Enhancing effects of Te substitution on the thermoelectric power factor of nanostructured SnSe1-xTex.

Nanostructured SnSe1-xTex (0 < x < 0.2) was prepared by the planetary ball milling method. The prepared materials were studied by various analytical techniques. XRD analysis shows the pure phase of SnSe when x ≤ 0.1 and the secondary phase of SnTe was observed when x ≥ 0.1, possibly due to the low solid solubility limit of Te in SnSe. FESEM images revealed that the grain sizes of all the samples were in the range of 100 to 500 nm. TEM images showed the grain structures, sizes and grain boundaries of the samples. XPS analysis confirmed the incorporation of Te in SnSe1-xTex and the binding states of the elements in the samples. The samples were made into pellets and sintered at high temperature. The electrical resistivity of the SnSe1-xTex pellets decreased by up to two orders of magnitude as the x value increased in the samples. Concomitantly, the Seebeck coefficient of the SnSe1-xTex samples decreased drastically as the x value increased in the samples. A power factor (PF) of 102.8 µW K-2 m-1 was obtained for the SnSe0.9Te0.1 sample at 550 K, which is higher than the reported values for SnSe and SnSe1-xTex. When substituting Se with Te, the band structure of SnSe changes, which significantly enhances the thermoelectric PF of SnSe1-xTex for x ∼ 0.1. The PF decreased when the x value was increased further (x ≥ 0.1), possibly due to the precipitation of the SnTe phase. These experimental results demonstrate that the addition of a reasonable amount of Te is a promising approach for improving the thermoelectric properties of SnSe.

Structural, Morphological and Photocatalytic Activity of YMnO3 Nanorods.

In this work rod-like YMnO3 were successfully prepared by hydrothermal method. The crystal structure and morphology of prepared samples were characterized by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structural information was confirmed from Raman spectrum and the functional group of the sample was studied from FTIR spectrum. X-ray photoelectron spectroscopy studies confirm the formation and oxidation states of YMnO3. The optical properties of the prepared samples were investigated using UV-vis spectroscopy. The photocatalytic activity of YMnO3 nanorods was evaluated by degradation of methyl orange (MO) under both ultraviolet and visible-light irradiation. The result shows that the YMnO3 nanorods exhibit maximum photocatalytic activity in the degradation of MO.

Band alignment and depletion zone at ZnO/CdS and ZnO/CdSe hetero-structures for temperature independent ammonia vapor sensing.

An optical-fiber based evanescent ammonia vapor sensor was constructed with surface-passivated growth of zinc oxide (ZnO) nanostructures, which was achieved through a three-step wet chemical process. Initially, the ZnO nanostructures were synthesized using a wet-chemical method and subsequently surface-passivated with chalcogenide material compounds namely cadmium sulphide (CdS) and cadmium selenide (CdSe) nanoparticles individually using a citric acid assisted chemical synthesis technique. Finally, surface-passivated ZnO was deposited on the cladding modified optical-fiber using a dip coating process. X-ray diffraction (XRD), tunneling electron microscopy (TEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) analyses confirmed the growth of CdS and CdSe nanoparticles on the surface of ZnO nanoparticles. The atomic composition and the full width at half maximum (FWHM) of the oxygen O 1s oxidation state represented in the X-ray photoelectron spectra were lower and narrower for ZC2 nanostructures implying that the available surface oxygen had reacted well and promoted the uniform shell-like growth of CdSe nanoparticles on the ZnO. The significance of the surface-passivated ZnO was realized from UV-Vis diffuse reflectance spectroscopy (DRS) and a photo-luminescence (PL) study and was implemented in a room temperature optical-fiber based evanescent ammonia vapor sensor. The nano-sized CdS particles decorated on the surface of ZnO demonstrate a high vapor sensing behavior. The sensing enhancement was nearly 3 times larger than the core-shell like ZnO/CdSe (ZC2) nanostructures and was attributed to the effective interaction of the incident light and the sensing media, the change in the refractive index of the modified cladding regime, the rate of vapor adsorption and the effective charge-carrier transport between the so-formed hetero-junction interfaces. The ZC2 shows insignificant ammonia vapor adsorption and sensing due to decreased free carrier density produced within the ZnO host lattice and an increased potential barrier width between the ZnO/CdSe hetero-structures.

