Ali Ghaffarinejad

A selective modified carbon paste electrode for determination of cyanide using tetra-3,4-pyridinoporphyrazinatocobalt(II).

A chemically modified carbon paste electrode with 3,4-tetra pyridinoporphirazinatocobalt(II) (Co(3,4 tppa) was applied to the determination of free cyanide ion. The electrode has a linear range between 1.5x10(-5)M and 1.0x10(-2)M with a Nernstian slope of 60+/-1.5mV/decade and its detection limit is 9x10(-6)M. The response time of electrode is 5min. The proposed electrode was applied successfully for the determination of cyanide in commercially available spring water. Some anions, such as SCN(-), I(-), Cl(-), Br(-) and oxalate that are usually serious interfering species for most of cyanide selective electrodes, did not have any interfering effect for this proposed electrode.

Method for Preparation of a Sol−Gel-Derived Carbon Ceramic Electrode Using Microwave Irradiation

A fast and new method for preparation of a sol-gel carbon ceramic electrode (CCE) by microwave (MW) irradiation is introduced. In comparison to previous preparation methods which require a very long time (mostly 48 h for ceramic completion and drying in air), this method requires only a few minutes. Furthermore, before MW irradiation an ultrasonic wave was applied to influence the gelation time and dispersion of particles in the sol-gel. The composition of the proposed carbon ceramic was characterized by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy, which was very similar to the air-dried sol-gel carbon ceramics. The proposed electrode was used for determination of dopamine (DA); the results show that this method has a wider linear range (LR) and lower detection limit (DL) than the air-dried CCE and exhibits a greater sensitivity for determination of DA compared to a recently reported CCE.

Enhanced visible light photocurrent response and photodegradation efficiency over TiO2–graphene nanocomposite pillared with tin porphyrin

In this study, a nanostructure material of pillared graphene made of tin porphyrin functionalized graphene-TiO2 composite (TG) was successfully synthesized. The prepared compound showed high activity in the photodegradation reaction under irradiation of visible light. To investigate the effect of graphene as well as dye sensitization on the photoactivity of the catalysts, photocatalytic properties and photocurrent responses of the photocatalyst were examined. Results showed that the composite of graphene-TiO2 containing 3% graphene had the highest photoactivity. Besides, tin porphyrin-pillared TG composite (TGSP) material exhibited an excellent visible light photocatalytic performance in degradation of methyl orange dye. The photoelectrochemical investigations determined that compared with the pure TiO2 electrode, the TGSP electrode exhibited a 23-fold enhancement of photocurrent intensity, suggesting the synergistic effect of the TiO2, the graphene, and the tin porphyrin photosensitizer in these photocatalysts. Furthermore, the mechanism of the photocatalytic process of the synthesized catalysts and the charge transfer mechanism in the prepared TGSP via its band edge positions was also discussed.

Synthesis, characterization, and photocurrent generation of a new nanocomposite based Cu–TCPP MOF and ZnO nanorod

A series of MOF/ZnO nanocomposites with different ZnO nanorod content were synthesized via a facile hydrothermal reaction. X-ray diffraction (XRD), UV-vis spectroscopy, field-emission scanning electron microscopy (FE-SEM), EDX, BET and FT-IR were employed to characterize the prepared samples. According to the UV-vis spectroscopy, the porphyrin center was filled with a Cu atom in Cu–TCPP. BET analysis shows that the surface area of Cu–TCPP MOF/ZnO nanorods composite was decreased compared to Cu–TCPP MOF. Therefore, ZnO nanorods covered the surface of the Cu–TCPP MOF crystals and distributed between the MOF nanosheets. Photocurrent measurements determined that MOF/ZnO nanocomposite with 15% of ZnO nanorod exhibited higher photoactivity under visible light irradiation. In the prepared nanocomposite, MOF sheets act as electron transport channels to efficiently separate the photogenerated charge carriers from ZnO nanorods. It is hoped that our current work could promote increased interest in designing the nanocomposites of one-dimensional semiconductor and two-dimensional MOFs for different photoassisted applications.

Determination of l-histidine by modified carbon paste electrode using tetra-3,4-pyridinoporphirazinatocopper(II)

This paper describes a potentiometric method for determination of l-histidine (l-his) in aqueous media, using a carbon paste electrode modified with tetra-3,4-pyridinoporphirazinatocopper(II) (Cu (3,4tppa)). The electrode exhibits linear response to the logarithm of the concentration of l-histidine from 2.4 x 10(-5) to 1.0 x 10(-2)M, with a response slope of -49.5 +/- 1mV and response time of about 1.5min. The detection limit according to IUPAC recommendation was 2.0 x 10(-5)M. The proposed electrode shows a good selectivity for l-his over a wide variety of anions. This chemically modified carbon paste electrode was successfully used for the determination of l-his in a synthetic serum and RANDOX control serum solutions.

