry. This study demonstrates the feasibility of using gelatin for the synthesis of Pd-TiO2 catalyst.

    • Sol–gel synthesis of palladium nanoparticles supported on reduced graphene oxide: an active electrocatalyst for hydrogen evolution reaction

      Fereshteh Chekin

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      In this work, the synthesis and characterization of palladium nanoparticle-reduced graphene oxide hybrid (Pd–rGO) material is reported. Techniques of X-ray diffraction, transmission electron microscope (TEM), energy-dispersive X-ray, FT-IR spectroscopy, thermogravimetric analysis and cyclic voltammetry were used to characterize the structure and properties of the Pd–rGO. Results demonstrate the effect of Pd on the reduced GO. The average particle size of the Pd nanoparticles supported on rGO obtained from TEM is about 12–18 nm. Moreover, glassy carbon electrode (GCE) modified with palladium nanoparticle–graphene oxide hybrid (Pd–rGO/GCE) was prepared by casting of the Pd–rGO solution on GCE. The electrochemical and catalytic activity of the Pd–rGO/GCE was studied in 0.1 M H2SO4 solution. The Pd–rGO/GCE electrode exhibited remarkable electrocatalytic activity for the hydrogen evolution reaction (HER). At potential more negative than −0.4 V vs. Ag|AgCl|KCl3M, the current is mainly due to hydrogen evolution reaction. Finally, the kinetic parameters of hydrogen evolution reaction are also discussed on the Pd–rGO/GCE.

    • Glassy carbon electrodes modified with gelatin functionalized reduced graphene oxide nanosheet for determination of gallic acid

      Fereshteh Chekin Samira Bagheri Sharifah Bee Abd Hamid

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      A simple approach for the preparation of gelatin functionalized reduced graphene oxide nanosheet (Gel-RGONS) by chemical reduction of graphene oxide (GO) using gelatin as both reducing agent and stabilizing agent in an aqueous solution was developed. The morphology and structure of the Gel-RGONS were examined by X-ray diffraction, transmission electron microscopy, ultraviolet–visible spectroscopy and Raman spectroscopy. Gelatin acted as a functionalizing reagent to guarantee good dispersibility and stability of the r in distilled water. Moreover, a new electrochemical sensor was developed based on Gel-RGONS modified glassy carbon electrode (Gel-RGONS/GCE). Gel-r exhibits excellent electrocatalytic activity to gallic acid (GA) oxidation. The experimental conditions such as pH, adsorption time and scan rate were optimized for the determination of GA. Under optimum conditions, the sensor responded linearly to GA in the concentration of 1.0 × 10−6 to 1.1 × 10−4 M with detection limit of 4.7 × 10−7 M at 3𝜎 using linear sweep voltammetry (LSV). The method has been successfully applied to the determination of GA in sample of black tea.

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