Influence of Fe-Doping on the Structural, Morphological, Optical, Magnetic and Antibacterial Effect of ZnO Nanostructures.

Pure and Fe-doped ZnO nanostructures with different weight ratios (0.5, 1.0, 1.5, and 2.0 at wt% of Fe) were successfully synthesized by a facile microwave combustion method using urea as a fuel. The detailed structural characterization was performed by means of X-ray diffraction (XRD), high resolution scanning electron microscopy (HR-SEM), energy dispersive X-ray analysis (EDX), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). XRD patterns refined by the Rietveld method indicated that Fe-doped ZnO have a single pure phase with wurtzite structure, suggesting that Fe ions are successfully incorporated into ZnO crystal lattice by occupying Zn ionic sites. Interestingly, the morphology was found to change substantially from grains to nanoflakes and then into nanorods with the variation of Fe-content. The optical band gap estimated using DRS was found to be red-shifted from 3.220 eV for the pure ZnO nanostructures, then decreases up to 3.200 eV with increasing Fe-content. Magnetic studies showed that Fe-doped ZnO nanostructures exhibit room temperature ferromagnetism (RTFM) and the saturation magnetization attained a maximum value of 8.154 x 10(-3) emu/g for the highest Fe-content. The antibacterial activity of pure and Fe-doped ZnO nanostructures against a Gram-positive bacteria and Gram-negative bacteria was investigated. Pure ZnO and Fe-doped ZnO exhibited antibacterial activity, but it was considerably more effective in the 1.5 wt% Fe-doped ZnO nanostructures.

Synthesis of silver­bismuth oxide encapsulated hydrazone functionalized chitosan (AgBi2O3/FCS) nanocomposite for electrochemical sensing of glucose, H2O2 and Escherichia coli O157:H7.

In this work, silver­bismuth oxide encapsulated 1,3,5-triazine-bis(4-methylbenzenesulfonyl)-hydrazone functionalized chitosan (SBO/FCS) nanocomposite was synthesized by a simple hydrothermal method. The amine (-NH2) group was functionalized by the addition of cyanuric acid chloride followed by 4-methylbenzenesulfonol hydrazide. The SBO/FCS has been characterized by FT-IR, X-ray diffraction, XPS, HR-SEM, HR-TEM, AFM, and thermogravimetry (TGA). Under the optimum conditions, the SBO/FCS sensor showed brilliant electrochemical accomplishment for the sensing of glucose and H2O2 by a limit of detection (LOD) of 0.057 µM and 0.006 µM. It also showed linearity for glucose 0.008-4.848 mM and for H2O2 of 0.01-6.848 mM. Similarly, the sensor exhibited a low sensitivity to glucose (32 µA mM-1 cm-2) and a good sensitivity to H2O2 (295 µA mM-1 cm-2). In addition, that the prepared electrode could be used to sense the glucose and H2O2 levels in real samples such as blood serum and HeLa cell lines. The screen printed electrode (SPE) immunosensor could sense the E. coli O157:H7 concurrently and quantitatively with a linear range of 1.0 × 101-1.0 × 109 CFU mL-1 and a LOD of 4 CFU mL-1. Likewise, the immunosensor efficiently detect spiked E. coli O157:H7 in milk, chicken, and pork samples, with recoveries ranging from 89.70 to 104.72 %, demonstrating that the immunosensor was accurate and reliable.

Hydrothermal synthesis of ZnZrO2/chitosan (ZnZrO2/CS) nanocomposite for highly sensitive detection of glucose and hydrogen peroxide.