Application of electrodeposited cobalt hexacyanoferrate film to extract energy from water salinity gradients

Emission of greenhouse gases and limited amount of fossil fuels lead to the emerging need for renewable and sustainable energy sources. The Gibbs free energy released when river water flows into the sea can be utilized as a source of energy. The Mixing Entropy Battery (MEB) is a novel electrochemical cell which efficiently extracts energy from this natural salinity. It consists of cationic and anionic electrodes. Each of these electrodes interacts selectively with one type of ions. In this work the “MEB” principle is applied. The battery is constructed with two inexpensive and easily prepared electrodes including carbon paste electrode modified by cobalt hexacyanoferrate film (CPE-CoHCF) as cathode, and silver/silver chloride as anode. The feasibility of electrochemical oxidation, reduction and cycling of CoHCF were demonstrated. The AgCl/CPE-CoHCF cell showed the standard cell potential of 0.497 V. A power density of about 24000 μW g−1 with 65% efficiency was achieved with this system, which is a considerable improvement over previous reported results.

A simple method for determination of d-penicillamine on the carbon paste electrode using cupric ions

The interaction of D-penicillamine (PA) with copper at the carbon paste electrode (CPE) in the presence of cupric ions (Cu(2+)) was used for the determination of PA at very low potential (0.1 V vs. Ag/AgCl) without applying of any modifier. The electrochemical response of copper is changed considerably in the presence of negligible amount of PA. In this report some important parameters, such as pH effect, Cu(2+) concentration and scan rate are studied, which the selected conditions were acetate buffer (pH=6) and 1 mM Cu(2+). The linear range for PA was from 1.0×10(-6) to 1.0×10(-4) M with an experimental detection limit of 1.0×10(-7) M. The relative standard deviation for 6 measurements was 3.8%. The interfering effects of some important inorganic ions were investigated, which there was no significant effect on the PA measurements. Also three organic interferences including ascorbic acid (AA), uric acid (UA) and l-cysteine (Cys) were examined, which the effect of AA was not notable, the interference of UA was moderate and for Cys was significant, but moderate at the levels which fined in the urine samples. This method was applied successfully for the determination of PA in urine sample.

Development of a new method based on scanner electrochemistry: applied for the speciation of Iron(II) and Iron(III)

A new, simple and inexpensive method was developed based on scanner electrochemistry as an appropriate alternative to visible spectroelectrochemistry. The electrochemical cell containing the sample solution was scanned by a flatbed scanner and color values were analyzed by software in the RGB color system. The validity of this new method was studied by speciation of iron(II) and (III). The speciation was performed by complexation of iron species with SCN−. Parameters, such as time and potential of electrolysis, which affect the system were optimized.

Synthesis of palladium–carbon nanotube–metal organic framework composite and its application as electrocatalyst for hydrogen production

There are very rare reports on using metal–organic framework (MOF) catalysts for electrochemical hydrogen production. In this study, a composite of palladium, single-walled carbon nanotube (SWCNT) and MOF-199 (Pd/SWCNTs@MOF-199) was synthesized by hydrothermal method, and its application as electrocatalyst in carbon paste electrode (CPE) structure for hydrogen production was studied. Scanning electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller and thermal gravimetric analysis were used to characterize Pd/SWCNTs@MOF-199 catalyst. The performance of the proposed modified CPE for electrochemical hydrogen production was studied by cyclic voltammetry, linear sweep voltammetry, electrochemical impedance spectroscopy and chronoamperometry techniques. The effect of solution pH and the amount of binder and catalyst in the paste composition were investigated. The results showed that the CPE modified with Pd/SWCNTs@MOF-199 reveals better catalytic characteristics such as highest catalytic activity and lowest onset potential compared to CPE and CPE modified with MOF-199 for hydrogen production in aqueous solution.

Rapid and efficient lead(II) ion removal from aqueous solutions using Malva sylvestris flower as a green biosorbent

In this study, for the first time, Malva sylvestris flower as a natural and green biosorbent was used for rapid and efficient removal of toxic Pb2+ ions from aqueous solutions. The proposed biosorbent is very cheap and is found in most parts of the world. Various influential parameters including solution pH, biosorbent particle size and dosage, contact time, stripping speed, initial metal ion concentration and temperature were investigated by Taguchi experimental design to optimize the biosorption performance. Under optimized conditions (pH, 4.5; sorbent particle size, mesh number 30; sorbent dosage, 0.2 g; contact time, 15 min; stripping speed, 500 rpm; initial metal ion concentration, 60 mg L−1; temperature, 55 °C), the maximum biosorption capacity of Malva sylvestris was 25.64 mg g−1. The obtained data fitted better to a Langmuir isotherm compared to a Freundlich isotherm model. The interfering effect of some common cations on the adsorption capacity of Pb2+ was investigated, and there was no significant interference from the mentioned cations. The experimental adsorption data were fitted to a pseudo-second order kinetic model with an initial adsorption rate constant of 204.08 mg g−1 min−1. The changes of adsorption with time showed that most of the process is completed within the first 3 minutes.