ORCID Profile
0000-0002-4657-382X
Current Organisation
VNUHCM - University of Science
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Publisher: American Chemical Society (ACS)
Date: 03-10-2018
Publisher: Elsevier BV
Date: 07-2023
Publisher: Springer Science and Business Media LLC
Date: 23-04-2022
Publisher: Viet Nam National University Ho Chi Minh City
Date: 27-12-2020
Abstract: Zinc oxide (ZnO) material possesses various morphologies which have given ZnO many fascinating applications in practice. Thus, the controlled synthesis of morphology and size of ZnO microstructures has attracted great interest. Many synthetic methods exhibited their effectiveness in producing pure ZnO, and the hydrothermal synthesis expresses its own considerable advantages for controlling the morphology of ZnO with low particle-size distribution. Moreover, the hydrothermal synthesis can be performed under mild condition rather than the conventional harsh ceramic method. In this work, we performed hydrothermal synthesis by altering different initial seeds by pre-treating of Zinc acetate solution prior to hydrothermal action. Characterization methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and Infrared (IR) spectroscopy were used to determine the morphology and surface functional groups of ZnO final products. Firstly, we processed the pretreatment of Zinc acetate solution by annealing it at 90 ◦C for 1h before putting the solution into autoclave together with NH3 solution for hydrothermal synthesis (this process is called as two-step hydrothermal synthesis). Secondly, the reaction temperatures (120 ◦C, 150 ◦C, 180 ◦C) were investigated to provide the role of temperature synthesis in controlling size and shape of ZnO, and at 150 ◦C, ZnO particles were formed with reasonable uniform morphology. Finally, we examined the effects of initial seeds by pre-treating Zinc acetate solution with H2O2, or, the initial seeds change from only Zn(OH)2 (without H2O2) to mutual existence of Zn(OH)2 and ZnO2 (with H2O2). In this case, ZnO Wurtzite phase was obtained with 100% purity at 180 ◦C, or at higher temperature than other s les whose ZnO Wurtzite phase was formed at only 150 ◦C. The results show that the nature of initial seeds greatly impact not only on the shape and size, but also on the surface functional groups of ZnO final product.
Publisher: Wiley
Date: 22-07-2020
DOI: 10.1002/MRC.5033
Publisher: American Chemical Society (ACS)
Date: 12-11-2012
DOI: 10.1021/CM302549K
Publisher: Elsevier BV
Date: 02-2018
Publisher: Elsevier BV
Date: 04-2022
Publisher: AIP Publishing
Date: 02-10-2017
DOI: 10.1063/1.4993614
Abstract: The intrinsic ionic conductivity of polyethylene oxide (PEO)-based block copolymer electrolytes is often assumed to be identical to the conductivity of the PEO homopolymer. Here, we use high-field 7Li nuclear magnetic resonance (NMR) relaxation and pulsed-field-gradient (PFG) NMR diffusion measurements to probe lithium ion dynamics over nanosecond and millisecond time scales in PEO and polystyrene (PS)-b-PEO-b-PS electrolytes containing the lithium salt LiTFSI. Variable-temperature longitudinal (T1) and transverse (T2) 7Li NMR relaxation rates were acquired at three magnetic field strengths and quantitatively analyzed for the first time at such fields, enabling us to distinguish two characteristic time scales that describe fluctuations of the 7Li nuclear electric quadrupolar interaction. Fast lithium motions [up to O(ns)] are essentially identical between the two polymer electrolytes, including sub-nanosecond vibrations and local fluctuations of the coordination polyhedra between lithium and nearby oxygen atoms. However, lithium dynamics over longer time scales [O(10 ns) and greater] are slower in the block copolymer compared to the homopolymer, as manifested experimentally by their different transverse 7Li NMR relaxation rates. Restricted dynamics and altered thermodynamic behavior of PEO chains anchored near PS domains likely explain these results.
No related grants have been discovered for Tan Vu HUYNH.