Sn1-x Fe- x O-2 (x = 0, 1, 2, 3, and 4 %) of the diamagnetic/ferromagnetic phase were synthesized by the conventional hydrothermal method. X-ray diffraction spectra confirm that all the samples have a tetragonal structure. Electronic distribution over the unit cell of Sn1-x Fe- x O-2 showed the dependence of electronic density on the x. The crystallite size of the obtained samples was in the range of 42-72 nm. Impedance spectroscopy was employed to investigate the variation of the electrical impedance and some related parameters as frequency functions in the range of 75 k Hz-10 MHz at room temperature. The dielectric behavior was explained using the Maxwell-Wagner model of interfacial polarization. The ac conductivity results were used to evaluate the maximum barrier height, the minimum hopping distance, and the density of the localized states at the Fermi level. The effect of adding the iron ion into the tin dioxide compound was apparent, as the electrical and magnetic properties as well as the morphology were affected, although the crystal structure phase still has the same tetragonal crystal system for the different iron concentration (Fe from x = 0 up to x = 0.04) with slight variation in the lattice constants. The magnetic measurements illustrated that the Fe-doped SnO2 nanoparticles exhibit ferromagnetic ordering at room temperature. Variation of the Fe content affects the ferromagnetic characteristics of the samples.

The complex crystal and magnetic structure of strontium-doped ytterbium manganites using high-resolution neutron diffraction at low temperature starting from 2.6 K has been studied. Yb0.6Sr0.4MnO3 was crystallized with the mixed phases of crystal structure: orthorhombic with Pbnm space group enclosing Jahn–Teller Mn3+ ions, and hexagonal crystal system of P63cm space group describing JT ions free phase over the whole temperature range. From the refinement of the neutron diffraction patterns, a distinguished difference in the behaviors of the two phases was observed with a variation in temperature where opposite lattice—temperature-dependent behavior was found. The magnetic ordering in hexagonal symmetry was frustrated and was having a canted spin of Mn magnetic moments in the plane of the Г2-type symmetry. Mn ions were arranged together in the well-separated triangular layers parallel to (ab) plane as a result of the antiferromagnetic exchange interaction between the spins of atoms in the most nearest neighbors, which make the Mn spin subsystem of low-dimensional and frustrated at TN≈150 K. The other phase of the orthorhombic crystal system showed the C-type antiferromagnetic at TN≈70 K. The contribution of Yb atom in the magnetic ordering down to T = 2.6 K has not been registered. The magnetization–temperature dependence of Yb0.6Sr0.4MnO3 at different applied magnetic field was calculated using Monte Carlo simulation based on Ising model. Theoretically calculated model and experimental data were in good agreement. The complex magnetic ordering of the Yb0.6Sr0.4MnO3 for the mixed crystal structure was well described by Ising model.

Well-crystalline ZnO nanourchins were synthesized by facile hydrothermal process at low-temperature. X-rays diffraction patterns revealed that as-synthesized ZnO nanourchins exhibited good crystalline nature with typical hexagonal wurtzite phase. From the morphological characterization, the synthesized nanomaterials consisted of uniform spines and systematically arranged on a periphery and resembled to urchin like morphology. As-synthesized ZnO nanourchins were extensively utilized for photocatalyst and sensing devices. As-synthesized ZnO nanourchins as photocatalysts exhibited a good degradation rate of 98.5% within 80 min towards the degradation of acricline orange (AO) dye under UV light illumination. In sensing applications, the fabricated phenyl hydrazine chemical sensor based on ZnO nanourchin electrode accomplished high reproducible sensitivity of similar to 42.1 mu A mM(-1) cm(-2) along with a good limit of detection 78.6 mu M with correlation coefficient (R) of 0.98701. The enhanced sensing behavior and photodegradation of AO dye can be attributed to the large surface-to-volume ratio of as synthesized ZnO nanourchins, which provide large surface areas for the absorption of active oxygenated species. (C) 2014 Elsevier B.V. All rights reserved.

This paper reports the temperature-dependant electrical characteristics of n-ZnO hexagonal nanorods/p-Si heterojunction diodes. The n-ZnO hexagonal nanorods were grown on p-Si substrate by a simple thermal evaporation process using metallic zinc powder in the presence of oxygen. The spectroscopic characterization revealed well-crystalline nanorods, quasi-aligned to the substrate and possessing hexagonal shape. The as-grown nanorods exhibited a strong near-band-edge emis- sion with very weak deep-level emission in the room-temperature photoluminescence spectrum, confirming good optical properties. Furthermore, the electrical properties of as-grown ZnO nanorods were examined by fabricating n-ZnO/p-Si heterojunction assembly and the I-V characteristics of the fabricated heterojunction assembly were investigated at different temperatures. The fabricated n-ZnO/p-Si heterojunction diodes exhibited a turn-on voltage of ~5 V at different temperatures with a mean built-in-potential barrier of 1.12 eV. Moreover, the high values of quality factor obtained from I-V analysis suggested a non-ideal behavior of Schottky junction.

