The preparation of zinc silicate/ZnO particles and their use as an efficient UV absorber

The formation of zinc silicate/ZnO particles synthesized by a two-step method and their incorporation into PMMA is presented. In the first step a segmented-flow tubular reactor was used for the continuous room-temperature preparation of a zinc silicate/Zn(OH)₂ gel that was thermally treated after rinsing and drying in the second step. The same preparation procedure was also employed for the synthesis of pure ZnO and pure zinc silicate particles. It was found that the presence of the zinc silicate phase significantly influenced the final particle size, decreased the degree of crystallization and reduced the particles’ UV absorption capabilities. The reduced photocatalytic activity of the zinc silicate/ZnO particles indicated that the majority of ZnO crystallites were formed inside the zinc silicate matrix. The nanocomposite prepared from zinc silicate/ZnO particles (0.04 wt.%) and PMMA showed high UV shielding and at the same time sufficient transmittance in the visible-light region.     

Tuning of BiFeO3 multiferroic properties by light doping with Nb

Bulk ceramic samples of BiFeO₃ were light doped (up to 1%) with Nb⁵⁺ in the place of Fe³⁺ (B-site doping) and their multiferroic properties were investigated using XRD, SEM, polarization (PMTS) and magnetization (SQUID) techniques. It is shown that even the small percentages of doping can notably change electric and magnetic behavior. Electric conductivity differs by two orders of magnitude between samples doped with 0.2% and 1% Nb. The ferroelectric behavior strongly depended on conduction mechanism, and transition from space-charge-limited current (SCLC) conduction to trap-filled limited (TFL) conduction regime reflected on a change in hysteresis patterns, particularly for the samples with 0.2% and 0.5% Nb. Separation of ZFC-FC magnetization curves occurred for all Nb concentrations and increased with Nb doping. Weak ferromagnetic behavior and the increase of remnant magnetization with Nb concentration was observed from the hysteresis measurements. Coercive field changed drastically compared to the pure BiFeO₃, namely, the sample with 1% Nb exhibited very high coercive magnetic field of ~ 10?kOe.     

A new antimicrobial glucosinolate autolysis product, 4-isothiocyanatobutanoic acid,from the diffuse wallflower (Erysimum diffusum): Methyl 4-isothiocyanatobutanoate,a long unrecognized artifact of the isolation procedure?

A GC–MS analysis of Erysimum diffusum Ehrh. (Brassicaceae) glucosinolate autolysis products led to the identification of a new mustard oil constituent – 4-isothiocyanatobutanoic acid. The identity of the new glucosinolate breakdown product was confirmed by means of co-injection of the synthetic compound in the GC with the root autolysate and derivatization reaction to the well known methyl ester. Methyl ester of this acid was long believed to be a genuine glucosinolate hydrolysis product but we now provide evidence that it could be an artifact of the isolation procedure. 4-Isothiocyanatobutanoic acid was assayed for antimicrobial activity and demonstrated significant inhibitory (10–220 μg/ml) and microbicidal (10–1175 μg/ml) activity against important human pathogens.     

The most important bioactive components of cold pressed oil from different pumpkin (Cucurbita pepo L.) seeds

The composition and content of certain bioactive components of the cold pressed oil obtained from six samples of pumpkin seeds (Cucurbita pepo L.) cultivated in Serbia were analyzed by GC and GC/MS. The composition and content of fatty acids, tocopherols and phytosterols, and the total content of squalene were determined. The results indicate oil's excellent quality, with high contents of monounsaturated fatty acids (37.1 ± 0.70–43.6 ± 0.69 g/100 g of total fatty acids), total tocopherols (38.03 ± 0.25–64.11 ± 0.07 mg/100 g of oil), sterols (718.1 ± 6.1–897.8 ± 6.8 mg/100 g of oil) and especially squalene (583.2 ± 23.6–747 ± 16 mg/100 g of oil). High content of squalene, phytosterols and monounsaturated fatty acids recommend the use of this type of the oil in the nutritional and medical purposes.     

Single step recovery of lipase from Penicillium cyclopium by aqueous two-phase extraction

Recovery of lipase from Penicillium cyclopium by aqueous two-phase extraction was studied with maximal possible crude enzyme loads. In polyethylene glycol/dextran and polyethylene glycol/salt systems the influences of molecular weight and concentration of polyethylene glycol, phase-forming salt and phase volume ratio were evaluated. Lipase partition coefficient 9 followed by the top phase yield 95.7% and purification factor 3.4 were achieved in 15% (w w^?1) polyethylene glycol 4000/15% (w w^?1) KH₂PO₄/70% (w w^?1) crude enzyme. Efficient single-step recovery of lipase followed by partial enzyme purification indicated possible integration of production and primary bioseparation step by aqueous two-phase extraction. By varying phase volume ratio, the concentration of phosphate was reduced without decrease in lipase recovery.     

