| 1. |
- Borah, Sandhya Banti Dutta, et al.
(författare)
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Heavy Metal Ion Sensing By Surface Plasmon Resonance on Gold Nanoparticles
- 2014
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Ingår i: ADBU Journal of Engineering Technology. - : Don Bosco University. - 2348-7305. ; 1
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Tidskriftsartikel (refereegranskat)abstract
- Surface Plasmon resonance (SPR) based heavy metal ions sensor is one of the most sensitive sensor for detecting toxic metal ions. It is an inexpensive, portable and also feasible for real time detection. SPR sensor is a type of optical sensor in which toxic metal ions get adsorbed on the functionalized metal (mostly Au) film causes the change in refractive index of the metal (Au)-dielectric (sensing) medium. The change of the refractive index leads to a shift in the angular spectrum of the reflected light and can be accurately monitored by optical methods. In this paper,we are trying to optimize the detection level of heavy metal ions by surface plasmon resonance on gold nanoparticles using UV-VIS spectroscopy. Polymer like chitosan is being used with gold nanoparticles to detect copper and zinc ions and detection till very low concentrations of the toxic metal ions is obtained.
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| 2. |
- Abiso, Ahmad Muhammad, et al.
(författare)
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Advances in copper-based catalysts for sustainable hydrogen production via methanol steam reforming
- 2024
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Ingår i: Chemical Engineering Journal Advances. - : Elsevier BV. - 2666-8211. ; 19
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Forskningsöversikt (refereegranskat)abstract
- Efficient hydrogen production through Methanol Steam Reforming (MSR) is an area of high importance due to its environmental suitability and superior energy efficiency compared to methane steam reforming. Therefore, we present a comprehensive investigation into the development of copper-based catalysts for MSR. Over the past decades, research in this domain has intensified, encompassing Cu-based catalysts that exhibit notable promise. Strategies to enhance catalytic activity and stability involve the utilisation of mesoporous support materials with tuneable properties, novel promoters, and the introduction of mixed oxides and metal organic framework amongst others. Furthermore, the paper underscores the significance of catalyst morphology and metal precursors in determining their final performance. Several new catalysts have shown remarkable selectivity for hydrogen while minimizing carbon monoxide production even at elevated temperatures, positioning them as strong candidates for environmentally friendly commercial hydrogen production through methanol steam reforming. Valuable insights into synthesis approaches and catalyst performance variations across different research groups are also presented.
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| 3. |
- Ahmed, Aseel Bala, et al.
(författare)
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Microwave-enhanced degradation of phenol over Ni-loaded ZnO nanorods catalyst
- 2014
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Ingår i: Applied Catalysis B. - : Elsevier. - 0926-3373 .- 1873-3883. ; 156-157, s. 456-465
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Tidskriftsartikel (refereegranskat)abstract
- Nickel was loaded onto hydrothermally-grown ZnO nanorods on cordierite substrates and tested as catalysts in microwave-enhanced degradation of phenol from its aqueous solution (100 ppm) at 70 degrees C. Effects of metal loadings (1, 10 and 20 mM impregnation solutions) on the degradation of phenol in aqueous solution was investigated. The catalyst performances were monitored based on phenol degradation, product distributions and carbon dioxide (CO2) evolutions. Based on the type of the catalysts, two different mechanistic pathways for the decomposition were observed-through catechol and/or hydroquinone as intermediates. It was found that the 10mM nickel loaded sample catalyzed the degradation through one pathway with hydroquinone as the benzenediol intermediate formed, while the 20 mM nickel impregnated sample catalyzed the reaction through two pathways, producing catechol as well as hydroquinone by products. These differences in reaction pathways were attributed to the variation in the composition of the nickel compounds and surface structures between the two catalysts. Furthermore, the effect of hydrogen peroxide (H2O2) as an oxidant was explored. It was found that although addition of H2O2 led to an increase in the degree of phenol degradation, it also led to enhanced catalyst leaching. There was also an increase in CO2 evolution due to the addition of H2O2. It was observed that 20 mM nickel-loaded sample without the addition of H2O2 exhibited optimum performance in terms of phenol degradation and CO2 evolution with no drawback of catalyst leaching. Catalytic microwave enhanced degradation is an effective means for the removal of dissolved organic compounds from wastewater.
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| 4. |
- Al-Abri, M., et al.
(författare)
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Chlorination disadvantages and alternative routes for biofouling control in reverse osmosis desalination
- 2019
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Ingår i: npj Clean Water. - : Nature Research. - 2059-7037. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- With an ever-increasing human population, access to clean water for human use is a growing concern across the world. Seawater desalination to produce usable water is essential to meet future clean water demand. Desalination processes, such as reverse osmosis and multi-stage flash have been implemented worldwide. Reverse osmosis is the most effective technology, which uses a semipermeable membrane to produce clean water under an applied pressure. However, membrane biofouling is the main issue faced by such plants, which requires continuous cleaning or regular replacement of the membranes. Chlorination is the most commonly used disinfection process to pretreat the water to reduce biofouling. Although chlorination is widely used, it has several disadvantages, such as formation of disinfection by-products and being ineffective against some types of microbes. This review aims to discuss the adverse effect of chlorination on reverse osmosis membranes and to identify other possible alternatives of chlorination to reduce biofouling of the membranes. Reverse osmosis membrane degradation and mitigation of chlorines effects, along with newly emerging disinfection technologies, are discussed, providing insight to both academic institutions and industries for the design of improved reverse osmosis systems.
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| 5. |
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| 6. |
- Al Alawai, Reem, et al.
(författare)
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Role of bonding mechanisms during transfer hydrogenation reaction on heterogeneous catalysts of platinum nanoparticles supported on zinc oxide nanorods
- 2016
-
Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; , s. 200-206
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Tidskriftsartikel (refereegranskat)abstract
- For supported heterogeneous catalysis, the interface between a metal nanoparticle and the support plays an important role. In this work the dependency of the catalytic efficiency on the bonding chemistry of platinum nanoparticles supported on zinc oxide (ZnO) nanorods is studied. Platinum nanoparticles were deposited on ZnO nanorods (ZnO NR) using thermal and photochemical processes and the effects on the size, distribution, density and chemical state of the metal nanoparticles upon the catalytic activities are presented. The obtained results indicate that the bonding at Pt-ZnO interface depends on the deposition scheme which can be utilized to modulate the surface chemistry and thus the activity of the supported catalysts. Additionally, uniform distribution of metal on the catalyst support was observed to be more important than the loading density. It is also found that oxidized platinum Pt(IV) (platinum hydroxide) provided a more suitable surface for enhancing the transfer hydrogenation reaction of cyclohexanone with isopropanol compared to zero valent platinum. Photochemically synthesized ZnO supported nanocatalysts were efficient and potentially viable for upscaling to industrial applications.
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| 7. |
- Al-Fori, M., et al.
(författare)
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Antifouling properties of zinc oxide nanorod coatings
- 2014
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Ingår i: Biofouling. - : Taylor & Francis. - 0892-7014 .- 1029-2454. ; 30:7, s. 871-882
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Tidskriftsartikel (refereegranskat)abstract
- In laboratory experiments, the antifouling (AF) properties of zinc oxide (ZnO) nanorod coatings were investigated using the marine bacterium Acinetobacter sp. AZ4C, larvae of the bryozoan Bugula neritina and the microalga Tetraselmis sp. ZnO nanorod coatings were fabricated on microscope glass substrata by a simple hydrothermal technique using two different molar concentrations (5 and 10 mM) of zinc precursors. These coatings were tested for 5 h under artificial sunlight (1060 W m(-2) or 530 W m(-2)) and in the dark (no irradiation). In the presence of light, both the ZnO nanorod coatings significantly reduced the density of Acinetobacter sp. AZ4C and Tetraselmis sp. in comparison to the control (microscope glass substratum without a ZnO coating). High mortality and low settlement of B. neritina larvae was observed on ZnO nanorod coatings subjected to light irradiation. In darkness, neither mortality nor enhanced settlement of larvae was observed. Larvae of B. neritina were not affected by Zn2+ ions. The AF effect of the ZnO nanorod coatings was thus attributed to the reactive oxygen species (ROS) produced by photocatalysis. It was concluded that ZnO nanorod coatings effectively prevented marine micro and macrofouling in static conditions.
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| 8. |
- Al-Hamdi, Abdullah M., et al.
