Solid State Phenomena Vol. 307

Abstract: Graphene-Zinc Oxide (Gr-ZnO) nanocomposites films were successfully synthesized via facile electrodeposition method in an aqueous solution under Gr concentration conditions. Gr, as a highly conductive carbon, acts as an anchor for ZnO nanosheets and plays a substantial role in controlling the degree of dispersion of ZnO nanosheets onto indium-doped tin oxide (ITO) substrate to form Gr-ZnO nanocomposite. Atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM) analysis of Gr-ZnO nanocomposite samples confirmed that the presence of ZnO nanosheets with a high degree of dispersity and crystallinity which is well linked to the thin layer of Gr nanoparticle on ITO substrate. The surface roughness of the films found increased to ~270 nm on Gr-ZnO as compared to Gr ~44 nm and ZnO ~3 nm. Further, the x-ray diffraction spectroscopy (XRD) analysis showed the result is in good agreement with Raman spectroscopy study. The cyclic voltammetry (CV) of Gr-ZnO nanocomposite revealed that the effect of electron-hole recombination process was increased and the presence of Gr in ZnO photoanode provides the fastest redox reaction and hence offers the fastest electron transfer in photoanode.

Abstract: Increasing populations of about 29.24 million people in Malaysia along with rapid improvement and development results in increasing of the energy usage demands [1]. It is estimated that primary sources of energy consumption in the world is 86.4 % from fossil fuels which consists of 36.0 % from petroleum, 27.4 % from coal, 23.0 % from natural gas [2]. However, fossil fuels energy sources are non-renewable and also contribute to pollution. In order to fulfill the needs of energy used, solar light is expected to become a leading next-generation for clean and sustainable energy resources. The main interest of solar energy over other energy sources is that sunlight can be directly harvested into solar energy with the use of small and tiny photovoltaic (PV) solar cells [3].

Abstract: This article reports on the role of potassium (K) as dopant in Cu₂ZnSn (S,Se)₄, CZTSSe thin film in context of optical properties. Thin film precursor solution is prepared in dimethyl sulfoxide (DMSO) solvent, and doped by K with six different concentrations. The prepared solution are deposited on heated soda lime glass (SLG) substrates using spray pyrolysis technique, followed by selenization process using three-step temperature approach. UV-Visible spectra show high absorption coefficient, α, more than 10⁴cm^-1 and bandgaps in narrow range 0.98eV to 1.10eV. X-ray diffractograms show that all samples exhibit kesterite structure with preferential orientation along (112) orientation. Field Emission Scanning Electron Microscopy was used to determine the morphologies of the K-doped CZTSSe thin films. 1.5 mol % of K has shown better characteristics as an absorber layer among other tested samples.

Abstract: Cyclic voltammetry can be used to investigate the chemical reactivity of species ion via oxidation and reduction process. The purpose of this study is to determine the level energy of high occupied molecule orbital (HOMO) and low unoccupied molecule orbital (LUMO) in polythiophene (PT), Poly (3-thiophene acetic acid) (P3TAA), polypyrrole (PPY) and chlorophyll (Chlo) through oxidation and reduction of molecular ions by cyclic voltammetry method. PT, P3TAA, PPY and Chlo solutions were prepared in a solvent of acetonitrile at the concentration range of 10^-2 to 10^-4 M. The current-voltage measurements for these solutions are performed using cyclic voltammetry method on input voltage from -2.0 V to 2.0 V. The working electrode used is indium tin oxide (ITO). The result of voltammogram is showed that the activity of PT species were produced three oxidation and one reduction processes. The formal reduction potential, E^o_¢ is 0.83 (positive) meaning that oxidation process was dominant. So that the reaction of PT species was exhibited irreversible electrochemical behavior. The reaction of P3TAA species was exhibited reversible electrochemical behavior, where the range value of oxidation, DE_pa and reduction, DE_pc were in range of 0.825 V to 1.120 V and -0.230 V to 0.131 V respectively. PYY species reaction was exhibited irreversible electrochemical behavior where two oxidation states occur within -0.145 V to -0.202 V and 0.870 V to 1.63 V respectively. The species activity of Chlo was exhibited irreversible electrochemical behavior where only the oxidation process was obviously appeared at range of 0.80 V to 0.95 V. The LUMO energy levels of PT, P3TAA PPY and Chlo were 5.84 eV, 5.34 eV, 1.10 eV and 3.85 eV respectively, while HOMO energy levels of PT, P3TAA PPY and Chlo were 4.61 eV, 4.25eV, 3.70 eV and 5.93 eV. The average value of energy gap of PT, P3TAA, PPY and Chlo were 1.23 eV, 1.08 eV, 2.23 eV and 1.10 eV respectively.

Abstract: Biofouling and biofilms exist as ubiquitous, undesirable accumulation of flora and fauna upon a given substrate when being immersed into an aquatic medium. Therefore, a novel antifouling based materials with the incorporation of nanotechnology has been developed for the prevention of biofouling in its initial stage through photocatalytic treatment. This study investigated the antimicrobial properties of photoactive Cerium (Ce) doped ZnO powder and explores its potential properties for future antifouling application. ZnO nanoparticles was doped with 0.4 mol% Ce was synthesized through the combination of modified citrate gelation technique and solid state sintering. The successful preparation of Ce doped ZnO was confirmed by XRD and SEM. The antimicrobial activity of Ce doped ZnO against E. coli and S. aureus was determined through antibacterial susceptibility test by agar well diffusion method whilst its photocatalytic inactivation efficiency against selected bacteria was analysed through photodegradation testing under UV light irradiation. The findings demonstrated that the synthesized Ce doped ZnO powder exhibited antibacterial effect against Gram-positive bacteria (S. aureus) and excellent photocatalytic efficiency to inactivate both Gram-negative (E. coli) and Gram-positive (S. aureus). 2 g/L of Ce doped ZnO catalyzed the 100% disinfection of both bacteria in 180 min of UV light exposure. Thus, this proved that Ce doped ZnO powder has the potential as efficient antifouling agent.

