Search results for "ZnO"
showing 10 items of 264 documents
Correlation between Zn vacancies and photoluminescence emission in ZnO films.
2006
Photoluminescence and positron annihilation spectroscopy have been used to characterize and identify vacancy-type defects produced in ZnO films grown on sapphire by metal-organic chemical-vapor deposition. The photoluminescence of the samples in the near band edge region has been studied, paying particular attention to the emission at 370.5 nm (3.346 eV). This emission has been correlated to the concentration of Zn vacancies in the films, which has been determined by positron annihilation spectroscopy. Jesus.Zuniga@uv.es Vicente.Munoz@uv.es
Enhanced optical properties of Cd–Mg-co-doped ZnO nanoparticles induced by low crystal structure distortion
2020
Abstract The growth of CdxMg0.125-xZn0.875O nanoparticles with yellow-orange luminescence is achieved up to 2.5 at. % Cd via a modified sol–gel process. X-ray diffraction analysis confirmed that all the nanoparticles have the hexagonal wurtzite structure. It is found that Cd doping has a considerable effect on the crystal size, microstrain, band gap, and photoluminescence of the Mg0·125Zn0·875O structure, originating from a preferred crystallographic orientation along the (101) plane of the wurtzite structure. The shift and broadening of the E2(high) mode observed in the Raman spectra due to growth-induced strain corroborates the small distortion observed in the X-ray diffraction data. The …
Synthesis and photoluminescence properties of hybrid 1D core–shell structured nanocomposites based on ZnO/polydopamine
2020
In the present work, we report on the modelling of processes at the zinc oxide and polydopamine (ZnO/ PDA) interface. The PDA layer was deposited onto ZnO nanorods (NRs) via chemical bath deposition. The defect concentrations in ZnO before and after PDA deposition were calculated and analysed. The ZnONRs/PDA core–shell nanostructures were studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman and Fourier-transform infrared (FTIR) spectroscopy, photoluminescence (PL) measurements, and diffuse reflectance spectroscopy. The TEM and electron energy loss spectroscopy (EELS) measurements confirmed the conformal coating of PDA, while the PL emission from ZnO and ZnONRs/P…
Optical properties of ZnO deposited by atomic layer deposition (ALD) on Si nanowires
2018
International audience; In this work, we report proof-of-concept results on the synthesis of Si core/ ZnO shell nanowires (SiNWs/ZnO) by combining nanosphere lithography (NSL), metal assisted chemical etching (MACE) and atomic layer deposition (ALD). The structural properties of the SiNWs/ZnO nanostructures prepared were investigated by X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopies. The X-ray diffraction analysis revealed that all samples have a hexagonal wurtzite structure. The grain sizes are found to be in the range of 7-14 nm. The optical properties of the samples were investigated using reflectance and photoluminescence spectroscopy. The study o…
Photocatalysis of rhodamine B and methyl orange degradation under solar light on ZnO and Cu2O thin films
2020
We report the photocatalytic properties of ZnO and Cu2O thin films deposited on glass substrates at room temperature by DC sputtering and pulsed laser deposition. The photoactivity of the films was investigated through the degradation of rhodamine B (RhB) and methyl orange (MO) under solar light. In order to select the most suitable film of ZnO for the of RhB and MO degradation, the relationship between the characteristics (e.g. energy levels and defects concentration) of ZnO films and their effectiveness in the photocatalytic yield of RhB and MO been studied, where several films were deposited by using different oxygen partial pressures (PO2: 0.05–1.3 mbar), while Cu2O films were grown und…
