The study includes a conductometric chemical sensor design using aligned MnO nanorods. Nanostructuring is an emerging field of prominence due to its capacity to introduce unprecedented properties in materials with potential applications. A hydrothermally prepared in situ MnO sample appears with an urchin rod-like morphology, which changes to a spherical shape upon annealing. An aluminum anodic membrane/template (AAO) is used for the growth of the nanorods and also as a medium to support the sensor. The aligned MnO nanorods are formed in the pores of the AAO by vacuum infiltration approach, which is later on annealed. The gold electrical contacts are deposited on the top or bottom ends of the MnO-embedded AAO to ensure conductometric sensing along the length of the MnO nanorods. In comparison to the MnO film-based sensor, the MnO nanorods in the AAO template have enhanced sensitivity for detecting ethanol and acetone vapor at room temperature. The novel property observed is a result of the large surface area and number of oxygen vacancies of the uniformly aligned and parallel assemblies of the nanorods. The sensor exhibits the lowest response time at 4 s for ethanol and 2 s for acetone at room temperature with a concentration of 50 ppm. The response time is 7 and 5 s, respectively, for 25 ppm. The maximum sensitivities of the sensor at room temperature for ethanol and acetone gases are 67% and 68%, respectively, for 50 ppm concentration. The growth mechanism of the aligned nanorods formed in the AAO template is well established through FESEM analysis. The XPS and HRTEM study give additional evidence for the presence of oxidation states and structure of the prepared nanostructures, respectively.

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Polycrystalline samples of Na 0.5 La 0.25 Sm 0.25 Cu 3 Ti 4 O 12 ceramics were prepared by solid state sintering. Its crystallographic structure, electrical properties and dielectric behaviour are investigated over wide ranges of temperature (30-325 • C) and frequency (42 Hz-1 MHz). Rietveld refinement of the powder diffraction data has confirmed a cubic, single phase structure with space group Im3. This ceramic material exhibits colossal value of dielectric constant with very low values of loss factor, over wide frequency ranges and thus highlights the quality of the sample to be used for the fabrication of capacitive devices. Impedance spectroscopic studies have revealed that the compound is electrically heterogeneous. The scaling behaviour of Z suggests a temperature independent distribution of relaxation time. The mismatch in the peak frequencies of Z /Z max and M /M max suggest that the relaxation mechanism is dominated by short range movement of charge carriers.

Efficient ultrafast optical limiting using single walled carbon nanotubes functionalized noncovalently with free base and metalloporphyrins Nonlinear optical absorption and optical power limiting properties of Fe 2 O 3 hexagonal nanomorphotype are investigated using open aperture Z-scan technique with the 5 ns and 100 fs laser pulses, at 532 nm and 800 nm excitation domains. At relatively low pulse energies (below 5 lJ), sample shows saturable absorption (SA), but on going to the higher energies an interesting switchover from saturable absorption to effective two photon absorption is observed in both excitation domains. The magnitude of effective two photon absorption coefficients is calculated to be in the range of 10 À10 m/W for nanosecond and 10 À15 m/W for femtosecond laser pulse energies, respectively. XRD and TEM study reveals the polycrystalline nature, hexagonal morphology, and size of the nanostructure. The luminescence emission property is examined by photoluminescence spectroscopy (PL). It is found that some strange features exist in the luminescence spectra that are consistent with the nanoparticles size distribution. The PL emission lines are explained as originated from various optical band edges due to the size induced quantum confinement and band gap resonant PL absorption/emission behavior of semiconductor nanostructures. V C 2015 AIP Publishing LLC.

Morphology dependent nonlinear optical power limiting of CdO nanomorphotypes.

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