The present work deals with the theoretical investigation of electronic structure features and stability of adenine–thymine (AT) and rare tautomer of adenine–thymine (rAT) base pairs along with their complexes with Cu2+cation and their interactions with BN doped fullerene ( C58BN ). All the calculations have been performed with density functional theory using B3LYP functional. Electronic structures of the two base pairs are almost identical. Hence, it is rather difficult to distinguish between the two base pairs on the basis of their electronic properties. As per our theoretical calculations, we have observed that, BN modified fullerene could act as a nano-biosensor for detection of mispairing between these two complementary bases as well as their Cu2+complexes.

The Bi0.7(Ba0.8Sr0.2)0.3Fe0.7Ti0.3O3 ceramic is synthesized by a solid state reaction method and characterized by X-ray diffraction (XRD), SEM, Raman spectra and impedance spectroscopy. Besides, the XRD pattern shows perovskite phase with rhombohedral structure (R3c space group) at room temperature. Furthermore, the ferroelectric-paraelectric phase transition (TC) and G-type antiferromagnetic Neel temperature (TN) is detected by Raman spectroscopy. Meanwhile, the electrical conductivity of the sample is investigated in the temperature and the frequency range 713–773K and 100–1000kHz respectively by means of impedance spectroscopy. The Nyquist plots (−Z″ versus Z′) frequency plots are well fitted to an equivalent circuit model. The ac conductivity data obey the universal power law. The nature of variation of dc conductivity suggests Arrhenius type of electrical conductivity. The temperature dependence of the alternative current conductivity (σg) and direct current conductivity (σdc) confirm the presence of the ferroelectric–paraelectric phase transition.

Quantum chemical calculations were carried out to study the electronic structure and stability of adenine–thymine and the rare tautomer of adenine–thymine base pairs along with their Cu2+ complexes and their interactions with AlN-modified fullerene (C58AlN) using Density Functional Theory (B3LYP method). Since, these two forms of base pairs and their Cu2+ complexes have almost similar electronic structures, their chemical differentiation is an extremely difficult task. In this investigation, we have observed that AlN-doped C60 could be used as a potentially viable nanoscale sensor to detect these two base pairs as well as their Cu2+ complexes.

A capacitive sensor based on porous silicon (PSi) for detection of various polar (ethanol, methanol, acetone, acetonitrile, chloroform) and non-polar organic solvents (n-hexane, toluene) was described. The meso-PSi layer with an average pore size of 30 nm was prepared by a galvano static electrochemical etching of crystalline silicon in HF-based solution. Surface passivation was conducted by anodic oxidation process and the electrical contacts were made exclusively onto the front porous structure. The asfabricated sensor exhibits highly sensitive and reversible response toward polar organic molecules during the real-time measurements of capacitance, whereas the capacitive sensing behavior was irreversible and opposite in direction in case of non-polar solvents. The response time was in the order of acetone < methanol < acetonitrile < ethanol < chloroform. The observed response could be understood as the impact of charge redistribution on the pore walls upon organic infiltration, along with changes in the dielectric constant of the porous layer. A comparative study of such different responses is provided. Excellent repeatability of the device was obtained after twelve cyclic tests of acetone, demonstrating stability of the sensor. Long-term stability for the sensor was also observed after four weeks storage. The present approach is useful for the development of a simple, cost-effective sensor for detection of various chemical analytes. (C) 2014 Elsevier B.V. All rights reserved.

In the present study, quantum chemical calculations were carried out to investigate the electronic structures and stabilities of adenine and its rare tautomer along with their Cu2+ complexes. Density Functional Theory (B3LYP method) was used in all calculations. The two Cu2+ complexes of adenine have almost similar energies and electronic structures; hence, their chemical differentiation is very difficult. For this purpose, interactions of these complexes with AlN modified fullerene (C-60) have been studied. Theoretical investigations reveal that AlN-doped C-60 may serve as a potentially viable nanoscale sensor for detection of the two Cu2+ complexes of adenine. (C) 2014 Elsevier Ltd. All rights reserved.

