Efficient Photocatalytic and EMI Shielding Properties of CdO/ La2O3 Nanocomposites

The pure CdO and CdO/La 2 O 3 , and CdO/La 2 O 3 /PVP nanocomposites were synthesized by microwave irradiation method. The prepared samples are analyzed by X-Ray diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), Scanning electron microscope (SEM), Transmission electron microscope (TEM), UV visible spectrometer, Photoluminescence (PL), and Vibrating sample magnetometer (VSM). XRD and FTIR studies confirmed the formation of binary metallic nanocomposites. SEM and TEM analysis authenticate that the addition of lanthanum oxide and PVP influences the size and morphology of CdO nanoparticles the bandgap value can be tuned by the addition of La 2 O 3 and PVP. Photoluminescence spectra show the violet emission in the region between 432 nm to 460 nm and the green emission peak at 529 nm for all three synthesized samples. CIE color coordinates for CdO and CdO/La 2 O 3 , and CdO/La 2 O 3 /PVP nanocomposites were also estimated from emission spectrum. The VSM results confirmed that the nanocomposites possess the weak ferromagnetic properties due to the inclusion of La 2 O 3 and PVP. The dielectric constant, electrical conductivity and dielectric loss values at room temperature have been analyzed for CdO and CdO/La 2 O 3 , and CdO/La 2 O 3 /PVP nanocomposites. Among the three synthesized samples, the CdO/La 2 O 3 /PVP nanocomposite attain high electromagnetic shielding efficiency. Furthermore, the rare earth element lanthanum oxide and PVP enhances the efficiency of photocatalytic degradation of MB dye.

Synthesis and Photocatalytic Activity of β-Ga2O3 Nanostructures for Decomposition of Formaldehyde under Deep Ultraviolet Irradiation

An attempt to degrade volatile organic compounds (VOCs) and sterilize air simultaneously is highly desirable to improve indoor air quality. With the help of deep ultraviolet (UVC) lighting, harmful bacteria that exists in the air can be destroyed. Thus, a new photocatalytic substance that can break down VOCs under UVC irradiation is required. Here, we demonstrate the photocatalytic activity of β-Ga2O3 nanostructures, synthesized via the solvothermal method for removing formaldehyde (HCHO) under deep ultraviolet irradiation. The Raman and XRD results indicated that as-synthesized nanostructures showed β-crystalline phase with a monoclinic structure. The photoluminescence spectrum exhibited a broad and strong green emission peak at 510 nm, which was likely attributed to a considerable amount of oxygen and gallium vacancies formed during the calcinating process. The photocatalytic efficiency for decomposing HCHO at room temperature under deep ultraviolet irradiation (278 nm) of the synthesized β-Ga2O3 nanoparticles is higher than that of the β-Ga2O3 nanorods. Both nanoparticles and nanorods obeyed the pseudo-first-order Langmuir-Hinshelwood kinetic model with a degradation rate constant of 0.057 and 0.033 min−1, corresponding to the efficiency of 82% and 62% in the formaldehyde removal, respectively.

Structural and Photoluminescence Characteristics of Cu Doped CdS Nanoparticles

EDTA surfactant assisted bare and Cu doped CdS nanoparticles were prepared by simple chemical coprecipitation method. As the prepared samples were characterized by energy dispersive analysis of X-rays (EDAX), X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), Raman spectroscopy and photoluminescence spectroscopy (PL). Existence of Cu in host lattice with near stoichiometric ratio was corroborated by EDAX spectra. X-ray diffraction patterns revealed that cubic structure as that of CdS host lattice. TEM images suggested that spherical nature of nanoparticles with a size ranging from 4–6 nm. Room temperature photoluminescence (PL) spectra revealed that pristine host lattice nanoparticles demonstrate a strong green emission peak located at 525 nm as well as weak red emission shoulder situated at 598 nm. Auxiliary in Cu doped CdS samples, the luminescence intensity was gradually reduced as well as the green emission peak was shifted to red region (660 nm). With increase of Cu content in host matrix a red shift is found in the PL emission peak.

Photoluminescence Properties of (Ba1-(x+y)SrxEuy)2Si6O12N2 Phosphors for White LED Applications

(Ba1-(x+y)SrxEuy)2Si6O12N2 oxynitride phosphors were successfully synthesized by the solid-state reaction method at 1200°C under a H2(5%) + N2(95%) atmosphere. The Sr2+ content (x) was varied in the range 0-0.6 and the Eu2+ content varied in the range 0.05-0.25, with the Si/(Ba+Sr+Eu) ratio fixed at 3. Results showed that the emission characteristics of (Ba1-(x+y)SrxEuy)2Si6O12N2 phosphors under UV or blue-light excitation was strongly dependent on the chemical composition. The phosphor (Ba0.95Eu0.05) Si6O12N2 showed an intense green emission peak at 520 nm, whilst the phosphor (Ba0.45Sr0.5Eu0.05)Si6O12N2 had a weaker emission maximum at 548 nm. Ba2+ substitution with Sr2+ decreased the lattice volume of the (Ba1-(x+y)SrxEuy)2Si6O12N2 phosphors and was responsible for the red-shift in the emission peak. Optimization of the Eu2+ concentration at a fixed Sr2+ content of 0.2 identified the phosphor (Ba0.65Sr0.2Eu0.15)2Si6O12N2 as a potential alternative to YAG:Ce yellow phosphors for white LED applications.

Photoluminescent Properties of Al Doped ZnO by Microwave Induced Combustion Method

Al-doped ZnO nanomaterials were synthesized by microwave-induced combustion method using urea as main fuel, aluminum nitrate provide doping ions and zinc nitrate as oxidant. The effects of microwave power, amount of urea and ratio aluminum nitrate to zinc nitrate on the properties of synthesized sampler were investigated .X-ray, diffraction(XRD), scanning electron microscope(SEM), and photoluminescence(PL) were used to characterize the properties of the sample respectively. The experimental results show that ZnO nanomaterials with cubic ZnO crystal phase of best optical property are obtained at 340W when molar ratio of the zinc nitrate to aluminum nitrate is 40% and fuel just completely reaction. The average primary granularity of the synopsized sample is about 56rnm estimated according to Scherrer Equation. PL test results indicate that the Ultraviolet(UV) emission peak in 360nm can be attributed to the recombination of free excitations through an excitation-excitation collision process, and the green emission peak in 470nm is commonly referred to a deep-level or trap-state.

Preparation and Optical Properties of Carbon Fiber/ZnO Core-Shell Structure by a Simple Method

A core-shell structure material, carbon fiber/ZnO was prepared by a surface modification precipitation process in aqueous solution. The structure, absorptive properties and photoluminescence properties of the composites were investigated. Results showed that the energy bandgap of samples calculated from the absorptive spectra was about 3.30eV. The green emission peak of the samples was ascribed to the oxygen vacancies.

Non-Linear Optical Properties of Zinc Oxide Nanowires

High quality zinc oxide (ZnO) nanowires were grown on n-type Si (100) using vapor-liquid-solid process. We obtained the photoluminescence spectra of ZnO nanowires based on nonlinear optical process using an ultrashort wavelength femtosecond laser as a pumping source. The spectra shows the second harmonic generation phenomenon, as well as the exciton–exciton collision peak at 388 nm and the green emission peak at 515 nm caused by oxygen vacancy. A laser emission peak near 392 nm was observed when pump intensity surpassed 52 mJ/cm2 and a sharp peak about 0.5 nm wide emerged when the energy intensity reached 700 mJ/cm2. We attribute this excitation process to a two-photon absorption process enhanced by Rabi oscillation.