In this work, pure ZnZrO2 and chitosan supported (ZnZrO2/CS) nanocomposite have been synthesized at low coast by hydrothermal method. FT-IR, Micro Raman, PXRD, HR-SEM-EDAX, HR-TEM, AFM, BET and XPS were used to analyze the structural and morphological properties of the fabricated nanocomposites. The fabricated ZnZrO2 and ZnZrO2/CS nanocomposites were measured for their electrocatalytic activity towards glucose and hydrogen peroxide determinations. The ZnZrO2/CS sensor exhibited wide detection range (5 µM to 5.85 mM), high sensitivity (6.78 µA mM-1 cm-2), LOD (2.31 µM), and long-term stability for glucose detection in alkaline solution. Also, as a multifunctional electrochemical sensor, ZnZrO2/CS sensor exhibits excellent sensing ability towards hydrogen peroxide, with a wide dynamic range (20 µM to 6.85 mM), a high sensitivity (2.22 µA mM-1 cm-2), and a LOD (2.08 µM) (S/N = 3). The electrochemical measurement shows that the ZnZrO2/CS sensor has excellent catalytic activity and a much LOD than ZnZrO2. The modified electrode showed excellent anti interference nature. Furthermore, this ZnZrO2/CS electrode was used to detection of glucose and H2O2 in human blood serum and HeLa cells respectively.

Silver-functionalized bismuth oxide (AgBi2O3) nanoparticles for the superior electrochemical detection of glucose, NO2- and H2O2.

In this study, silver-functionalized bismuth oxide (AgBi2O3) nanoparticles (SBO NPs) were successfully synthesized by a highly efficient hydrothermal method. The as-synthesized SBO nanoparticles were characterized using FT-IR, P-XRD, XPS, HR-SEM, and HR-TEM analytical methods. It was found that the NPs were in spherical shape and hexagonal crystal phase. The newly prepared SBO electrode was further utilized for the detection of glucose, NO2- and H2O2 by cyclic voltammetry (CV) and amperometric methods. The electrodes exhibited high sensitivity (2.153 µA mM-1 cm-2 for glucose, 22 µA mM-1 cm-2 for NO2- and 1.72 µA mM-1 cm-2 for H2O2), low LOD (0.87 µM for glucose, 2.8 µM for NO2- and 1.15 µM for H2O2) and quick response time (3 s for glucose, 2 s for both NO2- and H2O2 respectively). The sensor exhibited outstanding selectivity despite the presence of various interferences. The developed sensor exhibited good repeatability, reproducibility, and stability. In addition, the sensor was used to measure glucose, H2O2 in human serum, and NO2- in milk and river water samples, demonstrating its potential for use in the real sample.

Heterostructures of polyaniline and Ce-ZnO nanomaterial coated flexible PET thin films for LPG gas sensing at standard environment.

The n-type Ce doped ZnO (Ce-ZnO) and p-type polyaniline (PANI) heterojunction were successfully synthesized via simple chemical solution method for sensing liquefied petroleum gas (LPG) at standard environment. The morphology and structures of as-prepared Ce-ZnO & PANI nanoparticles were analyzed by numerous kinds of techniques. Ce-ZnO & PANI nanoparticles were mixed with n-methylpyrrolidone (NMP) which is coated over the gold coated PET electrode by doctor blade method and dried overnight at 60 °C to form p-n junction. The as-formed p-n junction is to be driven with the help of 1.5 V potential at ambient temperature. X-ray photoelectron spectroscopy results of Ce-ZnO nanoparticles confirmed the existence of Ce4+ and the improved amount of both chemisorbed oxygen and oxygen vacancy after the formation of Ce-ZnO heterojunction. The maximum response of 80% was realized for hollow Ce-ZnO/PANI sensor at 100 ppm. The proposed material is a novel candidate to detect the LPG even at low (30) ppm and this study reveals the possibility of developing a potentially inexpensive hollow Ce-ZnO/PANI sensor for sensing LPG efficiently.

Facile Synthesis of Phase Tunable MoO3 Nanostructures and Their Electrochemical Sensing Properties.

MoO3 nanostructures with tunable phases such as α-MoO3, ß-MoO3 and their mixed phases were synthesized via a simple solid state decomposition method and employed as electrocatalyst for the detection of biomolecule. The phase and crystal structure of the synthesized MoO3 nanostructures were confirmed through X-ray diffraction (XRD) studies. The MoO3 nanostructures were also characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV-Vis spectroscopy for their structural, chemical state and optical properties, respectively. The observed results confirmed the successful formation of phase tunable MoO3 nanostructures. The surface texture and morphology of the samples was characterized by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The obtained images showed the formation of hexagons, cubes and rods morphology of MoO3. The synthesized MoO3 nanostructures were used to modify the surface of glassy carbon electrode (GCE) to detect biomolecule (quercetin).

