Md. I. Zahid, A. Malarkodi, Sreenarayanan Meera, K. Meera, K.S. Joseph Wilson and R. Mohan Kumar
Single crystal of sodium 4-hydroxybenzenesulfonate dihydrate (Na-4-HBS) was grown from an aqueous solution by slow evaporation method. Powder X-ray diffraction study was carried out to identify the lattice parameters of the crystal. FT-IR spectral analysis confirmed the existence of various functional groups in the compound. The optical transmittance, cut-off wavelength and band gap energy were estimated from the UV-Vis studies. Photoluminescence studies revealed the transition mechanism by optical excitation. The variation of dielectric properties and AC conductivity of the grown crystal with frequency was studied at different temperatures. Measurements of mechanical properties of Na-4-HBS were carried out to find the hardness of the material. The laser induced surface damage threshold and relative second harmonic generation nonlinear optical properties of the grown crystal were studied using Q-switched Nd:YAG laser.
K. Ulutas, S. Yakut, D. Bozoglu, D. Deger, M. Arslan and A. Erol
Pure GaAs and GaAs1−xBix alloys with different Bi ratios (1 %, 2.5 %, 3.5 %) fitted with silver contacts were measured with a dielectric spectroscopy device. Dielectric characterization was performed at room temperature in the frequency range of 0.1 Hz to 1 MHz. GaAs exhibits three relaxation regions corresponding to space-charge, dipolar and ionic polarizations in sequence with increasing frequency while GaAs1−xBix samples show only a broad dipolar polarization in the same frequency range. This result proves the filling of the lattice with Bi through making a new bonding reducing the influence of ionic polarization. This finding supports the previous results concerning optical properties of GaAs1−xBix, presented in the literature.
A novel reddish-orange emitting phosphor Eu-activated KLaSiO4 was synthesized by the conventional solid-state reaction at 1200 °C. The luminescence properties of KLaSiO4:Eu phosphor were investigated, and the critical concentration of the activator ion (Eu3+) was established as 0.02 mol per formula unit. Chromaticity coordinates of a typical KLa0.98SiO4:0.02Eu phosphor were x = 0.614 and y = 0.385. The phosphor exhibited reddish-orange luminescence with dominating emission at 612 nm, corresponding to 5D0 → 7F2 of Eu3+. Furthermore, the phosphor was characterized by excellent thermal stability, implying its potential use in white light emitting diodes.
Anu Dhupar, Suresh Kumar, Vandana Sharma and J.K. Sharma
In the present work, mixed structure Zn(S,O) nanoparticles have been synthesized using solution based chemical coprecipitation technique. Two different zinc sources (Zn(CH3COO)2·2H2O and ZnSO4·7H2O) and one sulfur source (CSNH2NH2) have been used as primary chemical precursors for the synthesis of the nanoparticles in the presence and absence of a capping agent (EDTA). The structural, morphological, compositional and optical properties of the nanoparticles have been analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transmission infra-red (FT-IR) and UV-Visible (UV-Vis) spectroscopy. XRD revealed the formation of mixed phases of c-ZnS, h-ZnS and h-ZnO in the synthesized nanoparticles. The surface morphology was analyzed from SEM micrographs which showed noticeable changes due to the effect of EDTA. EDX analysis confirmed the presence of zinc, sulfur and oxygen in Zn(S,O) nanoparticles. FT-IR spectra identified the presence of characteristic absorption peaks of ZnS and ZnO along with other functional group elements. The optical band gap values were found to vary from 4.16 eV to 4.40 eV for Zn(S,O) nanoparticles which are higher in comparison to the band gap values of bulk ZnS and ZnO. These higher band gap values may be attributed to the mixed structure of Zn(S,O) nanoparticles.
Crystallization of γ-glycine in the presence of selected concentration (9 g/mL) of tailor-made additive magnesium sulfate heptahydrate salt (MgSO4·7H2O) has been studied at ambient temperature by adopting slow solvent evaporation procedure. The morphological modifications of glycine crystals grown from pure aqueous solutions of glycine and from glycine solutions containing magnesium species in the amount of 0.1 g/mL to 16 g/mL have been investigated thoroughly. The crystalline nature and phase identification of the crystalline material were confirmed by X-ray powder diffraction and SXRD studies. NMR studies revealed the information about the molecular conformation in solution, phase changes, functional groups and chemical environment. FT-IR spectra revealed distinct difference between α and γ-glycine polymorphs in the region around 880 cm−1 to 930 cm−1. The grown γ-glycine crystal had a lower cut-off value at 200 nm and the bandgap value evaluated from the Tauc plot was found to be 5.83 eV. The marked differences between α and γ-polymorphs of glycine were also revealed by DSC thermograms. The mechanical strength of the γ-glycine crystal was studied with the help of Vickers microhardness instrument. Kurtz-powder NLO study proved the generation of second harmonics (i.e. green light emission) in the grown γ-glycine crystal and its efficiency was calculated as 1.44 times better than that of the reference material potassium dihydrogen phosphate.
