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We report on the nature of charge-neutral exciton emission decay, exciton-trion conversion as well as their phonon coupling in exfoliated WSe2 nanosheets subjected to ~ 1.3 MeV energetic γ-photons. Steady-state photoluminescence (PL) spectra, upon deconvolution, showed prominent emission peaks at ~ 680 nm, ~ 712 nm, and ~ 730 nm and ascribed to 2s, and 1s excitons and trions respectively, while the chalcogen vacancy (VSe) mediated defect emission peak found at ~ 790 nm. From the X-ray photoelectron spectroscopy (XPS) analysis, we noticed a clear shifting of the fundamental peaks due to W and Se toward higher binding energy values and were attributed to the radiation-induced alteration in the oxidation states locally, taking advantage of the manifestation of point defects/vacancies. Moreover, the time-resolved PL spectra signify an anomalous variation in the fast parameter (0.4–0.86 ns), and with slow parameter (2.46–3.82 ns) getting slower with increasing γ-dose. A slight variation in the exciton-phonon coupling factor is noted with Se-ph < 1 indicating a weaker interaction and featuring maximal envelope over all the phonon replica near the zero-phonon line. In contrast, trion-phonon coupling factor, St-ph > 1, or < 1 depending on its spin degeneracy (ζ = 2 s + 1; with 2, for s = 1/2 and 4 for s = 3/2). The highest St-ph value determined was ~ 1.82 ± 0.2 which declines monotonically with increasing dose but remained greater than unity up to a γ-dose as high as 96 kGy. The implication of trion-phonon coupling has immense scope in nano-photovoltaics, and nano-electronics as well as heat sinks in nanogenerators. [ABSTRACT FROM AUTHOR]

We propose a simple theoretical calculation scheme based on the phenomenological Fourier heat-flow formalism to study thermal transport behaviors in nanoscale copper rods. The axial heat transport is characterized by a new super-oscillatory feature along with small-amplitude heat spikes. It is anticipated that these atypical spikes are generated by accumulation of localized ' hotspots' that have low heat dissipation characteristics. In the case of radial transport, we witness the existence of three distinct heat regimes owing to buildup of hot electrons after experiencing ballistic scattering events. It is important to note that, even though the nanorod diameter is comparable to or smaller than the electron mean free path length, λmfp ∼ 30 nm; multiple ballistic electronic scattering from the outer surface of the nanorods and subsequent accrual into several layers through secondary collisional events has led to concentric heat zones. The hotspots disappear when the nanorod diameter exceeds λmfp. [ABSTRACT FROM AUTHOR]

We demonstrate a nanoscale palladium (Pd) based inverse surface plasmon resonance (ISPR) setup for sensing highly inflammable hydrogen (H 2 ) gas. The ISPR setup was employed in Kretschmann configuration to assess the sensitivity of the Pd-films when subjected to H 2 gas exposure. With an adequate broadening of the SPR peak maxima, the SPR angle was found to shift from a value of 46.57° to 50.97°, when the concentration of H 2 was varied between 0% and 0.9%. The shifting can be attributed to the transient development of isolated PdH x ( x < 1) clusters within Pd lattices, resulting in an appreciable change of refractive index locally. The dynamical behaviour of switching on/off states exhibited by a ∼20 nm Pd-film and exposed to 0.1% H 2 gas was monitored over several cycles repetitively. The ISPR based H 2 sensor, as demonstrated in ambient environment, would find scope to detect low level H 2 in industrial and other hazardous areas. [ABSTRACT FROM AUTHOR]

Barbules of the peacock feather have been used as the natural template for developing assemblies of zinc oxide (ZnO) nanospheres. The different colored barbules consisting of various photonic crystals (extracted from eye-pattern) were characterized in terms of the stop-bands identified in the respective Reflectance spectra. The stop-bands of the photonic crystals are found to get red-shifted after the loading of ZnO nanospheres and was reasoned to the modification of photonic band gap. The ZnO nanosphere decorated barbules show well defined photoluminescence response with dominant defect related emission of ZnO. The artificially grown inorganic structures on natural templates form a basis of new hybrid system that can help in exploiting photonic band gap engineering and light wave modulation with high selectivity. [ABSTRACT FROM AUTHOR]

Polymer embedded cadmium sulfide nanoparticles/quantum dots were synthesized by a chemical route using polyvinyl alcohol (lmw) as the desired matrix. In an attempt to measure the electrical properties of nano-CdS/Ag samples, we propose that contribution from surface traps are mainly responsible in determining the I∼ V and C∼ V characteristics in high frequency ranges. To be specific, beyond 1.2 MHz, the carrier injection from the trap centers of the embedded quantum dots is ensured by large current establishment even at negative biasing condition of the junction. The unexpected nonlinear signature of C∼ V response is believed to be due to the fact that while trying to follow very high signal frequency (at least 10-3 of recombination frequency), there is complete abruptness in carrier trapping (charging) or/and detrapping (decay) in a given CdS nanoparticle assembly. The frequency dependent unique role of the trap carriers certainly find application in nanoelectronic devices at a desirable frequency of operation. [ABSTRACT FROM AUTHOR]