Optically transparent single crystals of 2-amino 4-methylpyridinium salicylate were successfully grown by slow evaporation solution growth technique at room temperature. The grown crystal was characterized by various characterization techniques such as single crystal X-ray diffraction, Fourier transform infrared microscopy, optical, dielectric and Z-scan studies. The presence of various functional groups was identified by Fourier transform infrared technique. UV-Vis-NIR studies implied the absence of absorption in the visible region. Dielectric studies were carried out in the frequency range from 50 Hz to 5 MHz. Thermogravimetric/differential thermal analysis and nuclear magnetic resonance spectra studies were also performed for the grown crystal. Nonlinear refractive index, absorption coefficient and third order nonlinear optical susceptibility of the crystals were evaluated by Z-scan studies.
S. Balaprabhakaran, J. Chandrasekaran, B. Babu, R. Thirumurugan and K. Anitha
Hexamethylenetetramine succinate was synthesized and good quality single crystals with the size of 14 mm × 6 mm × 4 mm were grown by the slow evaporation solution growth technique at room temperature. The single crystal XRD revealed that the grown crystal belongs to the monoclinic system with the space group of P21/c. The presence of functional groups in the crystal was identified using FT-IR technique. The optical behavior was examined through UV-Vis-NIR studies. The photoconductivity study exhibited the positive photoconductivity nature of the grown crystal. Microhardness studies revealed the soft nature of the crystal. The nonlinear refractive index (n2), nonlinear absorption coefficient (β) and third order nonlinear optical susceptibility χ(3) of the crystals were measured by Z-scan studies.
Zhaoyong Wang, Weifen Jiang, Yifan Lu, Xinlian Wang, Xiaoya Huang and Ning Yao
TiO2 thin films were deposited by the energy filtrating magnetron sputtering (EFMS) technique and the traditional direct current magnetron sputtering (DMS) technique. The influence of the filtering electrode mesh number on the structure and optical properties of TiO2 thin films was investigated. The structure, surface morphology and optical properties were characterized by XRD, SEM and ellipsometric spectroscopy, respectively. Results show that the TiO2 thin films deposited by the DMS and EFMS techniques at the same deposition parameters are composed of the anatase phase exclusively. TiO2 thin films deposited at lower deposition rate by the EFMS technique have lower crystallinity, smaller particle size and smoother surface. With increasing the mesh number, the refractive index, extinction coefficient and optical band gap are larger.
Dinara Sobola, Pavel Kaspar, Jindrich Oulehla, Ştefan Ţălu and Nikola Papež
The purpose of this work is the study of the correlation between the thickness of tantalum pentoxide thin films and their three-dimensional (3D) micromorphology. The samples were prepared on silicon substrates by electron beam evaporation. The differences in surface structure of the processed and reference samples were investigated. Compositional studies were performed by energy-dispersive X-ray spectroscopy. Stereometric analysis was carried out on the basis of atomic force microscopy (AFM) data, for tantalum pentoxide samples with 20 nm, 40 nm, 60 nm, 80 nm and 100 nm thicknesses. These methods are frequently used in describing experimental data of surface nanomorphology of Ta2O5. The results can be used to validate theoretical models for prediction or correlation of nanotexture surface parameters.
Mounia Guergouri, Rafik Bensegueni and Leïla Bencharif
New monomer, 4,4’-[(2,3-dihydrothieno[3,4-b][1,4]diorin-5-yl)vinyl]-1,1’-biphenyl (BPE), was synthesized, characterized and polymerized electrochemically via a potentiostatic method. The corresponding polymer poly(4,4’-[(2,3-dihydrothieno[3,4-b][1,4] diorin-5-yl)vinyl]-1,1’-biphenyl) (PBPE) obtained as a thin-layer film, was characterized by cyclic voltammetry, X-ray photoelectron spectroscopy, infrared spectroscopy and UV-Vis spectroscopy. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the obtained polymer were determined from cyclic voltammograms as –4.89 eV and –3.81 eV, respectively. Its optical and electrochemical band gaps were calculated, and found to be 1.08 eV and 1.49 eV, respectively. PBPE can be used as a donor material in bilayer organic photovoltaic solar cells having PCBM as acceptor material.
Adedibu Sunny Akingboye, Isaac Babatunde Osazuwa and Muraina Zaid Mohammed
Electrical resistivity tomography (ERT) was used for delineating significant subsurface hydrogeological features for sustainable groundwater development in Etioro-Akoko area, Southwestern Nigeria. This study was necessitated by challenges posed on groundwater supplies from wells and boreholes in Etioro-Akoko and the neighbouring fast growing towns and villages. Field data were acquired over the area with ABEM Lund Resistivity Imaging System and were subsequently processed and inverted through RES2DINVx64 software. Results showed four distinct subsurface layers: topsoil, weathered layer, fractured bedrock and fresh bedrock (basal unit). Localised bedrock depressions occasioned by fracturing and deep weathering of less stable bedrock minerals were delineated with resistivity and thickness values ranging from 50 to 650 Ωm and 12 to > 25 m, respectively. The localised depressions mirrored uneven bedrock topography and served as the preferential groundwater storage and hydrogeological zones in the area. The two hydrogeological zones significant for groundwater development included overburden-dependent aquifers and fractured dependent bedrock aquifers. It was, therefore, concluded that groundwater storage potential was depended on hydrogeological zones particularly at major localised bedrock depressions where fractures and groundwater recharges/discharges were evident. Wells and boreholes were proposed at bedrock depressions with thickness value not less than 12 and > 25 m, respectively, for enhanced groundwater sustainability and quality assurance in the area.