(författare)
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Efficient photocatalytic degradation of phenol in aqueous solution by SnO2:Sb nanoparticles
- 2016
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 370, s. 229-236
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Tidskriftsartikel (refereegranskat)abstract
- Photodegradation of phenol in the presence of tin dioxide (SnO2) nanoparticles under UV light irradiation is known to be an effective photocatalytic process. However, phenol degradation under solar light is less effective due to the large band gap of SnO2. In this study antimony (Sb) doped tin dioxide (SnO2) nanoparticles were prepared at a low temperature (80 degrees C) by a sol-gel method and studied for its photo catalytic activity with phenol as a test contaminant. The catalytic degradation of phenol in aqueous media was studied using high performance liquid chromatography and total organic carbon measurements. The change in the concentration of phenol affects the pH of the solution due to the by-products formed during the photo-oxidation of phenol. The photoactivity of SnO2:Sb was found to be a maximum for 0.6 wt.% Sb doped SnO2 nanoparticles with 10 mg L-1 phenol in water. Within 2 h of photodegradation, more than 95% of phenol could be removed under solar light irradiation.
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| 9. |
- Al-Hamdi, Abdullah M., et al.
(författare)
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Gadolinium doped tin dioxide nanoparticles : an efficient visible light active photocatalyst
- 2015
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Ingår i: Journal of Rare Earths. - : Elsevier. - 1002-0721 .- 2509-4963. ; 33:12, s. 1275-1283
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Tidskriftsartikel (refereegranskat)abstract
- Photocatalytic degradation of phenol with sol-gel prepared rare earth doped tin dioxide (SnO2) nanoparticles was reported. Gadolinium doped tin dioxide (SnO2:Gd) nanoparticles were found to absorb higher visible light compared to lanthanum, neodymium and cerium doped materials that were studied in detail. Photocatalytic degradation of phenol under artificial white light and sunlight in the presence of SnO2: Gd nanoparticles was studied with high performance liquid chromatography (HPLC), capillary electrophoresis (CE), total organic carbon (TOC) measurements and the determination of chemical oxygen demand (COD). Clear correlations between the results obtained from these multiple measurements were found, and a kinetic pathway for the degradation process was proposed. Within 150 min of solar irradiation, the TOC of a 10 ppm phenol solution in water was reduced by 95%-99%, thus demonstrating that SnO2: Gd nanoparticles are efficient visible light photocatalysts.
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| 10. |
- Al-Hamdi, A. M., et al.
(författare)
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Intermediate formation during photodegradation of phenol using lanthanum doped tin dioxide nanoparticles
- 2016
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Ingår i: Research on chemical intermediates (Print). - : Springer Netherlands. - 0922-6168 .- 1568-5675. ; 42:4, s. 3055-3069
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Tidskriftsartikel (refereegranskat)abstract
- Lanthanum (La)-doped tin dioxide (SnO2) nanoparticles were synthesized by a modified sol–gel method at room temperature. The samples were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The photocatalytic activity of La:SnO2 samples were investigated by studying the degradation profile of phenol and its by-products in water. The treated samples were analyzed by HPLC–UV and a UV–Vis spectrophotometer. Benzoquinone, catechol, resorcinol, hydroquinone, acetic acid, and 2-propanol were identified as phenol degradation intermediates. Maximum concentration acquired was in the order of catechol, resorcinol, hydroquinone, and benzoquinone, which was observed in the beginning stages while iso-propanol and acetic acid were observed in the final stages of phenol degradation. We achieved a complete photodegradation of a 10 ppm aqueous phenol solution and intermediates with 0.6 % of SnO2:La nanoparticles in 120 min under artificial solar irradiation. A maximum degradation rate constant of 0.02228 min−1 of propanol and a minimum of acetic acid 0.013412 min−1 were recorded at 37 °C.
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| 11. |
- Al-Hamdi, Abdullah M, et al.
(författare)
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Photocatalytic degradation of phenol by iodine doped tin oxide nanoparticles under UV and sunlight irradiation
- 2015
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Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388. ; 618, s. 366-371
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Tidskriftsartikel (refereegranskat)abstract
- Iodine doped tin oxide (SnO2:I) nanoparticles were prepared by sol-gel synthesis and their photocatalytic activities with phenol as a test contaminant were studied. In the presence of the catalysts, phenol degradation under direct sunlight was comparable to what was achieved under laboratory conditions. Photocatalytic oxidation reactions were studied by varying the catalyst loading, light intensity, illumination time, pH of the reactant and phenol concentration. Upon UV irradiation in the presence of SnO2:I nanoparticles, phenol degrades very rapidly within 30 min, forming carboxylic acid which turns the solution acidic. Phenol degradation rate with 1% iodine doped SnO2 nanoparticles is at least an order of magnitude higher compared to the degradation achieved through undoped SnO2 nanoparticles under similar illumination conditions.
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| 12. |
- Al-Hamdi, A. M., et al.
(författare)
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Photocatalytic degradation of phenol in aqueous solution by rare earth-doped SnO2 nanoparticles
- 2014
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Ingår i: Journal of Materials Science. - : Springer Science+Business Media B.V.. - 0022-2461 .- 1573-4803. ; 49:14, s. 5151-5159
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Tidskriftsartikel (refereegranskat)abstract
- The influence of heterogeneous semiconductors on the photodegradation of phenol in water was investigated using doped tin dioxide (SnO2) nanoparticles. Photocatalysts of SnO2 were synthesized with lanthanum (La), cerium (Ce), and neodymium (Nd) dopants. These photocatalysts were synthesized from tin tetrachloride by sol-gel method with different dopant concentrations, and its photocatalytic degradation was investigated up to 0.8 % under UV-A light in aqueous suspensions. The photocatalytic oxidation reactions were studied by varying photocatalyst composition, light intensity, reaction time, pH of the reaction medium, and phenol concentration. It was found that the photocatalytic activity of rare earth-doped SnO2 for phenol decomposition under UV light irradiation was considerably higher than that of pure SnO2 nanoparticles. The experimental results also indicate that more than 95 % phenol was effectively oxidized in the presence of an aqueous suspension of La: SnO2 nanoparticles within 120 min of UV light irradiation.
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| 13. |
- Al-Hinai, A. T., et al.
(författare)
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Application of Eh-pH diagram for room temperature precipitation of zinc stannate microcubes in an aqueous media
- 2014
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Ingår i: Materials research bulletin. - : Elsevier. - 0025-5408 .- 1873-4227. ; 49:1, s. 645-650
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Tidskriftsartikel (refereegranskat)abstract
- Potential-pH diagram assisted-design for controlled precipitation is an attractive method to obtain engineered binary and ternary oxide particles. Aqueous synthesis conditions of zinc stannate (ZnSnO3) particles at low temperature were formulated with the assistance of potential-pH diagram. The pH of a solution containing stoichiometric amounts of Zn2+ and Sn4+ was controlled for the precipitation in a one pot synthesis step at room temperature (25 degrees C). The effect of the concentration of the reactants on the particle size was studied by varying the concentration of the precursor (Zn2+ + Sn4+) solution. Scanning electron micrographs show that the particles are monodispersed micron sized cubes formed by the self-organization olnano-sized crystallites. The obtained microcubes characterized by X-ray Diffraction and thermo gravimetric analysis (TGA) show that the particles are in ZnSnO3.3H(2)O form.
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| 14. |
- Al-Hinai, Muna H., et al.
(författare)
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Antimicrobial Activity Enhancement of Poly(ether sulfone) Membranes by in Situ Growth of ZnO Nanorods
- 2017
-
Ingår i: ACS Omega. - : AMER CHEMICAL SOC. - 2470-1343. ; 2:7, s. 3157-3167
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Tidskriftsartikel (refereegranskat)abstract
- Composite poly(ether sulfone) membranes integrated with ZnO nanostructures either directly blended or grown in situ have enhanced antibacterial activity with improved functionality in reducing the biofouling in water treatment applications. The pore structure and surface properties of the composite were studied to investigate the effect of the addition of ZnO nanostructures. The hydrophilicity of the blended membranes increased with a higher content of ZnO nanoparticles in the membrane (2-6%), which could be further controlled by varying the growth conditions of ZnO nanorods on the polymer surface. Improved water flux, bovine serum albumin rejection, and inhibition of Escherichia coli bacterial growth under visible light irradiation was observed for the membranes decorated with ZnO nanorods compared to those in the membranes simply blended with ZnO nanoparticles. No regrowth of E. coli was recorded even 2 days after the incubation.
