Pd-catalysed C-H functionalisation of free carboxylic acid has gained significant attention over the last few years due to the predominance of carboxylic acid moieties in pharmaceuticals and agrochemicals. But their...

No abstract

Chloromethylated polystyrene-divinylbenzene has been functionalized with dithiooxamide. The resulting chelating resin (DTOA) has been characterized by elemental analyses, infrared spectroscopy, thermogravimetric analysis, and metal ion sorption capacities. It has been used for the preconcentration and separation of Cu(II), Zn(II), Cd(II), and Pb(II) prior to their determination by FAAS. Parameters such as the amount of the resin, effect of pH, equilibration rate, sorption and desorption of metal ions, and effect of diverse ions have been studied. The maximum sorption capacities found are 0.97, 0.12, 0.08, and 0.12 mmol g À1 for Cu(II), Zn(II), Cd(II), and Pb(II) at pH 6.0, 5.5, 1.0, and 5.5, respectively. The preconcentration factors are 100, 100, 50, and 50 for Cu(II), Zn(II), Cd(II), and Pb(II), respectively. Recoveries of the metal ions were 96 6 5, 97 6 6, 96 6 5, and 96 6 5 at 95% confidence level, whereas the limits of detection are 2.0, 1.3, 2.5, and 25.0 mg L À1 for Cu(II), Zn(II), Cd(II), and Pb(II), respectively. The calibration curves were linear up to 12 mg mL À1 (R 2 ¼ 1.000), 2 mg mL À1 (R 2 ¼ 0.998), 2 mg ml À1 (R 2 ¼ 1.000), and 5 mg mL À1 (R 2 ¼ 0.979) for Cu(II), Zn(II), Cd(II), and Pb(II), respectively. The reliability of the method has been tested by analyzing certified samples.

In the present work, polymorphic phase transformation of Bi2O3 nanoparticles by the mechanical alloying method has been investigated in detail. X-ray diffraction study reveals that the room temperature stable monoclinic α-phase of Bi2O3 can be stabilized into body-centered cubic γ-phase by applying mechanical energy only to the Bi2O3 powder, without adding any dopant to the Bi2O3 matrix. The crystallite size of the γ-phase is reduced up to ∼24 nm after 18 h of milling the analytical grade α-Bi2O3 powder. Optical band gaps of all synthesized nanocrystalline powders are found to be in the semiconductor region (2.76–3.02 eV). Oxygen ion conductivity increases with the increase of γ-phase and becomes maximum in the 18 h milled sample, in which full phase transformation (α- to γ-phase) has occurred. The metastability of the γ-phase is revealed on further mechanical alloying up to 20 h when milled powder decomposes primarily to α-phase along with other crystalline polymorphic phases which are identified by X-ray diffraction as well as Raman spectra. The temperature dependence of complex conductivity follows the Arrhenius relation and also supports the semiconducting nature of the sample as obtained by optical band gap measurement. The small polaron hopping between localized states is confirmed from the real part of the complex conductivity data. The milling time and measuring temperature independent nature of the conductivity and the relaxation mechanism is confirmed from the master plot of complex impedance and ac conductivity spectra.

No abstract