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Open access

Tran Hoang Quang Minh, Nguyen Huu Khanh Nhan, Nguyen Doan Quoc Anh, Tran Thanh Nam and Hsiao-Yi Lee

Abstract

Based on some advantageous properties, such as fast response time, environment friendliness, small size, long lifetime, and high efficiency, white LEDs are increasingly used in common illumination applications. In this research, by co-doping of redemitting Sr2Si5N8:Eu2+ phosphor and adding SiO2 particles to yellow-emitting YAG:Ce phosphor compounds, a new approach for improving color uniformity and color rending index of remote-phosphor structure white LEDs is proposed and demonstrated. The obtained results clearly indicate that the color rendering index (CRI) and color uniformity (DCCT) significantly depend on Sr2Si5N8:Eu2+ concentration. The results provide a potential practical solution for manufacturing remote-phosphor white LEDs (RP-WLEDs) in the near future.

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Dawei Gao, Chunxia Wang, Yu Jian, Weiwei Li and Pengyu Dong

Abstract

Highly ordered TiO2 nanotube arrays (TiO2 NTs) were prepared by anodic oxidizing method on a surface of Ti substrate. Fabrication of nitrogen-doped TiO2 nanotube arrays (N-TiO2 NTs) was carried out by immersion in ammonia solution. CdS nanoparticles loaded N-doped TiO2 nanotube arrays (CdS/N-TiO2 NTs) were obtained by successive ionic layer adsorption and reaction (SILAR) technique. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL) emission spectra and ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy (DRS). The results indicate that the TiO2 nanotube diameter and wall thickness are 100 nm to 120 nm and 20 nm to 30 nm, respectively. Moreover, the morphology and structure of the highly ordered TiO2 NTs are not affected by N-doping. Furthermore, CdS nanoparticles are evenly distributed on the surface of TiO2 NTs. Finally, the photocatalytic activity of CdS/N-TiO2 NTs was evaluated by degradation of MO under visible-light irradiation. Compared with TiO2 NTs, N-TiO2 NTs, CdS/N-TiO2 NTs exhibited enhanced photocatalytic properties, and the highest degradation rate of CdS/N-TiO2NTs could reach 97.6 % after 90 min of irradiation.

Open access

Esra Öztürk and Erkul Karacaoglu

Abstract

In this study, silicate systems, M2SiO4 (M = Ca, Zn) were produced by solid state reaction and doped with 1 mol% Eu3+ rare-earth ion. Their heat treatments, which were conducted at 1200 °C and above for minimum 3 hours under an open atmosphere, were applied according to the DTA/TG results. Powder X-ray diffraction XRD analyses were performed to determine the phase properties of the phosphor systems after the sintering process. It was proved that the structures of two of the phosphor systems were well formed in except that the Zn2SiO4 had some ZnO secondary phases. The expected photoluminescence (PL) results were presented and the transitions of the Eu3+ ions were observed for both phosphors.

Open access

Fatemeh Mostaghni and Yasaman Abed

Abstract

In this study, we present a systematic study of linear and nonlinear optical properties of Para Red with the aim of Z-scan technique and quantum mechanical calculations. The Z-scan experiments were performed using a 532 nm Nd: YAG (SHG) CW laser beam. Para Red exhibited a strong nonlinear refractive index, nonlinear absorption coefficient and third-order nonlinear susceptibility 3.487 × 10-6cm2/W, 2.341 × 10-1cm/W and 2.157 × 10-4esu, respectively. Also, quantum chemical analysis was used for the calculation of the dipole moment μ, dipole polarizability α, anisotropy of polarizability ∆α and molecular hyperpolarizabilities (β,γ). The results revealed that Para Red has large first and second hyperpolarizabilities. However, from the obtained results, it was found that Para Red can be a promising material for applications in the development of non-linear optical materials.