Enhanced electrochemical performance of α-MoO3/graphene nanocomposites prepared by an in situ microwave irradiation technique for energy storage applications.

Nanoparticles of α-molybdenum oxide (α-MoO3) are directly grown on graphene sheets using a surfactant-free facile one step ultrafast in situ microwave irradiation method. The prepared α-MoO3 and α-MoO3/G nanocomposites are analysed by different characterization techniques to study their structural, morphological and optical properties. Transmission electron microscope images reveal the intercalation of three dimensional (3D) α-MoO3 nanoparticles into 2D graphene sheets without any agglomeration. The electrochemical results exhibit improved performance for the α-MoO3/G composite electrode compared to pristine α-MoO3 owing to its structural superiority. The specific capacitance (C s) values of the α-MoO3/G composite and pristine α-MoO3 are measured to be 483 and 142 F g-1 respectively at a current density of 1 A g-1. The α-MoO3/G composite maintains a very strong cyclic performance after 5000 cycles. The capacitance retention of the composite electrode shows stable behavior without any degradation confirming its suitability as an enduring electrode material for high-performance supercapacitor applications.

Bifunctional investigation of ultra-small SnO2 nanoparticle decorated rGO for ozone sensing and supercapacitor applications.

Ultrasmall SnO2 nanoparticles with an average size of 7 nm were synthesized by a hydrothermal method and composited with reduced graphene oxide (rGO) through an ultrasonic assisted solution process. The structural, functional, morphological and compositional properties of synthesised SnO2 and rGO/SnO2 were studied by XRD, FTIR, HRSEM, HRTEM, XPS and Raman analyses. The prepared materials were developed as a film over a PVA/KOH conductive layer coated substrate with varying thickness of 3, 5 and 7 µm to study their ozone sensing characteristics at room temperature. The physico-chemical properties reveal that the fabricated SnO2 and rGO/SnO2 nanocomposite films have a strong interaction with the ozone gas. Among the fabricated composite films rGO/SnO2-S1 film exhibits high ozone sensing response (38%) at room temperature. Additionally, the electrochemical performance of SnO2 and rGO/SnO2 nanocomposites was analysed and the rGO/SnO2 nanocomposite exhibited higher specific capacitance (545 F g-1) than that of pure SnO2 (236 F g-1) at a current density of 1 A g-1 with higher cyclic stability (96%) than that of pure SnO2 (86%) at the current density of 20 A g-1 for a continuous 5000 charge-discharge cycles. Thus, the rGO/SnO2 nanocomposite showed an excellent ozone sensing and energy storage performance.

Effect of co-sensitization of InSb quantum dots on enhancing the photoconversion efficiency of CdS based quantum dot sensitized solar cells.

The effect of co-sensitization of CdS and InSb Quantum Dots (QDs) on the enhancement of efficiency of Quantum Dots Sensitized Solar Cells (QDSSCs) has been investigated. InSb is synthesized by a facile solvothermal method using indium metal particles and antimony trichloride as precursors. From TEM images the average particle size of InSb was found to be less than 25 nm. The I-V data showed photoconversion efficiency (PCE) of 0.8% using InSb QDs as a sensitizer layer for QDSSC. However, co-sensitization of InSb QDs and CdS QDs on the TiO2 photoanode in QDSSCs showed an enhanced PCE of 4.94% compared to that of CdS sensitized solar cells (3.52%). The InSb QD layer broadens the light absorption range with reduced spectral overlap causing an improvement in light harvesting along with suppression of surface defects which reduced the recombination losses. As a result, co-sensitized TiO2/CdS/InSb QDSSC exhibits a greatly improved PCE of 4.94%, which is 40% higher than that of TiO2/CdS (3.52%) based QDSSCs due to improved light absorption with low recombination losses.

Anticorrosion Behavior of ZnO Nanoparticles Coated on Mild Steel in NaCl Solution.

