Synthesis of ZnO doped ceria nanoparticles via azeotropic distillation processing

The synthesis of nano-sized ZnO-doped CeO2 of 20 nm in crystal size by a coprecipitation technique was investigated by different scanning calorimetries/thermalgravimetrics（DSC/TG）, X-ray diffraction （XRD）, transmission electron microscopy （TEM） and ultraviolet （UV） absorbance. Azeotropic distillation processing was performed to effectively eliminate the residual water inside the as-prepared precipitate. Doping of ZnO results in the formation of solid solution. The crystal size of the nanoparticles increases with the increase of the doped ZnO amount, the calcination temperature and time. Doped CeO2 nanoparticles show excellent visible-light property and ultraviolet-absorption activity. Doping of ZnO doesn＇t not weaken the UV-shielding property of ceria.     

Optical properties of antimony-implanted ZnO epilayers

Antimony ions were implanted into ZnO films grown on c-plane sapphire by pulsed-laser deposition. Raman scattering modes of the Sb-implanted samples were found to be influenced by the implantation dose. A characteristic peak at 576 cm^− 1 was observed with an asymmetric shape due to ion damage to the lattice of the implanted ZnO films. When the implant dose was low, the height of the peak was reduced by rapid thermal annealing at 400-600 °C and the symmetry of the spectra was recovered. However, when the Sb dose exceeded 1 × 10¹⁵ cm^− 2, the peak maintained unchanged after rapid thermal annealing at temperatures up to 600 °C. A broad and low Raman peak was observed at 437 cm^− 1, which is related to the surface damage caused by the energetic ion bombarding. Photoluminescence measurement showed a decrease of the bandedge emission at 3.36 eV, a clear effect of defects induced by the implantation, and confirmed partial recovery of the crystal by rapid annealing.     

Growth of uniform ZnO nanoparticles by a microwave plasma process

ZnO nanoparticle coatings with a controlled size distribution have been grown on quartz substrates by a novel microwave plasma assisted spray (MPAS) technique. This study presents the analysis of structure, photoluminescence, and magnetic properties of particle coatings with two distinctly different mean particle sizes (400 nm and 200 nm). X-ray diffraction patterns show a typical wurtzite structure without any impurity phases for the nanoparticle coatings. SEM and TEM investigations have shown the grown nanoparticles to be spherical and well separated with a narrow size distribution. Nanoparticles are polycrystalline with smaller grain sizes associated with the smaller particle sizes. Photoluminescence (PL) spectra reveal the presence of oxygen vacancy related defects in the 400 nm nanoparticles, which become less pronounced in the 200 nm nanoparticles. The 400 nm nanoparticles are found to exhibit room-temperature ferromagnetism with a clear hysteretic behavior, while the 200 nm nanoparticles are diamagnetic even down to 10 K. These results suggest the oxygen vacancies were the cause for defect-induced ferromagnetism in the 400 nm nanoparticles.     

Effects of Bi doping on the optical properties of Er:Y2O3

The influences of Bi³⁺ doping on the optical properties of Er³⁺:Y₂O₃ are investigated under UV and IR excitations. The emission intensity of Er³⁺ is remarkably enhanced by the introduction of Bi³⁺ under both two excitations. The emission enhancement under UV excitation originates from the energy transfer from Bi³⁺ to Er³⁺, while under IR excitation it can be attributed to the modification of the local crystal field around the Er³⁺.     

Preparation of homogeneous ZnO nanoparticles via precipitation-pyrolysis with Zn5（CO3）2（OH）6 as precursor

1 Introduction Recently, demands for high product performance products have necessitated a precise control of ZnO particle properties for applications such as electrode of solar cells and photocatalysts. Much attention is given to the high chemical reacti…     

An investigation on linear optical properties of dilute Cr doped ZnO thin films synthesized via sol-gel process

Cr doped ZnO thin films were prepared via sol-gel method. The effects of dopant concentration (0%, 1.5% and 3%) annealing temperature and film thickness on UV-Vis spectra of prepared films were investigated. Also, the thickness and surface topology of thin films were investigated by thickness profile meter (DEKTAK) and Atomic Force Microscopy (AFM), respectively. In addition, the band gap and Urbach energy of prepared films were calculated completely for the samples. The results showed that by increasing the dopant concentrations, the microstrain of the prepared thin film structures also increases while the band-gap values decrease. Meanwhile, an increase in annealing temperature makes a decrease in band gap and microstrain of thin films. The increase in thickness resulted in red shift in band gap and reduction in interior microstrains.     

