Pr3+ doped BaMoO4 octahedron to shuttle-like microcrystals: synthesis and luminescence properties

Octahedron to shuttle-like microcrystals of highly ordered BaMoO₄:Pr³⁺ have been successfully prepared through a facile hydrothermal method assisted with PVP (K30) (polyvinylpyrrolidone). Comprehensive structural, morphological studies like X-ray diffraction, scanning and transmission electron microscopy were employed to characterize the as synthesized microcrystals. In the hydrothermal process, a very small amount of PVP was added which not only acts as a surfactant to facilitate the formation of BaMoO₄:Pr³⁺, but also acts as a surface capping agent. By varying the reaction time, octahedron to shuttle-like morphologies has been obtained and rest of the parameters like, molar ratio and temperature are kept as constant have crucial influence on the shape evolution and microstructures. Photoluminescence (PL) studies on BaMoO₄:Pr³⁺ showed strong red emission upon UV illumination, and this implied potential application in the luminescent field.     

Optimization,synthesis and characterization of vanadium-substituted thick-walled three-dimensional SBA-16

A systematic study was carried out to examine the viable synthesis condition at high acidic condition for the direct incorporation of a high level of vanadium into the 3D cubic arrangement of SBA-16 molecular sieves. The extent of mesopore structural ordering was determined by X-ray diffraction, N₂ physisorption, SEM and TEM analysis. The coordination and nature of the V sites were characterized by FT-Raman, electron spin resonance, ²⁹Si nuclear magnetic resonance spectroscopy, UV–visible diffuse reflectance spectroscopy and NH₃–TPD analysis. The surface area of calcined V-SBA-16 was ～1000 m²/g, while the mesopore volume of the SBA-16 cage ranged from 0.3 to 0.6 cm³g^?1. The pore size distribution was ～3.0 nm with a wall thickness of ～9.7 nm at the maximum. The Si/V ratios as determined by ICP-OES technique was varied from 438 to 8, respectively. The calcined samples exhibited promising catalytic activity in the oxidation of styrene with tert-butyl hydroperoxide as an oxidant.     

Morphological properties of Ag₂SeTe nano thin films prepared by thermal evaporation

Semiconducting silver selenide telluride (Ag₂SeTe) thin films were prepared with different thicknesses onto glass substrates at room temperature using thermal evaporation technique. The structural properties were determined as a function of thickness by X‐ray diffraction exhibiting no preferential orientation along any plane; however, the films are found to have peaks corresponding to mixed phase. The morphology of these films was studied using scanning electron microscope and atomic force microscopy respectively, and is reported. The morphological properties are found to be very sensitive to the thin film thickness. The composition of the films is also estimated using energy dispersive analysis using X‐rays and are also reported.     

Direct Observation of the Self-Aggregation of R3R4 Bi-repeat of Tau Protein

Abstract: Different cryo-EM derived atomic models of in vivo tau filaments from patients with tauopathies consisted of R3 and R4 repeats of the microtubule-binding domain. In comparison, only the R3 repeat forms the core of the heparin-induced fibrils of the three repeat tau isoforms. For developing therapeutics, it is desirable to have an in vitro tau aggregation system producing fibrils corresponding to the disease morphology. Here we report the self-aggregation of truncated tau segment R3R4 peptide without requiring heparin for aggregation induction. We used NMR spectroscopy and other biophysical methods to monitor the self-aggregation of R3R4. We identified the hexapeptide region in R3 and β-turn region in R4 as the aggregation initiating region of the protein. The solid-state NMR of self-aggregated R3R4 fibrils demonstrated that in addition to R3 residues, residues of R4 were also part of the fibril filaments. The presence of both R3 and R4 residues in the aggregation process and the core of fibril filaments suggest that the aggregation of R3R4 might resemble the in vivo aggregation process.     

