S. Reena Devi, S. Suresh, S. Kalaiyarasi, M. Nizammohideen and R. Mohan Kumar
A novel 4-methylpyridinium 3-nitrophthalate (4MP3NP) was synthesized and the crystals were grown by using slow evaporation method. The structural data of the grown crystal was collected by single crystal X-ray diffraction. It revealed that the 4MP3NP crystal belongs to triclinic crystal system with a space group P1. Structure of the synthesized compound was established using SHELXL 97 program package. The crystalline nature and composition of the grown crystal was established using high resolution X-ray diffraction and FT-IR analyses. UV-Vis transmittance and photoluminescence studies revealed the optical transmission window and electronic transition mechanism of ions, respectively. The laser damage threshold of the grown crystal was estimated by Nd:YAG laser and these results were mutually related to specific heat capacity of the grown crystal. The third-order nonlinear optical susceptibility of the grown crystal was studied by Z-scan technique.
In this work, multi-walled carbon nanotubes (MWCNTs) with significantly different mean diameters were produced by catalytic CVD over Ni and Co-based supported catalysts. Our results indicate that Ni nanoparticles in the Ni/MgO catalyst are responsible for controlling the inner diameters of the carbon nanotubes. Contrary, Co nanoparticles in the Co/MgO catalyst control the outer diameters of MWCNTs. The “base-growth” mechanism and smaller diameters of the MWCNTs grown on the Ni/MgO catalyst are associated with a strong metal-support interaction (SMSI) resulting from NixMg1−xO mixed oxide formation. The concept of the weak metal-support interaction (WMSI) between Co nanoparticles and MgO for the Co/MgO catalyst confirms the “tip-growth” mechanism of the MWCNTs.
Zohra Nazir Kayani, Mahek Zaheen Butt, Saira Riaz and Shahzad Naseem
NiO nanoparticles were fabricated by sol-gel route using ammonium hydroxide and nickel nitrate as precursors. The NiO nanoparticles were calcinated at 400 °C and 1000 °C. The nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), thermogravimetry analysis/differential thermal analysis (TGA/DTA). The structural properties were evaluated by X-ray diffraction (XRD). XRD confirmed the formation of well-crystallized and high purity NiO phase. The XRD showed that the peaks were sharpened and the crystallite size increased as the calcination temperature increased. The average crystallite size ranged from 12 nm to 20 nm, when calcined at temperatures 400 °C and 1000 °C, respectively. Fourier transform infrared spectroscopy (FT-IR) revealed the chemical composition and confirmed the formation of NiO nanoparticles. The nanoparticles showed paramagnetic behavior.
Single-phase Eu3S4 was obtained via CS2 gas sulfurization of Eu2O3 nanospheres at 773 K for longer than 0.5 h. The primary particle size of Eu3S4 became larger than that of Eu2O3 during the sulfurization process. Pure synthetic Eu3S4 powders were unstable and transformed to EuS at 873 K under vacuum. Eu3S4 compacts were sintered in temperature range of 773 K to 1173 K and they transformed to EuS at 1473 K during spark plasma sintering. Specific heat of sintered Eu3S4 did not show an anomalous behavior in the range of 2 K to 50 K. The magnetic susceptibility of polycrystalline Eu3S4 followed a Curie-Weiss law from 2 K to 300 K. Magnetization of polycrystalline Eu3S4 was larger than that of single crystal Eu3S4 when the magnetic field was less than 3.5 kOe.
Theoretical formalism based on the orthogonalized plane wave method supplemented by a potential scaling scheme was used to predict the temperature dependence of energy gap of CuSi2P3 semiconductor. A computer code in Pascal was used to perform the variation of fundamental energy gap with temperature in the range of 150 K to 800 K. The dependence of energy gap on temperature for lattice dilation contribution, lattice vibration contribution and total temperature effect were performed separately. The results revealed that, as temperature increases, the top of the valence band and the bottom of the conduction band increase, while the energy band gap decreases. Generally, at low temperatures, the energy gap varies slowly and exhibits a nonlinear dependence and approaches linearity as temperature increases. The calculated energy gap of CuSi2P3 at T = 300 K is 0.4155 eV. The temperature coefficients in the linear region due to lattice dilation contribution, lattice vibration contribution and total temperature effect were calculated as –1.101 × 10−5 eV/K, –1.637 × 10−4 eV/K and –1.7523 × 10−4 eV/K, respectively. Also, the ratio of temperature coefficient of the energy gap due to LV contribution to its value and LD contribution in the linear region is equal to 14.868. That ratio is compared to those of CuGe2P3 and III-V compounds, where those of the latter show a systematic change with Eg. Moreover, the Eg of all the compounds shows a quadratic dependence on the inverse of mean bond length.