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| 15. |
- Al-Hinai, M. H., et al.
(författare)
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Phase transformation behavior of zinc metastannates obtained by aqueous precipitation at different temperatures
- 2014
-
Ingår i: Journal of Materials Science. - : Springer-Verlag New York. - 0022-2461 .- 1573-4803. ; 49:20, s. 7282-7289
-
Tidskriftsartikel (refereegranskat)abstract
- Phase transformation studies in ZnO-SnO2 system from zinc metastannate (ZnSnO3) to zinc orthostannate (Zn2SnO4) with annealing temperature are reported. Non-centrosymmetric oxides show unique symmetry dependent and spontaneous polarization properties, which are technologically important. ZnSnO3 particles were synthesized by a simple aqueous synthesis at low temperatures designed with the assistance of potential-pH diagrams. ZnSnO3 particles synthesized at 4 A degrees C are more porous losing the ilmenite structure upon annealing at 200 A degrees C, while the other samples prepared at higher temperatures (25-65 A degrees C) becomes amorphous at 300 A degrees C. The phase transformation into the inverse spinel orthostannate phase occurs around 750 A degrees C in all the samples.
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| 16. |
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| 17. |
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| 18. |
- Al-Naamani, Laila, et al.
(författare)
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Chitosan-zinc oxide nanocomposite coatings for the prevention of marine biofouling
- 2017
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 168, s. 408-417
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Tidskriftsartikel (refereegranskat)abstract
- Marine biofouling is a worldwide problem affecting maritime industries. Global concerns about the high toxicity of antifouling paints have highlighted the need to develop less toxic antifouling coatings. Chitosan is a natural polymer with antimicrobial, antifungal and antialgal properties that is obtained from partial deacetylation of crustacean waste. In the present study, nanocomposite chitosan-zinc oxide (chitosan-ZnO) nanoparticle hybrid coatings were developed and their antifouling activity was tested. Chitosan-ZnO nanoparticle coatings showed anti-diatom activity against Navicula sp. and antibacterial activity against the marine bacterium Pseudoalteromonas nigrifaciens. Additional antifouling properties of the coatings were investigated in a mesocosm study using tanks containing natural sea water under controlled laboratory conditions. Each week for four weeks, biofilm was removed and analysed by flow cytometry to estimate total bacterial densities on the coated substrates. Chitosan-ZnO hybrid coatings led to better inhibition of bacterial growth in comparison to chitosan coatings alone, as determined by flow cytometry. This study demonstrates the antifouling potential of chitosan-ZnO nanocomposite hybrid coatings, which can be used for the prevention of biofouling. (C) 2016 Elsevier Ltd. All rights reserved.
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| 19. |
- Al-Naamani, Laila, et al.
(författare)
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Chitosan-zinc oxide nanoparticle composite coating for active food packaging applications
- 2016
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Ingår i: Innovative Food Science & Emerging Technologies. - : Elsevier. - 1466-8564 .- 1878-5522. ; 38, s. 231-237
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Tidskriftsartikel (refereegranskat)abstract
- In this study antimicrobial properties of chitosan and chitosan-zinc oxide (ZnO) nanocomposite coatings on PE films were studied. Oxygen plasma pretreatment of PE films led to increased adhesion by 2% of chitosan and the nanocomposite coating solutions to the packaging films. Scanning Electron Microscopy (SEM) revealed uniform coatings on PE surfaces. Incorporation of ZnO nanoparticles into the chitosan matrix resulted in 42% increase in solubility; swelling decreased by 80% while the water contact angle (WCA) increased from 60 to 95 compared to chitosan coating. PE coated with chitosan-ZnO nanocomposite films completely inactivated and prevented the growth of food pathogens, while chitosan-coated films showed only 10-fold decline in the viable cell counts of Salmonella enterica, Escherichia coli and Staphylococcus aureus after 24-h incubation compared to the control. Industrial relevance: One of the greatest challenges of food industry is microbial contamination. The present study suggests that PE coating with chitosan-ZnO nanocomposite is a promising technique to enhance antimicrobial properties of the films. Chitosan-ZnO nanocomposite coatings improved antibacterial properties of PE by inactivating about 99.9% of viable pathogenic bacteria. Hence, our results show the effectiveness of the nanocomposite coating in the development of active food packaging in order to prolong the shelf life of food products.
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| 20. |
- Al-Naamani, Laila, et al.
(författare)
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Nanocomposite Zinc Oxide-Chitosan Coatings on Polyethylene Films for Extending Storage Life of Okra (Abelmoschus esculentus)
- 2018
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Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 8:7
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Tidskriftsartikel (refereegranskat)abstract
- Efficiency of nanocomposite zinc oxide-chitosan antimicrobial polyethylene packaging films for the preservation of quality of vegetables was studied using okra Abelmoschus esculentus. Low density polyethylene films (LDPE) coated with chitosan-ZnO nanocomposites were used for packaging of okra samples stored at room temperature (25 degrees C). Compared to the control sample (no coating), the total bacterial concentrations in the case of chitosan and nanocomposite coatings were reduced by 53% and 63%, respectively. The nanocomposite coating showed a 2-fold reduction in total fungal concentrations in comparison to the chitosan treated samples. Results demonstrate the effectiveness of the nanocomposite coatings for the reduction of fungal and bacterial growth in the okra samples after 12 storage days. The nanocomposite coatings did not affect the quality attributes of the okra, such as pH, total soluble solids, moisture content, and weight loss. This work demonstrates that the chitosan-ZnO nanocomposite coatings not only maintains the quality of the packed okra but also retards microbial and fungal growth. Thus, chitosan-ZnO nanocomposite coating can be used as a potential coating material for active food packaging applications.
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| 21. |
- Al-Saadi, Mubarak J., et al.
(författare)
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Influence of Atomic Hydrogen, Band Bending, and Defects in the Top Few Nanometers of Hydrothermally Prepared Zinc Oxide Nanorods
- 2017
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Ingår i: Nanoscale Research Letters. - : Springer. - 1931-7573 .- 1556-276X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- We report on the surface, sub-surface (top few nanometers) and bulk properties of hydrothermally grown zinc oxide (ZnO) nanorods (NRs) prior to and after hydrogen treatment. Upon treating with atomic hydrogen (H*), upward and downward band bending is observed depending on the availability of molecular H2O within the structure of the NRs. In the absence of H2O, the H* treatment demonstrated a cleaning effect of the nanorods, leading to a 0.51 eV upward band bending. In addition, enhancement in the intensity of room temperature photoluminescence (PL) signals due to the creation of new surface defects could be observed. The defects enhanced the visible light activity of the ZnO NRs which were subsequently used to photocatalytically degrade aqueous phenol under simulated sunlight. On the contrary, in the presence of H2O, H* treatment created an electronic accumulation layer inducing downward band bending of 0.45 eV (similar to 1/7th of the bulk ZnO band gap) along with the weakening of the defect signals as observed from room temperature photoluminescence spectra. The results suggest a plausible way of tailoring the band bending and defects of the ZnO NRs through control of H2O/H* species.
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| 22. |
- Al-Sabahi, Jamal, et al.
(författare)
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Controlled defects of zinc oxide nanorods for efficient visible light photocatalytic degradation of phenol
- 2016
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Ingår i: Materials. - : MDPI. - 1996-1944. ; 9:4
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental pollution from human and industrial activities has received much attention as it adversely affects human health and bio-diversity. In this work we report efficient visible light photocatalytic degradation of phenol using supported zinc oxide (ZnO) nanorods and explore the role of surface defects in ZnO on the visible light photocatalytic activity. ZnO nanorods were synthesized on glass substrates using a microwave-assisted hydrothermal process, while the surface defect states were controlled by annealing the nanorods at various temperatures and were characterized by photoluminescence and X-ray photoelectron spectroscopy. High performance liquid chromatography (HPLC) was used for the evaluation of phenol photocatalytic degradation. ZnO nanorods with high surface defects exhibited maximum visible light photocatalytic activity, showing 50% degradation of 10 ppm phenol aqueous solution within 2.5 h, with a degradation rate almost four times higher than that of nanorods with lower surface defects. The mineralization process of phenol during degradation was also investigated, and it showed the evolution of different photocatalytic byproducts, such as benzoquinone, catechol, resorcinol and carboxylic acids, at different stages. The results from this study suggest that the presence of surface defects in ZnO nanorods is crucial for its efficient visible light photocatalytic activity, which is otherwise only active in the ultraviolet region.
