Anuar Kassim

Cathodic electrodeposition of SnS in the presence of EDTA in aqueous media

Cathodic electrodeposition in the presence of EDTA in aqueous solution was found to offer some noteworthy improvements in our attempt to synthesise an SnS thin film. EDTA has shown its capacity for improving the longevity of the deposition bath as well as the adhesion of the deposited film on a titanium substrate. Photoelectrochemical analysis reveals outstanding photoactivity of the electrodeposited thin film, while an optical study shows an energy gap of approximately 1.1 eV. The effects of chelating agent were extracted from the results of cyclic voltammetry, photoelectrochemical test, scanning electron microscopy and X-ray diffraction spectroscopy. The latter which displays better defined signals reaffirms the appreciable improvement in the polycrystallinity of the thin film. Analysis of peak locations, coincidentally, confirms that SnS of Herzenbergite form has been obtained.

Effects of preparation temperature on the conductivity of polypyrrole conducting polymer

An attempt has heen made to investigate the effect of temperature on the conductivity of polypyrrole conducting polymer films prepared by an electrochemical method in an aqueous medium using camphor sulfonate as the dopant. The polymer was grown from aqueous solutions employing a range of temperatures (l–60°C). It was found that with increase in temperature the conductivity decreased and the optimum temperature was found to be between 10 and 30°C. The results showthatthe polymer formed at low temperature has higher conductivity and is stronger than that formed at higher temperatures. Characterization by X-ray scattering shows that interlayer distance, dBragg (Å), increases with increasing temperature. The morphology of the films formed was studied by using a scanning electron microscope (SEM). The changes in conductivity and physical appearance were interpreted as being due to compactness in the molecular packing and formation ofαβ linkages in the film.

Novel conductive polypyrrole/zinc oxide/chitosan bionanocomposite: synthesis, characterization, antioxidant, and antibacterial activities

An antibacterial and conductive bionanocomposite (BNC) film consisting of polypyrrole (Ppy), zinc oxide (ZnO) nanoparticles (NPs), and chitosan (CS) was electrochemically synthesized on indium tin oxide (ITO) glass substrate by electrooxidation of 0.1 M pyrrole in aqueous solution containing appropriate amounts of ZnO NPs uniformly dispersed in CS. This method enables the room temperature electrosynthesis of BNC film consisting of ZnO NPs incorporated within the growing Ppy/CS composite. The morphology of Ppy/ZnO/CS BNC was characterized by scanning electron microscopy. ITO–Ppy/CS and ITO–Ppy/ZnO/CS bioelectrodes were characterized using the Fourier transform infrared technique, X-ray diffraction, and thermogravimetric analysis. The electrical conductivity of nanocomposites was investigated by a four-probe method. The prepared nanocomposites were analyzed for antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl assay. The results demonstrated that the antioxidant activity of nanocomposites increased remarkably by addition of ZnO NPs. The electrical conductivity of films showed a sudden decrease for lower weight ratios of ZnO NPs (5 wt%), while it was increased gradually for higher ratios (10, 15, and 20 wt%). The nanocomposites were analyzed for antibacterial activity against Gram-positive and Gram-negative bacteria. The results indicated that the synthesized BNC is effective against all of the studied bacteria, and its effectiveness is higher for Pseudomonas aeruginosa. The thermal stability and physical properties of BNC films were increased by an increase in the weight ratio of ZnO NPs, promising novel applications for the electrically conductive polysaccharide-based nanocomposites, particularly those that may exploit the antimicrobial nature of Ppy/ZnO/CS BNCs.

Electrodeposited SnS thin films from aqueous solution

Considerable efforts have been made in recent years in the search for low-cost materials for solar energy conversion. Among the materials of great interest are polycrystalline metal chalcogenides. These can be synthesized by means of low-temperature chemical precipitation or vapour deposition techniques, as described in previous works [1, 2]. The materials may also be electrosynthesized, either cathodically [3‐5] or anodically [6‐8] from an aqueous or nonaqueous medium. Electrochemical methods, especially those performed in an aqueous medium, have recently received enormous attention due to their simplicity and cost effectiveness [9‐15]. In addition, they have the advantages of being low temperature processes, with low material wastage and with the possibility of using lower grade materials. This method has been extensively applied in the preparation of CdS and CdSe thin films. We report here the possibility of cathodic electrodeposition of another promising compound, tin sulphide (SnS), from aqueous solution. The electrodeposition was carried out on either titanium or an indium-doped tin oxide (ITO) glass substrate in a standard three-electrode cell. A saturated calomel electrode (SCE) or sometimes an Ag AgCl electrode was used as the reference electrode, while platelet or spiral Pt (99.9%) was used as the counter electrode. The deposition potential was controlled by an EG&G Princeton Applied Research (PAR) Versastat driven by model 270 Electrochemical Analysis System software. The substrate was polished and chemically and ultrasonically cleaned before being used. The electrodeposition bath was prepared from anhydrous SnCl2, sodium thiosulphate (Na2S2O3) and disodium ethylenediaminetetra-acetic acid (EDTA) salts using N2purged purified water from a Milli-Q water purification system. The resultant solution was acidified to a pH of about 1.5. The solution was continuously deaerated with N2 during electrodeposition. Prior to electrodeposition, cyclic voltammetry was run in order to determine the viable potential and to elucidate the electrochemical processes at the

Thermodynamic study of the complexation of p-isopropylcalix[6]arene with Cs+ cation in dimethylsulfoxide-acetonitrile binary media.

