Synchrotron XANES Spectra of Superparamagnetic Iron Oxides Synthesized by Ultrasonic-Assisted Co-Precipitation

2013 ◽  
Vol 481 ◽  
pp. 36-39
Author(s):  
W. Tangwatanakul ◽  
C. Sirisathitkul ◽  
N. Muensit ◽  
T. Monnor ◽  
R. Yimnirun
Keyword(s):  
Iron Oxide ◽  
Reaction Time ◽  
Oxide Nanoparticles ◽  
Edge Structure ◽  
X Ray ◽  
Superparamagnetic Iron Oxides ◽  
Ultrasonic Assisted ◽  
Co Precipitation ◽  
X Ray Absorption ◽  
Ultrasonic Homogenizer

Iron oxide nanoparticles were synthesized by employing an ultrasonic homogenizer in conjunction to the co-precipitation of Fe (NO3)3·9H2O, FeCl2·4H2O and NaOH. Synchrotron X-ray absorption near edge structure (XANES) spectra could be fitted with the contributions from hematite (α-Fe2O3) and, to a lesser extent, metallic Fe. The increase in reagent concentrations increased the Fe fraction which partly explained the change in magnetization of superparamagnetic particles. Nevertheless, the α-Fe2O3 composition was increased by using a longer reaction time.

Simple Preparation of Cuprous Oxide Nanoparticles for Catalysis of Azide–alkyne Cycloaddition

2018 ◽  
Vol 42 (3) ◽  
pp. 166-169 ◽  
Author(s):  
Mojtaba Amini ◽  
Sakine Ramezani ◽  
Alireza Pourvahabi Anbari ◽  
Abolghasem Beheshti ◽  
Sanjeev Gautam ◽  
...  
Keyword(s):  
Cuprous Oxide ◽  
Benzyl Chloride ◽  
Significant Loss ◽  
Oxide Nanoparticles ◽  
X Ray Diffraction ◽  
Edge Structure ◽  
X Ray ◽  
Organic Azides ◽  
Cuprous Oxide Nanoparticles ◽  
X Ray Absorption

Cuprous oxide (Cu2O) nanoparticles were prepared by two simple methods and their structural, morphological and electronic properties were investigated by X-ray diffraction analysis, X-ray absorption near-edge structure, energy dispersive X-ray analysis and scanning electron microscopy. Cuprous oxide nanoparticles efficiently catalyse 1,3-dipolar cycloaddition of a variety terminal alkynes and organic azides producing the corresponding 1,2,3-triazole derivatives in excellent yields without use of any additives. Phenylacetylene and benzyl chloride were chosen as model starting compounds for the optimisation of the reaction conditions, such as effect of solvent, reaction temperature and time of reaction in the presence of a-Cu2O nanoparticles as a catalyst. The results showed that using cuprous oxide nanoparticles (0.035 mmol) and heating at 70 °C in water, the reaction of phenylacetylene with benzyl chloride and sodium azide gave 1-benzyl-4-phenyl-1 H-1,2,3-triazole almost quantitatively in 6 h of reaction time. A study of the recyclability and reusability of the catalyst revealed that a-Cu2O could be reused at least five times without significant loss of yield.

scholarly journals Neptunium Reactivity During Co-Precipitation and Oxidation of Fe(II)/Fe(III) (Oxyhydr)oxides

Geosciences ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 27 ◽  
Author(s):  
Hannah E. Roberts ◽  
Katherine Morris ◽  
J. Frederick W. Mosselmans ◽  
Gareth T. W. Law ◽  
Samuel Shaw
Keyword(s):  
Green Rust ◽  
Solution Chemistry ◽  
Natural Environments ◽  
Edge Structure ◽  
X Ray ◽  
End Point ◽  
Mineral Phases ◽  
Oxidation In Air ◽  
Co Precipitation ◽  
X Ray Absorption

Fe(II) bearing iron (oxyhydr)oxides were directly co-precipitated with Np(V)O2+ under anaerobic conditions to form Np doped magnetite and green rust. These environmentally relevant mineral phases were then characterised using geochemical and spectroscopic analyses. The Np doped mineral phases were then oxidised in air over 224 days with solution chemistry and end-point oxidation solid samples collected for further characterisation. Analysis using chemical extractions and X-ray absorption spectroscopy (XAS) techniques confirmed that Np(V) was initially reduced to Np(IV) during co-precipitation of both magnetite and green rust. Extended X-Ray Absorption Fine Structure (EXAFS) modelling suggested the Np(IV) formed a bidentate binuclear sorption complex to both minerals. Furthermore, following oxidation in air over several months, the sorbed Np(IV) was partially oxidised to Np(V), but very little remobilisation to solution occurred during oxidation. Here, linear combination fitting of the X-Ray Absorption Near Edge Structure (XANES) for the end-point oxidation samples for both mineral phases suggested approximately 50% oxidation to Np(V) had occurred over 7 months of oxidation in air. Both the reduction of Np(V) to Np(IV) and inner sphere sorption in association with iron (oxyhydr)oxides, and the strong retention of Np(IV) and Np(V) species with these phases under robust oxidation conditions, have important implications in understanding the mobility of neptunium in a range of engineered and natural environments.

