Fabrication of polyaniline/TiO2 nanocomposite ammonia vapor sensor

Polyaniline/Titanium dioxide (PANi/TiO2) nanocomposite was fabricated from PANi, prepared by oxidative chemical polymerization and TiO2, synthesized by sol gel method. The PANi/TiO2 thin film sensors were prepared by spin coating technique. PANi/TiO2 nanocomposites were characterized by XRD and SEM. The cross sensitivity of thin film sensor indicate that the sensor exhibit selectivity to ammonia (NH3). The gas sensing measurements were carried out for different concentrations of NH3. The gas sensing study revealed that the response value increases with increasing concentration of NH3. Moreover, as concentration of NH3 increases, the response time decreases while recovery time increases, which can be attributed to the varying adsorption and desorption rates of an ambient gas with increasing concentration. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2791

Fabrication of polyaniline/TiO2 nanocomposite ammonia vapor sensor

Polyaniline/Titanium dioxide (PANi/TiO2) nanocomposite was fabricated from PANi, prepared by oxidative chemical polymerization and TiO2, synthesized by sol gel method. The PANi/TiO2 thin film sensors were prepared by spin coating technique. PANi/TiO2 nanocomposites were characterized by XRD and SEM. The cross sensitivity of thin film sensor indicate that the sensor exhibit selectivity to ammonia (NH3). The gas sensing measurements were carried out for different concentrations of NH3. The gas sensing study revealed that the response value increases with increasing concentration of NH3. Moreover, as concentration of NH3 increases, the response time decreases while recovery time increases, which can be attributed to the varying adsorption and desorption rates of an ambient gas with increasing concentration. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2791

Effect Of Annealing On Structure, Morphology, Electrical And Optical Properties Of Nanocrystalline TiO2 Thin Films

Semi-transparent and highly conducting nanostructured titanium oxide thin films have been prepared by sol-gel method. Thin films of TiO2 deposited on glass substrates using spin coating technique and the effect of annealing temperature (400 - 700 °C) on structural, microstructural, electrical and optical properties were studied. The X-ray diffraction and Atomic force microscopy measurements confirmed that the films grown by this technique have good crystalline tetragonal mixed anatase and rutile phase structure and homogeneous surface. The study also reveals that the rms value of thin film roughness increases from 7 to 19 nm. HRTEM image of TiO2 thin film (annealed at 700 °C) shows that a grain of about 50 - 60 nm in size is really aggregate of many small crystallites of around 10 - 15 nm. Electron diffraction pattern shows that the TiO2 films exhibited tetragonal structure. The surface morphology (SEM) of the TiO2 film showed that the nanoparticles are fine with an average grain size of about 50 - 60 nm. The optical band gap slightly decreases from 3.26 - 3.24 eV and the dc electrical conductivity was found in the range of 10-6 to 10-5(Ω·cm)-1 when the annealing temperature is changed from 400 to 700 °C. It is observed that TiO2 thin film annealed at 700 °C after deposition provide a smooth and flat texture suited for optoelectronic applications. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/967

Nanocrystalline MoBi2Se5 Ternary Mixed Metal Chalcogenide Thin-films for Solar Cell Applications

AbstractOptical, structural, morphological and photoelectrochemical properties were investigated of ternary MoBi2Se5 thin film prepared by simple arrested precipitation technique (APT). The precursors used were molybdenum, bismuth, triethanolamine complexes (TEA) along with organic additives. Ammonium molybdate, Bismuth nitrate and sodium selenosulphite were used as sources of Mo4+, Bi3+ and Se2− ions. The optical band gap of thin film was estimated to be 1.78eV. X-ray diffraction data reveals that the grown MoBi2Se5 thin film was highly nanocrystalline with orthorhombic structure. Scanning electron microscopy studies reveal that porous layer having elongated fibrous morphology with high surface area. The film was obtained with a well-defined composition, very close to the expected one. PEC application of prepared thin film were checked in Sulphide / Poly sulphide electrolyte which revealed that MoBi2Se5 thin film deposited on FTO coated glass exhibited maximum values of fill factor (FF) and conversion efficiency (η) with n type semiconductor nature

Tin Oxide Nanostructure Fabricated by Thermal Evaporation as Potential NO2 Sensor

Tin oxide (SnO2) gas sensor has been fabricated on glass substrate by using thermal evaporation and further characterize by scanning electron microscopy, atomic force microscopy and EDAX analysis for confirming its morphology and composition. The chemiresistive gas sensing performance of SnO2 films were studied towards various oxidizing and reducing gases. The experimental results reveal that, SnO2 films were vastly sensitive and selective towards NO2 gas than other test gases. SnO2 sensor exhibit maximum response of 160 % for 100 ppm NO2 gas with very fast response time at optimal operating 200 °C temperature. The SnO2 sensor manifests remarkably enhanced sensing performance, including fast response and recovery time, high sensitivity, and good stability, suggests of the promising application in the NO2 gas sensing field

Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model

We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω0T<5.58×10-8, Ω0V<6.35×10-8, and Ω0S<1.08×10-7 at a reference frequency f0=25 Hz. © 2018 American Physical Society

Erratum: "A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo" (2021, ApJ, 909, 218)

[no abstract available

On the progenitor of binary neutron star merger GW170817

On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ∼40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy's center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy's star formation history, provided the stellar populations are older than 1 Gyr