Effect of Bi doping on the quenching concentration of H11/2/S3/2 level of Er

Bi³⁺ and Er³⁺ codoped Y₂O₃ was prepared by sol-gel method. The upconversion emission was investigated under 980 nm excitation. For samples without Bi³⁺, the quenching concentration of ²H_11/2/⁴S_3/2 level of Er³⁺ is 3.0 mol%. However, by 1.5 mol% Bi³⁺ doping the quenching concentration increases to 5.0 mol%; meanwhile, the green emission is enhanced 1.9 times. The results indicate that both the quenching concentration and the emission intensity of ²H_11/2/⁴S_3/2 level can be increased by Bi³⁺ doping.     

Morphology controlled synthesis of ZnO nanoparticles for in-vitro evaluation of antibacterial activity

Novel hierarchical flower- and nanorod-shaped ZnO nanoparticles with uniform morphological features were successfully synthesized through controlled precipitation method in aqueous media without using any surfactant or template. To elucidate the growth mechanism of the synthesized nanoparticles, the effects of pH, reaction time and temperature were studied systematically. Selected ZnO samples were then subjected to SEM, FT-IR and XRD analysis. XRD patterns confirmed well crystalline nature of the as-synthesized powders. Furthermore, synthesized nanoparticles (hierarchical flowers as ZnO-1 and nanorods as ZnO-2), as well as commercial ZnO (ZnO-Com), were then investigated for in-vitro evaluation of antibacterial activity against various bacterial strains of clinical importance. Results showed that ZnO-2 exhibited higher antibacterial activity to all tested strains than ZnO-1, while ZnO-Com showed no antibacterial response in the applied experimental conditions. In addition, ZnO concentration-dependent antibacterial study unfolded that size of inhibition zones increased significantly from ~30 to 33 mm against Streptococcus mutans and from ~28 to 30 mm against Escherichia coli with increasing ZnO-2 concentration from 0.25 to 0.75 µg/µL. The present study, therefore, suggests that the application of synthesized ZnO nanoparticles as the antibacterial agent may be effective for inhibiting certain pathogenic bacteria in biomedical sides.     

Effect of Co substitution on the structural and optical properties of ZnO nanoparticles synthesized by sol-gel route

Co doped ZnO nanoparticles were synthesized by sol-gel method and characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive X-ray analysis (EDAX), UV-Visible absorption spectroscopy and Fourier transform infrared spectroscopy (FTIR). XRD analysis revealed the formation of single phase structure of all samples which was further supported by FTIR data. With the increase in Co concentration from 0% to 5%, crystallite size was observed to vary from 27.1 to 21.3 nm. It suggests the prevention of crystal growth as a result of Co doping in ZnO. It was also evident from the absorption spectra that the absorbance tends to increase with the increase in dopant concentration. Optical band gap was found to increase slightly with the increase in Co content, confirming the size reduction as a result of Co doping.     

Growth and photocatalytic activity of ZnO nanosheets stabilized by Ag nanoparticles

The Ag nanoparticles-stabilized ZnO nanosheets were prepared using a liquid-liquid two-phase method with (n-Dodecyl)trimethylammonium bromide (DTAB) as a phase transfer agent at the room temperature. The silver nanoparticles which are conductors with the character of attracting energy can make the ZnO sheets stabilize under the higher energy electrons. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectroscopy and fluorescence. The results demonstrate that the silver nanoparticles load on the surface of ZnO sheets and make the ZnO sheets stabilize. Furthermore, the formation mechanism of ZnO sheets stabilized by silver nanoparticles was also proposed and discussed in detail. Moreover, the photocatalysis test shows that the ZnO sheets stabilized by silver nanoparticles exhibit a higher photocatalytic activity than the pure ZnO nanosheets, thereby implying that the Ag/ZnO interfaces promote the separation of photogenerated electron-hole pairs and enhance the photocatalytic activity.     

