Current Perspectives on Chemical Sciences Vol. 7

The formation of porous silicon by Pd nanoparticles-assisted chemical etching of single-crystal Si with resistivity ? = 0.01 ?·cm at 25°C, 50°C and 75°C in HF/H₂O₂/H₂O solution was studied. Porous layers of silicon were studied by optical and scanning electron microscopy, and gravimetric analysis. It is shown that por-Si, formed by Pd nanoparticles-assisted chemical etching, has the property of ethanol electrooxidation. The chromatographic analysis of ethanol electrooxidation products on por-Si/Pd shows that the main products are CO₂, CH₄, H₂, CO, O₂, acetaldehyde (CHO)⁺, methanol and water vapor. The mass activity of the por-Si/Pd system was investigated by measuring the short-circuit current in ethanol solutions. The influence of the thickness of porous silicon and wafer on the mass activity and the charge measured during ethanol electrooxidation was established. Additionally, the mechanism of charge transport during ethanol electrooxidation was established. The high porosity of the sample ensures access of the reactants to the surface of por-Si/Pd and removal of the reaction products. The gradual reduction of the gas evolution rate was due to contamination of the surface with reaction products. The porous silicon thickness, porosity and solution composition are the main factors defined EEO efficiency.

A new and more sensitive method is developed for the determination of carbaryl pesticide, carbaryl from various environmental samples. Carbaryl on its alkaline hydrolysis gives 1-naphthol which is further diazotized with diazonium salts of 4-bromoaniline in an alkaline medium is explained. A yellow dye were obtained by coupling of the pesticide with DBA. The absorbance maxima of yellow coloured dye formed is measured at 517 nm. Beer’s law is obeyed over the concentration range of 0.5 to 8.0 ?g mL^-1 of carbaryl in a final volume of 25 mL. Molar absorptivity and Sandell’s sensitivity were found to be 6.71×10⁵ L mol^-1 cm^-1 and 0.0301 ?g cm^-2 respectively. Some variables were studied in order to optimize the reaction conditions. The experimental results indicate that the procedure can eliminate the fundamental interferences developed by other pesticides and non-target ions, thus the method was more sensitive. The reagent provided a new, simple and highly sensitive method for the determination of carbaryl in various geological and environmental samples. It is a temperature independence method and stability of the colored product are the added advantages. This method has been successfully applied for the determination of carbaryl in water, soil, rice, vegetable and various outdoor environmental samples.

The hydroformylation of camphene and other terpenes has been studied with homogeneous Rh, Co, and Pt metal complexes. Rh(CO)₂(acac)/P(OPh)₃ catalyst system has been found to be very active with almost total selectivity to aldehyde products. The role of ligands, solvents, Rh:P ratio and reaction conditions on the activity and selectivity towards camphene hydroformylation have been assessed. Kinetics of hydroformylation of camphene was investigated in the presence of [Rh(CO)₂(acac)]/ P(OPh)₃ catalyst in a temperature range of 363–383K.