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| 23. |
- Al-Sabahi, Jamal, et al.
(författare)
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Efficient visible light photocatalysis of benzene, toluene, ethylbenzene and xylene (BTEX) in aqueous solutions using supported zinc oxide nanorods
- 2017
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 12:12
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Tidskriftsartikel (refereegranskat)abstract
- Benzene, toluene, ethylbenzene and xylenes (BTEX) are some of the common environmental pollutants originating mainly from oil and gas industries, which are toxic to human as well as other living organisms in the ecosystem. Here we investigate photocatalytic degradation of BTEX under visible light irradiation using supported zinc oxide (ZnO) nanorods grown on glass substrates using a microwave assisted hydrothermal method. ZnO nanorods were characterized by electron microscopy, X-ray diffraction (XRD), specific surface area, UV/visible absorption and photoluminescence spectroscopy. Visible light photocatalytic degradation products of BTEX are studied for individual components using gas chromatograph/mass spectrometer (GC/MS). ZnO nanorods with significant amount of electronic defect states, due to the fast crystallization of the nanorods under microwave irradiation, exhibited efficient degradation of BTEX under visible light, degrading more than 80% of the individual BTEX components in 180 minutes. Effect of initial concentration of BTEX as individual components is also probed and the photocatalytic activity of the ZnO nanorods in different conditions is explored. Formation of intermediate byproducts such as phenol, benzyl alcohol, benzaldehyde and benzoic acid were confirmed by our HPLC analysis which could be due to the photocatalytic degradation of BTEX. Carbon dioxide was evaluated and showed an increasing pattern over time indicating the mineralization process confirming the conversion of toxic organic compounds into benign products.
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| 24. |
- Al-Sabahi, J., et al.
(författare)
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Visible light photocatalytic degradation of HPAM polymer in oil produced water using supported zinc oxide nanorods
- 2018
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Ingår i: Chemical Engineering Journal. - : Elsevier B.V.. - 1385-8947 .- 1873-3212. ; 351, s. 56-64
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Tidskriftsartikel (refereegranskat)abstract
- Polymer flooding displacement ability during petroleum extraction from the earth's crust plays an important role in enhanced oil recovery processes. Produced water, as a byproduct, still contain high concentrations of petroleum hydrocarbons and partially hydrolyzed polyacrylamide (HPAM) which is a serious environmental concern. Remediating produced water economically is a big challenge for meeting the permissible discharge limits leading to failure in the effectiveness of the conventional water treatment technologies. Advanced oxidation processes (AOPs) are playing increasing role in the treatment of polluted water and is receiving much attention in recent times as a green and safer water treatment technology. Here we report a new approach to use vertically aligned zinc oxide nanorods (ZnO NRs) supported on substrates engineered for improving their visible light harvesting capacity for effective solar photocatalytic degradation of HPAM. The viscosity of collected oilfield produced water containing HPAM were found to be reduced dramatically when the samples are photocatalytically degraded using ZnO nanorod catalysts irradiated with simulated solar light showing a reduction of 51% within 6 h. With high pressure liquid chromatography 68, 62, 56 and 45% removal of 25, 50, 100 and 150 ppm HPAM, respectively, was demonstrated. The pH of the solution was observed to move to acidic region due to acetamide, nitrate, propionamide and acetic acid which are the intermediate byproducts formed during degradation as determined by mass spectrometry. Zinc oxide nanorod coatings showed about 74% removal efficiency over 5 cycles with less than 1.2% removal of zinc ions after 6 h of light irradiation.
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| 25. |
- Al-Soubaihi, Rola, et al.
(författare)
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Comparative investigation of structure and operating parameters on the performance and reaction dynamic of CO conversion on silica aerogel and fumed-silica-supported Pd catalysts
- 2022
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Ingår i: SURFACES AND INTERFACES. - : Elsevier BV. - 2468-0230. ; 29, s. 101776-
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Tidskriftsartikel (refereegranskat)abstract
- The catalyst morphology, metal-support interaction, and reaction conditions greatly influence the catalytic performance and reaction dynamics. Similarly, the dispersion of the metal within the support plays a crucial in the thermal stability and sintering of the catalyst. Furthermore, temperature-dependent conversion hysteresis is well-known to occur during ignition and extinction of exothermic CO oxidation over supported Pd catalysts due to the variation of CO adsorption on the surface or bulk oxidation of Pd and the ability of the catalyst regenerate the active sites. Herein, the catalytic performance and the hysteresis behavior of mesoporous silica aerogel supported Pd (Pd/a-SiO2), and commercial fumed silica-supported Pd (Pd/f-SiO2) were investigated compared using CO oxidation as a probe reaction under different reaction conditions and operating parameters (i.e., catalyst weight, ramp rate, and flow rate). Surface and morphologic examination using XPS, FTIR, and of Pd/a-SiO2 and Pd/f-SiO2 reveal a strong correlation between the catalyst surface and structure and its catalytic performance and stability under different reaction parameters. Moreover, this study presents the effect of surface area, particle size, and size distribution on diffusion and mass transport of reactants (CO, O-2) and products (CO2) and active sites accessibility. This study showed that Pd/f-SiO2 had better efficiency under high (turbulence) flow. Moreover, intrinsic apparent activation energy (E-a) and the number of active sites were calculated from the Kinetics of CO oxidation fitted using Arrhenius plots indicate that the ramp rate has less effect on Pd/f-SiO2 catalytic behavior. though, Pd/f-SiO2 had higher relative active sites than Pd/a-SiO2, (E-a) was lower. Cyclic stability and long-term stabilities showed that both catalysts are stable and can regenerate the active sites. The current study contributes to understanding the catalysts' surface, structural and morphological properties on the catalysts' performance toward CO oxidation and other reactions under dynamic conditions.
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| 26. |
- Al-Soubaihi, Rola, et al.
(författare)
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Investigation of palladium catalysts in mesoporous silica support for CO oxidation and CO2 adsorption
- 2023
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Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 9:7
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation of Carbon monoxide (CO) to Carbon dioxide (CO2) is one of the most extensively investigated reactions in the field of heterogeneous catalysis, and it occurs via molecular rearrangements induced by catalytic metal atoms with oxygen intermediates. CO oxidation and CO2 capture are instrumental processes in the reduction of green-house gas emissions, both of which are used in low-temperature CO oxidation in the catalytic converters of vehicles. CO oxidation and CO2 adsorption at different temperatures are evaluated for palladium-supported silica aerogel (Pd/SiO2). The synthesized catalyst was active and stable for low-temperature CO oxidation. The catalytic activity was enhanced after the first cycle due to the reconditioning of the catalyst's pores. It was found that the presence of oxide forms of palladium in the SiO2 microstructure, influences the performance of the catalysts due to oxygen vacancies that increases the frequency of active sites. CO2 gas adsorption onto Pd/SiO2 was investigated at a wide-ranging temperature from 16 to 120 degrees C and pressures similar to 1 MPa as determined from the isotherms that were evaluated, where CO2 showed the highest equilibrium adsorption capacity at 16 degrees C. The Langmuir model was employed to study the equilibrium adsorption behavior. Finally, the effect of moisture on CO oxidation and CO2 adsorption was considered to account for usage in real-world applications. Overall, mesoporous Pd/SiO2 aerogel shows potential as a material capable of removing CO from the environment and capturing CO2 at low temperatures.
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| 27. |
- Al-Soubaihi, Rola, et al.
(författare)
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Low-temperature CO oxidation by silver nanoparticles in silica aerogel mesoreactors
- 2023
-
Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 455, s. 140576-
-
Tidskriftsartikel (refereegranskat)abstract
- Low-temperature carbon monoxide (CO) oxidation on silver/silica aerogel (Ag/SiO2 AG) catalyst prepared by one-pot sol-gel synthesis followed by supercritical ethanol drying method is reported. Highly stable and sinterproof catalyst led to easy reactant diffusion to the active sites. The Ag/SiO2 AG catalyst showed enhanced catalytic activity toward low-temperature CO oxidation by preventing agglomeration of silver nanoparticles inside pores and facilitating well-dispersed active sites to enhance the mass heat transfer in the mesopores. Catalyst pretreatment conditions were found to play a crucial role in achieving high CO conversion efficiency at low light-off temperatures. Inverse counter-clockwise CO oxidation hysteresis was found to occur after the first run. The active sites contributing to this enhanced catalytic behavior were confirmed to be Ag0 from XPS, XRD, and TEM analysis. The catalyst exhibited good thermal stability up to 450 degrees C over repeated number of cycles.
