Pd-nanoparticle-decorated ZnO nanowires: ultraviolet photosensitivity and photoluminescence properties

ZnO nanowires (NWs) have been decorated with Pd nanoparticles of sizes less than 10 nm (Pd-ZnO NWs) via a chemical solution route. The microstructural characterizations have been done using field emission scanning electron and high-resolution transmission electron microscopes. The effects of attaching Pd nanoparticles to the walls of ZnO NWs have been investigated by studying the ultraviolet (UV) photosensitivity and photoluminescence (PL) properties. The surface-modified NWs show a UV photosensitivity more than double and a response seven times faster compared to the bare NWs. The photocarrier relaxation under the steady UV illumination condition is quite different in Pd-ZnO NWs. The higher and faster photosensitivity has been explained on the basis of photocarrier transfer from the conduction band of ZnO to the Fermi level of Pd and subsequent electron trapping by the adsorbed O(2) molecules on the NWs' surface, which have been presented through a proposed model. The PL spectrum of Pd-ZnO NWs shows that the intensities of the band-edge and defect-related emissions decrease and increase, respectively, due to Pd anchoring, the effect being pronounced as the density of Pd nanoparticles increases.     

An efficient triazole-based fluorescent “turn-on” receptor for naked-eye recognition of F− and AcO−: UV–visible,fluorescence and 1H NMR studies

An efficient colorimetric receptor was developed by a simple convenient method which exhibited naked-eye sensitivity for fluoride and acetate in a biologically competing solvent like DMSO. The receptor developed, portrayed a substantial change in the UV–visible absorption characteristics upon addition of fluoride and acetate anions over other anions. The binding constants showed that the binding ability of receptor towards F^? anion was slightly higher than that of the AcO^? anion. Job's plots indicated the formation of a (1:1) complex (receptor:anion) of receptor with fluoride and acetate anions respectively. A “turn on” fluorescence response with a red shift was observed upon fluorescence titration. ¹H NMR titration experiments revealed the mechanism to be driven by the hydrogen bonding interaction of amide NH and phenol OH of the receptor molecule which was followed by deprotonation in the receptor by the F^? and AcO^? anions.     

Thermal stability and electrical characteristics of poly(2-ethyleaniline)-Au nanocomposite

The Present work reports the synthesis of poly2-ethyleaniline (PEANI) by oxidative polymerization of 2-ethyleaniline and its composite with gold nanoparticles (AuNPs) via in situ chemical synthesis route (simultaneous polymerization and precipitation). PEANI and its nanocomposite were characterized by thermogravimetric analysis-differential Scanning Calorimetry, X-ray diffraction and Fourier transform-infrared. The structural confirmation of the polymer was confirmed by FT-IR which shows strong absorption starting at ~1,600 cm^?1 and extended to near-IR, Attributed to the presence of free carrier in the polymer. XRD of Polymer shows large X-rays peaks indicating that the material is rather amorphous with a certain degree of crystallinity where as XRD of PEANI-Au nanocomposite confirms the incorporation of AuNPs in composite. The TEM image showed the formation of PEANI-AuNPs core shell nanostructure. From TGA–DSC studies it was confirmed that the decomposition of the polymer in the composite is lowered by 254 °C as compare to PEANI alone, resulting in weak structure. Whereas I–V characteristics’ shows that the composite has about 10 % lower conductance values than the polymer alone.     

Optimisation of fluid flow phenomena inside transport duct of a DREF‐III friction spinning machine. Part III: CFD approach

The present paper is Part III of a series of papers dealing with the air‐flow inside the transport duct of a DREF‐III friction spinning machine. The design of the transport duct used in a DREF‐III friction spinning machine has been modified and improved. The air‐flow analysis inside the transport duct was carried out using the computational fluid dynamics (CFD) software FLUENT after creating the transport duct geometry in the geometrical model software ‘GAMBIT’. The boundary conditions namely inlet, outlet, moving wall and wall were specified for the transport duct in GAMBIT and were then exported to FLUENT, where the pressure and velocity values were specified. The simulations were then done using k‐? model for turbulent flow. FLUENT solves the basic fluid dynamics equations namely the energy and momentum equations along with the additional equations. Air‐flow behaviour has been simulated in the various modelled modified transport ducts. Slots were created near the inlet and they were given an inclined profile in order to reduce the reverse flow by guiding the air‐flow. The transport duct with one pair of slots at 30° angle was finally selected based on techno‐economic aspects. The physical properties of finer and coarser count yarns made from the modified as well as the conventional transport duct were compared for assessing the enhancement of properties with transport duct modification.     

