Z.A. ALOthman

Effect of ionic liquid on activity, stability, and structure of enzymes: A review

Ionic liquids have shown their potential as a solvent media for many enzymatic reactions as well as protein preservation, because of their unusual characteristics. It is also observed that change in cation or anion alters the physiochemical properties of the ionic liquids, which in turn influence the enzymatic reactions by altering the structure, activity, enatioselectivity, and stability of the enzymes. Thus, it is utmost need of the researchers to have full understanding of these influences created by ionic liquids before choosing or developing an ionic liquid to serve as solvent media for enzymatic reaction or protein preservation. So, in the present review, we try to shed light on effects of ionic liquids chemistry on structure, stability, and activity of enzymes, which will be helpful for the researchers in various biocatalytic applications.

Synthesis, Characterization, and Analytical Applications of a New Composite Cation Exchange Material Acetonitrile Stannic(IV) Selenite: Adsorption Behavior of Toxic Metal Ions in Nonionic Surfactant Medium

A composite cation exchange material acetonitrile stannic(IV) selenite was prepared under different experimental conditions. The ion exchange capacity of the material was improved from 0.75 to 1.83 meq g−1 in comparison to its inorganic counterpart, stannic selenite. The material was characterized on the basis of X-ray, TGA, FTIR, and SEM studies. Ion-exchange capacity, pH titration, elution behavior, and distribution studies were also carried out to determine the preliminary ion-exchange properties of the material. Furthermore, it was investigated that this ion exchange material has a good reusability after 8 times regeneration. The sorption behavior of metal ions was studied in nonionic surfactants namely triton x-100 and tween. On the basis of distribution coefficient studies, several binary separations of metal ions viz- Pb2+-Th4+, Ni2+-Th4+, Ni2+-Zn2+, Cu2+-Ce4+, Al3+-Bi3+, and Al3+Zn2+ was achieved on the packed column of this ion exchange material. The practical applicability of this cation-exchanger was demonstrated in the separation of Th4+ from a synthetic mixture of Th4+, Ca2+, Sr2+, Ni2+, and Mg2+ as well as Cu2+ and Zn2+ from a brass alloy sample. Thus, all the studies suggest that acetonitrile stannic(IV) selenite has excellent potential for the removal of metal ionic pollutant species from aqueous media effectively.

Anticorrosive assay-guided isolation of active phytoconstituents from Anthemis pseudocotula extracts and a detailed study of their effects on the corrosion of mild steel in acidic media

In this study, anticorrosive properties of various extracts (methanolic, aqueous methanolic and water extracts) of Anthemis pseudocotula for mild steel in 1.0 M HCl media is screened for the first time. Among the various tested extracts, the methanolic extract of A. pseudocotula shows the highest corrosion inhibition activity. Anticorrosive assay-guided isolation of this methanolic extract results in the isolation of a highly potent anticorrosive compound, APB (luteolin-7-O-β-D-glucoside). The anticorrosive effects of APB on mild steel in 1.0 M HCl media were evaluated in detail using gravimetric, Tafel plots, linear polarization, electrochemical impedance spectroscopy and SEM and EDS techniques. Tafel plots reveal that APB acts as a mixed-type inhibitor. The adsorption behaviour of this green inhibitor on the mild-steel surface obeys the Langmuir adsorption isotherm. A surface morphology study through SEM and EDS analysis displays a noteworthy upgraded surface morphology of the mild steel plate in the presence of the green inhibitor in 1.0 M HCl media. The results obtained from electrochemical tests and weight loss measurements are in good agreement which shows excellent inhibition efficiency for the natural compound APB.

A membrane filtration procedure for the enrichment, separation, and flame atomic absorption spectrometric determinations of some metals in water, hair, urine, and fish samples

AbstractA cellulose acetate membrane filter was applied for solid-phase extraction of Cd(II), Co(II), Cu(II), Fe(III), Ni(II), and Pb(II) from urine, hair, fish, and various water samples. The analyte ions were adsorbed on membrane filter as Cochenille red complexes and then eluted using 10 mL 3 M CH3COOH. The matrix effects from concomitants and analytical parameters, including pH, sample volume, membrane type, and flow rates, were investigated. The analyte ion detection limit for the proposed method was in the range 1.0–5.2 μg/L. The preconcentration factors were calculated as 30 for Cu(II), 40 for Co(II), Ni(II), Cd(II) as well as Pb(II), and 50 for Fe(III). The proposed method was validated by analyzing certified reference materials. This method was successfully applied to water, hair, fish, and urine samples with good results.

Improved Photoelectrochemical Cell Performance of Tin Oxide with Functionalized Multiwalled Carbon Nanotubes-Cadmium Selenide Sensitizer.