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| 28. |
- Al Soubaihi, Rola Mohammad, et al.
(författare)
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CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst
- 2021
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Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (T-ig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than T-ig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at T-ig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.
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| 29. |
- Al Soubaihi, Rola Mohammad, et al.
(författare)
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Critical Review of Low-Temperature CO Oxidation and Hysteresis Phenomenon on Heterogeneous Catalysts
- 2018
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Ingår i: Catalysts. - : MDPI. - 2073-4344. ; 8:12
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Forskningsöversikt (refereegranskat)abstract
- There is a growing demand for new heterogeneous catalysts for cost-effective catalysis. Currently, the hysteresis phenomenon during low-temperature CO oxidation is an important topic in heterogeneous catalysis. Hysteresis provides important information about fluctuating reaction conditions that affect the regeneration of active sites and indicate the restoration of catalyst activity. Understanding its dynamic behavior, such as hysteresis and self-sustained kinetic oscillations, during CO oxidation, is crucial for the development of cost-effective, stable and long-lasting catalysts. Hysteresis during CO oxidation has a direct influence on many industrial processes and its understanding can be beneficial to a broad range of applications, including long-life CO2 lasers, gas masks, catalytic converters, sensors, indoor air quality, etc. This review considers the most recent reported advancements in the field of hysteresis behavior during CO oxidation which shed light on the origin of this phenomenon and the parameters that influence the type, shape, and width of the conversion of the hysteresis curves.
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| 30. |
- Al-Soubaihi, Rola, et al.
(författare)
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Silica and carbon decorated silica nanosheet impact on primary human immune cells
- 2018
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Ingår i: Colloids and Surfaces B. - : Elsevier B.V.. - 0927-7765 .- 1873-4367. ; 172, s. 779-789
-
Tidskriftsartikel (refereegranskat)abstract
- Silica nanosheets (SiO 2 NS) are considered to be a promising material in clinical practice for diagnosis and therapy applications. However, an appropriate surface functionalization is essential to guarantee high biocompatibility and molecule loading ability. Although SiO 2 NS are chemically stable, its effects on immune systems are still being explored. In this work, we successfully synthesized a novel 2D multilayer SiO 2 NS and SiO 2 NS coated with carbon (C/SiO 2 NS), and evaluated their impact on human Peripheral Blood Mononuclear Cells (PBMCs) and some immune cell subpopulations. We demonstrated that the immune response is strongly dependent on the surface functionalities of the SiO 2 NS. Ex vivo experiments showed an increase in biocompatibility of C/SiO 2 NS compared to SiO 2 NS, resulting in a lowering of hemoglobin release together with a reduction in cellular toxicity and cellular activation. However, none of them are directly involved in the activation of the acute inflammation process with a consequent release of pro-inflammatory cytokines. The obtained results provide an important direction towards the biomedical applications of silica nanosheets, rendering them an attractive material for the development of future immunological therapies.
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| 31. |
- Al-Soubaihi, Rola, 1975-
(författare)
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Study CO oxidation, Hysteresis behavior, and CO2 adsorption on mesoporous silica supported metal nano catalyst
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Over the past decades, mesoporous silica has emerged as a new material with interesting physical and chemical properties, such as high surface-to-volume ratio, stability, and the feasibility of surface functionalization, amongst others. Mesoporous silica provides an opportunity to improve conventional commercial catalyst supports, and sorbent due to its low-cost synthesis. In this research field, investigations on various materials prepared by different techniques as potential support have been reported. The main objective of the studies was to produce highly stable mesoporous materials for energy and environmental applications using simple and low-cost synthesis.In this thesis, we utilized the sol-gel and self-templating processes in synthesizing three types of highly porous silica nanomaterials, mainly aerogels (SiO2 AG), xerogel (SiO2 XG), and nanosheets (SiO2 NS). SiO2 AG and SiO2 XG were synthesized using the sol-gel method, while SiO2 NS was synthesized using the soft-templating hydrothermal technique. SiO2 AG, SiO2, XG, and SiO2 NS are explored as catalyst support for low-temperature carbon monoxide (CO) oxidation and compared to commercial Fumed Silica. The synthesized materials are investigated as metal support materials (M/SiO2) for environmental applications such as CO oxidation and carbon dioxide (CO2) adsorption. The morphology of the synthesized materials was investigated experimentally using several characterization techniques such as X-ray Diffraction (XRD), X-ray Photo-electron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), Thermo-Gravimetry-Differential Scanning Calorimetry (TGA-DSC), gas adsorption by Brunauer–Emmett–Teller (BET) method, Fourier Transform Infra-Red spectroscopy (FTIR), UV-Vis spectroscopy, and Temperature Programmed Reduction (TPR) for understanding the surface chemistry of supports. The M/SiO2 was subjected to a detailed study of the morphology before, during, and after the low-temperature CO oxidation reaction under various pretreatment and reaction parameters for a better understanding of the chemical and physical changes occurring on the catalyst. It was found that the catalyst structure, surface area, and morphology of M/SiO2 play a crucial role in the catalytic performance and stability under different reaction conditions compared to unsupported metal catalysts by preventing agglomeration of metal nanoparticles inside pores and aiding in a better dispersion of active sites to boost the mass heat transfer in the silica mesopores. The catalyst pretreatment conditions can affect CO conversion efficiency at low light-off temperatures (Tig) because of their effect on surface area, particle size, and size distribution of metal nanoparticles, which have a substantial effect on diffusion and mass transport of reactants (CO, O2) and products (CO2) and active sites accessibility. The lowest Tig ~ 195 ℃ and 65 ℃ for aerogel-supported palladium (Pd/a-SiO2) and aerogel-supported silver (Ag/a-SiO2) catalysts treated in the CO/O2 mixture, respectively. Moreover, the effect of reaction conditions on the catalytic CO oxidation was studied. The intrinsic apparent activation energy (Ea) and the number of active sites were calculated experimentally from the Kinetics of CO oxidation and fitted using Arrhenius plots, Ea for Pd/a-SiO2 ~ 87.6 kJmole-1. In this dissertation, we have also investigated the conversion hysteresis effect during carbon monoxide (CO) oxidation on metal/silica (M/SiO2) as a function of different pre-treatment and reaction conditions. The hysteresis behavior has been explored on Pd/SiO2, which showed a normal hysteresis due to the increased stability of the active sites. In contrast, the Ag/a-SiO2 showed an inverse counter-clockwise CO oxidation hysteresis. Cyclic and long-term stabilities of the catalysts were investigated, where Pd/a-SiO2 showed good stability for four consecutive cycles and long-term stability for ~ 27 hrs.Furthermore, Pd/SiO2 was investigated for CO2 adsorption under dry and humid conditions. The adsorption isotherms under variant temperatures and pressures were studied experimentally by evaluating the CO2 gas adsorption onto Pd/a-SiO2 at low and moderate temperatures and pressures and fitted theoretically using the Langmuir fitting model. The material showed the highest equilibrium adsorption capacity of CO2 at low temperatures (3.25 molekg-1 at 16 ℃ and 1 MPa). Moreover, the moisture effect was investigated and found to play a role in reducing CO oxidation efficiency and increasing CO2 adsorption. The main objective of the studies was to produce highly stable mesoporous-supported Catalysts for multi-energy and environmental applications using simple and low-cost synthesis.
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| 32. |
- Al-Soubaihi, Rola, et al.
(författare)
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Synthesis of hierarchically porous silica aerogel supported Palladium catalyst for low-temperature CO oxidation under ignition/extinction conditions
- 2020
-
Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 292
-
Tidskriftsartikel (refereegranskat)abstract
- Synthesis of well-dispersed palladium nanoparticles within silica aerogel pores with controlled size was carried out using sol-gel synthesis under supercritical ethanol drying. The high concentration of silanol groups on silica (SiO2) surface facilitated a superior palladium (Pd) loading up to 10 wt %. The synthesized Pd/SiO2 nanocomposite aerogels were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopic methods. The silica aerogel supported catalysts were found to have a wide pore size distribution. TEM investigations confirmed that Pd nanocrystals were located within the SiO2 microspores and mesopores. The catalyst was evaluated for carbon monoxide (CO) oxidation reaction under ignition/extinction conditions. The synthesized catalyst demonstrated a high catalytic activity at low operating temperatures (<200 °C) compared to unsupported Pd nanoparticles or bare SiO2 aerogels. This enhancement in CO oxidation activity with Pd/SiO2 aerogel catalysts are attributed to the small Pd particles, Pd interaction with the surface of the underlying SiO2 and the better dispersion of Pd particles within the SiO2 pores. Porosity played a more important role during the extinction cycle as a result of the slow dissipation of the heat leading to hysteresis. We demonstrate the influence of porosity of catalyst supports on the size, dispersion, and catalytic activity of Pd nanoparticles.