Removal of Zn, Pb, Cu and Fe ions from unspent and spent engine oil was studied using Termite soil. Improper disposal of spent engine oil leads to a buildup of essential inorganic nutrients such as phosphorus, calcium, and magnesium, and trace amounts of lead, zinc, iron, copper and cobalt. These elements if in excess accumulate in plant tissues. Process parameters such as contact time and adsorbent dosage were varied. Values from contact time were used for predicting kinetics equation of their uptake. At optimum time of 40 minutes, percentage adsorption was of the order Fe>Zn>Cu>Pb for both spent and unspent engine oil. Kinetics equation such as Elovich, Intra-particle, Pseudo-first order and Pseudo-second order were tested. Results obtained shows that their sequestering pattern fit into the pseudo-second order kinetics. Initial reaction rates, h (mg/g.min) and ? (mg. g^-1min^-1) for all metal ions obtained from Pseudo-second order and Elovich kinetic models followed the trends Zn>Fe>Cu>Pb and Zn>Fe>Pb>Cu respectively in spent engine oil while for unspent engine oil, the trend was Fe>Zn>Cu>Pb for h (mg/g.min) and Zn>Fe>Pb>Cu for ? (mg. g^-1min^-1). Electrostatic attraction existing on the surface of the adsorbent assisted in the high initial reaction of Zn and Fe ions, implying good affinity of the ions for the adsorbent. Desorption constant ? (g/mg) was of the trend Cu>Pb>Fe>Zn and Cu>Pb>Zn>Fe for spent and unspent engine oils respectively. Intra-particle diffusion constant kid (mgg-1 min-1/2) followed a similar pattern, revealing strong binding between Zn and termite soil than any of the metal ion. Several kinetics models were tested but pseudo-second order kinetics was the best for predicting the kinetics for uptake of the studied metal ions. This pilot research has been able to suggest a kinetic process for uptake of the studied ions from spent and unspent engine oil.

The present study is focused on the binding interaction of sulfadoxine with bovine serum albumin under simulated physiological conditions using spectrofluorimetry. Various spectroscopic and other methods like Raman, CD, lifetime measurement, molecular modelling were also employed during the course of study. It was noticeable that sulfadoxine did quench the intrinsic fluorescence of BSA via static quenching process. The change in the secondary structure of BSA and binding mechanism was investigated with the spectral and docking studies.

Aims: To screen the Kenyan Ganoderma lucidum for phytochemicals, determine the chemical composition and antimicrobial activity.

Study Design: Hexane, ethyl acetate and methanol extraction; phytochemical study and anti-microbial activities were analysed on Kenyan G. lucidum mushroom. Structural determination of the isolated compound was done using spectral evidences and in comparison with literature. The antibacterial properties of the compound was done using disc diffusion method.

Place and Duration of Study: Department of Pure and Applied Chemistry, Masinde Muliro University of Science and Technology, between January and November, 2019.

Methodology: Sequential extraction of dried samples of Kenyan G. lucidum were done using solvents hexane, ethyl acetate and methanol. Separation of extracts of Ganoderma lucidum was done using chromatographic methods and compounds determined using spectroscopic data and in comparison with literature. The crude extracts and compound were assayed against Escherichia coli, Klebsiella pneumoniae, Methicillin-Resistant Staphylococcus aureus (MRSA), Pseudomonas aeroginosa, and Criptococcus neoformans using agar well diffusion method. The compound was assayed against Escherichia coli, Klebsiella pneumoniae, Methicillin–Resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Streptococcus pyogenes. Standard antibiotic namely; ampicillin was used as the control. Disc diffusion method was used and zones of inhibition, after respective incubation periods, were used to quantify antibacterial activity.

Results: The following group of compounds were present in the mushroom; terpenoids, carbohydrates, phenolic compounds, glycosides and polyoses. Hexane and methanol extracts showed significant activity at (p= 0.022) against MRSA while ethyl acetate extract was active against Streptococcus pyogenes (p=0.05). From hexane extract of Ganoderma lucidum, Ergosta-5, 7, 22-triene-3?, 14? – diol (22Z) was isolated. Ethylacetate and methanol extracts produced a mixture of complex compounds. Ergosta-5,7,22-triene-3?,14?-diol (22Z) exhibited significant activity against Methicillin-Resistance Staphylococcus aureus (MRSA) (p=0.022) and Streptococcus pyogenes (p = 0.05). The most sensitive microbe was Streptococcus pyogenes.

Conclusion: Kenyan Ganoderma lucidum contains terpenoids, carbohydrates, phenolic compounds, glycosides, flavonoids and phytosterols. Crude extracts (hexane, ethyl acetate and methanol) were active against MRSA and Streptococcus pyogenes. One major compound, Ergosta-5, 7, 22-triene-3?, 14? – diol (22Z) was isolated, characterized and antibacterial activity determined.

