Kinetics of the interaction of Cd(II)-histidine complex with ninhydrin in absence and presence of cationic and anionic micelles

Kinetics of the interaction of Cd(II)-histidine complex with ninhydrin has been carried out at pH 5.02 (acetic acid-sodium acetate buffer) under varying conditions of reactant concentrations, temperature, and surfactant concentrations. The order of the reaction with respect to Cd(II)-histidine complex was unity while it was fractional with respect to ninhydrin. On the basis of these studies a mechanism has been proposed. In the absence of the surfactants, the reaction followed rate equation: while, in presence of surfactants, the following rate equation was obeyed: Anionic micelles of sodium dodecyl sulphate catalyze the reaction with the rate reaching a maximum at ca. 0.10 mol dm⁻³ surfactant. The surfactant decreases activation enthalpy and makes it more negative. Cationic micelles of cetyltrimethylammonium bromide strongly inhibit the reaction and increase the activation enthalpy but make the activation entropy more positive than the SDS micelles. Added salts (KNO₃ and NaCl) inhibit the catalysis, and the effect is more with the latter. The rate constants, binding constants with surfactants, and the index of cooperativity have been evaluated. © 1997 John Wiley & Sons, Inc.     

First-principles study of vibrational properties of TiSiO4 clusters

First-principles calculations were performed to investigate the vibrational properties of monomers and dimers of titania, silica, and titania-silica hybrid clusters. Density functional theory-based formulism was employed to optimize the geometry at the B3LYP level and calculate the infrared and Raman spectra of the clusters by using the GGA-PBE exchange-correlation functional. It was found that the vibrational spectra of Ti₂O₄, Si₂O₄, and TiSiO₄ hybrid clusters provide fingerprint information about structures and structural transitions during the formation of cluster structures. In the case of Si₂O₄ the mode at 410 cm⁻¹ exhibited the largest vibration of Si atoms, whereas in the case of Ti₂O₄ the mode at 442 cm⁻¹ exhibited the largest vibration of Ti atoms. The hybrid cluster TiSiO₄ was structured using two different methods to explore the effects of starting geometry on the structures and vibrational modes of the clusters. The structural properties of the clusters remained unchanged but vibrational modes were found to be different. It is found that Si shows notable vibrations, but the metal atom Ti merely shows any vibration in the case of TiSiO₄ hybrid clusters. The low and intermediate frequency modes were stiffened, whereas the three highest frequency modes were softened when the starting geometry of the hybrid clusters was changed from Si₂O₄ to Ti₂O₄.     

Time-dependent density functional theory investigations on structural modification in carbazole-based organic photosensitizers to improve electron injection in dye-sensitized solar cell

The time-dependent density functional theory approach, implemented at hybrid-B3LYP, GGA-PBE, and density functional-based tight binding levels of theory, was used to model photoinjection in organic dye/TiO₂ quantum dot to explore the prospects of improvement of dye-sensitized solar cell (DSSC). The photosensitizer used in this study consisted of six carbazole-based organic dyes, a cyanoacrylic acid group as an acceptor and an oligothiophene π-bridge spacer. The modifications were made in the dyes by increasing the length of the spacer by adding thiophene and oxadiazole rings at different positions of the donor-acceptor bridge. The structural variations appeared to alter the electronic and optical properties of dyes studied via energy levels and excitation spectra. The UV-Vis spectra calculated for all the dyes in solvents exhibited a red shift in spectral peaks with an increase in the polarity of the solvents. The findings of the study pointed toward the indirect photoinjection of the dye-(TiO₂)₉₆ complex for six different dyes. The substitution of the oxadiazole ring at the center and addition of a thiophene ring at the edge of the spacer produced two dyes that exhibited the lowest injection energies of 0.11 and 0.17 eV, along with the regeneration energies of 1.18 and 1.12 eV, respectively. The dyes reported here may have promising applications in photoanode for enhancing the performance of DSSC.     

Detailed investigation of optimized alkali catalyzed transesterification of Jatropha oil for biodiesel production

The non-edible oils are believed to be one of the major feedstock for the production of biodiesel in future.In the present study,we investigated the production of Jatropha oil methyl esters(JOMEs) via alkali-catalyzed transesterification route.The biophysical characteristics of Jatropha oil were found within the optimal range in accordance with ASTM standards as a substitute diesel fuel.The chemical composition and production yield of as-synthesized biodiesel were confirmed by various analytical techniques such as FT-IR,1H NMR,13 C NMR and gas chromatography coupled with mass spectrometry.A high percentage conversion,～96.09%,of fatty acids into esters was achieved under optimized transesterification conditions with 6 :1 oil to methanol ratio and 0.9 wt% Na OH for 50 min at ～60°C.Moreover,twelve fatty acids methyl esters(FAME) were quantified in the GC/MS analysis and it was interesting to note that the mass fragmentation pattern of saturated,monounsaturated and diunsaturated FAME was comparable with the literature reported values.     

Thermal analysis of peristaltic flow of nanosized particles within a curved channel with second-order partial slip and porous medium

Journal of Thermal Analysis and Calorimetry - In a thermo-dynamical system, maximum transfer of energy takes the center of attention. Industrial advancement in recent years augmented the need for...     

Thermal analysis in swirling flow of titanium dioxide–aluminum oxide water hybrid nanofluid over a rotating cylinder

Journal of Thermal Analysis and Calorimetry - The purpose of this study is to examine the flow features and heat transfer in the presence of nanoparticles which are used to enhance the...     

Theoretical–Computational Study of Atmospheric DBD Plasma and Its Utility for Nanoscale Biocompatible Plasmonic Coating

In this study, time-dependent, one-dimensional modeling of a surface dielectric barrier discharge (SDBD) device, driven by a sinusoidal voltage of amplitude 1–3 kV at 20 kHz, in argon is described. An SDBD device with two Cu-stripe electrodes, covered by the quartz dielectric and with the discharge gap of 20 × 10⁻³ m, was assumed, and the time-dependent, one-dimensional discharge parameters were simulated versus time across the plasma gap. The plasma device simulated in the given arrangement was constructed and used for biocompatible antibacterial/antimicrobial coating of plasmonic particle aerosol and compared with the coating strategy of the DBD plasma jet. Simulation results showed discharge consists of an electrical breakdown, occurring in each half-cycle of the AC voltage with an electron density of 1.4 × 10¹⁰ cm⁻³ and electric field strength of 4.5 × 10⁵ Vm⁻¹. With SDBD, the surface coating comprises spatially distributed particles of mean size 29 (11) nm, while with argon plasma jet, the nanoparticles are aggregated in clusters that are three times larger in size. Both coatings are crystalline and exhibit plasmonic features in the visible spectral region. It is expected that the particle aerosols are collected under the ionic wind, induced by the plasma electric fields, and it is assumed that this follows the dominant charging mechanisms of ions diffusion. The cold plasma strategy is appealing in a sense; it opens new venues at the nanoscale to deal with biomedical and surgical devices in a flexible processing environment.