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| 33. |
- Alsharaeh, E. H., et al.
(författare)
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Sol-Gel-Assisted Microwave-Derived Synthesis of Anatase Ag/TiO2/GO Nanohybrids toward Efficient Visible Light Phenol Degradation
- 2017
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Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 7:5
-
Tidskriftsartikel (refereegranskat)abstract
- A simple microwave-assisted (MWI) wet chemical route to synthesize pure anatase phase titanium dioxide (TiO2) nanoparticles (NPs) is reported here using titanium tetrachloride (TiCl4) as starting material. The as-prepared TiO2 NPs were characterized by electron microscopy, X-ray diffraction, UV/visible absorption spectroscopy, and infrared and Raman spectroscopic techniques. Further modification of the anatase TiO2 NPs was carried out by incorporating plasmonic silver (Ag) NPs and graphene oxide (GO) in order to enhance the visible light absorption. The photocatalytic activities of the anatase TiO2, Ag/TiO2, and Ag/TiO2/GO nanocomposites were evaluated under both ultraviolet (UV) and visible light irradiation using phenol as a model contaminant. The presence of Ag NPs was found to play a significant role to define the photocatalytic activity of the Ag/TiO2/GO nanocomposite. It was found that the Ag performed like a sink under UV excitation and stored photo-generated electrons from TiO2, whereas, under visible light excitation, the Ag acted as a photosensitizer enhancing the photocatalytic activity of the nanocomposite. The detailed mechanism was studied based on photocatalytic activities of Ag/TiO2/GO nanocomposites. Therefore, the as-prepared Ag/TiO2/GO nanocomposite was used as photocatalytic materials under both UV and visible light irradiation toward degradation of organic molecules.
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| 34. |
- Alvarado Ávila, María Isabel, et al.
(författare)
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Cellulose as sacrificial agents for enhanced photoactivated hydrogen production
- 2023
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Ingår i: Sustainable Energy & Fuels. - : Royal Society of Chemistry (RSC). - 2398-4902. ; 7:8, s. 1981-1991
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Tidskriftsartikel (refereegranskat)abstract
- The search for new energy sources together with the need to control greenhouse gas emissions has led to continued interest in low-emitting renewable energy technologies. In this context, water splitting for hydrogen production is a reasonable alternative to replace fossil fuels due to its high energy density producing only water during combustion. Cellulose is abundant in nature and as residuals from human activity, and therefore a natural, ecological, and carbon-neutral source for hydrogen production. In the present work, we propose a sustainable method for hydrogen production using sunlight and cellulose as sacrificial agents during the photocatalytic water splitting process. Platinum (Pt) catalyst activates hydrogen production, and parameters such as pH of the system, cellulose concentration, and Pt loading were studied. Using different biomasses, we found that the presence of hemicellulose and xyloglucan as part of the molecular composition considerably increased the H-2 production rate from 36 mu mol L-1 in one hour for rapeseed cellulose to 167.44 mu mol L-1 for acid-treated cellulose isolated from Ulva fenestrata algae. Carboxymethylation and TEMPO-oxidation of cellulosic biomass both led to more stable suspensions with higher rates of H-2 production close to 225 mu mol L-1, which was associated with their water solubility properties. The results suggest that cellulosic biomass can be an attractive alternative as a sacrificial agent for the photocatalytic splitting of water for H-2 production.
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| 35. |
- Alvarado Ávila, María Isabel, et al.
(författare)
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Cerium Oxide on a Fluorinated Carbon-Based Electrode as a Promising Catalyst for Hypochlorite Production
- 2022
-
Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:42, s. 37465-37475
-
Tidskriftsartikel (refereegranskat)abstract
- Sodium hypochlorite (NaOCl) is widely used as a disinfectant agent for water treatment and surface cleaning. A straightforward way to produce NaOCl is by the electrolysis of an aqueous sodium chloride (NaCl) solution. This process presents several side reactions decreasing its efficiency with hypochlorite reduction on the cathode surface being one of the main detrimental reactions. In this work, we have studied carbon-based electrodes modified with cerium oxide (CeO2), fluorine, and platinum nanoparticles as cathodes for hypochlorite production. Fluorination was carried out electrochemically; the polyol method was used to synthesize platinum nanoparticles; and the hydrothermal process was applied to form a CeO2 layer. Scanning electron microscopy, FTIR, and inductively coupled plasma (ICP) indicated the presence of cerium oxide as a film, fluorine groups on the substrate, and a load of 3.2 mg/cm2 of platinum nanoparticles and 2.7 mg/cm2 of CeO2. From electrochemical impedance spectroscopy, it was possible to demonstrate that incorporating platinum and fluorine decreases the charge transfer resistance by 16% and 28%, respectively. Linear sweep voltammetry showed a significant decrease in hypochlorite reduction when the substrate was doped with fluorine from -16.6 mA/cm2 at -0.6 V to -9.64 mA/cm2 that further reduced to -8.78 mA/cm2 with cerium oxide covered fluorinated electrodes. The performance of the cathode materials during hypochlorite production improved by 80% compared with pristine activated carbon cloth (ACC) electrodes. The improvement toward hindering NaOCl reduction is probably caused by the incorporation of a partial negative charge upon doping with fluorine.
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| 36. |
- Alvarado Ávila, María Isabel, et al.
(författare)
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Improved chlorate production with platinum nanoparticles deposited on fluorinated activated carbon cloth electrodes
- 2020
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Ingår i: Cleaner Engineering and Technology. - : Elsevier BV. - 2666-7908. ; 1
-
Tidskriftsartikel (refereegranskat)abstract
- Sodium chlorate is one of the main oxidizing agents used in the wood industry due to their capability of use as an elemental chlorine-free (CEF) bleaching. A simple way to produce chlorates is by the electrolysis of an aqueous sodium chloride (NaCl) solution. In the present study activated carbon cloth electrodes (ACC) modified with fluorine and platinum nanoparticles (Pt–F/ACC and Pt/ACC) were used as one of the electrodes. Electrofluorination was used for fluorination of the anodes and polyol method was used for the synthesis of platinum nanoparticles. Chlorate production using a typical solution of 100 g/l of sodium chloride (NaCl) and 2 g/l sodium chromate (Na2Cr2O7) and an applied current of 0.540 A was studied. Prior to the electrolysis assays, the microstructural properties of the electrodes were characterized by scanning electron microscopy and surface modifications and bonding using infra-red (FTIR) spectroscopy. Electrochemical properties were determined using cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. Interaction between fluorine (F) and platinum (Pt) on the electrode leads to an improvement of the electrocatalytic properties for chlorine evolution as observed from the increase in the current efficiency from 37.5% at 78.5% after 150 min of continuous electrolysis using Pt–F/ACC anodes. The results suggest that modified activated carbon material is an attractive and economical alternative as electrodes for chlorate production.
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| 37. |
- Anceno, A. J., et al.
(författare)
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Nanoparticle self-assembly via facile (Bio)chemistry : Charge-stabilized metal nanoparticles on microbial cell surfaces
- 2010
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Ingår i: Journal of Bionanoscience. - : American Scientific Publishers. - 1557-7910. ; 4:1-2, s. 92-98
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Tidskriftsartikel (refereegranskat)abstract
- With a view of achieving up-scaled nutrition-driven biomimetic assembly of gold nanoparticles, the self-assembly of glutamate- or chitosan stabilized colloidal gold was attempted using viable microbial cells as templates in nutrient rich or poor assembly environment. The likelihood of achieving self-assembly given the type of microbial template, nanoparticle stabilization and predominant biochemical conditions is discussed. While the realization of industrially useful microcomponents from the assembly route maybe technically remote as yet, it was found that present nanoparticles and suitable assembly environment find immediate application in conventional microscopy or as contrast enhancers in the routine study of microbial cell morphology.
