| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Boutonnet, Magali, et al.
(författare)
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Microemulsion droplets to catalytically active nanoparticles : How the application of colloidal tools in catalysis aims to well designed and efficient catalysts
- 2017
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Ingår i: Catalysis Today. - : Elsevier. - 0920-5861 .- 1873-4308. ; 285, s. 89-103
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Tidskriftsartikel (refereegranskat)abstract
- In this review, we report the successful application of a colloidal tool, namely microemulsions (ME) in the design of catalysts for various applications. First, a brief introduction to MEs and the water-in-oil (w/o) ME reaction method is given. The first ME formulations used for catalyst synthesis are discussed. Catalytic activity of the materials obtained from those initial studies, both as particles deposited onto a support as well as directly as nanoparticles in ME suspension is described. Then various application examples which highlight several important properties of the catalysts obtained from w/o ME are given. For example, particle size control achieved with ME is very relevant to surface sensitive reactions, whose selectivity depends greatly on metal particle size. Another important aspect is related to the unique microenvironment of MEs which results in specific interactions within the formed materials; this is particularly important for certain catalysts such as mixed oxide particles, conferring them with special properties and enhanced performance. Comparison of activity and selectivity of impregnation-prepared versus ME-prepared materials is given for several catalytic reactions. Finally, the more recently developed oil-in-water (o/w) ME method is described, along with examples of materials obtained by this method as catalysts, including photocatalysis. The different aspects discussed in this review demonstrate the importance of the ME reaction method for the design of nanocatalysts with enhanced activity and selectivity.
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| 3. |
- Di Carlo, Gabriella, et al.
(författare)
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Design of Cobalt Nanoparticles with Tailored Structural and Morphological Properties via O/W and W/O Microemulsions and Their Deposition onto Silica
- 2015
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Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 5:1, s. 442-459
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Tidskriftsartikel (refereegranskat)abstract
- Cobalt nanostructures with different size and morphology, i.e., spherical nanoparticles, nanorods, and particles arranged into elongated structures, were prepared using micelles and microemulsions as confined reaction media. The syntheses were carried out using three types of systems: aqueous surfactant solutions, oil-in water (O/W), and water-in-oil (W/O) microemulsions. The influence of the surfactant and the precipitating agent used for synthesis was also investigated. For this purpose, cobalt nanostructures were prepared using different non-ionic surfactants, namely Synperonic((R)) 10/6, Pluronic((R)) P123 and a mixture of SPAN 20-TWEEN 80. Three different precipitating agents were used: sodium borohydride, sodium hydroxide, and oxalic acid. Our findings revealed that by changing the type of reaction media as well as the precipitating agent it is possible to modify the shape and size of the cobalt nanostructures. Moreover, the use of O/W microemulsion generates better results in terms of colloidal stability and uniformity of particle size with respect to W/O microemulsion. The different cobalt nanostructures were supported on commercial and mesoporous silica; transmission electron microscopy (TEM) images showed that after deposition the Co nanocrystals remain well dispersed on the silica supports. This behavior suggests their great potential in catalytic applications.
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| 4. |
- Lakshmanan, Ramnath, et al.
(författare)
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Removal of total organic carbon from sewage wastewater using poly(ethylenimine)-functionalized magnetic nanoparticles
- 2014
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:4, s. 1036-1044
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Tidskriftsartikel (refereegranskat)abstract
- The increased levels of organic carbon in sewage wastewater during recent years impose a great challenge to the existing wastewater treatment process (WWTP). Technological innovations are therefore sought that can reduce the release of organic carbon into lakes and seas. In the present study, magnetic nanoparticles (NPs) were synthesized, functionalized with poly(ethylenimine) (PEI), and characterized using TEM (transmission electron microscopy), X-ray diffraction (XRD), FTIR (Fourier transform infrared spectroscopy), CCS (confocal correlation spectroscopy), SICS (scattering interference correlation spectroscopy), magnetism studies, and thermogravimetric analysis (TGA). The removal of total organic carbon (TOC) and other contaminants using PEI-coated magnetic nanoparticles (PEI-NPs) was tested in wastewater obtained from the Hammarby Sjöstadsverk sewage plant, Sweden. The synthesized NPs were about 12 nm in diameter and showed a homogeneous particle size distribution in dispersion by TEM and CCS analyses, respectively. The magnetization curve reveals superparamagnetic behavior, and the NPs do not reach saturation because of surface anisotropy effects. A 50% reduction in TOC was obtained in 60 min when using 20 mg/L PEI-NPs in 0.5 L of wastewater. Along with TOC, other contaminants such as turbidity (89%), color (86%), total nitrogen (24%), and microbial content (90%) were also removed without significant changes in the mineral ion composition of wastewater. We conclude that the application of PEI-NPs has the potential to reduce the processing time, complexity, sludge production, and use of additional chemicals in the WWTP.