Open access

Maxwell Selase Akple and Holali Kwami Apevienyeku

Abstract

A novel and low-cost synthesis of tungsten disulfide (WS2) transition metal dichalcogenide was carried out via gas-solid reaction in a horizontal quartz reactor. In this process, the prepared hollow WO3 precursor was sulfided with CS2 at 550 °C at different durations under N2 gas atmosphere. The as-prepared WS2 samples were formed by substitution of O by S during the sulfidation process. The characterization of these samples was performed employing X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), Brunauer-Emmett-Teller (BET) specific surface area, X-ray photoelectron spectroscopy (XPS) and UV-Vis absorption spectroscopy. The characterization results showed that the as-prepared WS2 samples were of high quality and purity. No significant differences were observed in various WS2 samples synthesized during different sulfidation periods. The calculated results obtained from the density functional theory (DFT) indicate that WS2 has an indirect band gap of ca. 1.56 eV, which is in agreement with experimental band gap of ca. 1.50 eV. Combining the experimental and DFT results suggests that the novel method used in the synthesis of WS2 has a potential application for large scale production. The obtained WS2 are of high quality and can be implemented in photocatalysis, catalysis, photovoltaics, optoelectronic devices and photosensor devices.

Open access

Durga Verma, R. P. Patel and Mohan L. Verma

Abstract

In the present paper, TL and PL study of Dy3+doped Sr2SiO4:Eu2+phosphor is reported. A polycrystalline sample of Sr2SiO4:Eu2+, Dy3+ was prepared by combustion method. The obtained phosphor was characterized by powder X-ray diffraction, scanning electron microscopy, UV-Vis spectroscopy, PL and thermoluminescence. The results of the XRD studies obtained for Sr2SiO4:Eu2+, Dy3+ phosphor revealed its monoclinic structure. The average crystallite size was calculated as 12.77 nm. Thermoluminescence study was carried out for the phosphor using UV irradiation and a single glow peak was found. The thermoluminescence glow curves of the samples were measured at various concentrations of co-dopant. The kinetic parameter has been calculated using Chen’s glow curve method. In this paper, the photoluminescence and afterglow behavior of these phosphors are reported.

Open access

Ali A. Aljubouri, Abdulqader D. Faisal and Wafaa K. Khalef

Abstract

Single phase, adherent films of copper oxide nanowires (CuO NWs) were successfully grown on a glass substrate. Titanium nanofilm was pre-coated on the glass substrate to assist the growth of a layer adherent to the substrate. The copper film of 1.5 μm thickness was deposited via physical vapor deposition technique followed by thermal oxidation in air at various temperatures for 4 h. The product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis) and Fourier transformation infrared (FT-IR) spectroscopy to find the crystal structure, morphology, phases, and optical properties of the deposited films. The CuO NWs film with 60%transmittance at wavelengths greater than 800 nm was obtained. It can be used as an infrared thermal imaging filter and in optoelectronic devices. The fabricated temperature sensor exhibited high sensitivity in the temperature range of 20 °C to 180 °C.

Open access

Deniss Brodņevs

Abstract

Remotely piloted operations of lightweight Unmanned Air Vehicles (UAV) are limited by transmitter power consumption and are always restricted to Line-of-Sight (LOS) distance. The use of mobile cellular network data transfer services (e.g. 3G HSPA and LTE) as well as long-range terrestrial links (e.g. LoraWAN) makes it possible to significantly extend the operation range of the remotely piloted UAV. This paper describes the development of a long-range communication solution for the UAV telemetry system. The proposed solution is based on (but not restricted to) cellular data transfer service and is implemented on Raspberry Pi under Gentoo Linux control. The goal of the project is to develop a flexible system for implementing optimized redundant network solutions for the Non-LOS remote control of the UAV

Open access

Anurag V. Tiwari and Y R M Rao

Abstract

The rutting and cracking of pavements has become very common problem in India. Also the quantity of plastic waste has significantly increased in the recent year due to industrialization and population growth. Improper disposal of these plastic wastes has caused various environmental problems, hence the alternative use of waste plastic in bituminous concrete for road construction has been encouraged by the community. In the present study the Indirect Tensile Strength Test has been carried out on Marshall Samples confirming to ASTM D6931-12. Three different processes (dry process, wet process and combined process) of mixing of waste plastic were used during experimentation. It was found that the indirect tensile strength (ITS) and tensile strength ratio (TSR) of sample significantly increase up to 8%, 6% and 12% for dry process, wet process and combined process respectively for LDPE and HDPE type of waste plastic.