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| 38. |
- Anceno, A J, et al.
(författare)
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Of Quantum Dots and Microbes : Smart materials for fluorescence based characterization of environmental microflora
- 2013
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Ingår i: Proc. of the Intl. Conf. on Future Trends in Structural, Civil, Environmental and Mechanical Engineering – FTSCEM 2013. - : SEEK Digital Library. ; , s. 61-65
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Konferensbidrag (refereegranskat)abstract
- Manganese doped zinc sulfide (ZnS:Mn2+) quantum dots (QDs) were surface derivatized for use as versatile fluorescent reporters is the study of microorganisms of relevance in environmental bioprocesses. When intracellularly introduced into permeabilized target bacterial cells, mercaptoacetic acid (MAA) or dithiothreitol (DTT) treatedZnS:Mn2+QDs proved to be good visualization enhancers for morphological observations with epifluorescence microscopy. Alternatively, cell surface adhesion of chitosan capped ZnS:Mn2+QDs also led to a similar effect, namely of QD enhanced contrast of target cells from intrinsic background fluorescence. When DTT surface derivatized ZnS:Mn2+QDs were conjugated with oligonucleotide probes and used in fluorescent in situ hybridization (FISH) analysis, specific detection of bacterial strains representative ofsome proteobacterial classes was achieved.
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| 39. |
- Annaduzzaman, Md, 1986-
(författare)
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Chitosan biopolymer as an adsorbent for drinking water treatment : Investigation on Arsenic and Uranium
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In many countries over the world (including Sweden), metal toxicity in freshwater resources causes a severe drinking water quality problem and poses a threat to the environment and human health. Among the different toxic metals in the water resources of Sweden, arsenic and uranium are the biggest threats to health. These elements, over long time consumption, may even lead to cancer and/or neurological disorder. Most of the wells are installed in crystalline and sedimentary bedrock and the received water comes from water bearing fractures in the bedrock. The handling of such water is an issue and there is a need to reduce the arsenic and uranium exposure by improving processes and technologies. It is a very serious problem demanding a safe, sustainable and eco-friendly arsenic and uranium removal technology prior to drinking water supply. Different treatment systems are available, but many of them are not suitable due to their high cost, operation complexity and waste management issues. Through this study, chitosan biopolymer the second largest abundant polysaccharide on earth after cellulose, was verified as a potential adsorbent for arsenic(V) and uranium(VI) removal from water solution. Adsorbent characterizations were also conducted by XRD, FTIR, SEM, UV-visible spectrum and TGA/DTA investigations. Bench-scale batch experiments were conducted using chitosan biopolymer (DDA-85%) as an adsorbent to determine the arsenic(V) and uranium(VI) removal efficiency, by allowing four important effective parameters e.g. chitosan dosages, pH, contact time and contaminant concentration. The adsorption data at optimum conditions were fitted with Langmuir, Freundlich and Dubinin-Radushkhevic (D-R) isotherm and Lagergren pseudo-first-order and pseudo-second-order kinetic model to investigate the adsorption process. The characterization of materials assured the presence of effective amino, hydroxyl, and carboxyl groups of chitosan. Another advanntage is that the materials are bio-degradable. The results show that the arsenic(V) and uranium(VI) removal efficiency was 100% and 97.45% after 300 minutes with optimum pH of 6.0 and 7.0 respectively. The optimum adsorbent dosages and initial concentration were 60 and 80g/L and 100 and 250 µg/L respectively. The adsorption process was suitably described by Freundlich isotherm (R2 = 0.9933) and Langmuir isotherm (R2 = 0.9858) correspondingly for arsenic(V) uranium(VI) compared to other isotherms. This is an important indicator of homogeneous monolayer adsorption of metals. For both of arsenic(V) and uranium(VI), pseudo-second-order explained the adsorption kinetics better than pseudo-first-order and the second-order kinetic regression coefficient (R2) were 0.9959 and 0.9672 correspondingly. Connecting to the above mentioned results, it can be summed up that the chitosan biopolymer (DDA 85%) can be used as an inexpensive, sustainable and environment-friendly treatment option for arsenic(V) and uranium(VI) contaminated drinking water.
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| 40. |
- Asem, Heba, 1987-
(författare)
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Synthesis of Polymeric Nanocomposites for Drug Delivery and Bioimaging
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanomaterials have gained great attention for biomedical applications due to their extraordinary physico-chemical and biological properties. The current dissertation presents the design and development of multifunctional nanoparticles for molecular imaging and controlled drug delivery applications which include biodegradable polymeric nanoparticles, superparamagnetic iron oxide nanoparticles (SPION)/polymeric nanocomposite for magnetic resonance imaging (MRI) and drug delivery, manganese-doped zinc sulfide (Mn:ZnS) quantum dots (QDs)/ SPION/ polymeric nanocomposites for fluorescence imaging, MRI and drug delivery.Bioimaging is an important function of multifunctional nanoparticles in this thesis. Imaging probes were made of SPION and Mn:ZnS QDs for in vitro and in vivo imaging. The SPION have been prepared through a high temperature decomposition method to be used as MRI contrast agent. SPION and Mn:ZnS were encapsulated into poly (lactic-co-glycolic) acid (PLGA) nanoparticles during the particles formation. The hydrophobic model drug, busulphan, was loaded in the PLGA vesicles in the composite particles. T2*-weighted MRI of SPION-Mn:ZnS-PLGA phantoms exhibited enhanced negative contrast with r2* relaxivity of 523 mM-1 s-1. SPION-Mn:ZnS-PLGA-NPs have been successfully applied to enhance the contrast of liver in rat model.The biodegradable and biocompatible poly (ethylene glycol)-co-poly (caprolactone) (PEG-PCL) was used as matrix materials for polymeric nanoparticles -based drug delivery system. The PEG-PCL nanoparticles have been constructed to encapsulate SPION and therapeutic agent. The encapsulation efficiency of busulphan was found to be ~ 83 %. PEG-PCL nanoparticles showed a sustained release of the loaded busulphan over a period of 10 h. The SPION-PEG-PCL phantoms showed contrast enhancement in T2*-weighted MRI. Fluorescein-labeled PEG-PCL nanoparticles have been observed in the cytoplasm of the murine macrophage cells (J774A) by fluorescence microscopy. Around 100 % cell viability were noticed for PEG-PCL nanoparticles when incubated with HL60 cell line. The in vivo biodistribution of fluorescent tagged PEG-PCL nanoparticles demonstrated accumulation of PEG-PCL nanoparticles in different tissues including lungs, spleen, liver and kidneys after intravenous administration.
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| 41. |
- Ashour, Radwa M., et al.
(författare)
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Rare Earth Ions Adsorption onto Graphene Oxide Nanosheets
- 2017
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Ingår i: Solvent extraction and ion exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 35:2, s. 91-103
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Tidskriftsartikel (refereegranskat)abstract
- Graphene oxide (GO) was synthesized and used as a coagulant of rare earth elements (REEs) from aqueous solution. Stability and adsorption capacities were exhibited for target REEs such as La(III), Nd(III), Gd(III), and Y(III). The parameters influencing the adsorption capacity of the target species including contact time, pH, initial concentration, and temperature were optimized. The adsorption kinetics and thermodynamics were studied. The method showed quantitative recovery (99%) upon desorption using HNO3 acid (0.1 M) after a short contact time (15 min).
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| 42. |
- Ashour, Radwa M., et al.
(författare)
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Selective separation of rare earth ions from aqueous solution using functionalized magnetite nanoparticles : kinetic and thermodynamic studies
- 2017
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Ingår i: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 327, s. 286-296
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Tidskriftsartikel (refereegranskat)abstract
- Separation of rare earth ions (RE3+) from aqueous solution is a tricky problem due to their physico-chemical similarities of properties. In this study, we investigate the influence of the functionalized ligands on the adsorption efficiency and selective adsorption of La3+, Nd3+, Gd3+ and Y3+ from aqueous solution using Magnetite (Fe3O4) nanoparticles (NPs) functionalized with citric acid (CA@Fe3O4 NPs) or L-cysteine (Cys@Fe3O4 NPs). The microstructure, thermal behavior and surface functionalization of the synthesized nanoparticles were studied. The general adsorption capacity of Cys@Fe3O4 NPs was found to be high (98 mg g−1) in comparison to CA@Fe3O4 NPs (52 mg g−1) at neutral pH 7.0. The adsorption kinetic studies revealed that the adsorption of RE3+ ions follows a pseudo second-order model and the adsorption equilibrium data fits well to the Langmuir isotherm. Thermodynamic studies imply that the adsorption process was endothermic and spontaneous in nature. Controlled desorption within 30 min of the adsorbed RE3+ ions from both Cys@Fe3O4 NPs and CA@Fe3O4 NPs was achieved with 0.5 M HNO3. Furthermore, Cys@Fe3O4 NPs exhibited a higher separation factor (SF) in the separation of Gd3+/La3+, Gd3+/Nd3+, Gd3+/Y3+ ions compared to CA@Fe3O4 NPs.