(La2/5Ba2/5Ca1/5)(Mn(2/5)-x Ni x Ti3/5)O3: Rietveld studies, dielectric and magnetic properties of new perovskite-related oxides

Oxides of the type (La_2/5Ba_2/5Ca_1/5)(Mn_(2/5)-x _Ni x _Ti3/5)O₃ (0 ≤ x ≤ 0.4) have been synthesized by the ceramic route. All the above oxides have been found to crystallize in the cubic perovskite structure. Rietveld refinement of the Ni-based oxide, (La_2/5Ba_2/5Ca_1/5)(Ni_2/5Ti_3/5)O₃ gave rise to a composition (La_0.44Ba_0.38Ca_0.18) (Ni_0.42Ti_0.58)O_2.85(6) and the refined lattice parameter obtained was 3.9411(2) Å (space group Pm3m;R(F²) = 0.026,R _p = 0.074,wR _p = 0.087). A shift from antiferromagnetic to paramagnetic behaviour is observed with increase in nickel concentration, the Mn-rich phases showing antiferromagnetism around 5 K. There is a systematic decrease in the dielectric constant, ε and loss tangent with increase in Ni concentration (from ε = 592 forx = 0 to ε = 78 forx = 0.4).     

Studies on the Rheological Behavior of Polycarbosilane Part I: Effect of Time,Temperature and Atmosphere

Silicon carbide based fibers are generally prepared by the melt spinning of ceramic material precursors like polycarbosilane (PCS) and the hetero-metal substituted derivatives (M-PCS). Therefore, the rheological behaviour of PCS in the melt with respect to time, temperature, atmosphere, molecular weight and polydispersity becomes very important for successful processing and for preparing green fibres. In the present study PCSs having different softening points were synthesized via the thermal backbone rearrangement of polydimethylsilane (PDMS) and their melt viscosity variation and thermosetting behavior were studied. Various conditions like, atmosphere (inert & air), temperature, time and shear rate were chosen as variables. In an inert atmosphere, the viscosity of all the PCSs decreases with increasing temperature then under isothermal conditions it remains almost constant for the low softening point samples (high polydispersity) whereas it rises for the high softening point samples (low polydispersity). It has been observed that invariably all of the PCSs crosslinked rapidly in air as compared to in an inert atmosphere of argon. The effect of temperature was found to be prominent with the increase in SiH/SiCH₃ ratio and the processing time reduces with an increase in processing temperature. The high molecular weight PCS thermosets easily due to enhanced crosslinking of the polymer as compared to low molecular weight PCS irrespective of the atmosphere. Thus, for processing of PCS it is essential to have a polydisperse sample and to maintain an inert atmosphere to prevent undesired crosslinking.     

LbL‐coated microcapsules as systems for encapsulation of optical brightening agent

We report the encapsulation of optical brightening agent (OBA) into hollow microcapsules prepared by the controlled Layer‐ by‐Layer (LbL) self‐assembly process, achieved by the sequential adsorption of oppositely charged polyelectrolytes using negatively charged silica template. Loading takes place by spontaneous deposition method which was proved by confocal laser scanning microscopy (CLSM) using rhodamine 6G (Rd6G) as a fluorescent probe. The loading of the OBA into the microcapsules was found to be dependent on the feeding concentration, pH of the medium, and loading temperature. The encapsulation efficiency of OBA decreased on increasing feeding concentration. Maximum loading was observed at pH 4 and amount of OBA loaded decreased with increase in pH. The loaded OBA was released in a sustained manner for 8 h. No degradation of the OBA was observed during the process of encapsulation and release. Polyelectrolyte capsules potentially offer an innovative way of encapsulating large amounts of active materials for a variety of applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Performance Enhancement and Signal Distortion Analysis of Virtually Doped Nanotube Tunnel FET with Embedded Ferroelectric Gate Oxide

Silicon - This paper demonstrates the effect of ferroelectric gate oxide on the electrostatic doped nanotube tunnel field-effect transistor (FE-ED-NTTFET). The proposed device is a dopingless...     

Design Considerations and Optimization of Electrostatic Doped Ferroelectric Nanotube Tunnel FET: Analog and Noise Analysis

Silicon - This paper proposed the electrostatically doped Ferroelectric Nanotube Tunnel FET (FE-NT-TFET). The proposed device is electrostatically doped, so the applied source voltage is...