Silica supported 12-tungstophosphoric acid catalysts for synthesis of 1,4-dihydropyridines under solvent-free conditions

12-Tungstophosphoric acid (PW) supported on different metal oxides (SiO₂, γ-Al₂O₃, KSF, K10) and activated carbon were prepared by impregnation method and their catalytic performances were evaluated in three component condensation of benzaldehyde, ethyl acetoacetate and ammonium acetate to afford corresponding 1,4-dihydropyridine. A high catalytic activity was found over silica supported PW. Effect of PW loading, catalyst loading and solvent was studied to introduce the best reaction condition. Based on the above experimental finding, catalytic performances was optimized with a loading of 40% PW onto SiO₂ (0.2 g) under solvent-free condition. The characterization data derived from FT-IR, XRD, and TGA-DSC techniques reveal that the PW on silica support exists in Keggin structure. In addition, acidity measurements were performed by potentiometric titration with n-butylamine. The activity of the catalysts is strongly dependent on their acidic characteristic which, in turn, depended on PW loading. Finally, a series of 4-aryl, N-alkyl, and N-aryl substituted 1,4-dihydropyridines have been synthesized in high to excellent yield in short reaction times. PW/SiO₂ was found to be reusable and a considerable catalytic activity still could be achieved after fourth run.     

Immobilization ofKluyvera citrophila penicillins acylase on controlled-pore ceramics

Penicillin acylase was purified fromKluyvera citrophila and immobilized on glutaraldehyde derivatives of silanized controlled-pore ceramics. The behaviour of the enzyme attached to TiO₂, Al₂O₃ and SiO₂ in the hydrolytic reaction are compared with that of the native enzyme as well as of the enzyme bound to CNBr-activated Sepharose 4B. The enzyme immobilized on TiO2 shows an efficiency of about 95% on the basis of protein bound. The penicillin acylase attached to SiO₂, unlike the enzyme immobilized on TiO₂, Al₂O₃ and Sepharose looses activity markedly in every cycle of use.     

Comparative study of three magnetic nano-particles (FeSO4, FeSO4/SiO2, FeSO4/SiO2/TiO2) in plasmid DNA extraction

Recent updates on Magnetic Nano-Particles (MNPs) based separation of nucleic acids have received more attention due to their easy manipulation, simplicity, ease of automation and cost-effectiveness. It has been indicated that DNA molecules absorb on solid surfaces via hydrogen-bonding, and hydrophobic and electrostatic interactions. These properties highly depend on the surface condition of the solid support. Therefore, surface modification of MNPs may enhance their functionality and specification. In the present study, we functionalized Fe₃O₄ nano-particle surface utilizing SiO₂ and TiO₂ layer as Fe₃O₄/SiO₂ and Fe₃O₄/SiO₂/TiO₂ and then compare their functionality in the adsorption of plasmid DNA molecules with the naked Fe₃O₄ nano-particles. The result obtained showed that the purity and amount of DNA extracted by Fe₃O₄ coated by SiO₂ or SiO₂/TiO₂ were higher than the naked Fe₃O₄ nano-particles. Furthermore, we obtained pH 8 and 1.5 M NaCl as an optimal condition for desorption of DNA from MNPs. The result further showed that, 0.2 mg nano-particle and 10 min at 55 °C are the optimal conditions for DNA desorption from nano-particles. In conclusion, we recommended Fe₃O₄/SiO₂/TiO₂ as a new MNP for separation of DNA molecules from biological sources.     

