Acetaldehyde adsorption and catalytic decomposition on Pd(1 1 0) and the dissolution of carbon

The reaction of acetaldehyde with the Pd(1 1 0) surface has been studied using a molecular beam reactor, TPD and LEED. Below 270 K acetaldehyde sticks to the surface with a high initial probability (∼0.8), but no gas phase products evolve. When the reaction is run at >270 K, hydrogen evolves into the gas phase early in the reaction together with methane in a non-steady-state fashion, but above 300 K there is a very efficient steady-state catalytic reaction at the surface; this reaction is the decarbonylation of acetaldehyde to produce methane and carbon monoxide in the gas phase. This behaviour continues up to about 400 K. However, when acetaldehyde is dosed at 423 K, the reaction rate slowly evolves through a maximum to a very low catalytic rate. Upon carrying out reactor experiments at 473 K and above, the reaction mechanism changes to total dehydrogenation, and CO and H₂ are produced at high steady-state rate, not withstanding the fact that carbon is continually being deposited onto the surface. This carbon does not appear to affect the reaction, which takes place on a surface with a c(2 × 2)-C layer present, since the extra carbon is lost from the reaction zone by diffusion into the bulk of the crystal.     

Spectral and Molecular Modeling Studies on Hydroxybenzaldehydes with Native and Modified Cyclodextrins

The inclusion complexation of 2-hydroxy-3-methoxybenzaldehyde (2HMB), 4-hydroxy-3-methoxybenzaldehyde (4HMB), 3,4-dimethoxybenzaldehyde (DMB) and 4-hydroxy-3,5-dimethoxybenzaldehyde (HDMB) with α-CD, β-CD, HP-α-CD and HP-β-CD were carried out by UV-Visible, steady-state and time-resolved fluorescence and PM3 methods. All the benzaldehydes shows dual fluorescence in aqueous and CD mediums and 1:1 inclusion complexes were formed with CDs. PM3 geometry optimizations results indicate that the HDMB/CD complex is significantly more favorable than the other complexes. The negative enthalpy changes suggest that the inclusion complexation processes are spontaneous. The geometry of the most stable complex shows that methoxy/OH group of HMBs is entrapped in the less polar CD cavities, while the aldehyde group present in the upper part of the CDs cavities.     

Encapsulation of alkylparabens with natural and modified α- and β-cyclodextrins

The inclusion complexation between methylparaben, ethylparaben, propylparaben, butylparaben with α-CD, β-CD, hydroxypropyl α-cyclodextrin and hydroxypropyl β-cyclodextrin were carried out by UV–Vis, steady state and time-resolved fluorescence, FT-IR, ¹H NMR techniques and semi-empirical method (PM3). The drug molecules are all given one emission maximum in water where as dual emission in all the CDs. CDs study revealed that the paraben molecules were formed 1:1 inclusion complex. The aliphatic side chain is present in the hydrophilic part whereas hydroxyl group is present in the hydrophobic part of the CD cavity. Nanosecond time-resolved studies indicated that paraben exhibited biexponential decay in water whereas triexponential decay in CDs solution. The complexation energy, thermodynamic parameters and HOMO–LUMO energy structure were calculated using quantum chemical calculation.     

Reduced graphene oxide/ZnFe2O4 nanocomposite as an efficient catalyst for the photocatalytic degradation of methylene blue dye

Research on Chemical Intermediates - This research effort reports the design and development of reduced graphene oxide/zinc ferrite (rGO/ZnFe2O4) nanocomposites for the photo-oxidative degradation...     

An in vitro and in vivo investigation into the suitability of bacterially triggered delivery system for colon targeting

The colon specific drug delivery systems based on polysaccharides; locust bean gum and chitosan in the ratio of 2 : 3, 3 : 2 and 4 : 1 were evaluated using in vitro and in vivo methods. The in vitro studies in pH 6.8 phosphate buffer containing 2% w/v rat caecal contents showed that the cumulative percentage release of mesalazine after 26 h were 31.25+/-0.56, 46.25+/-0.96, 97.5+/-0.26 (mean+/-S.D.), respectively. The in vivo studies conducted in nine healthy male human volunteers for the various formulations revealed that, the drug release was initiated only after 5 h (i.e.) transit time of small intestine and the bioavailability (AUC(0-->t*)) of the drug was found to be 85.24+/-0.10, 196.08+/-0.12, 498.62+/-0.10 microg x h/ml 26 (mean+/-S.D.), respectively. These studies on the polysaccharides demonstrated that the combination of locust bean gum and chitosan as a coating material proved capable of protecting the core tablet containing mesalazine during the condition mimicking mouth to colon transit. In particular, the formulation containing locust bean gum and chitosan in the ratio of 4 : 1 held a better dissolution profile, higher bioavailability and hence a potential carrier for drug targeting to colon.