Synthesis, optical and luminescent properties of nano-sized ZnO crystals in polymer matrix
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GOGLIDZE, Tatiana, DEMENTIEV, Igor, GONCEARENCO, Evghenii, NEDEOGLO, Natalia, NEDEOGLO, Dumitru. Synthesis, optical and luminescent properties of nano-sized ZnO crystals in polymer matrix. In: Materials Science and Condensed Matter Physics, Ed. 8-th Edition, 12-16 septembrie 2016, Chişinău. Chişinău: Institutul de Fizică Aplicată, 2016, Editia 8, p. 236. ISBN 978-9975-9787-1-2.
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Materials Science and Condensed Matter Physics
Editia 8, 2016
Conferința "International Conference on Materials Science and Condensed Matter Physics"
8-th Edition, Chişinău, Moldova, 12-16 septembrie 2016

Synthesis, optical and luminescent properties of nano-sized ZnO crystals in polymer matrix


Pag. 236-236

Goglidze Tatiana, Dementiev Igor, Goncearenco Evghenii, Nedeoglo Natalia, Nedeoglo Dumitru
 
Moldova State University
 
Disponibil în IBN: 1 august 2019


Rezumat

High-dispersive ZnO powders were synthesized by chemical method in aqueous solutions [1] of polymers: polyvinyl alcohol (PVA), polyacrylamide, synthanol. Zinc nitrate hexahydrate was used as a precursor; hexamethylenetetramine was used as a precipitator. Optical transmission spectra were studied for the film samples synthesized at various PVA concentrations and deposited on lavsan or glass substrates. Investigations were carried out using a CaryUV60 installation in the    200 – 1100 nm range. Transmission spectra (Fig. 1) are characterized by a sharp decrease in the region of 315 nm that corresponds to 3.94 eV, the value, which is over the ZnO band gap energy equal to 3.42 eV. This result is caused by the so-called blue-shift effect that lies in increasing band gap energy with decreasing size of semiconductor sample. The medium diameter of the crystallites, calculated from the observed short-wavelengths shift, is equal to 5.6 nm.         Figure 2 shows photoluminescence (PL) spectra of ZnO powders at 80K, which were chemically deposited from the solutions with various PVA concentrations. PL spectra were excited by laser radiation with λexc = 337 nm. For PVA concentration below 5.00%, the wide structured band in the blue-green (BG) spectral range with pronounced maxima near 450-480 and 525-540 nm in dependence on polymer concentration dominates in intensity. For ZnO, the green PL band localized at 450-500 nm is attributed to oxygen centres [2]. Low-temperature PL spectrum for ZnO powder synthesized at 0.10% PVA contains the pronounced narrow ultraviolet (UV) band at 378 nm that is caused by free exciton recombination [3]. For 5.00% PVA, the only UV band is observed, and its intensity dominates comparing to the spectra of other powders with lower PVA concentrations. The complex structure of this PL band allows distinguishing the exciton bands with maxima at 376, 378, 380, 386, and 392 nm at 80K [4]. When synthesizing ZnO at high polymer concentration of 5.00%, the last one prevents the formation of oxygen centres that leads to complete quenching of the BG PL bands. The PL spectra of ZnO powders synthesized in polyacrylamide and synthanol matrices consist of only one PL band in the BG spectral range with maximum at 420 nm.