西南峡谷型喀斯特区坡地土壤矿物质的空间分布特征

探明峡谷型喀斯特土壤矿物质的分布规律可以为喀斯特地区植被恢复和生态重建提供参考。基于动态监测样地(200 m×300 m)的网格取样,采用经典统计分析和地统计学方法分析土壤矿物质(SiO2、Fe2O3、CaO、MgO、Al2O3、MnO)的空间分布特征。结果表明,研究区土壤矿物质含量差异较大,但变异系数不大,SiO2和Al2O3占了土壤矿物质总量的85.99%;SiO2、Al2O3、MgO、MnO均服从正态分布,Fe2O3、CaO分别经过平方和倒数转换后也服从正态分布。土壤各矿物质半变异函数的最佳拟合模型均为指数模型,块金值与基台值比C0/(C0+C)均较小,具有中等或强烈的空间相关性,表明空间变异主要由结构性因素引起;Al2O3和MnO的变程较大,空间连续性较好,其它矿物质的变程较小且相近,空间依赖性较强;Kriging等值线图表明峡谷型喀斯特区土壤SiO2和MnO具有相似的空间分布,受坡位和人为干扰共同影响,基本呈现坡顶高、坡脚低的分布格局;Fe2O3、CaO和MgO的空间分布也相似,斑块较破碎,主要受地形的影响;Al2O3的空间格局呈单峰分布,沿海拔的升高而升高。因此,减少干扰、增加植被覆盖对土壤矿物质具有良好的保持和调控作用。     

Effect of surface hydroxyls on DME and methanol adsorption over γ-Al2O3 (hkl) surfaces and solvent effects: a density functional theory study

Methanol and dimethyl ether (DME) adsorption over clean and hydrated γ-Al₂O₃(100) and (110) surfaces was studied by using density functional theory (DFT) combined with conductor-like solvent model (COSMO) in gas phase and liquid paraffin. On clean γ-Al₂O₃ (100) and (110) surfaces, DME and methanol preferentially interact with Al3 and Al1 of the γ-Al₂O₃(110) and (100) surfaces, respectively. On hydrated γ-Al₂O₃(100) and (110) surfaces, the OH group can influence the adsorptive behavior of DME and methanol. The Al3 and Al1 active sites of the hydrated (110) and (100) surfaces are inactivated due to hydroxyl influence, respectively. Compared to the adsorption energies of DME and methanol adsorption over the clean and hydrated (110) and (100) surfaces in gas phase and liquid paraffin, it is found that the solvent effects can slightly reduce adsorptive ability.     

Perovskite modified catalysts with improved coke resistance for steam reforming of glycerol to renewable hydrogen fuel

Catalytic steam reforming of renewable feedstock to renewable energy or chemicals always goes with intense coking activities that produce carbonaceous products leading to low performance and eventual catalyst deactivation. Supported metal catalyst such as Ni/Al₂O₃ is known to catalysed gasification and decomposition of biomass feedstock largely for renewable fuel production with promising results. Catalyst deactivation from high carbon deposition, agglomeration and phase transformations resulting to rapid deactivation are some of the issues identified with the use of the catalyst. In this work, improvement on the coke resistance and catalytic properties of Ni/Al₂O₃ catalyst is sought via the use of a thermally stable and coke-resistant perovskite La_0.75Sr_0.25Cr_0.5Mn_0.5O_3-δ (LSCM) as catalyst promoter/modifier and involving Zirconia-doped Ceria (Ce-Zr) as alternative support in steam reforming of pure and by-product glycerol. The stabilizing influence of the LSCM on the Ni catalyst has improved stability against agents of deactivation with a consequent significant improvement of catalytic activity of Ni/Al₂O₃ in H₂ production and robust suppression of carbon deposition. Particularly, the synergy between the LSCM promoter and alternative Ce_0.75Zr_0.25O₂ support enhanced the basic and redox properties known for Ce_0.75Zr_0.25O₂ support in contrast to the week acid centres in γ-Al₂O₃ support which further improved nickel stability, catalyst–support interaction with a resultant high catalytic activity and robust coke suppression as a result of enhanced oxygen mobility. There is correlation between the product distribution, nature of coke deposited and reforming temperature as well as type of support and structural modification. Hence, integration of a robust perovskite material as a catalyst promoter and choice of support could be tailored in design and development of robust catalyst systems to improve the performance of supported metal catalysts, particularly the suppression of carbon deposition for hydrocarbon and biomass conversion to renewable fuel or chemicals.     