This work focuses on the environment protected, ecological procedure by the combination of ZnO nanoparticles utilizing the extraction of Ocimum sanctum. The prepared nanoparticles are examined by different methods like Fourier-transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Energy Dispersive X-ray Analysis (EDAX). A systematic study has been made on the result of ZnO nano-coating for the corrosion behavior of mild steel. The ZnO nanoparticles of average diameter in the range 18-22 nm were coated on mild steel in nickel bath solution. The anticorrosion properties on the coated mild steel was carefully tested in 3.5% NaCl solution by performing potentio-dynamic polarization measurement and electrochemical impedance spectroscopy. Surface morphology of the coated mild steel immersed in corrosive solution was judged by using SEM with EDAX. The ZnO nano coating has shown a perfect protection against corrosion and the shielding capability is in the range between 86-95%. The incorporation of ZnO nanoparticles has upgraded the process of mild steel in all corrosion media are subjected to investigation.

Surfactant-Free Synthesis of Nb2O5 Nanoparticles Anchored Graphene Nanocomposites with Enhanced Electrochemical Performance for Supercapacitor Electrodes.

Nb2O5/graphene nanocomposites without any surfactant are synthesized by an in situ microwave irradiation technique. Structural and morphological studies revealed that the prepared composites were composed of Nb2O5 nanoparticles intercalated into the graphene sheet. The thermal stability of graphene oxide, Nb2O5, and Nb2O5/graphene nanocomposite was studied by the TGA. The electrochemical properties are assessed by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy analyses. The specific capacitance of Nb2O5/graphene nanocomposites is greater (633 Fg-1) than pure Nb2O5 nanoparticles (221 Fg-1) and graphene (290 Fg-1) at a current density of 1 Ag-1. The long-term cyclic measurement confirms higher cyclic stability of the nanocomposite with capacitance retention of 99.3% after 5000 cycles without performance degradation. The composites exhibit higher electrochemical conductivity and allow effective ions and charge transport over the entire electrode surface with aqueous electrolyte. The electrochemical study suggests that Nb2O5/graphene nanocomposites have the potential to be an effective electrode for superior performance supercapacitor applications.

Enhancing the thermoelectric power factor of nanostructured ZnCo2O4 by Bi substitution.

Bi x ZnCo2-x O4 (0 ≤ x ≤ 0.2) nanoparticles with different x values have been prepared by the sol-gel method; the structural, morphological, thermal and thermoelectric properties of the prepared nanomaterials are investigated. XRD analysis confirms that Bi is completely dissolved in the ZnCo2O4 lattice till the x values of ≤0.1 and the secondary phase of Bi2O3 is formed at higher x value (x > 0.1). The synthesized nanomaterials are densified and the thermoelectric properties are studied as a function of temperature. The electrical resistivity of the Bi x ZnCo2-x O4 decreased with x value and it fell to 4 × 10-2 Ω m for the sample with x value ≤ 0.1. The Seebeck coefficient value increased with the increase of Bi substitution till the x value of 0.1 and decreased for the sample with higher Bi content (x ≤ 0.2) as the resistivity of the sample increased due to secondary phase formation. With the optimum Seebeck coefficient and electrical resistivity, Bi0.1ZnCo1.9O4 shows the high-power factor (α 2 σ 550 K) of 2.3 µW K-2 m-1 and figure of merit of 9.5 × 10-4 at 668 K respectively, compared with other samples. The experimental results reveal that Bi substitution at the Co site is a promising approach to improve the thermoelectric properties of ZnCo2O4.

Antimonene nanosheets with enhanced electrochemical performance for energy storage applications.