Abstract: Cerium (Ce) doped ZnO is a promising material for advanced photocatalysis. It is useful for inducing the treatment of many organic pollutants in water. However, the stability of its performance under varying temperature and saline condition has never been not fully assessed. In this study, powder form photocatalyst comprising 99.0 mol% ZnO and 1 mol% CeO₂ has been synthesized via modified citrate gelation technique and solid-state sintering at 1200 °C for 5 hours. The conversion of Ce doped ZnO from its precursors has been confirmed using XRD, SEM, and EDX techniques. The photocatalytic efficiency of the synthesized Ce doped ZnO under UV-C light (λ=265 nm) was determined. In the experiment, the operating temperature was varied between 25 to 40 °C, and the salinity of the treated solution was increased from 0 to 40 g/L NaCl. The findings revealed that the photocatalytic efficiency of Ce doped ZnO under UV light improved from 78.2% to 88.6% as the temperature increased from 25 to 40 °C. The performance of Ce doped ZnO decreased from 86.7% to 36.7% when the salinity increased from 0 g/L to 40 g/L. The elevation of temperature encouraged the photogeneration of electron-hole pairs on catalyst surface while the presence of chloride ions in treated medium caused scavenging of hydroxyl radicals or hole.

Abstract: Being one of the hazardous contaminants in the environment, continuous exposure to cadmium ions (Cd (II)) has been shown to severely affect the well being of both humans and animals. Therefore, development of a highly sensitive method to detect trace amounts of such substance in the environment acquires scientific pertinence. In this present work, carbon paste electrode modified with bis (benzylidene) ethelynediamine (BBE-CPE) was used for the determination of Cd (II) using square wave anodic stripping voltammetric (SWASV) technique. A response surface methodological approach employing the Box-Behnken design (BBD) based on four relevant variables; pH, deposition time, percentage ligand and deposition potential was used for optimizing the experimental conditions for detecting such ions. Under optimized conditions (supporting electrolyte: pH 4.5, deposition time: 350 s, ligand graphite composition: 6%, deposition potential: ‒1.1 V), a linear response over a wide range of Cd (II) concentrations (1–500 μg L⁻¹) with low detection limit (0.4 μg L^-1) and quantification limit (1.4 μg L^-1) were observed with deposition time being the most impacting factor. Pertinently, the BBE-CPE developed here exhibited exceptional recovery of Cd (II) concentrations in the sea and tap water samples, comparable with that observed under simulated conditions, suggesting its applicability for a variety of real samples.

Abstract: The optimization of the Copper ions (Cu ions) adsorption from aqueous solution for inclusion in prolonged the milling time of the extracted iron oxides from waste mill scales has been investigated. Different milling times were used to reduce the size of the raw mill scale which are 24, 48 and 72 h. The three adsorbents were characterized using XRD, FESEM and VSM. Adsorbents that milled for 72 hours gave pure magnetite from the XRD results. FESEM images revealed that prolonged the milling time might reduced the particle sizes. Magnetic hysteresis revealed that all the samples having ferromagnetic behavior. Batch adsorption experiment had been carried out with the three adsorbents and as the results, adsorbents that milled with 72 hours shown highest removal of Cu ions with 95% removal efficiency.

Abstract: Polyacrylamide gel system is widely been used in oilfield for water shutoff treatment. Gelation behavior such as proper gelation time provides a basic guideline on gel placement depth in reservoir layers. In this study, the gelation behavior of partially hydrolyzed polyacrylamide crosslinked with chromium(III) acetate (PHPA/Cr³⁺) reinforced with nano-silica was studied in term of gelation time and gel stability. The gelation time of PHPA/Cr³⁺ gel could be controlled with the addition of nano-silica where the gel has shown a delay in gelation time at low concentration of nano-silica. At 0.3 wt.% of nano-silica concentration, the gelation time has shown two times delay compared to the original gel system. The gel at the formulations of 0.7 wt.% and 1.0 wt.% nano-silica content remained stable with H code after 24 hours observation.

Abstract: Mixed matrix membrane (MMM), a developing research area, is a membrane formed by incorporating fillers in the polymeric membrane to enhance gas separation performance. In this study, MMMs comprised of blend rubbery block copolymers of polyether block amide (Pebax-1657) with a glassy polyethersulfone (PES) polymer and multi-walled carbon nanotubes (MWCNTs) were synthesized by dry phase inversion method and explored further by gas permeability test. Pebax-1657/PES/MWCNTs membrane resulted in an increased permeability as well as CO₂/CH₄ selectivity. The Pebax-1657/PES polymer blend MMM with 10wt% of MWCNTs has shown the most superior performance of CO₂ permeability, CH₄ permeability and CO₂/CH₄ selectivity in comparison with the pure Pebax-1657 resulted in 66.3% and 11.6% difference respectively.