Reversible removal of SO2 at low temperature by Bacillus licheniformis immobilized on γ-Al2O3

Bacillus licheniformis R08 biomass was immobilized on γ-Al₂O₃ and the effects of R08 biomass loading, SO₂ concentration, water vapor, oxygen and temperature on removal of SO₂ were investigated. The experimental results indicated that SO₂ saturation capacity increased with increasing R08 biomass loading and SO₂ concentration, but decreased with increasing adsorption temperature. Water vapor activated the adsorbent and promoted SO₂ removal. An increase in oxygen concentration from 5 to 10% had little effect on SO₂ removal. FTIR analysis revealed that the R08 biomass bound to γ-Al₂O₃ mainly by forming R-CO-O-Al bonds. X-ray photoelectron spectroscopy analysis indicated that γ-Al₂O₃ reacted with SO₂ and formed aluminum sulfate in the presence of oxygen when R08 biomass loading was 13.8%, but that amido groups of the R08 biomass reacted with SO₂ and formed sulfite when biomass loading was 32.4%. Ten continuous adsorption-desorption cycles showed that the adsorbent had an excellent regeneration performance.     

Graphene-MoS2 with TiO2SiO2 layers based surface plasmon resonance biosensor: Numerical development for formalin detection

In this article, numerically a surface plasmon resonance (SPR) biosensor is developed based on Graphene-M_OS₂ with TiO₂SiO₂ hybrid structure for the detection of formalin. Based on attenuated total reflection (ATR) method, we used angular interrogation technique to sense the presence the formalin by observing the change of “minimum reflectance with respect to SPR angle” and “maximum transmittance with respect to surface plasmon resonance frequency (SPRF)”. Here, we used Chitosan as probe analyte to perform chemical reaction with formalin (formaldehyde) which is consider as target analyte. Simulation results show a negligible variation of SPRF and SPR angle for improper sensing of formalin that confirms absence of formalin whereas for proper sensing is considerably countable that confirms the presence of formalin. Thereafter, a comparison of sensitivity for different sensor structure is made. It is observed that the sensitivity without TiO₂, SiO₂, MoS₂ and Graphene (conventional structure) is very poor and 73.67% whereas the sensitivity with graphene but without TiO₂, SiO₂ and MoS₂ layers is 74.67% consistently better than the conventional structure. This is due to the electron loss of graphene, which is accompanying with the imaginary dielectric constant. Furthermore, the sensitivity without TiO₂, SiO₂ and graphene but with MoS₂ layer is 79.167%. After more if both graphene and MoS2 are used and TiO₂ and SiO₂ layers are not used then sensitivity improves to 80.5%. This greater than before performance is due to the absorption ability and optical characteristics of graphene biomolecules and high fluorescence quenching ability of MoS₂. Further again, if TiO₂SiO₂ composite layer is used with the Graphene-MoS2 then the sensitivity enhances from 80.5% to 82.5%. Finally, the sensitivity for the proposed structure has been carried out, and result is 82.83%, the highest value among all the previous structures to integrate the advantages of graphene, MoS₂, TiO₂ and SiO₂.     

Effect of surface hydroxyls on dimethyl ether synthesis over the γ-Al2O3 in liquid paraffin: a computational study

In a recent paper (Zuo et al., Appl Catal A 408:130–136, 2011), the mechanism of dimethyl ether (DME) synthesis from methanol dehydration over γ-Al₂O₃ (110) was studied using density functional theory (DFT). Using the same method, the effect of surface hydroxyls on γ-Al₂O₃ in liquid paraffin during DME synthesis from methanol dehydration is investigated. It is found that DME is mainly formed from two adsorbed CH₃O groups via methanol dehydrogenation on both dehydrated and hydrated γ-Al₂O₃ in liquid paraffin. No close correlation between catalytic activity and acid intensity was found. Before and after water adsorption at typical catalytic conditions (e.g., 553 K), the reaction rate is not obviously changed on γ-Al₂O₃(100) surface in liquid paraffin, but the reaction rate decreases by about 11 times on the (110) in liquid paraffin. Considering the area of the (110) and (100) surfaces under actual conditions, the catalytic activity decreased mainly because the Al3 sites on the (110) surface gradually become inactive. Catalytic activity decreased mainly due to surface hydrophilicity. The calculated results were consistent with the experiment.