Co-Promoted Cu/ZnO Catalysts for Fischer-Tropsch Synthesis

2017 ◽  
Vol 266 ◽  
pp. 117-121
Author(s):  
Piyasak Akcaboot ◽  
Napat Kanokpornwasin ◽  
Monthida Raoarun ◽  
Patraporn Saiwattanasuk ◽  
Pinsuda Viravathana
Keyword(s):  
Tropsch Synthesis ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
Fischer Tropsch ◽  
Edge Structure ◽  
Fischer Tropsch Synthesis ◽  
X Ray ◽  
Cu Foil ◽  
Co Precipitation ◽  
X Ray Absorption

Co-promoted Cu/ZnO catalysts were studied for Fischer-Tropsch synthesis (FTS). All catalysts were prepared by the co-precipitation method, having the mass ratio of Co:Cu:Zn=0 (unpromoted), 0.05, 0.5:1:1, and characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). From XRD and XAS, the results confirmed the phase transformation of CuO to Cu foil and Co3O4 to Co foil in Co-promoted catalysts after reduction. After FTS reaction testing, the Co-promoted catalysts showed the decrease in methanol selectivity of 15 and 1.6% for 0.05Co-Cu/ZnO and 0.5Co-Cu/ZnO, respectively, and the increase in C5-C15 selectivity during 30 h of reaction.

scholarly journals Unravelling the growth mechanism of the co-precipitation of iron oxide nanoparticles with the aid of synchrotron X-Ray diffraction in solution

Nanoscale ◽  
2019 ◽  
Vol 11 (14) ◽  
pp. 6620-6628 ◽  
Author(s):  
Alec P. LaGrow ◽  
Maximilian O. Besenhard ◽  
Aden Hodzic ◽  
Andreas Sergides ◽  
Lara K. Bogart ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Iron Oxide Nanoparticles ◽  
Formation Mechanism ◽  
Growth Mechanism ◽  
Oxide Nanoparticles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Co Precipitation

The formation mechanism of iron oxide nanoparticles reveals an initial segregation into ferrihydrite seeds and a Fe2+ rich growth reservoir.

scholarly journals Spectroscopic Investigations of the Oxidative Polymerization of Hydroquinone in the Presence of Hexavalent Chromium

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Ching-Yun Cheng ◽  
Ya-Ting Chan ◽  
Yu-Min Tzou ◽  
Kai-Yue Chen ◽  
Yu-Ting Liu
Keyword(s):  
Reaction Time ◽  
Linear Combination ◽  
Oxidative Polymerization ◽  
Polymerization Reaction ◽  
Organic Complex ◽  
Edge Structure ◽  
X Ray ◽  
Naturally Occurring ◽  
Ft Ir ◽  
X Ray Absorption

Polyphenol polymerization receives much scientific attentions because it is an important reaction of humification processes. Through an oxidative polymerization reaction (OPR), hydroquinone (H2Q), a naturally occurring compound, has been found to be a vital precursor of humic substances in soils. Chromate (Cr(VI)), a strong oxidant, is widely distributed in the environment due to the inappropriate disposal of Cr-containing wastes. The OPR of H2Q in the presence of Cr(VI) may occur naturally. In the study, it was found that 400 mg L−1H2Q could be polymerized at pH 3.0 with 105 mg L−1Cr(VI). The results of FT-IR revealed the presence of both hydroquinone and benzoquinone nuclei in the polymer. The spectra of X-ray absorption near edge structure (XANES) demonstrated a decrease in Cr(VI) content during the OPR of H2Q. Based on the results of linear combination fitting (LCF) for the spectra of XANES, the proportions of Cr species in the precipitates mainly consisted of Cr(OH)3, and Cr-carboxylate contents increased gradually from 15.3 to 25.5% over the reaction time. After acidizing the supernatants at pH 1.0 for 1 d, Cr(III)-HA dominated Cr(III) species. This suggested that humic-like substances were formed during OPR of H2Q, possibly through the formation of Cr(III)-organic complex.

scholarly journals Spinel Iron Oxide by the Co-Precipitation Method: Effect of the Reaction Atmosphere

2021 ◽  
Vol 11 (12) ◽  
pp. 5433
Author(s):  
Sawssen Slimani ◽  
Carlo Meneghini ◽  
Maryam Abdolrahimi ◽  
Alessandro Talone ◽  
Jean Pierre Miranda Murillo ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Formation Mechanism ◽  
Xanes Spectrum ◽  
Inert Atmosphere ◽  
Morphological Properties ◽  
Precipitation Method ◽  
Edge Structure ◽  
X Ray ◽  
Reaction Atmosphere ◽  
Co Precipitation

Synthesis atmosphere (i.e., air and nitrogen) effects on the physical properties and formation mechanism of spinel iron oxide nanoparticles prepared via the co-precipitation method have been investigated using a multi-technique approach. The obtained magnetic nanoparticles (MNPs) were characterized using the X-ray diffraction, transmission electron microscopy (TEM), SQUID magnetometry, Mössbauer spectroscopy and X-ray absorption near-edge Structure spectroscopy techniques. The synthesis procedure leads to the formation of a spinel structure with an average crystallite size of 9.0(9) nm. The morphology of the particles synthetized under an inert atmosphere was quasi-spherical, while the nanoparticles prepared in air present a faceted shape. The small differences observed in morphological properties are explained by the influence of the reaction atmosphere on the formation mechanism of the MNPs. The magnetic characterization indicates that both samples exhibit superparamagnetic behavior at 300 K. The investigation by means of the Langevin approach at 300 K also leads to equal values for the mean size of the magnetic cores (Dm). Additionally, the analysis of the Mössbauer spectra revealed the lack of spin disorder for both samples, resulting in a high saturation magnetization. The fit of XANES spectrum suggests that about 2/3 of the iron ions reside in a local environment close to that of γ-Fe2O3 and about 1/3 close to that of Fe3O4 for the sample synthetized in inert atmosphere.

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