Mesoporous silicon (PSi) layer was used to create highly sensitive, electrically-based sensor for detection of liquid ethanol at room temperature. The PSi nanostructure that is generated in an electrochemical etching of crystalline silicon in HF-based solution was ~ 4.5 μm thick with an average pore size of 30 nm. The as-fabricated sensor exhibits highly sensitive, reversible response during the real-time measurements of capacitance and conductance. Excellent repeatability of the devise was obtained after six cyclic tests, demonstrating stability of the sensor. Long-term stability for the sensor performance was also observed after four weeks storage. The observed response could be understood in terms of the change in surface charge upon ethanol infiltration into the mesoporous structure.

This paper reports the fabrication of highly-sensitive and selective voltammetric/amperometric cholesterol biosensor based on cholesterol oxidase co-immobilized with α-Fe2O3 micro-pine shaped hierarchical structures. The α-Fe2O3 micro-pine shaped hierarchical structures were synthesized by facile hydrothermal process in large quantity and characterized in detail using various techniques. The detailed studies demonstrated that the as-synthesized α-Fe2O3 hierarchical structures are grown in very high density exhibiting well-crystallinity and demonstrating rhombohedral α-Fe2O3 crystal structures. The fabricated cholesterol biosensors based on α-Fe2O3 hierarchical structures exhibited a very high and reproducible sensitivity of 78.56μA/mMcm2 and detection limit (based on S/N ratio) of 0.018mM. The biosensor exhibited a linear dynamic range from 0.1-8.0mM and correlation coefficient of R=0.9951. A lower value of apparent Michaelis-Menten constant (Kmapp), of 0.007mM, exhibited a high affinity between the cholesterol and ChOx immobilized on α-Fe2O3 micro-pine shaped hierarchical structures. To the best of our knowledge, this is the first report in which α-Fe2O3 micro-pine shaped hierarchical structures are used for the fabrication of highly sensitive and selective cholesterol biosensor.

•Optical response functions and their derived reflectivity spectrum of Cd1−xMnxTe.•Absorption coefficient and optical conductivity of Cd1−xMnxTe.•Optical and dielectric properties of Cd1−xMnxTe magnetic semiconductors.•Application of generalized gradient approximation of Engel–Vosko to the density functional theory.

This paper reports the facile growth, characterization and efficient heterojunction diode application of well-crystalline aligned n-ZnO nanonails. The ZnO nanonails were grown on p-Silicon substrate by facile noncatalytic thermal evaporation process. Detailed morphological and structural studies revealed that the nanonails are grown in high density, possessing well-crystalline and wurtzite hexagonal phase. X-ray diffraction and Raman scattering confirm the wurtzite hexagonal phase structure whereas room-temperature photoluminescence studies affirms good optical properties for the as-grown nanonails. The as-grown aligned ZnO nanonails grown on silicon substrate are utilized to fabricate n-ZnO/p-Si heterojunction diode. The I V characteristics of the fabricated n-ZnO/p-Si heterojunction diode are studied at temperature <300 K and >= 300 K in the forward and reverse bias conditions. By detailed studies, it was found that the junction exhibits a diode-like behavior with a value of turn-on voltage of 5 V at almost all temperatures. The rectifying behavior of the fabricated heterojunction diode, at 5 V, is demonstrated by rectifying ratio of 4 at 77 K which decreases to 2 at 277 K. Moreover, the delivered current at this turn-on voltage is the least and in the order of similar to 1 mu A, at 77 K. This cur rent gradually increases to 6 pc,A which occurs, at the same turn-on voltage, when the temperature changes in the range of 77 <= T <= 277 K and drastically increases to similar to 400 mu A at 427 K while the rectifying ratio is dropped to similar to 0.4. For the reverse-bias voltage of 5 V, the leakage current changes from similar to 10(-7) A at 77 K to similar to 10(-3) A at 427 K. These results show that the turn-on voltage, breakdown voltage and leakage current have exhibited similar behavior in reverse bias due to the increase in temperature.

This work demonstrated the successful and facile large-scale synthesis and characterizations of SnS2 nanoflakes. The detailed morphological studies revealed that the synthesized products were nanoflakes and were grown in large quantity. The XRD pattern and detailed compositional studies confirmed that the synthesized SnS2 nanoflakes were well-crystalline and possessing hexagonal SnS2 phase. The synthesized SnS2 nanoflakes were used as efficient photocatalysts for photocatalytic degradation and effective electron mediators for the fabrication of chemical sensor. The photocatalytic properties of SnS2 nanoflakes towards the photocatalytic degradation of Rhodamine B dye under visible light irradiation showed reasonably good degradation of ∼61%. Moreover, the as-synthesized SnS2 nanoflakes were used as efficient electron mediators for the fabrication of nitroaniline chemical sensor by simple I-V technique. Very high-sensitivity of ∼ 505.82±0.02 mAcm−2.(mole/L)−1 and experimental detection limit of ∼15×10−6 (mole/L) in a short response time of ∼10.0 s with LDR in the range of 15.6×10−6–0.5×10−3 mole L−1 were observed for the fabricated nitroaniline chemical sensor. The observed results indicated that the SnS2 nanoflakes can efficiently be used as visible-light-driven photocatalysts and the fabrication of ultra-high sensitive chemical sensors.