Analysis of the mechanism of intensification of fermentation process using yeast cells in a suspension of high-dispersed oxides

The differential microcalorimetry was used to explore an influence of particles of silicon dioxide, and also other high-dispersed oxides (0.05% of masses.) in water suspension of yeast cells on intensification of the process of their fermentation in endogenous metabolic conditions. It was shown that intensification of the processes of the vital activity of yeast microorganisms was observed in the specified interval of the concentration of silicon dioxide hydrosol particles. Mechanisms of interaction between SiO₂ particles and a surface of a cellular organism, as well as interaction between SiO₂ particles and one of metabolism products — carbon dioxide were studied. It was found out, that Al₂O₃, TiO₂ hydrosols also had a stimulating effect, but it is lower compared to that of SiO₂.     

Toxic effects of nanoparticles on bioluminescence activity,seed germination,and gene mutation

The potential environmental toxicities of several metal oxide nanoparticles (NPs; CuO, TiO₂, NiO, Fe₂O₃, ZnO, and Co₃O₄) were evaluated in the context of bioluminescence activity, seed germination, and bacterial gene mutation. The bioassays exhibited different sensitivities, i.e., each kind of NP exhibited a different level of toxicity in each of the bioassays. However, with a few exceptions, CuO and ZnO NPs had most toxic for germination of Lactuca seed (EC₅₀ 0.46 mg CuO/l) and bioluminescence (EC₅₀ 1.05 mg ZnO/l). Three NPs (Co₃O₄, TiO₂, and Fe₂O₃) among all tested concentrations (max. 1,000 mg/l) showed no inhibitory effects on the tested organisms, except for Co₃O₄ NPs on bioluminescence activity (EC₅₀ 62.04 mg/l). The sensitivity of Lactuca seeds was greater than that of Raphanus seeds (EC₅₀ 0.46 mg CuO/l versus 26.84 mg CuO /l ). The ranking of metal toxicity levels on bioluminescence was in the order of ZnO?>?CuO?>?Co₃O₄?>?NiO?>?Fe₂O₃, TiO₂, while CuO?>?ZnO?>?NiO?>?Co₃O₄, Fe₂O₃, TiO₂ on germination. No revertant mutagenic ratio (greater than 2.0) of Salmonella typhimurium TA 98 was observed under any tested condition. These findings demonstrate that several bioassays, as opposed to any single one, are needed for the accurate assessment of NP toxicity on ecosystems.     

Transesterification of Nannochloropsis oculata microalga’s lipid to biodiesel on Al2O3 supported CaO and MgO catalysts

In this study, we present the activities of Al₂O₃ supported CaO and MgO catalysts in the transesterification of lipid of yellow green microalgae, Nannochloropsis oculata, as a function of methanol amount and the CaO and MgO loadings at 50 °C. We found that pure CaO and MgO were not active and CaO/Al₂O₃ catalyst among all the mixed oxide catalysts showed the highest activity. Not only the basic site density but also the basic strength is important to achieve the high biodiesel yield. Biodiesel yield over 80 wt.% CaO/Al₂O₃ catalyst increased to 97.5% from 23% when methanol/lipid molar ratio was 30.     

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O₂ pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (>80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO₂, Al₂O₃, WO₃ and Ag₄O₄.     

Nitroxide-Stimulated H2O2 Decomposition by Peroxidases and Pseudoperoxidases

Many copper and iron complexes can be reduced by O^-₂ as well as by H₂O₂. According to the rates of reduction and the concentration of O^-₂ and H₂O₂, the metal complexes may serve either as catalyst of O^-₂ dismutation or as catalysts of the reaction between O^-₂ and H₂O₂ to form OH' radical (Haber-Weiss reaction). Various factors which influence whether metal complexes protect the biological systems from superoxide toxicity or enhance it are discussed.     