Morphological and optical property study of Li doped ZnO produced by microwave-assisted solvothermal synthesis
2021
Abstract ZnO materials have been at the centre of many studies for decades. Doping of ZnO by lithium atoms is a prospective approach for compensation of n-type conductivity in the unintentionally doped ZnO aimed at obtaining p-type semiconductor. In this study, we have synthesized ZnO rod-like powders doped with lithium ions (0–0.65 atom%) by the new microwave-assisted solvothermal method in order to obtain greater photoluminescence intensity of ZnO emissions in the UV region. The obtained powders contain nanoparticles from 20 nm up to 250 nm depending on Li content. X-ray diffractometry and Raman spectroscopy were employed to characterise the structure of ZnO powders, scanning electron mic…
Application of Room Temperature Photoluminescence From ZnO Nanorods for Salmonella Detection
2014
ZnO nanorods grown by gaseous-disperse synthesis are confirmed by XRD analysis to have the wurtzite crystal structure. The obtained crystallites, as found from SEM studies, are 57 +/- 9 nm in diameter and 470 +/- 30 nm long on the average. Two emission bands of photoluminescence from ZnO nanorods observed at room temperature are centered at 376 and 520 nm. A biosensitive layer is prepared by immobilization of anti-Salmonella antibodies from liquid solutions on the ZnO surface. Immobilization of the biosensitive layer onto ZnO nanorods is found to increase the intensity of PL. After further reaction with Salmonella antigens (Ags), the PL intensity is found to decrease proportional to Ag conc…
3-4 gadus vecu bērnu radošās darbības pieredzes bagātināšana gleznošanā pirmsskolā
2021
Darba autore ir Laura Staņeviča. Kvalifikācijas darbs tika izstrādāts par tēmu – „ 3-4 gadus vecu bērnu radošās darbības pieredzes bagātināšana gleznošanā pirmsskolā.” Kvalifikācijas darba mērķis ir noskaidrot un izpētīt, kā gleznošana pirmsskolā bagātina 3-4 gadus vecu bērnu radošās darbības pieredzi un attīstību. Caur gleznošanu ļoti spilgti var noteikt bērna fizisko un sensoro attīstību, kas ļoti palīdz pedagoga turpmākai nodarbību plānošanai. 3- 4 gadus veci bērni ir ļoti piemēroti izpētei, kā gleznošana bagātina radošo darbības pieredzi - jo bērni šajā vecumā kļūst patstāvīgi, atvērti un zinātkāri, bērni vēlas izzināt visu nezināmo sev apkārt, šajā vecumā izteikti bērnam attīstās senso…
5-6 gadu vecu bērnu valodas bagātināšana vizuālās mākslas nodarbībās
2020
Kvalifikācijas darba tēma: 5-6 gadu vecu bērnu valodas bagātināšana vizuālās mākslas nodarbībās. Darba autore: Elīna Lacare. Pētījuma objekts: vizuālās mākslas nodarbības. Pētījuma priekšmets: bērnu valoda. Pētījuma mērķis: teorētiski analizēt un empīriski pārbaudīt kā vizuālās mākslas nodarbībās pirmsskolā bagātināma 5 – 6 gadus vecu bērnu valoda. Pētījuma jautājums: kā vizuālās mākslas nodarbībās pirmsskolā bagātināma 5 – 6 gadu vecu bērnu valoda. Pētījuma uzdevumi: 1.Teorētiski analizēt literatūru par bērna valodu un tās bagātināšanas iespējām. 2.Teorētiski analizēt literatūru par vizuālās mākslas mācību saturu un pedagoģisko darbību pirmsskolā. 3.Empīriski pārbaudīt teorētiskās atziņas …
Vecākā pirmsskolas vecuma bērnu pašvadības sekmēšana gleznošanā
2019
Vecākā pirmsskolas vecuma bērnu pašu vadītas nodarbības, tai skaitā gleznošana ir aktuāls jautājums, ne tikai Skola 2030 kontekstā, bet arī būtisks mācīšanās veids, lai bērni aizejot uz skolu, ir zinātkāri un radoši, lai, paši būtu spējīgi meklēt risinājumus dažādos jautājumos un spētu izmantot savas zināšanas, nevis balstoties uz iemācītiem šabloniem. Pašavadīta mācīšanās ir termins, kurš dominē 21. gadsimta pedagoģijas ideālos un mērķos, raugoties uz to, ka laikmetam mainoties, mainās ne tikai tehnoloģijas, arī skatījums uz informācijas iegūšanas veidiem. Arī Skola 2030 pašvadīta mācīšanās ir būtisks kompetenču izglītības komponents, kurš atmet veco laiku mācību metodes, kur bērni „iekala…