Omer Kaygili, Niyazi Bulut, Tankut Ates, Ismail Ercan, Suleyman Koytepe, Turgay Seckin, Cengiz Tatar, Bayram Gunduz and Hanifi Kebiroglu
In the present study, the dopant effect of Zn on the crystal structure, thermal properties and morphology of magnesium aluminate (MgAl2O4) spinel (MAS) structure was investigated. A pure and two Zn-containing MASs (e.g. MgAl1.93Zn0.07O4 and MgAl1.86Zn0.14O4) were synthesized for this purpose via a wet chemical method, and the as-prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, differential thermal analysis (DTA), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy techniques. It was found that the crystal structure, thermal properties and morphology of the MAS system change with the increase in the amount of Zn. MgO phase formation was observed. The values of the lattice parameter, unit cell volume and crystallite size increased, and the crystallinity percentage decreased. The morphology was also affected by adding of Zn.
Madiha Sarfraz, Nasar Ahmed, Khizar-ul-Haq, Shabnam Shahida and M. A. Khan
Transition metals, such as chromium (Cr) and manganese (Mn) doped zinc oxide (ZnO) magnetic nanoparticles, were synthesized via sole gel auto-combustion method. The prepared magnetic (Zn1−(x+y)MnxCryO, where x, y = 0, 0.02, 0.075) nanoparticles were calcined in an oven at 6000 °C for 2 hours. The morphologies of the nanoparticles were investigated using different techniques. X-ray diffraction (XRD) analysis revealed that the hexagonal wurtzite structure of the synthesized nanoparticles was unaffected by doping concentration. The crystallite size measured by Scherrer formula was in the range of 32 nm to 38 nm at different doping concentrations. Nanosized particles with well-defined boundaries were observed using a field emission scanning electron microscopy (FE-SEM). Fourier transform infrared (FT-IR) spectra showed a wide absorption band around 1589 cm−1 in all the samples, corresponding to the stretching vibration of zinc and oxygen Zn–O bond. A blue shift in optical band gaps from 3.20 eV for ZnO to 3.08 eV for Zn0.85Mn0.075Cr0.075O nanoparticles was observed in diffuse reflectance spectra, which was attributed to the sp-d exchange interactions. The field-dependent magnetization M-H loops were measured using vibrating sample magnetometer (VSM). The VSM results revealed diamagnetic behavior of the ZnO nanoparticles which changed into ferromagnetic, depending on the doping concentration and particle size. The compositions of Zn, Cr, Mn and O in the prepared samples were confirmed by using the energy dispersive X-ray spectroscopy (EDX). Our results provided an interesting route to improve magnetic properties of ZnO nanoparticles, which may get significant attention for the fabrication of magnetic semiconductors.
In the present work, a new organic second order NLO material: L-isoleucinium p-toluenesulfonate monohydrate (LIPT) is synthesized and reported for the first time. The LIPT is crystallized in a non-centrosymmetric monoclinic space group P21. Structural and hydrogen bond nature of the compound is analyzed using single crystal X-ray diffraction studies. The crystal exhibits very good optical properties such as wide optical transparency in the region of 210 nm to 1100 nm and the ultraviolet wavelength emission (λ = 283 nm). The second harmonic generation efficiency is found to be 1.7 times the standard KDP. Good thermal, mechanical properties and low dielectric constant at high frequency range show that the material may be a potential candidate for optoelectronic applications.
In this communication, we report on Cu2SnS3 quantum dots synthesized by the solvothermal process using different solvents. The optical properties of the quantum dots are analyzed by UV-Vis-NIR and photoluminescence spectroscopy. The results suggest that Cu2SnS3 material has tunable energy bandgap and appropriate wavelength for fabrication of light emitting diodes and laser diodes as sources for fiber optic communication. They exhibit wide absorption in the near infrared range. Further morphological studies with the use of atomic force microscope confirm the surface topography and the existence of quantum dots. The observed characteristics prove the efficiency of Cu2SnS3 quantum dots for O-band wavelength detection used in fiber optic communication and solar cell applications.
This paper attempts to describe an effective method for producing a composite of quantum dots consisting of CdSe (core) with CdS (shell). This nanoparticles composite was synthesized from modified organometallic precursors. The sizes of the nanoparticles were estimated from X-ray diffraction data using Debye-Scherer formula and compared with high resolution electron microscopy (HRTEM) and optical spectra. The shape of CdSe/CdS NPs is nearly spherical and revels that the CdS shell with the thickness ~0.6 nm almost fully covers the CdSe core (higher contrast). Using UV-Vis spectroscopy, a systematic red shift in the absorption and emission spectra was observed after the deposition of CdS which confirms the shell growth over the CdSe core. In the CdSe/CdS core/shell structure, the holes are confined to the core, while the electrons are delocalized as a result of similar electron affinities of the core and the shell. The increased time of synthesis resulted in shell thickness increase. The observed properties of prepared CdSe/CdS QDs demonstrate the capability of the nanocomposite for using in the optoelectronics and photonics devices.