Glucose biosensor based on the room-temperature phosphorescence of TiO2/SiO2 nanocomposite

The direct immobilization of glucose oxidase (GOD) on TiO₂/SiO₂ nanocomposite and its application as glucose biosensor were investigated. The room-temperature phosphorescence of TiO₂/SiO₂ nanocomposite can be quenched by hydrogen peroxide (H₂O₂). The detection of glucose may be accomplished by monitoring the formation of hydrogen peroxide which generated in the oxidation process of glucose with the catalysis of GOD. To our surprise, by using a 96-hole polyporous plate accessory of fluorescence spectrophotometer, the biosensor exhibits excellent linear response to glucose concentrations ranging from 1.0 × 10⁻⁹ to 1.0 × 10⁻² M with a detection limit of 1.2 × 10⁻¹⁰ M. The TiO₂/SiO₂ nanocomposite can be used as both supporting material and signal transducer. The phosphorescence intensity and color of the biosensor change obviously and even could be observed with naked eyes by continuous addition of glucose. Based on the room-temperature phosphorescence of TiO₂/SiO₂ nanocomposite, a new method of solid substrate-room-temperature phosphorimetry (SS-RTP) for glucose determination is proposed. A glucose biosensor was fabricated with wide determination concentration range, low detection limit, high sensitivity, and fast response time. And the biosensor has been successfully applied to the determination of glucose in human blood serum. The coacervation of GOD enzyme and its interaction with TiO₂/SiO₂ nanocomposite enlarge the surface area and enhance the chemical stability of GOD. The nice biocompatibility, large surface area, good chemical stability and nontoxicity of the TiO₂/SiO₂ nanocomposite have made this material suitable for functioning as biosensor.     

Fabrication of two- and three-dimensional model catalyst systems with monodispersed platinum nanoparticles as active metal building blocks

Well-defined Pt monodispersed nanoparticles within the catalytically relevant 1–10 nm size regime were synthesized in solution phase by several synthetic methods which differed in the choice of reducing agent, surface stabilizer, reaction temperature and solvent. Three-dimensional model catalysts were fabricated by incorporating the metal nanoparticles into ordered channels of high surface area mesoporous oxides such as SiO₂, Al₂O₃ and Ta₂O₅ through either sonication or direct synthesis of the oxide support around the particles. Deposition of the same nanocrystals onto silica supports by means of the Langmuir–Schaeffer technique produced two-dimensional model catalysts.     

Sugar complexes with alkaline earth metal ions. Synthesis,structure, and spectroscopic studies of Mg(II), Sr(II), and Ba(II) complexes of d-glucur

Interaction between D-glucuronic acid and alkaline earth metal ions leads to the formation of the complexes such as M(D-glucuronate)X· nH₂O and M(D-glucuronate)₂ · nH₂O, where M = Mg(II), Sr(II), and Ba(II), X = Cl^? or Br^?, and n = 2–4. Owing to the distinct spectral similarities with the structurally known Ca(D-gluguronate)Br · 3H₂O compound, the metal cations bind to three sugar moieties (through O₆, O₅ of the first, O₆', O₄ of the second, and O₁, O₂ of the third residue) and to two H₂O molecules, forming an eight-coordination geometry around each metal ion, in M(D-glucuronate)X · nH₂O (except for Mg(II) ion, which is six-coordination). The metal ions in M(D-glucuronate)₂-nH₂O show six-coordination in different structural environments. The strong hydrogen bonding network of the free acid is weakened upon metalation and the sugar moiety crystallizes as α-anomer, in these series of metal-sugar complexes.     

Cytotoxicity,permeability, and inflammation of metal oxide nanoparticles in human cardiac microvascular endothelial cells