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| 43. |
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| 44. |
- Bahari, Helma Sadat, et al.
(författare)
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Chitosan nanocomposite coatings with enhanced corrosion inhibition effects for copper
- 2020
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 162, s. 1566-1577
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Tidskriftsartikel (refereegranskat)abstract
- A biopolymer coating on copper was prepared based on chitosan nanocomposite and its corrosion inhibition efficiency was investigated. Inclusion of silica nanoparticles substantially reduces swelling ratio of chitosan coating while enhancing its thermal stability. The corrosion resistance of chitosan-based coatings is improved by introducing 2-mercaptobenzothiazole and silica in the matrix. It is found that upon crosslinking the chitosan coatings, a higher corrosion resistance could be achieved and the highest inhibition efficiency for chitosan nanocomposite coatings is calculated as 85%. The corrosion mechanism is found closely related to mass transition and diffusion process, and also the polarization resistance contributes to the impedance. Calculated impedance using Kramers-Kronig transformation shows good agreement with experimental values, thus validating the impedance measurements. This study exhibits the enhanced efficiency of nanocomposite and potential of chitosan coatings in corrosion prevention for copper.
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| 45. |
- Banerjee, S., et al.
(författare)
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UVA radiation induced ultrafast electron transfer from a food carcinogen benzo[a]pyrene to organic molecules, biological macromolecules, and inorganic nano structures
- 2013
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 117:14, s. 3726-3737
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Tidskriftsartikel (refereegranskat)abstract
- Reactions involving electron transfer (ET) and reactive oxygen species (ROS) play a pivotal role in carcinogenesis and cancer biochemistry. Our present study emphasizes UVA radiation induced ET reaction as one of the key aspects of a potential carcinogen, benzo[a]pyrene (BP), in the presence of a wide variety of molecules covering organic p-benzoquinone (BQ), biological macromolecules like calf-thymus DNA (CT-DNA), human serum albumin (HSA) protein, and inorganic zinc oxide (ZnO) nanorods (NRs). Steady-state and picosecond-resolved fluorescence spectroscopy have been used to monitor such ET reactions. Physical consequences of BP association with CT-DNA have been investigated through temperature-dependent circular dichroism (CD) spectroscopy. The temperature-dependent steady-state, picosecond-resolved fluorescence lifetime and anisotropy studies reveal the effect of temperature on the perturbation of such ET reactions from BP to biological macromolecules, highlighting their temperature-dependent association. Furthermore, the electron-donating property of BP has been corroborated by measuring wavelength-dependent photocurrent in a BP-anchored ZnO NR-based photodevice, offering new physical insights for the carcinogenic study of BP.
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| 46. |
- Barua, S, et al.
(författare)
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Liquified Petroleum Gas Sensing using Microballs of ZnO
- 2013
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Ingår i: lndian ]ournal of Science and Technology. - 0974-6846. ; 6:S3, s. 190-193
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Tidskriftsartikel (refereegranskat)abstract
- Liquefied petroleum gas (LPG) is extensively used in households and industries. It is a combustible gas and leakages can lead toexplosions. It is also toxic and exposure to it above a certain level can be fatal and as such real time monitoring and accidentalleakage detection is crucial. Metal oxide semiconductors are known for their gas sensing property. Spherical microstructures ofZnO, a wide band gap semiconductor, were synthesized following a simple hydrothermal route. Thin films of these microsphereswere used to detect LPG down to 1000 ppm by observing the change in electrical resistance. Platinum (Pt) nanoparticles weredeposited on the sensing mediurn as a catalyst to improve the performance of the sensors. Maximum response of 55.8% wasachieved for 5000 ppm ofLPG at 250oC.
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| 47. |
- Baruah, Sunandan, et al.
(författare)
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Development of a visible light active photocatalytic portable water purification unit using ZnO nanorods
- 2012
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Ingår i: Catalysis Science & Technology. - 2044-4753 .- 2044-4761. ; 2:5, s. 918-921
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Tidskriftsartikel (refereegranskat)abstract
- A ZnO nanorods based water purification unit was designed which operates with solar energy as the source of activation. The purifier was tested on two model bacteria Escherichia coli and Staphylococcus aureus with concentration as high as 1010 colony forming units (CFU) per litre, which is about 105 times higher than the bacterial concentration in tap water. Up to 99% (0.99 × 1010 CFU L−1) removal of viable bacterial cells was achieved under sunlight activation.
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| 48. |
- Baruah, Sunandan, et al.
(författare)
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Development of a visible light active photocatalytic portable water purification unit using ZnO nanorods
- 2012
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Ingår i: Catalysis Science & Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 2:5, s. 918-921
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Tidskriftsartikel (refereegranskat)abstract
- A ZnO nanorods based water purification unit was designed which operates with solar energy as the source of activation. The purifier was tested on two model bacteria Escherichia coli and Staphylococcus aureus with concentration as high as 10(10) colony forming units (CFU) per litre, which is about 10(5) times higher than the bacterial concentration in tap water. Up to 99% (0.99 x 10(10) CFU L-1) removal of viable bacterial cells was achieved under sunlight activation.
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| 49. |
- Baruah, S., et al.
(författare)
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Effect of seeded substrates on hydrothermally grown ZnO nanorods
- 2009
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Ingår i: Journal of Sol-Gel Science and Technology. - : Springer Berlin/Heidelberg. - 0928-0707 .- 1573-4846. ; 50:3, s. 456-464
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Tidskriftsartikel (refereegranskat)abstract
- We report a study on the effect of seeding on glass substrates with zinc oxide nanocrystallites towards the hydrothermal growth of ZnO nanorods from a zinc nitrate hexahydrate and hexamethylenetetramine solution at 95 °C. The seeding was done with pre-synthesized ZnO nanoparticles in isopropanol with diameters of about 6–7 nm as well as the direct growth of ZnO nanocrystallites on the substrates by the hydrolysis of pre-deposited zinc acetate film. The nanorods grown on ZnO nanoparticle seeds show uniform dimensions throughout the substrate but were not homogenously aligned vertically from the substrate and appeared like nanoflowers with nanorod petals. Nanorods grown from the crystallites formed in situ on the substrates displayed wide variations in dimension depending upon the preheating and annealing conditions. Annealing the seed crystals below 350 °C led to scattered growth directions whereupon preferential orientation of the nanorods perpendicular to the substrates was observed. High surface to volume ratio which is vital for gas sensing applications can be achieved by this simple hydrothermal growth of nanorods and the rod height and rod morphology can be controlled through the growth parameters.
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| 50. |
- Baruah, Sunandan, et al.
(författare)
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Enhanced visible light photocatalysis through fast crystallization of zinc oxide nanorods
- 2010
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Ingår i: Beilstein Journal of Nanotechnology. - : Beilstein-Institut. - 2190-4286. ; 1:1, s. 14-20
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Tidskriftsartikel (refereegranskat)abstract
- Hydrothermally grown ZnO nanorods have inherent crystalline defects primarily due to oxygen vacancies that enhance optical absorption in the visible spectrum, opening up possibilities for visible light photocatalysis. Comparison of photocatalytic activity of ZnO nanorods and nanoparticle films on a test contaminant methylene blue with visible light irradiation at 72 kilolux (klx) showed that ZnO nanorods are 12–24% more active than ZnO nanoparticulate films. This can be directly attributed to the increased effective surface area for adsorption of target contaminant molecules. Defects, in the form of interstitials and vacancies, were intentionally created by faster growth of the nanorods by microwave activation. Visible light photocatalytic activity was observed to improve by ≈8% attributed to the availability of more electron deficient sites on the nanorod surfaces. Engineered defect creation in nanostructured photocatalysts could be an attractive solution for visible light photocatalysis.
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