Antimonene is an exfoliated 2D nanomaterial obtained from bulk antimony. It is a novel class of 2D material for energy storage applications. In the present work, antimonene was synthesized using a high-energy ball milling-sonochemical method. The structural, morphological, thermal, and electrochemical properties of antimonene were comparatively analyzed against bulk antimony. X-ray diffractometry (XRD) analysis confirms the crystal structure and 2D structure of antimonene, as a peak shift was observed. The Raman spectra show the peak shift for the Eg and A1g modes of vibration of antimony, which confirms the formation of antimonene. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) images depict the exfoliation of antimonene from bulk antimony. Thermal analysis unveiled the thermal stability of antimonene up to 400 °C with only 3% weight loss. X-ray photoelectron spectroscopy (XPS) analysis reveals the formation of antimonene, which is free from contamination. The electrochemical properties of antimony and antimonene were investigated using cyclic voltammetry (CV) and chronopotentiometric (CP) analysis, using 2 M KOH as an electrolyte. Antimonene exhibited a relatively high specific capacitance of 597 F g-1 compared to ball-milled antimony (101 F g-1) at a scan rate of 10 mV s-1. Moreover, electrochemical impedance spectroscopy (EIS) analysis revealed that antimonene has a relatively low equivalence series resistance (RESR) and low charge transfer resistance (RCT) compared to bulk antimony, which favors high electrochemical performance. The cyclic stability of antimonene was studied for 3000 cycles, and the results show high cyclic stability. The electrochemical results demonstrated that antimonene is a promising material for energy storage applications.

Freestanding flexible, pure and composite form of reduced graphene oxide paper for ammonia vapor sensing.

Metal oxides based graphene nanocomposites were used for ammonia vapour sensing. The self-assembly process was adopted to prepare freestanding flexible pure rGO, CeO2-rGO and SnO2-rGO composite papers. The structural studies confirmed the formation of rGO composite papers. The ammonia vapor sensing was demonstrated using an impedance analyzer at different humidity levels as well as concentration. The CeO2-rGO composite paper achieved a sensitivity of 51.70 ± 1.2%, which was higher than that of pure rGO and SnO2-rGO composite paper. Both the surfaces (top and bottom) of the papers are active in efficiently sensing ammonia, which makes the present work unique. The results reveal that metal oxide/rGO papers can be effectively utilized in real time sensor application.

Redetermination of poly[µ-chlorido-hepta-chlorido-µ(3)-l-proline-µ(2)-l-proline-tetra-mercury(II)].

The asymmetric unit of the title compound, [Hg(4)Cl(8)(C(5)H(9)NO(2))(2)](n), consists of four HgCl(2) units and two L-proline ligands in the zwitterionic form. In each HgCl(2) unit, the Hg(II) ion is strongly bonded to two Cl atoms, and the Hg(II) ions in two of the HgCl(2) units are chelated by O atoms of two l-proline ligands, with one strong and one weak Hg-O bond. In the crystal structure, HgCl(2) and L-proline units are linked to form an extended chain along the a axis. The chain structure is further stabilized by N-H⋯Cl hydrogen bonds, and the chains are arranged in layers parallel to the ab plane. The structure of the title compound was originally determined by Ehsan, Malik & Haider [(1996). J. Banglad. Acad. Sci.20, 175] but no three-dimensional coordinates are available.

The theoretical and experimental vibrational studies of thiourea and silver nitrate (2:1) complex.

The theoretical and experimental vibrational studies for poly thiourea silver nitrate (2:1) complex using DFT method are performed on the basis of experimental data. During the geometry optimization process one equilibrium structure was found. The Mulliken charges, harmonic vibrational frequencies, Infrared and Raman intensities were calculated on the basis of quantum chemical density functional calculations using firefly (PC GAMESS) Version 7.1G. The clear - cut assignments of observed bands are performed on the basis of potential energy distribution (PED) analysis. Highest Occupied Molecular Orbital (HOMO) and the Lowest Occupied Molecular Orbital (LUMO) are obtained and graphically illustrated with minimum energy. The energy difference between HOMO and LUMO is analyzed. The other molecular properties like molecular electrostatic potential, Mulliken charges and thermodynamic properties of the title compound have also been calculated.

Effect of pH, thermal, electrical and thermomechanical properties of nonlinear optical L-threonine single crystals.

Nonlinear optical L-threonine single crystals have been grown at various pH values. The crystals were subjected to dielectric and thermomechanical measurements at various temperatures. The thermal strength of the grown crystal was also determined by differential scanning calorimetry (DSC) analysis. The results have been discussed in detail.