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The present study demonstrates the effect of light irradiation on the esterification of oleic acid catalyzed by immobilized Pseudomonas cepacia lipase. The reaction rates of all the experiments under light irradiation were found to be higher than dark conditions. The kinetics of reactions supported the Ping‐Pong Bi‐Bi mechanism with dead end inhibition by both the alcohol and acid substrates. Moreover, circular dichroism (CD) spectroscopy was used to analyze the effect of light on lipase enzyme. The CD spectroscopic studies confirmed that the conformational changes in the secondary structure of the lipase enzyme increased the reaction rate of light‐illuminated experiments, which might have opened up the active sites of enzymes and thus, resulted in higher reaction rates compared to dark reactions. These results have successfully demonstrated that the light illumination positively influenced the rate of P. cepacia enzyme‐catalyzed esterification reactions.

In this work, manganese dioxide/carbon nanotube (MnO2/CNT) have been synthesized by sonochemical-coprecipitation method and demonstrated that it could be an effective electrocatalyst for oxygen reduction reaction (ORR). Moreover, the effect of CNT inclusion with MnO2 was also investigated for ORR. The physical and electrochemical properties of the MnO2/CNT were examined by powder X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR) spectroscopy, Brunauer-Emmett-Teller (BET), Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy/Energy Dispersive X-ray (FESEM/EDX), Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Mott-Schottky and Rotating Disk Electrode (RDE) analysis. CV showed higher currents for the ORR in MnO2/CNT than CNT; however, ORR current dropped when the MnO2 loading was increased from 20–40 %. The EIS analysis showed that charge-transfer resistance for MnO2/CNT was significantly lower compared to the MnO2 indicating that MnO2 has good contact with CNT and the composite possess high electrical conductivity. Mott-Schottky results demonstrated that incorporation of CNT into MnO2 resulted in producing larger electron density in n-type MnO2/CNT compared to MnO2 which is liable for efficient electron donation from the Mn3+ to adsorbed oxygen in the rate determining step. RDE results showed that MnO2/CNT follows 4e− transfer pathway, indicating its ability to act as an effective ORR electrocatalyst.

The photovoltaic effect of the silicon (Si)/silicon carbide (SiC) quantum dot super lattice (QDSL) and multi-quantum well (QW) strucutres is presented based on numerical simulation and experimental studies. The QDSL and QW structures act as an intermediate layer in a p-i-n Si solar cell. The QDSL consists of a stack of four 4-nm Si nano disks and 2-nm SiC barrier layers embedded in a SiC matrix fabricated with a top-down etching process. The Si nano disks were observed with bright field-scanning transmission electron microscopy. The simulation results based on the 3D finite element method confirmed that the quantum effect on the band structure for the QDSL and QW structures was different and had different effects on solar cell operation. The effect of vertical wave-function coupling to form a miniband in the QDSL was observed based on the solar-cell performance, showing a dramatic photovoltaic response in generating a high photocurrent density Jsc of 29.24 mA/cm2, open circuit voltage Voc of 0.51 V, fill factor FF of 0.74, and efficiency η of 11.07% with respect to a i-QW solar cell with Jsc of 25.27 mA/cm2, Voc of 0.49 V, FF of 0.69, and η of 8.61% and an i-Si solar cell with Jsc of 27.63 mA/cm2, Voc of 0.55 V, FF of 0.61, and η of 10.00%. A wide range of photo-carrier transports by the QD arrays in the QDSL solar cell is possible in the internal quantum efficiency spectra with respect to the internal quantum efficiency of the i-QW solar cell. Copyright © 2015 John Wiley & Sons, Ltd.

Adsorption equilibrium and kinetic experiments have been conducted in batch mode to evaluate Cr(VI)-tea-leaves waste system. The equilibrium data followed the Langmuir adsorption isotherm and the adsorption was viewed as a physicochemical reversible process. A unified approach model was used to describe the adsorption system from both equilibrium and kinetic viewpoints. The model satisfactorily described both kinetic and equilibrium data. The adsorption and desorption rate constants were evaluated from the model fittings and were not dependent on initial concentration and adsorbent doses. pHzpc of the adsorbent was evaluated as 4.2 ± 0.1, and below that pH the adsorbent surface is positively charged. Adsorption of Cr(VI) was found highly pH-dependent, and the removal efficiency dropped sharply from 95 to 10% when pH of the system changed from 2 to 5. The surface functional groups of tea-leaves waste (before and after adsorption) were analyzed by Fourier transform infrared (FTIR) and the amine groups were found to take part in the adsorption of Cr(VI). The experimental result inferred that electrostatic attraction between the surface and the species is one of the major adsorption mechanisms for binding metal ions to the tea-leaves waste. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.

Conventional methods for the characterization of adsorption systems (determination of equilibrium and kinetic parameters) have been discussed. It is shown that the kinetic parameters determined by conventional methods are completely inconsistent with the equilibrium parameters. This inconsistency is due to the application of completely different models for equilibrium and kinetic study. In the present study adsorption is viewed as a Langmuir type physico-chemical reversible process and a three-parameter model is proposed which describes an adsorption system from both equilibrium and kinetic viewpoints. The model satisfactorily describes the kinetic and the equilibrium data reported by previous authors.

The reaction of o-chloranil with some methyl-substituted benzenes at elevated temperature was found to be a simple and selective route toward diarylmethanes without need for prior preparation of benzyl halides.