Manish Kumar Singh

Anisotropic Bianchi Type-III Bulk Viscous Fluid Universe in Lyra Geometry

An anisotropic Bianchi type-III cosmological model is investigated in the presence of a bulk viscous fluid within the framework of Lyra geometry with time-dependent displacement vector. It is shown that the field equations are solvable for any arbitrary function of a scale factor. To get the deterministic model of the universe, we have assumed that (i) a simple power-law form of a scale factor and (ii) the bulk viscosity coefficient are proportional to the energy density of the matter. The exact solutions of the Einstein’s field equations are obtained which represent an expanding, shearing, and decelerating model of the universe. Some physical and kinematical behaviors of the cosmological model are briefly discussed.

Fast grown self-assembled polythiophene/graphene oxide nanocomposite thin films at air–liquid interface with high mobility used in polymer thin film transistors

Successful practical application of a polymer or its nanocomposite depends on the ability to produce a high performance electronic device at a significantly lesser cost and time than those needed to manufacture conventional devices. Here, we present a facile and fast method for the self-assembly of a highly-orientated crystalline polymer nanocomposite thin film of poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] [PBTTT] and graphene oxide (GO) with large surface area at the air–liquid interface, which was assisted by the Floating Film Transfer Method (FTM). Prior to the fabrication of organic thin film transistors (OTFTs), the polymer nanocomposite thin film was studied using multiple techniques namely scanning electron microscopy (SEM), high resolution-transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), atomic force microscopy (AFM), grazing incident X-ray diffraction (GIXD), electronic absorption, Fourier transformed-infrared (FT-IR) spectroscopy, and cyclic voltammetry (CV). The results are also compared to those of pristine polymer thin film. Further, the organic thin film transistors (OTFTs) fabricated using the polymer nanocomposite show better device performance featuring ∼0.112 cm2 V−1 s−1 field effect mobility and 103 on/off ratio in ambient conditions. Our study highlights a technique that allows fast growth of self-assembled high-quality nanocomposite thin films for enhanced device performance.

Growth morphology and special diffraction characteristics of multifaceted gold nanoparticles

This paper deals with morphology of synthesized nano gold particles through seed based growth. Various types of morphologies have been observed. They primarily relate to decahedral and truncated tetrahedral shapes. Their relative abundance is dependent on temporal evolution of nanoparticles. These shapes are understood to have evolved from a seed having symmetry that is a supergroup of the point groups possessed by these nanoparticles. The usual pentagonal twinned morphologies observed under High Resolution Transmission Electron Microscopy have displayed two distinct types of interfaces. They have been attributed to cubic and icosahedral three-fold orientations. Such a discussion is lacking in literature. The five triangular faces of decahedral particles are essentially rotational twins resulting out of a common five-fold axis. Two special diffraction features for truncated tetrahedral particles have been observed. They refer to (i) triangular streaks around Braggs spots conforming to three fold symmetry of these particles and (ii) by observation of forbidden reflections of the type 1/3{422} and 2/3{422} along 〈422〉 directions. Latter has been understood in terms of intrinsic fault whereas former arises owing to shape transform of nanoparticles. The presence of faults has helped rationalize decrease of lattice parameter vis-à-vis that of standard FCC gold. The variation of intensities of these forbidden reflections seems to be arising out of density of such intrinsic faults in nano gold particles in addition to dynamical effects.