Well-crystalline flower-shaped ZnO nanostructures were synthesized by simple hydrothermal process at low-temperature of 145°C and utilized as a photocatalyst and photo-anode material for photocatalytic degradation and dye-sensitized solar cell applications, respectively. The detailed morphological and the structural characterizations revealed that the synthesized products were flower-shaped, grown in very high-density, and possessed well-crystalline wurtzite hexagonal phase. The chemical composition confirmed the pure phase and good optical properties of as-synthesized ZnO flowers. The as-synthesized ZnO flowers were used as an efficient photocatalyst for the photocatalytic degradation of Rhodamine B which exhibit ∼84% degradation within 140min. Moreover, the as-synthesized ZnO flowers were utilized as photo-anode material for the fabrication of dye-sensitized solar cells (DSSCs) which exhibited overall light-to-electricity conversion efficiency of ∼1.38%, open-circuit current (VOC) of 0.621V, short-circuit current (JSC) of ∼3.52mA/cm2 and fill factor (FF) of 0.64.

Well-crystalline ZnO nanowires were grown on Si(100) via non-catalytic thermal evaporation process using metallic zinc powder in presence of oxygen. The detailed morphological characterizations by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) confirmed that the synthesized products are nanowires with the typical diameter and lengths of approximately 55 +/- 5 nm and several micrometers, respectively and are grown in high density over the silicon substrate. The detailed structural characterizations by high-resolution TEM and X-ray diffraction confirmed that the synthesized nanowires are well-crystalline and possessing wurtzite hexagonal phase. The presence of Raman-active optical-phonon E2(high) mode at 437 cm(-1) in the Raman-scattering spectrum confirms good crystal quality for the as-grown ZnO nanowires. The electrical transport properties of the as-grown nanowires were explored by fabricating single nanowire based field effect transistors (FETs). The fabricated single ZnO nanowire based FET exhibits carrier concentration and electron mobility of approximately 7.49 x 10(17) cm(-3) and approximately 8.42 cm2V(-1)s(-1), respectively.

This paper reports a large-scale synthesis of ZnO balls made of fluffy thin ZnO nanosheets by simple solution process at low-temperature of 65±2°C. The synthesized ZnO structures were characterized in detail in terms of their morphological, structural, optical and photocatalytic properties. The detailed morphological characterizations, done by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), confirmed that the synthesized products are ZnO balls which are made by accumulation of hundreds of thin ZnO nanosheets. Interestingly, it is seen that the nanosheets are arranged in such a special fashion that they made ball-like morphologies. Detailed structural examinations revealed that of as-synthesized ZnO products are well-crystalline and possessing wurtzite hexagonal phase. The optical property, measured by UV-Visible spectroscopy, substantiated good optical properties for as-synthesized ZnO balls. The as-synthesized ZnO balls were utilized as an efficient photocatalysts for the photocatalytic degradation of methylene blue (MB) dye. Almost complete degradation of MB was observed in presence of ZnO balls composed of nanosheets within 70 min under UV-light irradiation. By comparing the photocatalytic performance with commercially available TiO(2)-UV-100, it was observed that the synthesized ZnO balls exhibited superior photocatalytic performance as compared to TiO(2)-UV-100 photocatalyst.

Nanocrystalline silicon (ns-Si) thin films deposited through plasma-enhanced chemical vapor deposition technique were studied. These films were grown at low deposition temperature of 200 degrees C and at different silane flow rates ([SiH4]). Characterization of these films with Raman spectroscopy, x-ray diffraction and atomic force microscopy revealed that no films deposited at [SiH4] = 0.0 sccm. In addition, the structural change from an amorphous to a nanocrystalline phase at [SiH4] = 0.2 sccm. The Fourier transform infrared spectroscopic analysis showed at low values of [SiH4] (0.1 sccm), no hydrogen incorporated in the nc-Si thin film. However, the intensity of the spectra around 2100 cm (1) is likely to decreases with increasing [SiH4]. We have observed photoluminescence (PL) at room temperature in the range of 1.7 eV to 2.4 eV for all the films. Presence of the very small crystallites (the size less than 20 nm) responsible for quantum confinement effect. Variations of the PL intensity, width and position are well correlation with the structural properties of the films such as crystalline size, crystalline volume fraction, and hydrogen content. Furthermore, the PL emissions also showed correlation with the distribution of spherical grains with the size below 50 nm distributed on the films surface.