Here we report functionalized multiwalled carbon nanotubes (f-MWCNTs)-CdSe nanocrystals (NCs) as photosensitizer in photoelectrochemical cells, where f-MWCNTs were uniformly coated with CdSe NCs onto SnO2 upright standing nanosheets by using a simple electrodeposition method. The resultant blended photoanodes demonstrate extraordinary electrochemical properties including higher Stern-Volmer constant, higher absorbance, and positive quenching, etc., caused by more accessibility of CdSe NCs compared with pristine SnO2-CdSe photoanode. Atomic and weight percent changes of carbon with f-MWCNTs blending concentrations were confirmed from the energy dispersive X-ray analysis. The morphology images show a uniform coverage of CdSe NCs over f-MWCNTs forming a core-shell type structure as a blend. Compared to pristine CdSe, photoanode with f-MWCNTs demonstrated a 257% increase in overall power conversion efficiency. Obtained results were corroborated by the electrochemical impedance analysis. Higher scattering, more accessibility, and hierarchical structure of SnO2-f-MWCNTs-blend-CdSe NCs photoanode is responsible for higher (a) electron mobility (6.89 × 10(-4) to 10.89 × 10(-4) cm(2) V(-1) S(1-)), (b) diffusion length (27 × 10(-6)),

Fe3O4 nanoparticles and ultrasound assisted dispersive liquid–liquid microextraction of lead(II) for its microsampling flame atomic absorption spectrometric determination in food and environmental samples

A method for the isolation of lead from aqueous samples as a Chicago sky blue 6B chelate, based on the combination of Fe3O4 nanoparticles and ultrasound assisted dispersive liquid–liquid microextraction (NPU-DLLME) prior to flame atomic absorption spectrometry, was developed. The amount of Fe3O4 nanoparticles added and the length of ultrasound exposure were optimized, and quantitative recovery was achieved at pH 6. The limit of quantification for solid samples was calculated to be 8.5 mg kg−1. The relative standard deviation (RSD) determined for a standard solution containing 4.5 μg Pb(II) was 2.7%. The evaluation of accuracy was performed with wastewater and corn bran certified reference materials. This method was applied for the determination of lead in water and a few spices.

A Comparative Study on Characterization of Aluminium Tungstate and Surfactant-Based Aluminium Tungstate Cation-Exchangers: Analytical Applications for the Separation of Toxic Metal Ions

Two cation-exchange materials, aluminium tungstate (AT) and sodium dodecyl sulphate–aluminium tungstate (SDS–AT), were synthesized. Both samples were characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy. The distribution coefficients for various metal ions on SDS–AT cation-exchange material were performed in different solvent systems. On the basis of distribution coefficient values, the SDS–AT cation-exchange material was found to be selective for the very toxic metal ion, Cr3+. The hybrid cation-exchange material offered a variety of technological opportunities for quantitative determination and separation of Cr3+ from synthetic mixtures of metal ions. Some binary and ternary separations of metal ions; viz., Cd2+–Cr3+, Zn2+–Cr3+, Cu2+–Cr3+, Pb2+–Cr3+, Mg2+–Pb2+–Cr3+ and Mg2+–Cd2+–Cr3+, were performed using a packed column of this material.

Recent analytical applications of nanoparticle sensitized lucigenin and luminol chemiluminescent reactions

There is an ever-increasing demand for rapid, sensitive, cost effective and selective detection methods for the analysis of many essential compounds. When chemiluminescence has been introduced to analytical chemistry as a detection technique, it has been shown to meet many of these requirements. This method has become a powerful tool for the determination of many compounds. Using this method, low detection limits can be obtained with simple and inexpensive instrumentation. Coupled with flow injection technique the method has become more popular for wider applications. Since many excellent reviews on the chemiluminogenic techniques have appeared in the literature in recent years, the present paper does not intend to cover the exhaustive studies in this area, but will selectively describe the analytical applications of nanoparticle sensitized lucigenin and luminol chemiluminescent reactions and evaluate their recent progress together with our present work.

Adsorptive performance of MOF nanocomposite for methylene blue and malachite green dyes: Kinetics, isotherm and mechanism

In the present study, Fe3O4@AMCA-MIL-53(Al) nanocomposite was utilized for the adsorptive removal of highly toxic MB and MG dyes from aqueous environment. The batch adsorption tests were performed at different contact time, pH, Fe3O4@AMCA-MIL-53(Al) dose, initial concentration of dyes and temperature. The maximum adsorption capacity of MB and MG dyes onto of Fe3O4@AMCA-MIL-53(Al) using Langmuir equation was 1.02 and 0.90 m mol/g, respectively. The isotherm and kinetic studies revealed that adsorption data were well fitted to Langmuir isotherm and pseudo-first-order kinetics models. Various thermodynamic parameters were also calculated and interpreted. The positive and negative values of ΔH° and ΔG° indicated that the adsorption was endothermic and spontaneous, respectively. The adsorptive binding of MB and MG on Fe3O4@AMCA-MIL53(Al) nanocomposite was directed by carboxylate and amide groups through electrostatic interaction, π-π interaction and hydrogen bonding. The desorption of both dyes from Fe3O4@AMCA-MIL-53(Al) was also performed using mixed solution of 0.01 M HCl/ethanol. Thus, we conclude that the Fe3O4@AMCA-MIL-53(Al) was an outstanding material for the removal of dyes from aqueous environment.

Zirconium oxide films: deposition techniques and their applications in dye-sensitized solar cells

AbstractZirconium oxide (ZrO2) is acquiring considerable attention of most of the research groups and leading to a large number of publications due to its unique properties, especially in the context of emerging trends in the third generation of solar cell research. ZrO2 films offer magnificent aspects related to physicochemical properties, and the properties are found to be dependent on synthesis methods. In the present review, various deposition techniques used to grow zirconium oxide thin films and their application to enhance the quantum efficiency of titanium oxide (TiO2) based dye-sensitized solar cells (DSSCs) are discussed. Also, the modulated performances of DSSCs fabricated by growing the conformal ZrO2 insulating films to retard interfacial recombination dynamics on preformed TiO2 films are discussed. Graphical abstractᅟ