Effect of annealing on the conversion of ZnS to ZnO nanoparticles synthesized by the sol-gel method using zinc acetate and thiourea

A systematic study is presented on the conversion of zinc sulfide to zinc oxide nanoparticles as a function of annealing temperature. Zinc acetate dihydrate (Zn(CH₃COO)₂.2H₂O) and thiourea (NH₂CSNH₂) are used as precursors to synthesize ZnS and then ZnO. The aqueous solution of the precursor was refluxed at 90 °C for over 12 h. The synthesized complex was then annealed at 300 °C, 500 °C, 700 °C, and 900 °C in air for one hour. From elemental analyses, it was found that the as-synthesized powder is a mixture of ZnS and ZnO, which annealing later converts to the zinc oxide phase only. The morphological observations revealed spherical particles of various sizes (20 nm to 300 nm) while increasing the annealing temperatures. A drastic change in the vibration bands is noticed with annealing. Photoelectron peaks related to sulfur and carbon are observed for synthesized powder, whereas, these peaks disappeared when annealed at 500 °C.     

Sol-gel derived Li-Mg co-doped ZnO films: Preparation and characterization via XRD, XPS, FESEM

Li-Mg co-doped ZnO films have been deposited onto glass substrates by sol-gel spin coating method. The structural and morphological properties of the films were characterized by X-ray diffractometer (XRD), X-ray photo-electron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM). The XRD spectra indicated that the films have polycrystalline nature. The crystallite size values decreased with the increasing Mg content. The chemical composition of the Li-Mg co-doped ZnO films were confirmed by XPS. Additionally, XPS results clearly showed the existence of Mg as a doping element into ZnO crystal lattice. The surface morphology of the films was found to depend on the concentration of Mg in the ZnO:Li. The absorption band edge values of the films were calculated and these values of the films increased with increasing Mg concentration. The refractive index dispersion curves of the films obeyed the single-oscillator model. The dispersion parameters such as E_o (single-oscillator energy) and E_d (dispersive energy) of the films were determined and increase with Mg content.     

Tunable light emission and similarities with garnet structure of Ce-doped LSCAS glass for white-light devices

In this paper, we report results concerning tunable light emission and color temperature in cerium-doped low-silica-calcium-alumino-silicate (LSCAS) glass for smart white-light devices. Spectroscopic results, analyzed using the CIE 1931 x-y chromatic diagram, show that this glass presents two broad emission bands centered at 475 and 540 nm, whose intensities can be tuned by the excitation wavelength. Moreover, the same emission can be achieved from a color temperature range from 3200 to 10,000 K, with a color-rendering index (CRI) of around 75% obtained by changing the optical path length of the sample. Our new phosphor LSCAS glass, which is a unique system that exhibits tunable yellow emission, combines all qualities for white-light devices.     

Synthesis of ZnS nanoparticles via hydrothermal process assisted by microemulsion technique

Uniform and spherical ZnS nanoparticles with a diameter of 5–10 nm were successfully synthesized at 160 °C via a facile hydrothermal process, where ZnS precursors were prepared by a microemulsion technique. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and photoluminescent (PL) spectra techniques, respectively. The results showed that the hydrothermal temperature exerted a more important effect than the holding time on the crystallization of ZnS crystallites. The as-prepared ZnS nanoparticles exhibited higher PL intensity than that of the normal ones of micrometer scale besides an obvious blue shift.     

Spray deposited superhydrophobic ZnO coatings via seed assisted growth

Superhydrophobic zinc oxide (ZnO) coatings were synthesized by a simple and cost-effective spray pyrolysis technique (SPT) via seed assisted growth onto the glass substrates at 723 K from an aqueous zinc acetate precursor solution. Initially, the ZnO seeds were synthesized from an aqueous 0.4 M zinc acetate solution onto the glass substrates at 723 K. For the seed assisted growth of ZnO, the solution concentrations (0.1 M to 0.4 M) were used and its effect on structural, morphological, optical and wettability properties of ZnO thin films was investigated. The synthesized films were found to be polycrystalline, with preferential growth along c-axis. Scanning electron microscopy (SEM) images show the uniform distribution of spherical grains of about 60-80 nm grain size. After seed assisted growth, film surface becomes very rough. The films were specular and transmittance of thin films decreases as the concentration of the precursor solution increases. The optical absorption spectrum shows a sharp absorption band-edge at 381 nm, corresponding to optical gap energy (Eg) of 3.25 eV. All samples are superhydrophobic in nature. The Zn4 sample shows the superhydrophobicity with highest value of the contact angle (CA) i.e. 165°. Such a superhydrophobic coatings can be useful in the anti-snow, anti-fog and self cleaning surfaces.     