S. Ajinsundar, R. S. Rimal Issac, S. Gopalakrishnan and N. Joseph John
In the present work, with an aim of developing new useful materials, carbon dot-graphene oxide-zinc oxide (CGZ) nanocomplexes were synthesized by the wet chemical method. Structure, morphology and chemical composition of prepared GCZ nanoparticles were determined by carrying out X-ray diffraction, scanning electron microscopy, Fourier transform infrared and energy dispersive X-ray absorption spectral measurements. The strong absorption band observed in the UV region for the prepared samples can be attributed to the band edge absorption. The dielectric parameters, viz. dielectric constant (∈r), dielectric loss (tanδ) and AC electrical conductivity (σ AC) were determined at various temperatures in the range of 30 °C to 150 °C at two different frequencies (100 Hz and 1 kHz). DC conductivity (σDC) measurement was also carried out at various temperatures in the range of 30 °C to 150 °C. In addition, the enhanced photocatalytic activity of CGZ has been explained and the mechanism elucidating the excellent performance of CGZ has been proposed.
Pravin Kumar Singh, S.K. Tripathi and D.K. Dwivedi
Thin films of Ge10–xSe60Te30Inx (x = 0, 2, 4 and 6) were developed by thermal evaporation technique. The annealing effect on the structural properties of Ge10–xSe60Te30Inx (x = 0, 2, 4 and 6) films has been studied by X-ray diffraction (XRD). The XRD results indicate amorphous nature of the as-prepared films whereas crystalline phases in annealed films were identified. Structural parameters such as average crystallite size, strain, and dislocation were determined for different annealing temperatures. Effect of annealing on optical constants of prepared films has been explored using UV-Vis spectrophotometer in the wavelength range of 400 nm to 1000 nm. Various optical constants were determined depending on annealing temperature. It has been noticed that the film transparency and optical bandgap Eg have been reduced whereas the absorption coefficient α and extinction coefficient k increased with increasing annealing temperature. It was found that the prepared samples obey the allowed direct transition. The reduction in optical bandgap with annealing temperature has been described by Mott and Davis model. Due to annealing dependence of the optical parameters, the investigated material could be utilized for phase change memory devices.
To enhance interfacial bonding between carbon fibers and epoxy matrix, the carbon fibers have been modified with multiwall carbon nanotubes (MWCNTs) using the dip- coating technique. FT-IR spectrum of the MWCNTs shows a peak at 1640 cm−1 corresponding to the stretching mode of the C=C double bond which forms the framework of the carbon nanotube sidewall. The broad peak at 3430 cm−1 is due to O–H stretching vibration of hydroxyl groups and the peak at 1712 cm−1 corresponds to the carboxylic (C=O) group attached to the carbon fiber. The peaks at 2927 cm−1 and 2862 cm−1 are assigned to C–H stretching vibration of epoxy produced at the defect sites of acid-oxidized carbon fiber surface. SEM image shows a better interface bonding between the fiber and the matrix of modified composites (MWCNTs-CF/Ep) than those of unmodified composite. The loss factor curve of CF-MWCNTs/Ep composites is the narrowest compared with neat epoxy and CF/Ep composites which evinces that the length distribution range of molecular chain segments in the matrix is the narrowest. From the dependence of the AC conductivity on temperature, we can see that σAC increases when temperature increases. The increase in electrical conductivity of the composites may be a result of the increased chain ordering due to annealing effect. The use of MWCNTs to modify the surface of carbon fiber resulted in a large amount of junctions among MWCNT causing an increase in the electrical and thermal conductivity by forming conducting paths in the matrix. The MWCNTs-CF/Ep composite shows better thermal stability than unmodified composites. The strong interaction between CF and MWCNTs can retard diffusion of small molecules from the resin matrix at high temperature and hence, result in the improved thermal stability of the modified CF/Ep composite.
Nonlinear optical single crystals of L-histidine nitrate (LHN) as well as 0.05 mol % Y2+ doped LHN and 0.10 mol % Y2+ doped LHN were successfully grown by slow evaporation technique at room temperature. The lower cutoff wavelength and transmittance were 339 nm, 343 nm, 347 nm and 84 %, 86 % and 87 % for LHN, 0.05 mol % and 0.10 mol % yttrium doped LHN, respectively. Powder XRD studies revealed that the grown materials belong to an orthorhombic system with the space group P212121. FT-IR peak at 534 cm−1 due to yttrium coordinated with oxygen was observed. The EDAX analysis confirmed the presence of such elements as C, N, O and Y in the grown materials. High intensity PL emission peak was obtained at 420 nm.