Zinc oxide: A case study in contemporary computational solid state chemistry

Computational techniques have been applied to study a broad range of chemical and physical properties of zinc oxide. Both interatomic-potential and density functional theory methods are used to investigate structural, thermodynamic, surface, and defect properties. We survey the structures and energies of nano-particulate zinc oxide.     

PHOTOCHROMIC PROPERTIES OF (E)-DICYCLOPROPYLMETHYLENE-(2,5-DIMETHYL-3-FURYLETHYLIDENE)-SUCCINIC ANHYDRIDE DOPED IN POLYSTYRENE THIN FILMS

Fulgide 1-E doped in polystyrene polymer films was heated at various annealing temperatures.Upon irradiation with UV light(366 nm),fulgide 1-E undergoes a conrotatory ring closure to the pink colored closed form 1-C.The later color was switched back to the original color when the films were irradiated with white light.The kinetics of photocoloration and photobleaching processes were followed spectrophotometrically by monitoring the absorbance of the ring closed product 1-C at itsλ_(max) of 525 nm.The fir...     

An Inhibitive Determination Method for Heavy Metals Using Bromelain,A Cysteine Protease

A heavy-metal assay has been developed using bromelain, a protease. The enzyme is assayed using casein as a substrate with Coomassie dye to track completion of hydrolysis of casein. In the absence of inhibitors, casein is hydrolysed to completion, and the solution is brown. In the presence of metal ions such as Hg²⁺ and Cu²⁺, the hydrolysis of casein is inhibited, and the solution remains blue. Exclusion of sulfhydryl protective agent and ethylenediaminetetraacetic in the original assay improved sensitivity to heavy metals several fold. The assay is sensitive to Hg²⁺ and Cu²⁺, exhibiting a dose–response curve with an IC₅₀ of 0.15 mg l⁻¹ for Hg²⁺ and a one-phase binding curve with an IC₅₀ of 0.23 mg l⁻¹ for Cu²⁺. The IC₅₀ value for Hg²⁺ is found to be lower to several other assays such as immobilized urease and papain assay, whilst the IC₅₀ value for Cu²⁺ is lower than immobilized urease, 15-min Microtox™, and rainbow trout.     

Environmental impact assessment of post illegal mining activities in Chini Lake with regards to natural radionuclides and heavy metals in water and sediment

Journal of Radioanalytical and Nuclear Chemistry - Comprehensive radiological survey and evaluation of heavy metal contamination were conducted in Chini Lake, which has been awarded a pristine...     

Molecular structure investigation and biological evaluation of Michael adducts derived from dimedone

Trimolecular salt Michael adducts 2a–c were synthesized in excellent yields up to 92 % via one-pot multicomponent reactions in an aqueous medium. The chemical structures of compounds 2a–c were characterized by X-ray single-crystal diffraction techniques. Calculations of the density functional theory for the synthesized compound were performed. The stability of the products was deduced by TGA analysis. Compounds 2a–c were screened in vitro for different bio-assays such as thymidine phosphorylase inhibition assay, urease inhibition assay, β-glucuronidase inhibition assays and cytotoxicity against PC-3 and HeLa cell lines.     

Dipolar cycloaddition based multi-component reaction: Synthesis of spiro tethered acenaphthylene–indolizine–pyridinone hybrids

The stereoselective syntheses of novel dispiro acenaphthylene–indolizine–pyridinone hybrid heterocycles have been achieved through one-pot four-component domino 1,3-dipolar cycloaddition–Michael addition–air oxidation sequence of reactions.     

Sol-gel TiO2 decorated on eggshell nanocrystal as engineered adsorbents for removal of acid dye

Calcined eggshell (CES) food residue was modified by depositing sol-gel titanium dioxide (TiO₂) nanoparticles with narrow size distribution onto it through in situ precipitation and a novel hybrid nano biosorbent, namely TiO₂-CES, was obtained. The deposition was characterized and the TiO₂-CES nano network was used for efficient adsorption of single azo class anionic dye acid red nylon 57 (AN57) from aqueous solutions and the adsorption was pH dependent. Lower pH favored the sorption at the tested different pHs of 1.0–8.0. The calcination temperature had a cogent influence on the adsorption process. The sorption process reached equilibrium within 40?min, and the mathematical models were positively verified and could be described by a pseudo-second-order pattern, while equilibrium was described with Langmuir-type equation. In addition, the reusability study has proven that 0.5?M HNO₃ was efficient enough to desorb AN57 from the hybrid nano sorbent. All results validated that TiO₂-CES is Eco-Friendly adsorbent material practical treatment of dyes contaminated water.     

Unexpected efficiency of cyclic amidine catalysts in depolymerizing poly(ethylene terephthalate)

This article describes studies on the catalytic activity of several nitrogen‐based organic catalysts for the depolymerization of poly(ethylene terephthalate) (PET), in which a few cyclic amidines work more effectively than a potent, bifunctional guanidine‐based catalyst 1,5,7‐triazabicyclo‐[4,4,0]‐dec‐5‐ene (TBD) in the presence of short chain diols that play a role in activation of carbonyl groups through hydrogen bonding. Further studies prove that the catalytic efficiency at the above specific conditions depends only on the extent of activation of a hydroxyl group rather than simply the pK_a of the bases. For glycolysis with excess short‐chain alkanediols, 1,8‐diazabicyclo[5.4.0]undec‐7‐ene is the best catalyst. In contrast, TBD shows outstanding catalytic activity in depolymerizations of PET with mono‐alcohols and longer‐chain diols. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Towards multifunctional antioxidants: synthesis, electrochemistry, in vitro and cell culture evaluation of compounds with ligand/catalytic properties

Numerous human diseases are linked to a biochemical condition known as oxidative stress (OS). Antioxidants are therefore becoming increasingly important as potential disease prevention and therapeutic agents. Since OS is a multi-stressor event, agents combining a range of different antioxidant properties, such as redox catalysis and metal binding, might be more effective and selective than mono-functional agents. Selenium derivatives of aniline and pyridine combine redox activity with metal binding properties. These multifunctional agents have a distinct electrochemical profile, and exhibit good catalytic activity in the glutathione peroxidase mimic and metallothionein assays. They also show antioxidant activity in a skin cell model of UVA-induced stress. These compounds might therefore provide the basis for novel agents combining two or more distinct antioxidant properties.     

Effects of pH on mechanical and morphological studies of silica filled polyvinyl chloride-50% epoxidized natural rubber (PVC-ENR50) nanocomposite

Effects of pH on mechanical properties as well as morphological studies of sol–gel derived in situ silica in polyvinyl chloride-50% epoxidized natural rubber (PVC-ENR50) nanocomposites are reported. In particular, a range of acid concentrations was investigated. These nanocomposites were prepared by solution casting technique and tetraethoxysilane (TEOS) was used as the silica precursor. The prepared nanocomposites were characterized using tensile test, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The tensile test indicated that the highest mechanical strength was at 30% TEOS added for the nanocomposite prepared at pH 2.0. At pH 1.0 and 1.5 the maximum tensile strength reading was at 20% TEOS added with value of 24.3 and 24.5 MPa, respectively. SEM and TEM revealed the dispersion of silica particles in the polymer matrix. For nanocomposites prepared at pH 1.0 and 1.5, the silica particles were finely dispersed with the average size of 60 nm until 20% TEOS added. Meanwhile for nanocomposite prepared at pH 2.0, silica particles were homogenously distributed in the polymer matrix with average diameter of 30 nm until 30% TEOS and agglomerated after 30% TEOS loading.