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- Li, Zhuofeng, et al.
(author)
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Inorganic/organic hybrid nanoparticles synthesized in a two-step radiation-driven process
- 2022
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In: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X .- 1879-0895. ; 197, s. 110166-
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Journal article (peer-reviewed)abstract
- In this work, we have synthesized inorganic-organic hybrid nanoparticles via radiation synthesis of inorganic nanoparticles (Ag and CeO2) in aqueous dispersions containing radiation-synthesized poly(N-vinyl pyrrolidone) (PVP) nanogels (NG). The experiments show that there are strong interactions between the inorganic precursors (Ag+ and Ce3+) and the nanogel prior to irradiation. The two hybrid systems (Ag/NG and CeO2/NG) were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD confirms the formation of crystalline Ag and CeO2. TEM reveals that the inorganic nanoparticles are evenly distributed in/on the nanogel. Both XRD and TEM show that size of the inorganic particles is controlled by the nanogel.
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- Li, Zhuofeng, et al.
(author)
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On the reactivity of aqueous radiolysis products towards carbon black used in in-situ radiation-synthesis of catalytic nanoparticles in graphite electrodes
- 2021
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In: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 173, s. 61-68
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Journal article (peer-reviewed)abstract
- Enhanced electrochemical performance of graphite electrodes can be achieved by incorporation of catalytic nanoparticles. One promising method for incorporation is in-situ radiation-synthesis where the radiolysis of water is used to drive the process of particle formation on carbon black. A potential problem is the direct reaction between radiolysis products and carbon black. In this work the reactivities of radiolytically produced HO·, (CH3)2C·OH, e-aq and H2O2 towards carbon black were investigated at room temperature with a dose rate 0.124 Gy s−1. HO· was found to react with carbon black with a rate constant of 20 ± 5 m s−1. For (CH3)2C·OH the corresponding value is 0.8 ± 0.1 m s−1. The reactivity of e-aq towards carbon black is negligible compared to that of (CH3)2C·OH. At concentrations <0.05 mmol L−1, H2O2 can react with carbon black with a rate constant of (6.7 ± 0.4) × 10−10 m s−1 mainly due to adsorption. At higher H2O2 concentrations catalytic decomposition producing HO· is also observed. It was also observed that the presence of carbon black increases the radiolytic formation of H2O2. In addition, the impact of carbon black reactivity on the radiation-synthesis of nanoparticles is discussed with an example from the literature.
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| 6. |
- Li, Zhuofeng, et al.
(author)
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Radiation Chemistry Provides Nanoscopic Insights into the Role of Intermediate Phases in CeO2 Mesocrystal Formation
- 2022
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In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 61:6
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Journal article (peer-reviewed)abstract
- The role of intermediate phases in CeO2 mesocrystal formation from aqueous CeIII solutions subjected to γ-radiation was studied. Radiolytically formed hydroxyl radicals convert soluble CeIII into less soluble CeIV. Transmission electron microscopy (TEM) and X-ray diffraction studies of samples from different stages of the process allowed the identification of several stages in CeO2 mesocrystal evolution following the oxidation to CeIV: (1) formation of hydrated CeIV hydroxides, serving as intermediates in the liquid-to-solid phase transformation; (2) CeO2 primary particle growth inside the intermediate phase; (3) alignment of the primary particles into “pre-mesocrystals” and subsequently to mesocrystals, guided by confinement of the amorphous intermediate phase and accompanied by the formation of “mineral bridges”. Further alignment of the obtained mesocrystals into supracrystals occurs upon slow drying, making it possible to form complex hierarchical architectures.
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| 7. |
- Li, Zhuofeng, 1991-, et al.
(author)
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Tuning morphology, composition and oxygen reduction reaction (ORR) catalytic performance of manganese oxide particles fabricated by γ-radiation induced synthesis
- 2021
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In: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 583, s. 71-79
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Journal article (peer-reviewed)abstract
- A γ-radiation induced synthesis method is used to fabricate manganese oxide catalysts through both reduction and oxidation routes. It is shown that the morphology, composition and electrochemical performance of the produced manganese oxide particles can be tuned by altering the redox conditions. The catalysts prepared via radiolytic oxidation have a hollow spherical morphology, possess γ-MnO2 structure and show high catalytic activity for the complete four-electron reaction pathway of the oxygen reduction reaction (ORR) in alkaline electrolyte. Meanwhile, the catalysts synthesized via radiolytic reduction possess a rod-like morphology with a Mn3O4 bulk structure and favour the incomplete two-electron reaction pathway for ORR. The high catalytic activity of the manganese oxide synthesized via the oxidation route can be attributed to high electrochemical surface area and increased amount of Mn3+ on the surface as compared to those in the sample obtained via the reduction route.
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| 8. |
- Li, Zhuofeng, 1991-
(author)
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γ-Radiation Induced Synthesis of Metal oxides : Control of Particle Size, Composition, and Morphology
- 2021
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Doctoral thesis (other academic/artistic)abstract
- Nanomaterials show a significant difference in chemical, mechanical, electronic, magnetic and optical properties compared with bulk counterparts. The synthesis is a key-step to achieve the unique properties of nanomaterials. As an efficient, clean and straightforward approach, the γ-radiation induced synthesis has been extensively applied to fabricate metal nanoparticles. However, with regard to production of metal oxide nanoparticles via γ-radiation induced synthesis, the knowledge is still insufficient. The following metal oxides have been selected as synthesis substances in this thesis: Cu2O, MnO2, Mn3O4 and CeO2. A prerequisite for utilization of the radiation-induced approach to engineer metal oxide nanomaterials is to optimize the reaction conditions for each specific nanofabrication case. The current study aims to understand the effects of different reaction conditions, i.e., pH, scavenger concentration, precursors, dose, and support materials, on the structural, and physico-chemical properties of the fabricated metal oxide nanomaterials. The pH of the reaction plays an important role in determining the thermodynamically stable metal oxide products in radiation-induced synthesis. (Paper I). When using high concentration of solutes, i.e., isopropanol (used as a hydroxyl radical scavenger), the solvent effects must be considered (Paper I). It is found that different metal cation precursors (same element but different oxidation state) can result in metal oxides differing in composition and morphology under different radiation-induced redox conditions (Paper II). By gradually increasing the dose, ceria nanoparticles in different growth stages can be captured, and their morphological development is studied by TEM (Paper IV). Based on this, a mechanism for nucleation of ceria nanoparticles and mesocrystal growth is proposed as a function of the dose. Support materials, i.e., carbon black and PVP nanogel, are used to engineer supported metal oxides. The reactivity of carbon black towards water radiolysis products (Paper III), and the size-controlling effect of nanogel on produced metal/metal oxide nanoparticles (Paper V) are investigated in this thesis. In addition, for the view of application, the primary electrochemical properties of radiation-induced synthesized carbon black supported samples are studied (Paper II).
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| 9. |
- Zhang, Wei, 1989-, et al.
(author)
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Single crystal structure and opto-electronic properties of oxidized Spiro-OMeTAD
- 2020
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In: Chemical Communications. - : Royal Society of Chemistry. - 1359-7345 .- 1364-548X. ; 56:10, s. 1589-1592
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Journal article (peer-reviewed)abstract
- Single crystals of Spiro(TFSI)2 were grown, the optical and electronic properties were characterized and compared with neutral Spiro-OMeTAD. Density-functional theory was used to get insights into binding and band structure properties. The flat valence bands indicate a rather limited orbital overlap in Spiro(TFSI)2.
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