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| Abstract: | Relatively oxygen-free mesoporous cubic ZnS particles were synthesised via a facile solvo-hydrothermal route using a water–acetonitrile combination. Boosted UV emission at 349 nm is observed from the ZnS prepared by the solvo-hydrothermal route. The increased intensity of this UV emission is attributed to activation of whispering gallery modes of almost elliptical microstructures made of porous nanostructures. |
| Description: | Applied Physics A (2013) 113:321–325 |
| URI: | http://dyuthi.cusat.ac.in/purl/4560 |
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| Boosted UV emis ... nm from mesoporous ZnS.pdf | (804.6Kb) |
| Abstract: | ZnO nanoflowers were synthesized by the hydrothermal process at an optimized growth temperature of 200 ◦C and a growth/reaction time of 3 h. As-prepared ZnO nanoflowers were characterized by x-ray diffraction, scanning electron microscopy, UV–visible and Raman spectroscopy. X-ray diffraction and Raman studies reveal that the as-synthesized flower-like ZnO nanostructures are highly crystalline with a hexagonal wurtzite phase preferentially oriented along the (1 0 1 1) plane. The average length (234–347 nm) and diameter (77–106 nm) of the nanorods constituting the flower-like structure are estimated using scanning electron microscopy studies. The band gap of ZnO nanoflowers is estimated as 3.23 eV, the lowering of band gap is attributed to the flower-like surface morphology and microstructure of ZnO. Room temperature photoluminescence spectrum shows a strong UV emission peak at 392 nm, with a suppressed visible emission related to the defect states, indicating the defect free formation of ZnO nanoflowers that can be potentially used for UV light-emitting devices. The suppressed Raman bands at 541 and 583 cm−1 related to defect states in ZnO confirms that the ZnO nanoflowers here obtained have a reduced presence of defects |
| Description: | J. Phys. D: Appl. Phys. 45 (2012) 425103 (6pp) |
| URI: | http://dyuthi.cusat.ac.in/purl/4555 |
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| Enhanced UV emi ... e hydrothermal process.pdf | (601.8Kb) |
| Abstract: | The magnetic properties of Mn-doped ZnO (ZnO:Mn) nanorods grown by hydrothermal process at a temperature of 200 8C and a growth time of 3 h have been studied. The samples were characterized by using powder X-ray diffraction with Rietveld refinement, scanning electron microscopy, energy-dispersive X-ray analysis and SQUID magnetometry. Mn (3 wt%) and (5 wt%)-doped ZnO samples exhibit paramagnetic and ferromagnetic behavior, respectively, at room temperature. The spin-glass behavior is observed from the samples with respect to the decrease of temperature. At 10 K, both samples exhibit a hysteresis loop with relatively low coercivity. The room-temperature ferromagnetism in 5 wt% Mn-doped ZnO nanorods is attributed to the increase in the specific area of grain boundaries, interaction between dopant Mn2þ ions substituted at Zn2þ site and the interaction between Mn2þ ions and Zn2þ ions from the ZnO host lattice |
| Description: | Phys. Status Solidi A 211, No. 5, 1155–1161 (2014) |
| URI: | http://dyuthi.cusat.ac.in/purl/4558 |
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| Mn2þ-induced ro ... ermally grown Mn-doped.pdf | (986.9Kb) |
| Abstract: | The research on nanocrystalline materials have been of great interest for more than 20 years due to its fundamental properties as well as development of technology based on it. Non-toxic semiconducting nanocrystals are important materials with wide range of applications in the areas of biotechnology, medicine, bio-optics and for the fabrication light emitting and harvesting devices. Majority of the II-VI semiconductors possess wide band gap along with high iconicity and are important materials for optoelectronic devices operating under the UV excitation sources. Among the II-VI semiconductors, ZnS is a material with good optical transmission in the visible region with large exciton binding energy of about 40 meV. ZnS usually crystallizes in cubic form which is zinc blende or sphalerite and its hexagonal form is in wurtzite phase. The cubic sphalerite phase of ZnS has a band gap of 3.68 eV whereas the hexagonal (wurtzite) phase has a band gap of 3.77 eV. Moreover, ZnS is a good host lattice phosphor for photonic applications and electroluminescent devices because of its wide band gap. The present thesis deals with the synthesis and photoluminescence studies of micro and nanostructured ZnS by hydrothermal and solvo-hydrothermal method. Thesis is also focused on bioimaging application of these materials. |
| URI: | http://dyuthi.cusat.ac.in/purl/5142 |
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| Dyuthi-T2176.pdf | (14.38Mb) |
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