Characterization of poly(vinyl alcohol)/gold nanocomposites obtained by in situ gamma-irradiation method

Gamma-irradiation induced reduction of gold (Au) ions was performed in aqueous poly(vinyl alcohol) (PVA) solution. PVA/Au nanocomposites with different contents of inorganic phase were prepared by solvent evaporation. The colloids and corresponding nanocomposites show visible light absorption with strong excitonic peak in the wavelength range from 520 to 550 nm. Morphological and structural characterizations of gold nanoparticles (Au NPs) and nanocomposites were performed by TEM, XRD, and FTIR measurements. Also, Mie and Maxwell-Garnett theories were applied to calculate optical properties of Au colloids and PVA/Au nanocomposites, respectively. The changes of heat resistance upon the increase of inorganic phase were correlated to the decrease in crystal perfection of polymer. Improvement of thermal stability of nanocomposites, compared with the neat PVA, was observed when the content of inorganic phase exceeds 1 wt %. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Carbon monoxide electrooxidation on Pt and PtRu modified zeolite X

Zeolite NaX was modified by Pt and Pt/Ru nanodispersed metallic clusters. This modification was achieved by zeolite impregnation with acetylacetonate salt/acetone solution, followed by acetone evaporation and thermal decomposition of organometallic complex. Samples characterization was performed by X-ray diffraction analysis, nitrogen adsorption?Cdesorption measurements and Raman spectroscopy. The incorporation of metal into zeolite cavities induced the amorphisation of the zeolite framework on the local level. The mixture of modified zeolite and 10?wt% of carbon black, in a form of thin layer, was pasted to a glassy carbon surface by Nafion. Electrocatalytic properties of metal-modified zeolites were tested in CO electrooxidation reaction. The mutual influence between Pt and Ru atoms enhanced electroactivity of Pt/Ru-modified zeolite toward carbon monoxide electrooxidation. The behavior of untreated 13X zeolite was investigated under the same condition in order to asses the influence of the support. Gradual deactivation of 13X electrode occurred.     

17,20S(OH)2pD Can Prevent the Development of Skin Fibrosis in the Bleomycin-Induced Scleroderma Mouse Model

Systemic sclerosis (SSc; scleroderma) is a chronic fibrotic disease involving TGF-β1. Low serum vitamin D (vit D) correlates with the degree of fibrosis and expression of TGF-β1. This study was designed to determine whether the noncalcemic vit D analog, 17,20S(OH)₂pD, suppresses fibrosis and mediators of the TGF-β1 pathway in the bleomycin (BLM) model of fibrosis. Fibrosis was induced into the skin of female C57BL/6 mice by repeated injections of BLM (50 μg/100 μL) subcutaneously. Mice received daily oral gavage with either vehicle (propylene glycol) or 17,20S(OH)₂pD using 5, 15, or 30 μg/kg for 21 days. The injected skin was biopsied; analyzed histologically; examined for total collagen by Sircol; and examined for mRNA expression of MMP-13, BMP-7, MCP-1, Gli1, and Gli2 by TR-PCR. Spleen was analyzed for lymphocytes using flow cytometry. Serum was analyzed for cytokines using a multiplexed ELISA. Results showed that all three doses of 17,20S(OH)₂pD suppressed net total collagen production, dermal thickness, and total collagen content in the BLM fibrosis model. 17,20S(OH)₂pD also increased MMP-13 expression, decreased MCP-1 and Gli-2 expression in vivo, and suppressed serum levels of IL-13, TNF-α, IL-6, IL-10, IL-17, and IL-12p70. In summary, 17,20S(OH)₂pD modulates the mediators of fibrosis in vivo and suppresses total collagen production and dermal thickness. This antifibrotic property of 17,20S(OH)₂pD offers new therapeutic approaches for fibrotic disorders.     

Effect of thermal oxidative ageing on the morphology of natural rubber networks as viewed by ESR

The change of network morphology of unfilled sulfur crosslinked natural rubber exposed to thermal oxidative ageing has been studied. Three model networks with different sulfur contents (efficient network, semi‐efficient and conventional vulcanizate) have been analysed by applying spin probe ESR, equilibrium swelling measurements and mechanical measurements. By combining the density distribution deduced from the complex ESR spectra and the equilibrium swelling density, it is shown that the major network changes occur in the networks with predominantly polysulfidic bonds (conventional network) after 96 h of ageing at 373 K. The effect of ageing on the network with predominantly monosulfidic bonds is much less pronounced. Both effects (main chain scission and additional local crosslinking) have been analysed in the course of prolonged ageing up to 240 h. A correlation between network structure and its mechanical performance is established. © 2000 Society of Chemical Industry