Synthesis of Small‐Sized,Porous, and Low‐Toxic Magnetite Nanoparticles by Thin POSS Silica Coating

In this communication, we report the synthesis of small‐sized (<10 nm), water‐soluble, magnetic nanoparticles (MNPs) coated with polyhedral oligomeric silsesquioxanes (POSS), which contain either polyethylene glycol (PEG) or octa(tetramethylammonium) (OctaTMA) as functional groups. The POSS‐coated MNPs exhibit superparamagnetic behavior with saturation magnetic moments (51–53 emu g^?1) comparable to silica‐coated MNPs. They also provide good colloidal stability at different pH and salt concentrations, and low cytotoxicity to MCF‐7 human breast epithelial cells. The relaxivity data and magnetic resonance (MR) phantom images demonstrate the potential application of these MNPs in bioimaging.     

Form I of desloratadine,a tricyclic anti­histamine

The title compound [systematic name: 8‐chloro‐11‐(piperidin‐4‐yl­idene)‐6,11‐dihydro‐5H‐benzo[4,5]cyclo­hepta­[2,1‐b]pyridine], C₁₉H₁₉ClN₂, was crystallized from ethyl acetate. The inter­esting feature of the reported structure is that it does not contain any strong hydrogen bonds, although the mol­ecule contains a secondary NH group, which is a good hydrogen‐bond donor.     

Palladium-catalysed three component synthesis of α,β-unsaturated amidines and imidates

Palladium-catalysed three component coupling of an alkenylbromide, isonitrile and an amine or alkoxide/phenoxide affords α,β-unsaturated-amidines and -imidates.     

Role of orientation in kinetics of nucleation and growth of crystals in polymers

A theoretical framework is provided for generalizing the inferences drawn from the results of earlier experimental studies of kinetics of crystallization in oriented poly(ethylene terephthalate). The framework is obtained by combining extensions of classical nucleation theories in polymers^3,4 and a theory of crystal growth with anisotropic incorporation of segments into growing crystals.¹⁵ It is shown that, while a very strong dependence of rate of primary nucleation on orientation does exist, there is a only a much weaker dependence of rate of crystal growth on the orientation of the crystallizing polymer. The theoretical formulation provided here would allow qualitative estimates for comparison with experiments.     

A simple and sensitive analytical method for the determination of antimony in environmental and biological samples.

The results of a study and application of leucocrystal violet for the determination of antimony in parts per million levels is described here. The proposed method is based on the reaction of antimony(III) with acidified potassium iodate to liberate iodine. The liberated iodine selectively oxidizes leucocrystal violet to crystal violet dye. The formed dye shows maximum absorbance at 590 nm. The color system obeys Beer's law in the concentration range from 0.4 - 3.6 microg antimony per 25 ml of final solution. The molar absorptivity and Sandell's sensitivity were found to be 7.32 x 10(5) l mol(-1) cm(-1) and 0.0016 microg cm(-2), respectively. All variables were studied in order to optimize the reaction. The proposed method is satisfactorily applicable for the analysis of antimony in various environmental and biological samples. The method is simple, highly sensitive, accurate and reliable.     

A shape-optimization technique for the capillary surface problem

Summary The problem of the construction of an equilibrium surface taking the surface tension into account leads to Laplace-Young equation which is a nonlinear elliptic free-boundary problem. In contrast to Orr et al. where an iterative technique is used for direct solution of the equation for problems with simple geometry, we propose here an alternative approach based on shape optimization techniques. The shape of the domain of the liquid is varied to attain the optimality condition. Using optimal control theory to derive expressions for the gradient, a numerical scheme is proposed and simple model problems are solved to validate the scheme.     

Photosensitization of TiO2 colloids by Erythrosin B in acetonitrile

Photosensitization by Erythrosin B of a TiO₂ colloidal dispersion in acetonitrile has been studied by fast kinetic spectroscopy. The dye molecules adsorbed on the TiO₂ surface had a significantly shorter lifetime (2&#x0303; 250 ps) compared to those in homogeneous solution (≈ 1.6 ns) in acetonitrile. The photosensitization of TiO₂ occurred more efficiently from the singlet than from the triplet state of the dye.     

Mechanistic evaluation of arsenite oxidation in TiO2 assisted photocatalysis

We report herein a detailed assessment of the roles of O2, H2O2, *OH, and O2-* in the TiO2 assisted photocatalytic oxidation (PCO) of arsenite. Although both arsenite, As(III), and arsenate, As(V), adsorb extensively onto the surface of TiO2, past studies relied primarily on the analysis of the arsenic species in solution, neglecting those adsorbed onto the surface of TiO2. We used extraction and analyses of the arsenic species adsorbed onto the surface of the TiO2 to illustrate that the oxidation of As(III) to As(V) occurs in an adsorbed state during TiO2 PCO. The TiO2 photocatalytic oxidation (PCO) of surface adsorbed As(III) in deoxygenated solutions with electron scavengers, Cu2+, and polyoxometalates (POM) yields oxidation rates that are comparable to those observed under oxygen saturation, implying the primary role of oxygen is as a scavenger of the conduction band electron. Pulse radiolysis and competition kinetics were employed to determine a rate constant of 3.6 x 10(6) M(-1) s(-1) for the reaction of As(III) with O2-*. Transient absorption studies of adsorbed hydroxyl radicals, generated by subjecting colloidal TiO2 to radiolytic conditions, provide convincing evidence that the adsorbed hydroxyl radical (TiO2+*OH) plays the central role in the oxidation with As(III) during TiO2 assisted photocatalysis. Our results suggest the reaction of superoxide anion radical does not contribute in the conversion of As(III) when compared to the reaction of As(III) with *OH radical during TiO2 PCO.