Preparation, characterization and photocatalytic activity of silver doped zinc oxide photocatalysts

In this study, silver doped zinc oxide and undoped zinc oxide photocatalysts were synthesized through precipitation-irradiation method. In order to evaluate the effect of irradiation time during synthesis, the photocatalysts were prepared at different irradiation duration of 12, 24 and 48 hours. The effect of Ag on the properties and photocatalytic performance of ZnO was also evaluated by preparing Ag-doped ZnO catalyst with different silver loading from 1 to 3 wt%. The resulting catalysts were characterized by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), Total surface Area Measurement (BET Method) and Band Gap Measurement. XRD patterns showed hexagonal structure of zinc oxide. FESEM results confirmed hexagonal structure of zinc oxide and also showed flake morphology with increasing irradiation time. However, both FESEM and TEM images showed high agglomerated particles but it should be noticed that agglomeration decreased with increasing irradiation time. In addition, increasing silver percentage doped on zinc oxide decreased the flake morphology and led to more agglomerated particles. The surface area of ZnO decreases with increasing irradiation time and with addition of Ag. The band gap energy of the ZnO remained constant with increasing radiation time but increased with the addition of 2 wt. % Ag. Due to high agglomeration, measurement of photocatalysts particle size was not conducted. The efficiency of produced ZnO and Ag doped ZnO was examined for degradation of Methyl orange as a model of pollutant under UV-irradiation. Influence of different parameters on degradation performance of Methyl orange such as mass of catalyst, initial concentration of dye, and initial pH were tested. The results showed that the efficiency of catalyst decreased with increasing irradiation time. It was observed that the removal percentage of dye increased with increasing silver loading on zinc oxide and the mass of catalysts up to an optimum amount. Furthermore, the maximum removal percentage was achieved at pH 5. In conclusion, the highest photodegradation activity of 81% of 10 ppm MO was achieved using 0.8 g of 2% Ag/ZnO catalyst at pH 5

Electrochemical DNA-nano biosensor for the detection of cervical cancer-causing HPV-16 using ultrasmall Fe3O4-Au core-shell nanoparticles

This paper reports a label-free biosensor for detecting human papillomavirus type 16 (HPV-16). For this purpose, the surface of the screen-printed carbon electrodes (SPCEs) was coated with Fe3O4-Au core-shell nanoparticles (NPs) using a green and facile eco-friendly method. The modified surfaces of the electrodes were then functionalized with thiolated single-strand DNA (ssDNA) probe human papillomavirus (HPV) DNA sequences. Next, the hybridization events with the immobilized probe DNA were monitored by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) using [Fe(CN)6]3‐/4− as the redox indicator. Our results demonstrate that the modified electrodes could distinguish the redox current signals of [Fe(CN)6] 3−/4− due to the absence/presence of the immobilized probe DNA. Furthermore, quantitative estimations of the concentration of the probe DNA were also possible. Optimal performance was obtained for probe DNA concentrations between 1 and 10 μM. The best performance of our HPV biosensor was obtained for probe DNA concentration of 5 μM, for which the limit of detection and sensitivity of our developed sensor resulted to be 0.1 nM and 2.4 μA/nM, respectively

Ultrasmall superparamagnetic Fe3O4 nanoparticles: honey-based green and facile synthesis and in vitro viability assay

Introduction: In the present research, we report a quick and green synthesis of magnetite nanoparticles (Fe3O4-NPs) in aqueous solution using ferric and ferrous chloride, with different percentages of natural honey (0.5%, 1.0%, 3.0% and 5.0% w/v) as the precursors, stabilizer, reducing and capping agent, respectively. The effect of the stabilizer on the magnetic properties and size of Fe3O4-NPs was also studied. Methods: The nanoparticles were characterized by X-ray diffraction (XRD) analysis, field emission scanning electron microscopy, energy dispersive X-ray fluorescence, transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and Fourier transform infrared spectroscopy. Results: The XRD analysis indicated the presence of pure Fe3O4-NPs while the TEM images indicated that the Fe3O4-NPs are spherical with a diameter range between 3.21 and 2.22 nm. The VSM study demonstrated that the magnetic properties were enhanced with the decrease in the percentage of honey. In vitro viability evaluation of Fe3O4-NPs performed by using the MTT assay on the WEHI164 cells demonstrated no significant toxicity in higher concentration up to 140.0 ppm, which allows them to be used in some biological applications such as drug delivery. Conclusion: The presented synthesis method can be used for the controlled synthesis of Fe3O4-NPs, which could be found to be important in applications in biotechnology, biosensor and biomedicine, magnetic resonance imaging and catalysis

