Luminescence Properties of Sm3+/Eu3+ Co-Doped ZnO Quantum Dots

2016 ◽  
Vol 16 (4) ◽  
pp. 3597-3601
Author(s):  
Fengyi Liu ◽  
Hong Li ◽  
Yajing Hu ◽  
Na Jin ◽  
Yun Mou ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Sol Gel ◽  
Spherical Shape ◽  
Hexagonal Wurtzite Structure ◽  
Luminescence Properties ◽  
Transmission Electron ◽  
Doped Zno ◽  
Zno Quantum Dots ◽  
Zno Qds ◽  
Co Doped

In order to improve luminescence properties of semiconductor ZnO quantum dots (QDs), Sm3+/Eu3+ co-doped ZnO QDs have been controllably synthesized by sol–gel method in this paper. ZnO QDs have a spherical shape with mean diameter at about 5–6 nm, which was characterized by high-resolution transmission electron microscopy (HRTEM). ZnO QDs have hexagonal wurtzite structure with parts of Sm3+ and Eu3+ incorporated into the lattice, which was demonstrated by X-ray Diffraction (XRD). Luminescence properties at room temperature (RT) of different amount of Sm3+ and 2 mol% Eu3+ doped ZnO QDs were examined in-depth by optical spectra. In contrast to the Pr3+/Eu3+ co-doped fluorescent performance researched in our previous study, the photoluminescence (PL) spectra indicates the unique luminescence properties of Sm3+/Eu3+ co-doped ZnO QDs. In addition, fluorescence lifetimes were obtained to illustrate the luminous mechanism.

Microstructure and Luminescence Properties of Tb3+ Doped ZnO Quantum Dots

2016 ◽  
Vol 16 (4) ◽  
pp. 3592-3596 ◽  
Author(s):  
Na Jin ◽  
Hong Li ◽  
Fengyi Liu ◽  
Ya-Hong Xie
Keyword(s):  
Quantum Dots ◽  
Surface Defects ◽  
Light Emission ◽  
Sol Gel ◽  
Spherical Shape ◽  
Hexagonal Wurtzite Structure ◽  
Quenching Effect ◽  
Doped Zno ◽  
Zno Quantum Dots ◽  
Zno Qds

In order to increase the exchange efficiency of solar cells by down-conversion, Tb3+ doped ZnO quantum dots (QDs) were successfully synthesized by sol–gel process. The X-ray diffraction (XRD) results indicate that ZnO QDs have hexagonal wurtzite structure. ZnO QDs have a spherical shape and diameter around 5 nm, which was confirmed by high-resolution transmission electron microscopy (HRTEM). The intensity of visible light emission peaks becomes strengthened and then weakened with the increase of Tb3+ doping concentration. When the concentration is more than 1%, because of the decrease of surface defects and concentration quenching effect, the emissive intensity is weakened. The enhancement of the PL emission peaks at 542 nm, 582 nm, and 619 nm was assigned to energy transfer between Tb3+ ions and ZnO QDs host. Moreover, the absorption spectra also demonstrates energy transfers from Tb3+ ions to ZnO QDs.

Studies on Optical Properties of CdS/ZnO Quantum Dots Prepared by Sol-Gel Method

2011 ◽  
Vol 364 ◽  
pp. 129-133 ◽  
Author(s):  
Liyana Mohd Lawi Ruhana ◽  
Taqiyuddin Mawardi Ayob Muhammad ◽  
Radiman Shahidan ◽  
Irman Abdul Rahman ◽  
Bohari M. Yamin
Keyword(s):  
Quantum Dots ◽  
Sol Gel ◽  
Emission Spectra ◽  
Blue Shift ◽  
Mixture Ratio ◽  
Gel Method ◽  
Sol Gel Method ◽  
Transmission Electron ◽  
Zno Quantum Dots ◽  
Zno Qds

CdS/ZnO quantum dots (QDs) were prepared at a temperature of 293 K by the sol-gel method with Triethanolamine (TEA) as a capping agent. The effect of CdS/ZnO mixture ratio of 1:9, 1:1 and 9:1 on the optical absorption and fluorescence spectra were investigated by UV-Vis and Fluorescence spectroscopy. By increasing ZnO composition, a blue-shift of absorption edge and emission spectra were observed. The band gap for 1:9, 1:1 and 9:1 were found to be 4.13, 3.93 and 3.11 eV, respectively. The morphology of the CdS/ZnO QDs for each mixing ratio was obtained by transmission electron microscope (TEM). The size of the QDs was found to be in the range of 5-10 nm with some agglomerated particles.