The removal of a most common toxic, environmental pollutant and carcinogen chromium (VI) was studied by batch technique for the adsorption and ion exchange method from water and organic solvent mixed media under various conditions like interaction time, pH, effect of organic solvents and temperature. Maximum adsorption of chromium (VI) on Tulsion A-2X (MP) was in the optimum pH range of 5.0-5.5. Increase in temperature decreased the adsorption of chromium (VI). Interaction time indicated that about 70% removal of chromium(VI) was within 15 min. Chromium (IV) adsorption was discussed based on first order kinetics and adsorption isotherms. Kinetics and adsorption models gave the best feasibility data of chromium(VI) and it was well interpreted by separation factor R_L between 0 to 1. Thus, it is concluded that the ion-exchange resin Tulsion A-2X (MP) could be employed in the removal of chromium(VI) from water and organic solvent mixed media.

A simple and rapid method was developed using cyclic, differential pulse and square wave voltammetric techniques for the determination of trace-level chalcone at a glassy carbon electrode. Chalcone could produce two anodic peaks at about 0.514 V and 1.478 V and a cathodic peak at about ?0.689 V. The differential pulse voltammerty presents a good linear response as compared to square wave voltammetry in the range of 0.2 - 10 ?M with a detection limit of 0.18 ?M. The proposed method was used successfully for its quantitative determination in spiked human plasma and urine as real samples. The proposed method offered the advantages of accuracy and time saving as well as simplicity of reagents and apparatus. In addition, the results obtained in the analysis of chalcone in spiked human plasma and urine samples demonstrated the applicability of the method for real sample analysis.

An efficient and clean preparation of acylals from aromatic aldehydes in the presence of synthetic phosphates (flourapatite and hydroxyapatite doped with ZnCl₂ and ZnBr₂) and acetic anhydride was achieved easily in high yields (86% - 97%) at room temperature under solvent-free conditions. Deprotec- tion of the resulting acylals has also been attained by using the same catalysts under microwave irradiation. This method consistently has advantage of ex- cellent yields (82% - 96%) and a short reaction time (3 - 4 min).

Multidisciplinary integrative approach that combine practical experimentation and mathematical modelling, material science and chemical engineering was adopted in order to study water–gas shift reaction (WGS) performance over nickel–ceria catalysts. Experimental studies on kinetic effect of metal fractions were performed in different lab-scale reactor configurations, such as fixed-bed and microchannel reactors. The quasi-steady state kinetics for the water–gas shift reaction between 250 and 550°C was evaluated using a very dilute gas (1% CO + 1.8% H₂O in ??). Experimental results were interpreted using computational models, and kinetic parameters were determined by regression analysis, while mechanistic aspects were considered only briefly. A set of experiments with realistic feed gas having a composition similar to product gas from methane partial oxidation (CO:H₂O:H₂:N₂ = 1:2:2:2) were conducted for WGS reaction in the microchannel reactor. These data were used for the model verification by simulation.

This research should be of interest to readers in focal areas of catalysis such as green processes and sustainable engineering, especially related to catalyst synthesis, characterization and its applications.

Green chemistry is the new and rapid developing branch of chemistry. It is a philosophy and study of the design of products or substances that will not be a harmful to the environment. . It is a modern science of chemistry that deals with the application of eco-friendly chemical compounds in the various areas of our life such as in everyday life uses. This area of chemistry had been developed by the need to avoid chemical hazards that organic and inorganic compounds had on the body of humans and animals. Chemistry plays a vital role in determining the quality of modern life. The chemical industry and other related industries supply us with a huge variety of essential products, from plastics to pharmaceuticals. However, these industries have the potential to seriously damage our environment. Green chemistry therefore serves to promote the design and efficient use of environmentally benign chemicals and chemical processes. This note presents the principles and concepts of Green Chemistry in our day today life.