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| 5. |
- Okoli, Chuka, et al.
(författare)
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Comparison and Functionalization Study of Microemulsion-Prepared Magnetic Iron Oxide Nanoparticles
- 2012
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:22, s. 8479-8485
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic iron oxide nanoparticles (MION) for protein binding and separation were obtained from water-in-oil (w/o) and oil-in-water (o/w) microemulsions. Characterization of the prepared nanoparticles have been performed by TEM, XRD, SQUID magnetometry, and BET. Microemulsion-prepared magnetic iron oxide nanoparticles (ME-MION) with sizes ranging from 2 to 10 rim were obtained. Study on the magnetic properties at 300 K shows a large increase of the magnetization similar to 35 emu/g for w/o-ME-MION with superparamagnetic behavior and nanoscale dimensions in comparison with o/w-ME-MION (10 emu/g) due to larger particle size and anisotropic property. Moringa oleifera coagulation protein (MOCP) bound w/o- and o/w-ME-MION showed an enhanced performance in terms of coagulation activity. A significant interaction between the magnetic nanoparticles and the protein can be described by changes in fluorescence emission spectra. Adsorbed protein from MOCP is still retaining its functionality even after binding to the nanoparticles, thus implying the extension of this technique for various applications.
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| 6. |
- Pardo-Tarifa, Fatima, et al.
(författare)
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Ce-promoted Co/Al2O3 catalysts for Fischer-Tropsch synthesis
- 2017
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Ingår i: International journal of hydrogen energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-3199 .- 1879-3487. ; 42:15, s. 9754-9765
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Tidskriftsartikel (refereegranskat)abstract
- The effect of ceria promotion on the performance of Co/Al2O3 catalyst was evaluated in a high pressure fixed bed reactor for Fischer Tropsch (FT) synthesis at close industrial conditions. Ce-Al2O3 supports with a molar ratio of Al/Ce = 8 were prepared by two different methods: one by co-precipitation of cerium and aluminum precursors in water in-oil microemulsion and the other one by aqueous impregnation of cerium nitrate on commercial alumina. These supports, together with the unmodified alumina carrier, were used to prepare four cobalt-based catalysts. These catalysts were characterized by XRD, SEM, EDX, TEM, N-2 adsorption/desorption, TPR and chemisorption techniques. The results show that the presence of CeO2 on the surface of the support favors the reducibility of cobalt oxides with a shift down in reduction temperature of about 70 degrees C. The catalytic evaluation of the catalysts revealed that cerium addition by impregnation increases the activity and selectivity to C5+ catalyst in FTS. The catalyst synthetized by microemulsion show lower catalytic performance. Nevertheless, the catalytic property of this material can be improved by increasing the crystalline micro-domains size of CeO2. (C) 2017 Hydrogen Energy Publications LLC.
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| 7. |
- Sanchez-Dominguez, Margarita, et al.
(författare)
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A novel approach to metal and metal oxide nanoparticle synthesis : the oil-in-water microemulsion reaction method
- 2009
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Ingår i: Journal of nanoparticle research. - : Springer Science and Business Media LLC. - 1388-0764 .- 1572-896X. ; 11:7, s. 1823-1829
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Tidskriftsartikel (refereegranskat)abstract
- A novel and straightforward approach, based on oil-in-water (o/w) microemulsions, was developed for the synthesis of inorganic nanoparticles at ambient conditions. It implies the use of organometallic precursors dissolved in nanometre-scale oil droplets of o/w microemulsions. Addition of reducing or oxidizing/precipitating agents results in the formation of metallic or metal oxide nanoparticles, respectively. Nonionic o/w microemulsion systems were chosen, and several key compositions were selected for nanoparticle synthesis at 25 A degrees C. High Resolution Electron Microscopy revealed that small nanoparticles of metals (Pt, Pd and Rh) and nanocrystalline metal oxide (cerium (IV) oxide with cubic type crystalline structure confirmed by XRD), of less than 7 nm can be obtained in mild conditions.