Temperature Effects on Fluorescence Intensity of Mn-Doped ZnO Quantum Dots Derived from a Sol–Gel Method

2015 ◽  
Vol 15 (10) ◽  
pp. 8023-8027
Author(s):  
Younghoon Kwon ◽  
Jongsung Kim
Keyword(s):  
Quantum Dots ◽  
Sol Gel ◽  
Effect Of Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Gel Technique ◽  
Doped Zno ◽  
Zno Qds ◽  
Mn Doped

Recently, various quantum dots (QDs) have been prepared and studied extensively due to their unique electrical and optical properties. Among them, ZnO has attracted much attention because it contains no heavy metals, is biocompatible, and can be easily prepared. In addition, doping QDs with transition metals such as Mn allows for their photo-physical properties to be modified. In this study, Mn-doped ZnO QDs were synthesized by a sol–gel technique, after which the effect of temperature on their fluorescence properties was investigated. The prepared QDs were characterized by X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. In addition, their photoluminescence (PL) intensities decreased linearly with temperature between 30 and 70 °C. Intensity also decreased as the amount of Mn increased. Finally, the slope of the PL temperature dependence decreased as the amount of Mn present increased.

Effect of cobalt doping on microstructures and dielectric properties of ZnO

2019 ◽  
Vol 97 (3) ◽  
pp. 227-232 ◽  
Author(s):  
Ye Zhao ◽  
Fan Tong ◽  
Mao Hua Wang
Keyword(s):  
Zno Nanoparticles ◽  
Sol Gel ◽  
Hexagonal Wurtzite Structure ◽  
Sem Analysis ◽  
Co Doping ◽  
In Doping ◽  
Zno Powders ◽  
Doped Zno ◽  
Zno Crystal ◽  
Co Doped

Pure and cobalt-doped ZnO nanoparticles (2.5, 5, 7.5, and 10 atom % Co) are synthesized by sol–gel method. The as-synthesized nanoparticles are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FE-SEM) analysis. The nanoparticles of 0, 2.5, and 5 atom % Co-doped ZnO exhibited hexagonal wurtzite structure and have no other phases. Moreover, the (101) diffraction peaks position of Co-doped ZnO shift toward a smaller value of diffraction angle compared with pure ZnO powders. The results confirm that Co ions were well incorporated into ZnO crystal lattice. Simultaneously, Co doping also inhibited the growth of particles, and the crystallite size decreased from 43.11 nm to 36.63 nm with the increase in doping concentration from 0 to 10 atom %. The values of the optical band gap of all Co-doped ZnO nanoparticles gradually decreased from 3.09 eV to 2.66 eV with increasing Co content. Particular, the dielectric constant of all Co-doped ZnO ceramics gradually increased from 1.62 × 103 to 20.52 × 103, and the dielectric loss decreased from 2.36 to 1.28 when Co content increased from 0 to 10 atom %.

Single-phased emission-tunable Mg and Ce co-doped ZnO quantum dots for white LEDs

2020 ◽  
Vol 231 ◽  
pp. 118096 ◽  
Author(s):  
Qiang Shi ◽  
Kai Ling ◽  
Susu Duan ◽  
Xue Wang ◽  
Shengxiang Xu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
White Leds ◽  
Doped Zno ◽  
Zno Quantum Dots ◽  
Co Doped

scholarly journals The Effects of Zinc Oxide (ZnO) Quantum Dots (QDs) Embedment on the Physicochemical Properties and Photocatalytic Activity of Titanium Dioxide (TiO2) Nanoparticles

2021 ◽  
Vol 32 (2) ◽  
pp. 71-85
Author(s):  
Anwar Iqbal ◽  
Usman Saidu ◽  
Farook Adam ◽  
Srimala Sreekantan ◽  
Normawati Jasni ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Zinc Oxide ◽  
Titanium Dioxide ◽  
Physicochemical Properties ◽  
Quantum Confinement Effect ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Fluorescent Light ◽  
Zno Quantum Dots ◽  
Zno Qds

In this study, a detailed investigation on the effect of zinc oxide (ZnO) quantum dots (QDs) embedment on the physicochemical properties of anatase titanium dioxide (TiO2) was conducted. The highly porous nanocomposite labelled as ZQT was prepared via the sol-gel assisted hydrothermal method. The powder X-ray diffraction (XRD) analysis indicates that the average crystallite size of the ZnO QDs, anatase TiO2 (TiO2 NPs) and ZQT were 4.45 nm, 9.22 nm and 11.38 nm, respectively. Photoluminescent (PL) analysis detected the presence of defects related to TiO2, oxygen vacancies and quantum confinement effect (QCE) of the ZnO QDs in ZQT. These features enhanced the photodegradation of tetracycline (TC) under 48 watt of fluorescent light irradiation when ZQT (98.0%) was used compared to TiO2NPs (32.4%) and ZnO QDs (68.8%). The photodegradation activity was driven by O2●− followed by ●OH and h+.