Facile and greener hydrothermal honey-based synthesis of Fe3 O 4 /Au core/shell nanoparticles for drug delivery applications

In the present research, we report a greener, faster, and low-cost synthesis of gold-coated iron oxide nanoparticles (Fe 3 O 4 /Au-NPs) by different ratios (1:1, 2:1, and 3:1 molar ratio) of iron oxide and gold with natural honey (0.5% w/v) under hydrothermal conditions for 20 minutes. Honey was used as the reducing and stabilizing agent, respectively. The nanoparticles were characterized by X-ray diffraction (XRD), UV-visible spectroscopy, field emission scanning electron microscope (FESEM), energy-dispersive X-ray spectroscopy (EDXS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), vibrating sample magnetometer (VSM), and fourier transformed infrared spectroscopy (FT-IR). The XRD analysis indicated the presence of Fe 3 O 4 /Au-NPs, while the TEM images showed the formation of Fe 3 O 4 /Au-NPs with diameter range between 3.49 nm and 4.11 nm. The VSM study demonstrated that the magnetic properties were decreased in the Fe 3 O 4 /Au-NPs compared with the Fe 3 O 4 -NPs. The cytotoxicity threshold of Fe 3 O 4 /Au-NPs in the WEHI164 cells was determined by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. It was demonstrated no significant toxicity in higher concentration up to 140.0 ppm which can become the main candidates for biological and biomedical applications, such as drug delivery. © 2018 Wiley Periodicals, Inc

Effect of pH, Acid and Thermal Treatment Conditions on Co/CNT Catalyst Performance in Fischer–Tropsch Reaction

Multiwalled carbon nanotubes (CNT) supported cobalt oxide was prepared as a catalyst by strong electrostatic adsorption (SEA) method. The CNT support was initially acid- and thermal-treated in order to functionalize the support to uptake more Co clusters. The Co/CNT were characterized by a range of analytical methods including transmission electron microscopy (TEM), temperature programmed reduction with hydrogen (H2-TPR), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic absorption spectroscopy (AAS), Zeta sizer particle size analysis and Brunauer-Emmett-Teller (BET) surface area analysis. TEM images showed cobalt particles were highly dispersed and impregnated at both exterior and interior walls of the CNT support with a narrow particle size distribution of 6-8 nm. In addition, the performance of the synthesized Co/CNT catalyst was tested using Fischer-Tropsch synthesis (FTS) reaction which was carried out in a fixed-bed micro-reactor. H2-TPR profiles indicated the lower reduction temperature of 420 °C was required for the FTS reaction. The study revealed that cobalt is an effective metal for Co/CNT catalysts at pH 14 and at 900 °C calcination temperature. Furthermore, FTS reaction results showed that CO conversion and C5+ selectivity were recorded at 58.7% and 83.2% respectively, which were higher than those obtained using a Co/CNT catalyst which pre-treated at a lower thermal treatment temperature and pH. © 2019 by the authors

Effect of Cobalt Catalyst Confinement in Carbon Nanotubes Support on Fischer-Tropsch Synthesis Performance

Pre-treating the multi-walled carbon nanotubes (CNTs) support by refluxing in 35 vol% nitric acid followed by heating at the temperature of 600 to 900 °C resulted in the formation of defects on the CNTs. Increasing the temperature of the pre-treatment of the CNTs from 600 °C to 900 °C, enhanced the fraction of cobalt-oxide nanoparticles encapsulated in the channels of CNTs from 31% to 70%. The performance of Co/CNTs in Fischer-Tropsch synthesis (FTS) was evaluated in a fixed-bed micro-reactor at a temperature of 240 °C and a pressure of 2.0 MPa. The highest CO conversion obtained over Co/CNTs.A.900 was 59% and it dropped by ~3% after 130 h of time-on-stream. However, maximum CO conversion using Co/CNTs.A.600 catalysts was 28% and it decreased rapidly by about 54% after 130 h of time-on-stream. These findings show that the combined acid and thermal pre-treatment of CNTs support at 900 °C has improved the stability and activity of the Co/CNTs catalyst in FTS