Mohd Anis, G.G. Muley, Mohd Shkir, S. Alfaify and H.A. Ghramh
Present investigation is aimed to explore the single crystal growth, microhardness and third order nonlinear optical (TONLO) properties of Nd3+ doped zinc tris-thiourea sulphate (ZTS) crystal. The commercial slow solvent evaporation technique has been chosen to grow a good quality ZTS (12 mm × 0.5 mm × 0.3 mm) and Nd3+ doped ZTS (11 mm × 0.6 mm × 0.4 mm) single crystals. Vickers microhardness test has been employed to analyze the influence of Nd3+ dopant on the hardness behavior of ZTS single crystal. The TONLO effects occurring in Nd3+ doped ZTS single crystal have been evaluated by means of Z-scan technique using a He–Ne laser operating at 632.8 nm. The close and open aperture Z-scan configuration have been used to determine the nature of TONLO refraction n2 and absorption β, respectively. The magnitudes of vital TONLO parameters, such as refraction n2, absorption coefficient β, figure of merit and susceptibility χ3 of the Nd3+ doped ZTS single crystal, have been determined using Z-scan transmittance data. The n2, β, and χ3 of Nd3+ doped ZTS single crystal were found to be of the order of 10−10 cm2/W, 10−6cm/W and 10−5 esu, respectively.
Titanium dioxide (TiO2) is one of the most favored metal oxide semiconductors for the use as photoanode in photoelectrochemical cells (PEC) splitting the water into hydrogen and oxygen. However, the major impediment is its large bandgap that limits its utilization as photoanode. Doping has evolved as an effective strategy for tailoring optical and electronic properties of TiO2. This paper describes the synthesis of undoped as well as iron (Fe, cationic) and nitrogen (N, anionic) doped nanocrystalline titanium dioxide by sol-gel spin coating method for solar energy absorption in the visible region. All the prepared thin films were characterized by X-ray diffraction and UV-Vis spectroscopy. Doping of both Fe and N into TiO2 resulted in a shift of absorption band edge towards the visible region of solar spectrum.
B.O. Adetoye, A.B. Alabi, T. Akomolafe, P.B. Managutti, N. Coppede, M. Villani, D. Calestani, A. Zappetini and C. Maurizio
One-dimensional (1D) zinc oxide (ZnO) nanostructures (nanorods) were synthesized on a glass slide and fluorine-doped tin oxide (SnO2/F or FTO) coated glass (FTO/glass) by a wet chemical method. The structural, morphological and optical analyses of the as-deposited ZnO nanostructures were performed by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and UV-Vis spectroscopy, respectively. The XRD results showed that the nanostructures as-deposited on the glass and the FTO/glass substrates were of ZnO wurtzite crystal structure, and the crystallite sizes estimated from the (0 0 2) planes were 60.832 nm and 64.876 nm, respectively. The SEM images showed the growth of densely oriented ZnO nanorods with a hexagonal-faceted morphology. The UV-Vis absorption spectrum revealed high absorbance properties in the ultraviolet range and low absorbance properties in the visible range. The optical energy band gap of the ZnO nanostructure was estimated to be 3.87 eV by the absorption spectrum fitting (ASF) method.
S. Anbu Chudar Azhagan, V.S. Kathiravan and N. Sathiya Priya
The influence of magnesium sulfate as an additive in the nucleation of α and γ-polymorphs of glycine crystallized from aqueous solutions has been explored for the first time. Based on crystallization experiments, it was concluded that lower concentration of magnesium sulfate, say less than 2 g/mL, favors α-nucleation sites, whereas the optimized concentration of magnesium sulfate impurity to yield -nucleation sites is 2 g/mL and above. The nucleation time span (in days), solubility and pH were measured for α- and γ-nucleation sites in the aqueous solutions doped with magnesium sulfate. The glycine polymorphs α- and γ-single crystals were grown by slow solvent evaporation technique at ambient temperature. Crystal habit of glycine polymorphs was investigated and analyzed using goniometry. The unit cell dimensions and space group of the as-grown crystal were identified by single crystal XRD analysis. Both α- and γ-polymorphs of glycine were characterized structurally by powder XRD studies. The percentage of magnesium present in the grown glycine crystals was estimated by inductively coupled plasma optical emission spectrometry elemental analysis (ICP-OES). The nonlinear optical properties of the γ-glycine crystals were examined by Q-switched high energy Nd:YAG laser. The second harmonic generation output efficiency of the as-grown gamma glycine single crystals was computed to be 1.31 times superior than that of the reference material potassium dihydrogen phosphate (KDP).
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.