Parameter estimation of integrating and time delay processes using single relay feedback test

Autotuning using relay feedback is widely used to identify low order integrating plus dead time (IPDT) systems as the method is simple and is operated in closed-loop without interrupting the production process. Oscillatory responses from the process due to ideal relay input are collected to calculate ultimate properties of the system that in turn are used to model the responses as functions of system model parameters. These theoretical models of relay response are validated. After adjusting the phase shift, input and output responses are used to find land mark points that are used to formulate algorithms for parameter estimation of the process model. The method is even applicable to distorted relay responses due to load disturbance or measurement noise. Closed-loop simulations are carried out using model based control strategy and performances are calculated.     

Structural and optical properties of Ag2SeTe nano thin films prepared by thermal evaporation

Semiconducting Ag₂SeTe thin films were prepared with different thicknesses onto glass substrates at room temperature using thermal evaporation technique. The structural properties were determined as a function of thickness by XRD exhibiting no preferential orientation along any plane, however the films are found to have peaks corresponding to mixed phase. The XRD studies were used to calculate the crystallite size and microstrain of the Ag₂SeTe films. The calculated microstructure parameters reveal that the crystallite size increases and micro strain decreases with increasing film thickness. The refractive index, dielectric constants and thereby the optical bandgap of the films were calculated from transmittance spectral data recorded in the range 400?C1200 nm by UV?CVIS-Spectrometer. The direct optical bandgap of the Ag₂SeTe thin films deposited on glass substrates with different thicknesses 50?C230 nm were found to be in the range 1.48?C1.59 eV. The carrier density value is estimated to be around 9.8 × 10²¹ cm^?1 for the film thickness of 150 nm. The compositions estimated from the optical band gap studies reveal a value of 0.75 for Tellurium concentration. These structural and optical parameters are found to be very sensitive to the thin film thickness.     

Micropatterning of porphyrin nanotubes thin film using focused laser writing

We report an effective process to create micropatterns on a thin film of porphyrin nanotubes PNTs on Si substrate using focused laser beam. The optical properties of the newly synthesized porphyrin nanotubes are investigated and micropatterning is demonstrated using laser fabrication, an increasingly important tool in various fields of research. We made use of this laser cutting method to create interesting and useful two-dimensional patterned structures. The shapes and sizes of the structures created can be controlled by varying the power of the laser, angle of incident of the focused laser beam, the relative speed with which the laser beam traverse through the film and the magnification of objective lens used.     

Dielectric and structural studies on sulphamic acid (SA) single crystal

Sulphamic acid single crystal of the size 14 × 8 × 6 mm³ has been grown by slow cooling solution growth method at 35.5 °C. Fermi resonance vibrations of N-S stretching and SO₃ rocking have been observed from micro-Raman analysis. Different shapes of etch patterns have been observed for etchants like water, ethanol and HCl for different etching periods. The dielectric constant and dielectric loss have been measured for different frequencies at different temperatures.     

Ce-substituted Lithium Ferrite:Preparation and Electrical Relaxation Studies

Ce-substituted lithium ferrite,Li_(0.5)Ce_xFe_(2.5-x)O_4(x = 0,0.05 and 0.1) compositions were synthesized from metal nitrates and citric acid by the solution combustion process by keeping the oxidizer to fuel ratio at unity.The thermal decomposition process was investigated by thermogravimetry—differential thermal analysis,which showed a stable phase formation above 600 C.The phase composition and molecular bonding of Li_(0.5)Ce_xFe_(2.5-x)O_4 were characterized by X-ray powder diffraction analysis and Fourier transform infrared spectroscopy,respectively.An extensive study of electrical relaxation process has been represented with impedance and modulus as a function of frequency at different temperatures.The activation energy obtained from both the formalisms was found to be equal within the error.The dc conductivity and hopping frequency were thermally activated and their activation energies were found to be in the range of 0.69-0.64 eV for x = 0.05.The scaling of modulus and impedance were used to understand the electrical relaxation behaviour of the compositions and they suggest the time temperature superposition principle.