Wide applications and extreme potential of metal oxide nanoparticles (NPs) increase occupational and public exposure and may yield extraordinary hazards for human health. Exposure to NPs has a risk for dysfunction of the vascular endothelial cells. The objective of this study was to assess the cytotoxicity of six metal oxide NPs to human cardiac microvascular endothelial cells (HCMECs) in vitro. Metal oxide NPs used in this study included zinc oxide (ZnO), iron(III) oxide (Fe₂O₃), iron(II,III) oxide (Fe₃O₄), magnesium oxide (MgO), aluminum oxide (Al₂O₃), and copper(II) oxide (CuO). The cell viability, membrane leakage of lactate dehydrogenase, intracellular reactive oxygen species, permeability of plasma membrane, and expression of inflammatory markers vascular cell adhesion molecule-1, intercellular adhesion molecule-1, macrophage cationic peptide-1, and interleukin-8 in HCMECs were assessed under controlled and exposed conditions (12–24 h and 0.001–100 μg/ml of exposure). The results indicated that Fe₂O₃, Fe₃O₄, and Al₂O₃ NPs did not have significant effects on cytotoxicity, permeability, and inflammation response in HCMECs at any of the concentrations tested. ZnO, CuO, and MgO NPs produced the cytotoxicity at the concentration-dependent and time-dependent manner, and elicited the permeability and inflammation response in HCMECs. These results demonstrated that cytotoxicity, permeability, and inflammation in vascular endothelial cells following exposure to metal oxide nanoparticles depended on particle composition, concentration, and exposure time.     

Excess processing of oxidative damaged bases causes hypersensitivity to oxidative stress and low dose rate irradiation

Abstract

Ionizing radiations such as X-ray and γ-ray can directly or indirectly produce clustered or multiple damages in DNA. Previous studies have reported that overexpression of DNA glycosylases in Escherichia coli (E. coli) and human lymphoblast cells caused increased sensitivity to γ-ray and X-ray irradiation. However, the effects and the mechanisms of other radiation, such as low dose rate radiation, heavy-ion beams, or hydrogen peroxide (H₂O₂), are still poorly understood. In the present study, we constructed a stable HeLaS3 cell line overexpressing human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) protein. We determined the survival of HeLaS3 and HeLaS3/hOGG1 cells exposed to UV, heavy-ion beams, γ-rays, and H₂O₂. The results showed that HeLaS3 cells overexpressing hOGG1 were more sensitive to γ-rays, OH^?, and H₂O₂, but not to UV or heavy-ion beams, than control HeLaS3. We further determined the levels of 8-oxoG foci and of chromosomal double-strand breaks (DSBs) by detecting γ-H2AX foci formation in DNA. The results demonstrated that both γ-rays and H₂O₂ induced 8-oxoguanine (8-oxoG) foci formation in HeLaS3 cells. hOGG1-overexpressing cells had increased amounts of γ-H2AX foci and decreased amounts of 8-oxoG foci compared with HeLaS3 control cells. These results suggest that excess hOGG1 removes the oxidatively damaged 8-oxoG in DNA more efficiently and therefore generates more DSBs. Micronucleus formation also supported this conclusion. Low dose-rate γ-ray effects were also investigated. We first found that overexpression of hOGG1 also caused increased sensitivity to low dose rate γ-ray irradiation. The rate of micronucleus formation supported the notion that low dose rate irradiation increased genome instability.     

DFT model cluster studies of O2 adsorption on hydrogenated titania sub-nanoparticles

In the present paper, we examine the general applicability of different TiO₂ model clusters to study of local chemical events on TiO₂ sub-nanoparticles. Our previous DFT study of TiO₂ activation through H adsorption and following deactivation by O₂ adsorption using small amorphous Ti₈O₁₆ cluster were complemented by examination of rutile-type and spherical Ti₁₅O₃₀ nanoclusters. The obtained results were thoroughly compared with experimental data and results of related computational studies using other TiO₂ models including periodic structures. It turned out that all considered model TiO₂ model systems provide qualitatively similar results. It was shown that atomic hydrogen is adsorbed with negligible activation energy on surface O atoms, which is accompanied by the appearance of reduced Ti³⁺ species and corresponding localized band gap 3d-Ti states. Oxygen molecule is adsorbed on Ti³⁺ sites spontaneously forming molecular O₂ ^– species by capturing an extra electron of Ti³⁺ ion, which results in disappearance of Ti³⁺ species and corresponding band gap states. Calculated g-tensor values of Ti³⁺ and O₂ ^– species agree well with the results of EPR studies and do not depend on the used TiO₂ model cluster. Additionally, it was shown that the various cluster calculations provide results comparable with the calculations of periodic structures with respect to the modeling of chemical processes under study. As a whole, the present study approves the validity of molecular cluster approach to study of local chemical events on TiO₂ sub-nanoparticles.