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| 8. |
- Sanchez-Dominguez, Margarita, et al.
(författare)
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Synthesis of CeO2, ZrO2, Ce0.5Zr0.5O2, and TiO2 nanoparticles by a novel oil-in-water microemulsion reaction method and their use as catalyst support for CO oxidation
- 2010
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861 .- 1873-4308. ; 158:1-2, s. 35-43
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Tidskriftsartikel (refereegranskat)abstract
- A novel and straightforward approach for the synthesis of mesoporous inorganic oxide nanoparticles, with a small particle size and high specific surface area is reported, by using oil-in-water microemulsions, in contrast to the typically used water-in-oil microemulsion method. The new strategy implies the use of organometallic precursors, dissolved in nanometer-scale oil droplets (stabilised by surfactant), and dispersed in a continuous aqueous phase. The potential of this approach is explored for producing nanocrystalline ceria, zirconia, ceria/zirconia mixed oxide and titania. Nanocrystalline cubic CeO2 and Ce0.5Zr0.5O2 were obtained under soft conditions, whilst ZrO2 and TiO2 presented wide X-ray diffraction peaks. The specific surface area (SSA) of the obtained materials was in the order of 200-370 m(2)/g and the particle size was very small (similar to 2-3 nm). The materials were calcined at 400 degrees C after which a high SSA was maintained (100-150 m(2)/g) and the crystallinity was improved, yielding tetragonal phases for both TiO2 (anatase) and ZrO2. The potential of the calcined materials as catalyst support was explored in the CO oxidation reaction by doping the oxides with Au (2 wt%). The obtained results demonstrate the feasibility of this approach for the preparation of various supports with high SSA for catalytic purposes.
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| 9. |
- Tiseanu, Carmen, et al.
(författare)
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Local structure and nanoscale homogeneity of CeO2-ZrO2 : differences and similarities to parent oxides revealed by luminescence with temporal and spectral resolution
- 2014
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 16:2, s. 703-710
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Tidskriftsartikel (refereegranskat)abstract
- Although homogeneity at the atomic level of CeO2-ZrO2 with a Ce/Zr atomic ratio close to unity is considered to be one of the main causes for the increased total oxygen storage capacity (OSC), the characterization approaches of homogeneity remain a major challenge. We propose a simple, yet effective method, to assess both structural and compositional homogeneity of CeO2-ZrO2 by using Eu3+ luminescence measured with time and dual spectral resolution (emission and excitation). For Eu3+-CeO2-ZrO2 calcined at 750 degrees C, the X-ray diffraction, Raman and High-Resolution Transmission Electron Microscopy data converge to a single pseudo-cubic phase. However, the evolution of Eu3+-delayed luminescence from cubic ceria-like to tetragonal zirconia-like emission reveals the formation of CeO2- and ZrO2-rich nanodomains and provides evidence for early phase separation. For Eu3+-CeO2-ZrO2 calcined at 1000 degrees C, the emission of Eu3+ reveals both structural and compositional inhomogeneity. Our study identifies the differences between the local structure properties of CeO2 and ZrO2 parent oxides and CeO2-ZrO2 mixed oxide, also confirming the special chemical environment of the oxygen atoms in the mixed oxide as reported earlier by Extended X-ray Absorption Fine Structure investigations.
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| 10. |
- Tiseanu, Carmen, et al.
(författare)
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Spectrally and temporarily resolved luminescence study of short-range order in nanostructured amorphous ZrO(2)
- 2011
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 110:10, s. 103521-
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Tidskriftsartikel (refereegranskat)abstract
- The local structure amorphous ZrO(2) doped with europium (Eu(3+)) and its evolution during crystallization was investigated by using spectrally and temporally resolved luminescence of europium. A small contribution of a crystalline, tetragonal-like local phase emission to the overall broad/amorphous emission could be observed in the amorphous state before calcination. Also, a non-negligible amount of amorphous type emission was still detectable with the crystalline europium-doped ZrO(2) obtained on calcination at 500 and 1000 degrees C being assigned to a disordered, monoclinic-like local phase.
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