Deposition and super liquid repellency of fluorinated ZnO nanoparticles on carbon fabrics

The liquid-repellent behavior of fluorinated zinc oxide (ZnO) nanoparticles deposited onto carbon fabric (CF) by a pulse microwave-assisted (MA) method followed by surface fluorination treatment was investigated. The MA process is performed at 80 °C within 10 min with different pH values of 5.5, 8 and 12. The hexagonal ZnO nanoparticles with an average size of 100 nm exhibit a well-defined wurtzite crystal structure without any heat treatment. The ZnO nanoparticles produced by MA synthesis at pH = 8 display the maximal density over CF substrate. The fluorination coating effectively imparts super water and oil repellencies on the ZnO–CF surface; i.e., the contact angles are 163° (water) and 153° (ethylene glycol, EG). The liquid repellencies toward water and EG droplets show an increasing function of surface density of ZnO nanoparticles. This result can be attributed to the fact that an air layer is confined in the nanoparticles, thereby inducing a rougher gas–vapor–solid contact line, referred to as the Cassie state. Based on the Young–Duprè equation incorporated with the Cassie parameter, the lowest work of adhesion (W_ad) values of the ZnO–CF surface for water and EG repellencies are estimated to be 3.16 and 4.93 mJ/m², respectively. Accordingly, this work sheds some light on the creation of a two-tier texture by an efficient MA route and on how the surface density of ZnO nanoparticles strongly affects the repellent behavior of the resultant ZnO–CF composites.     

The effect of Au/Ag ratios on surface composition and optical properties of co-sputtered alloy nanoparticles in Au–Ag:SiO2 thin films

Gold–silver alloy nanoparticles with various Au concentrations in sputtered SiO₂ thin films were synthesized by using RF reactive magnetron co-sputtering and then heat-treated in reducing Ar + H₂ atmosphere at different temperatures. The UV–visible absorption spectra of the bimetallic systems confirmed the formation of alloy nanoparticles. The optical absorption of the Au–Ag alloy nanoparticles exhibited only one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. The maximum absorption wavelength of the surface plasmon band showed a red shift with increasing Au content. XPS results indicated that the alloys were in metallic state, and they had a greater tendency to lose electrons as compared to their corresponding monometallic state. Moreover, the positive and negative shift of the Au(4f) core-level binding energies was observed for low and high Au concentration, respectively. Also a negative shift of the Ag(3d) binding energies was increased by increasing Au concentration. Diffusion of the particles toward the surface by increasing the temperature has also been illustrated by AFM images. Based on AFM observations, we have found that the particle size reduced from 35 to 20 nm by increasing the annealing temperature from 600 to 800 °C, while particle size increased by increasing Au concentration in films. In addition, lateral force microscopy (LFM) analysis showed that the alloy particles were uniformly distributed on the surface.     

Conductive and transparent Bi-doped ZnO thin films prepared by rf magnetron sputtering

Bi-doped ZnO thin films were grown on glass substrates by ratio frequency (rf) magnetron sputtering technique and followed by annealing at 400 °C for 4 h in vacuum (~ 10^− 1 Pa). The effect of argon pressure on the structural, optical, and electrical properties of the Bi-doped films were investigated. The XRD patterns show that the thin films were highly textured along the c-axis and perpendicular to the surface of the substrate. Some excellent properties, such as high transmittance (about 85%) in visible region, low resistivity value of 1.89 × 10^− 3 W cm and high carrier density of 3.45 × 10²⁰ cm^− 3 were obtained for the film deposited at the argon pressure of 2.0 Pa. The optical band gap of the films was found to increase from 3.08 to 3.29 eV as deposition pressure increased from 1 to 3 Pa. The effects of post-annealing treatments had been considered. In spite of its low conductivity comparing with other TCOs, Bi-doping didn't appreciably affect the optical transparency in the visible range of ZnO thin films.     

Efficient cerium-based sol-gel derived phosphors in different garnet matrices for light-emitting diodes

Efficiency of sol-gel derived Y_3−xAl₅O₁₂:Ce_x³⁺ (YAG:Ce) and Y_3−xMg₂AlSi₂O₁₂:Ce_x³⁺ (YMASG:Ce) phosphors, which are prospective for application in white light emitting diodes (LED), is studied. Sets of samples containing different cerium amount x from 0.015 to 0.06 and sintered at different temperatures (1400-1550 °C) were investigated. Importance of absorption peculiarities in agglomerates of phosphor nanocrystals is demonstrated by studying the excitation wavelength dependence of quantum efficiency and by applying PL measurements in confocal mode. Emission saturation is demonstrated to occur at higher excitation intensities than those typical for operating white LEDs.     

Preliminary Study on Electrical and Optical Properties of ZnO Film Grown by MOCVD

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