Synthesis by spray pyrolysis of gold nano species confined in iron oxide nanospheres effective in the reduction of 4-nitrophenol to 4-aminophenol.

The highly effective Au/Fe2O3-@Au/Fe2O3nanoreactors for the 4-nitrophenol (4-NP) reduction are successfully obtained by one-pot synthesis using the spray pyrolysis (SP) technique. The Au/Fe2O3-@Au/Fe2O3nanoreactors manifest superior catalytic activity in the reduction of 4-NP in the presence of sodium borohydride (NaBH4) compared to gold-iron oxide nanoreactors prepared via a colloidal approach. The negative effect of the reaction product accumulation, the 4-aminophenol (4-AP), on the catalytic reduction of 4-NP over Au/Fe2O3-@Au/Fe2O3is examined by a direct pre-injection of 4-AP to the reaction media. To the best of our knowledge, it is the first experimental evidence of gold active sites blocking by 4-AP. All obtained samples are characterized by the yolk-shell spherical hollow structure mainly consisted of two embedded hollow nanospheres. The reduction of iron oxide precursor concentration diminishes the diameter of final iron oxide nanospheres. According to STEM-EDS analysis and STEM, Au nano species are uniformly dispersed on both iron oxide nanospheres. The SP technique presently used to synthesize Au/Fe2O3-@Au/Fe2O3nanoreactors manifests high potential for the one-pot fabrication of a large variety of nanoreactors with various active materials applied as heterogeneous catalysts in numerous catalytic processes.

Ag@ZnO/MWCNT ternary nanocomposite as an active and stable catalyst for the 4-nitrophenol reduction in water.

The nitroaromatic compounds, known as organic pollutants, have arising attention due to their carcinogenic character, highly dangerous to human health. In this work, the Ag@ZnO/MWCNT ternary nanocomposite synthesized via conjugation of sonochemical and solvothermal treatments manifests high performance in the reduction of 4-nitrophenol in the aqueous media (TOF value of 246 min-1µmol metal-1). The incorporation of MWCNT onto the nanocomposite structure favored the reusing of the catalysts even after eight consecutive catalytic runs without catalysts cleaning nor product removal. Obtained samples were characterized by XRD, TEM, UV-vis, Raman and FTIR spectroscopies. It was found that ultrasonic treatment at relatively moderate conditions leads to functionalization of MWCNT, the appearance of C=C and OH groups and change of electronic properties of Ag@ZnO/MWCNT composite which provide its stable material dispersion in aqueous solution and high catalytic performance in the 4-nitrophenol reduction. This technique may be effectively applied for the functionalization of carbon including materials for their usage in an aqueous media.

Antibody-Functionalized Copper Oxide Nanoparticles with Targeted Antibacterial Activity.

Copper oxide nanoparticles (CuO-NPs) were functionalized with specific antibodies to target their antibacterial activity against Gram-positive or Gram-negative bacteria. The CuO-NPs were covalently functionalized to cover their surface with specific antibodies. The differently prepared CuO-NPs were characterized by X-ray diffraction, transmission electron microscopy and dynamic light scattering. The antibacterial activities of the unmodified CuO-NPs and the antibody-functionalized nanoparticles (CuO-NP-AbGram- and CuO-NP-AbGram+ ) were determined for both Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria. The antibody-functionalized NPs showed a differential increase of their antibacterial activity according to the specific antibody. The CuO-NP-AbGram- in E. coli showed reduced half maximal inhibitory concentration (IC50 ) and minimum inhibitory concentration (MIC) values when compared with unfunctionalized CuO-NPs. On the other hand, the CuO-NP-AbGram+ also showed reduced IC50 and MIC values in B. subtilis, when compared with non-functionalized CuO-NPs. Thus, the functionalized CuO nanoparticles with specific antibodies showed enhanced specificity of their antibacterial activity. The advantages of "smart" antibiotic nanoparticles are discussed.

Compact device for in situ ultraviolet-visible spectrophotometric measurement of photocatalytic kinetics.

In this work, we have designed a compact device that can be easily integrated with Ultraviolet-Visible spectrophotometers, utilizing Light Emitting Diode technology for in situ spectrophotometric measurements of photocatalytic reactions. Using our device, we present the test results for the breakdown of amaranth dye with Degussa P25 powder and compare them with those obtained from a conventional arc discharge reactor. The results show that the reaction constants obtained using our device are practically equivalent to those acquired with a conventional reactor. However, our device significantly simplifies the experimental task by requiring less test solution volume and fewer user interventions while enabling in situ monitoring of the reaction kinetics. Overall, the proposed approach offers a convenient and efficient means of studying photocatalytic materials for dye degradation.

Enhanced laccase activity of biocatalytic hybrid copper hydroxide nanocages.

Nanobiocatalysis is the combination of the unique properties of nano-sized materials and the efficiency and sophistication of catalytic properties of enzymes. In this work, Cu(OH)2 nanocages with an mean size of 170 nm were synthesized and used as a support for the covalent conjugation with fungal ligninolytic enzymes; versatile peroxidase and laccase. Both enzymes have the ability to degrade a wide range of pollutants. The nanocages were characterized, the orthorhombic arrangement of the nanocages was confirmed and TEM images showed that the nanocages are composed of nano-ribbons stacked around the particles. Interestingly, bioconjugated laccase-nanocages exhibited up to 18-times higher catalytic rate that these found for free enzyme, while activity of versatile peroxidase-nanocages was considerably reduced. The total turnover number for free laccase and laccase-nanocages are similar, suggesting that the activity increase is not due to the supply of Cu ions to a possible Cu-depleted active site of laccase. This enhancement of laccase activity when immobilized enzyme onto Cu(OH)2 nanocages could be important for the actual and potential industrial uses of laccases.

Long-distance detection of alpha-radioactivity: Method and device.

Negatively charged ions from the alpha particle tracks are detected by the discharge wire counter opened to the air. Ion clusters are transferred from the particle tracks to the detector volume by an air flux. It allows a remote detection of very low concentrations of alpha particles. In contrast to the existing long-range alpha particle detection technique this method employs a detector working in a counting mode using a gas discharge method with an open-air proportional counter that provides sharp selectivity and accuracy of measurements. The device allows to detect alpha contamination over large surface areas, including places hard to reach, using different nozzles such as the tube nozzle or disc nozzle. The basic parameters of the device are: detection distance--0.5 m; time of detection--10 s; the sensitivity per unit area--0.05 Bq/cm(2). Also the auto-calibration technique and results are presented. That allows using the device under different ambient conditions by making an automatic recalibration.