The complexation reactions between the macrocyclic ionophore, p-isopropylcalix[6]arene and Cs+ cation were studied in dimethylsulfoxide–acetonitrile (DMSO-AN) binary non-aqueous solvents at different temperatures using a conductometry method. The conductance data show that the stoichiometry of the (p-isopropylcalix[6]-arene·Cs)+ complex in all binary mixed solvents is 1:1. The stability of the complexes is affected by the composition of the binary solvent media and a non-linear behavior was observed for changes of log Kf of the complex versus the composition of the binary mixed solvents. The thermodynamic parameters (ΔH°c and ΔS°c) for formation of (p-isopropyl-calix[6]arene·Cs)+ complex were obtained from temperature dependence of the stability constant and the obtained results show that the (p-isopropylcalix[6]arene·Cs)+ complex is enthalpy destabilized, but entropy stabilized, and the values of the mentioned parameters are affected strongly by the nature and composition of the binary mixed solvents.

Multivariate Optimization in the Biosynthesis of a Triethanolamine (TEA)-Based Esterquat Cationic Surfactant Using an Artificial Neural Network

An Artificial Neural Network (ANN) based on the Quick Propagation (QP) algorithm was used in conjunction with an experimental design to optimize the lipase-catalyzed reaction conditions for the preparation of a triethanolamine (TEA)-based esterquat cationic surfactant. Using the best performing ANN, the optimum conditions predicted were an enzyme amount of 4.77 w/w%, reaction time of 24 h, reaction temperature of 61.9 °C, substrate (oleic acid: triethanolamine) molar ratio of 1:1 mole and agitation speed of 480 r.p.m. The relative deviation percentage under these conditions was less than 4%. The optimized method was successfully applied to the synthesis of the TEA-based esterquat cationic surfactant at a 2,000 mL scale. This method represents a more flexible and convenient means for optimizing enzymatic reaction using ANN than has been previously reported by conventional methods.

OPTICAL BAND GAP AND CONDUCTIVITY MEASUREMENTS OF POLYPYRROLE-CHITOSAN COMPOSITE THIN FILMS

Electrical conductivity and optical properties of polypyrrole-chitosan (PPy-CHI) conducting polymer composites have been investigated to determine the optical transition characteristics and energy band gap of composite films. The two electrode method and I–V characteristic technique were used to measure the conductivity of the PPy-CHI thin films, and the optical band gap was obtained from their ultraviolet absorption edges. Depending upon experimental parameter, the optical band gap (Eg) was found within 1.30–2.32 eV as estimated from optical absorption data. The band gap of the composite films decreased as the CHI content increased. The room temperature electrical conductivity of PPy-CHI thin films was found in the range of 5.84 × 10−7–15.25 × 10−7 S·cm−1 depending on the chitosan content. The thermogravimetry analysis (TGA) showed that the CHI can improve the thermal stability of PPy-CHI composite films.

Immobilization of tris(2 pyridyl) methylamine in a PVC-Membrane Sensor and Characterization of the Membrane Properties

BackgroundDue to the increasing industrial use of titanium compounds, its determination is the subject of considerable efforts. The ionophore or membrane active recognition is the most important component of any polymeric membrane sensor. The sensor’s response depends on the ionophore and bonding between the ionophore and the target ion. Ionophores with molecule-sized dimensions containing cavities or semi-cavities can surround the target ion. The bond between the ionophore and target ion gives different selectivity and sensitivity toward the other ions. Therefore, ionophores with different binding strengths can be used in the sensor.ResultsIn the present work, poly (vinyl chloride) (PVC) based membrane incorporating tris (2 pyridyl) methylamine (tpm) as an ionophore has been prepared and explored as a titanium(III) selective sensor.ConclusionsThe strengths of the ion–ionophore (Ti(OH)2+-tpm) interactions and the role of ionophore on membrane were tested by various techniques such as elemental analysis, UV–vis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and powder X-ray diffraction (XRD). All data approved the successful incorporation of organic group via covalent bond.

Synthesis and properties of poly(hydroxamic acid) from crosslinked poly(methacrylate)

Poly(hydroxamic acid) chelating ion-exchange resin was prepared from crosslinked poly(methacrylate) beads. The starting polymer was prepared by a suspension polymerization of methacrylate and divinyl benzene. Conversion of the ester groups into the hydroxamic acid was carried out by treatment with hydroxylamine in an alkaline solution. Hydroxamic acid capacity of the product was 2.71 mmol/g. The resin exhibited high affinity towards Fe(III) and Pb ions and its capacities for Fe(III), Pb, Cu, Ni and Co ions were pH dependent. The ability of the resin to carry out the separation of Fe(III)CuCo/Ni and PbNi ions is also reported.

Determining optimum conditions for lipase-catalyzed synthesis of triethanolamine (TEA)-based esterquat cationic surfactant by a Taguchi Robust design method.

A Taguchi robust design method with an L9 orthogonal array was implemented to optimize experimental conditions for the biosynthesis of triethanolamine (TEA)-based esterquat cationic surfactants using an enzymatic reaction method. The esterification reaction conversion% was considered as the response. Enzyme amount, reaction time, reaction temperature and molar ratio of substrates, [oleic acid: triethanolamine (OA:TEA)] were chosen as main parameters. As a result of the Taguchi analysis in this study, the molar ratio of substrates was found to be the most influential parameter on the esterification reaction conversion%. The amount of enzyme in the reaction had also a significant effect on reaction conversion%.