Mahlatse F. Manamela; Thuto E. Mosuang; Bonex W. Mwakikunga
Abstract
The mechano-chemical technique was employed to synthesise cobalt and indium single and double doped as well as the undoped ZnO nanopowder samples. The X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) results confirm that the prepared samples were of hexagonal wurzite form. A new peak ...
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The mechano-chemical technique was employed to synthesise cobalt and indium single and double doped as well as the undoped ZnO nanopowder samples. The X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) results confirm that the prepared samples were of hexagonal wurzite form. A new peak was observed in the diffraction pattern of the In doped ZnO nanopowders. Doping the ZnO nanoparticles with Co and In did not significantly affect the lattice parameters, even though the average grain sizes were found to be reduced. The morphology of the samples revealed by the scanning electron microscopy (SEM) images appear to be more spherical. The excitation wavelength of 350 nm was used in the photoluminescence (PL) study where various defects related emissions were observed for the doped and undoped ZnO nanoparticles. The energy band gap of the prepared samples was calculated from the ultraviolet-visible spectroscopy (UV-Vis) data. It was found that the doped ZnO nanoparticles had smaller energy band gap compared to the undoped ZnO nanoparticles. The Raman experiment were performed at the excitation wavelength of 514.532 nm and E2 (high) mode had the most intense peak. Copyright © 2018 VBRI Press.
Ravindra Kumar Jha; Raghubeer Singh; Debasree Burman; Sumita Santra; Prasanta Kumar Guha
Volume 1, Issue 2 , 2016, , Pages 125-130
Abstract
We report herein exfoliation of WS2, which is one of the most promising but less investigated among 2D TMDs in binary mixture of diethyl ether (with boiling point=34.6°C) and water. The bulk WS2 powder was first ball milled in toluene for few minutes and at low rpm. Subsequently the powder was kept ...
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We report herein exfoliation of WS2, which is one of the most promising but less investigated among 2D TMDs in binary mixture of diethyl ether (with boiling point=34.6°C) and water. The bulk WS2 powder was first ball milled in toluene for few minutes and at low rpm. Subsequently the powder was kept at 4°C for 20 hours in binary mixture of diethyl ether and water with their volume fraction varying from 10% to 90%, before taking for the ultrasonication. It should be noted that neither diethyl ether nor water is capable of disperse WS2 alone. Ultrasonic waves generate cavitation bubbles that collapse into high-energy jets, breaking up the layered crystallites and producing exfoliated nanoflakes. Hansen Solubility Parameters (HSP) for the binary mixture has been calculated and the mixture which minimizes the Hansen distance has been selected for further characterization of few layered nature of thin sheets. Field emission scanning electron microscopy (FESEM) has been utilized to monitor the progress in exfoliation at different stages. Atomic force microscopy (AFM) confirms the formation of <8nm thin sheets with lateral dimension of few hundred nm. Raman spectroscopy has been utilized for further confirmation. Transmission electron microscopy (TEM) has been utilized to show the crystallinity of nanosheets which agrees with the X-ray diffraction results. Ultra-violet-visible (UV-Vis) and Fourier transform infrared (FTIR) have been used as spectroscopy tools throughout the work. This exfoliation technique is unique in the sense of producing pristine nanosheets due to the involvement of very low boiling point solvents.