Ligand-Stabilized ZnO Quantum Dots: Molecular Dynamics and Experimental Study

2017 ◽  
Vol 70 (10) ◽  
pp. 1110 ◽  
Author(s):  
Rohul Hayat Adnan ◽  
Kai Lin Woon ◽  
Narong Chanlek ◽  
Hideki Nakajima ◽  
Wan Haliza Abd. Majid
Keyword(s):  
Molecular Dynamics ◽  
Quantum Dots ◽  
Emission Peak ◽  
Excitation Wavelength ◽  
Quantum Size ◽  
Transmission Electron ◽  
Zno Quantum Dots ◽  
Average Size ◽  
Semi Empirical ◽  
Zno Qds

Different aminoalcohol ligands, monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) were employed to passivate the surface of ZnO quantum dots (ZnO QDs). High-resolution transmission electron microscopy (HRTEM) imaging revealed that the higher branched aminoalcohols produced smaller sized ZnO QDs. The average size for ZnO/MEA, ZnO/DEA, and ZnO/TEA were found to be 3.2, 2.9, and 2.4 nm. TEA ligands were effective in producing stable, monodisperse ZnO QDs compared with DEA and MEA ligands. Molecular dynamics and semi-empirical calculations suggested that TEA and DEA ligands interact strongly with the partial charge of ZnO dangling bonds and have a large molar volume to hinder the diffusion of precursors through the ligands to the surface of ZnO resulting in a smaller particle size as compared with MEA ligands. As the size of ZnO QDs decreases from ZnO/MEA to ZnO/TEA, the absorption edge and emission peak maximum blue-shifts to a shorter wavelength due to the quantum size effect. The bandgap of ZnO/MEA, ZnO/DEA, and ZnO/TEA was determined to be 3.97, 4.07, and 4.23 eV, and the emission peak was found to be 472, 464, and 458 nm when excited using a 325 nm excitation wavelength, respectively.

Surfactant-free Colloidal Crystal of ZnO Quantum Dots

2009 ◽  
Vol 1207 ◽  
Author(s):  
Xi Zhang ◽  
Dazhi Sun ◽  
Hung-Jue Sue
Keyword(s):  
Electron Microscopy ◽  
Quantum Dots ◽  
Colloidal Crystal ◽  
Uv Light ◽  
X Ray ◽  
Transmission Electron ◽  
Close Packed Structure ◽  
Packed Structure ◽  
Zno Quantum Dots ◽  
Zno Qds

AbstractMonodisperse ZnO quantum dots (QDs) with a particle size of about 5 nm have been synthesized. Isopropanol together with hexane were utilized to precipitate ZnO nanoparticles to form condensed phases, ranging from white flocculation, to gel-like fluid, and to transparent solid. The morphology and structure in the transparent ZnO solid was characterized by UV-vis, X-ray diffraction, small-angle X-ray scattering, transmission electron microscopy, and scanning electron microscopy. The mechanisms for the formation of transparent ZnO QDs close-packed structure were monitored via UV-vis spectra, and found likely to be a colloidal crystal. The colloidal crystal is transparent and absorbs UV light efficiently. Possible conditions for the formation of the ZnO QDs colloidal crystal are discussed.

Structural, Optical and Magnetic Properties of Nanocrystalline Co-Doped ZnO Thin Films Grown by Sol–Gel

2017 ◽  
Vol 73 (1) ◽  
pp. 13-21 ◽  
Author(s):  
Zohra Nazir Kayani ◽  
Iqra Shah ◽  
Bareera Zulfiqar ◽  
Saira Riaz ◽  
Shahzad Naseem ◽  
...  
Keyword(s):  
Thin Films ◽  
Surface Morphology ◽  
Sol Gel ◽  
Hexagonal Wurtzite Structure ◽  
Magnetic Surface ◽  
Zno Thin Films ◽  
Zno Films ◽  
X Ray Diffraction ◽  
Doped Zno ◽  
Co Doped

AbstractCobalt-doped ZnO thin films have been deposited using a sol–gel route by changing the number of coats on the substrate from 6 to 18. This project deals with various film thicknesses by increasing the number of deposited coats. The effect of thickness on structural, magnetic, surface morphology and optical properties of Co-doped ZnO thin film was studied. The crystal structure of the Co-doped ZnO films was investigated by X-ray diffraction. The films have polycrystalline wurtzite hexagonal structures. A Co2+ ion takes the place of a Zn2+ ion in the lattice without creating any distortion in its hexagonal wurtzite structure. An examination of the optical transmission spectra showed that the energy band gap of the Co-doped ZnO films increased from 3.87 to 3.97 eV with an increase in the number of coatings on the substrate. Ferromagnetic behaviour was confirmed by measurements using a vibrating sample magnetometer. The surface morphology of thin films was assessed by scanning electron microscope. The grain size on the surface of thin films increased with an increase in the number of coats.

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