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This paper describes the establishment of free-standing rolled graphene oxide (roll-GO) and polypyrrole (Ppy) using a modified Hummer method and oxidative polymerization. Then, a photodetector was created by removing a thin film of the free-standing rolled graphene oxide from a filter paper and attaching it to a tape. The chemical structure of the roll-GO was confirmed using XRD and FTIR analysis, while SEM and TEM showed that it was rolled in nature. The material had a small bandgap of 2.4 eV and a high current density in light conditions. The photodetector responded well to monochromatic light, with Jph values changing from 0.027 to 0.019 mA/cm2 as the light wavelengths decreased from 340 to 730 nm. The photoresponsivity (R) and detectivity (D) values were high, at 340 nm (0.27 mA/W and 6.0 × 107 Jones, respectively) and at 730 nm (0.19 and 4.25 × 107 Jones, respectively). The addition of Ppy improved these parameters, with the Ppy/roll-GO/tape photoelectrode showing excellent R and D values of 0.33 mA/W and 7.34 × 107 Jones, respectively. Furthermore, the production of a photocurrent at V = 0 indicated that the Ppy/roll-GO layer could be used for solar cell applications. Overall, the results suggest that the prepared free-standing Ppy/roll-GO/tape photodetector has high potential for use in the optical region between 340 and 730 nm and may be suitable for industrial applications. [ABSTRACT FROM AUTHOR]

Due to a suitable band gap and high light absorption behavior, Bi2S3 is showing major success in photo-to-current conversion applications. In this current work, the authors used a low-cost nebulizer spray pyrolysis method to create nano-sized pure and unique Eu contents (1–5 wt.%)-loaded Bi2S3 thin layers by taking bismuth nitrate and thiourea as the source materials. The parent and Eu doped Bi2S3 thin films, deposited on a well-cleaned glass substrate at 350 °C, were analyzed using a variety of characterization approaches, including FESEM, EDS, XRD, PL, UV-Vis, and I-V, to describe the morphologies, compositions, crystallinity, defect states, band gap, and photodetection capability, respectively. The X-ray diffraction outcomes confirmed an orthorhombic polycrystalline structure for all Eu concentrations, and they were highly oriented along the (130) plane. Incorporation of Eu into the host matrix improves the intensity of all the peaks, and the crystallite size (25 nm) was found to be highest for the 3% Eu doped Bi2S3 thin film. The formation of a nanowire-like morphology was confirmed thorough field emission electron microscopy analysis, which is preferred for photo detectors. Upon excitation at 325 nm, grown pure and Eu doped Bi2S3 thin films indicated five emission peaks at 387, 418, 439, 480, and 523 nm, respectively. All the films showed significant absorption in the UV region, and importantly, a narrowing of the band gap is seen from 2.29 to 2.17 eV. Finally, the current-voltage characteristics of the pure and Eu doped Bi2S3 thin films were tested using silver contacts as electrodes. The results showed that the 3% Eu doped Bi2S3 sample showed a higher UV photocurrent characteristic, with high specific detectivity (1.82 × 1010 Jones), photoresponsivity (3.88 × 10−1 AW−1), external quantum efficiency (125%), and rapid photo response, as well as a recovery speed of 0.3 s and 0.4 s, due to the effective light absorption and photocarrier generation. We believe that our study may provide a cost-effective approach for UV photosensor applications. [ABSTRACT FROM AUTHOR]

Hierarchical and flower-like nanostructures have attained great attention over the past decades due to their unique and intriguing properties. Considering the advantages of their particular structure and properties, we prepared g-C3N4/MnO2 nanocomposite by microwave heating technique without using any catalysts, templates and organic reagents. The longitudinal and transverse relaxation time of as-synthesized nanocomposites were measured by using 0.55 T MRI instrument. Manganese is the primary origin for MRI and MR signals; therefore, different concentrations of the composite were dissolved in water. Relaxivities were measured by the inverse of relaxation times and plotted against the different concentrations of manganese. MRI results showed that the strength of the imaging signal is directly proportional to the Mn concentration, demonstrating that as-synthesized flower-like nanostructures have excellent T1-weighted MRI performance. This study indicates that the nanocomposite of g-C3N4/MnO2 could be a potential candidate as a bifunctional medical system that combines diagnostic imaging and targeted therapy. [ABSTRACT FROM AUTHOR]

MoO3 thin films are fabricated using nebulizer spray pyrolysis technique, which is doped with Fe at various concentrations of 1, 2, 3, and 4% for ammonia gas sensors application at room temperature. X-ray diffraction (XRD) study confirms the growth of the crystal by Fe doping up to 3%, nano rods shape morphology of the thin film samples observed by field emission scanning electron microscope (FESEM), reduction in bandgap is evidenced via UV-VIS spectrophotometer. Gas sensing study is performed using gas analyzing chamber attached with Keithley source meter. Since 3% Fe doped MoO3 sample displayed nano rods over the film surface which exhibits highest sensitivity of 38,500%, in a short period of raise and decay time 54 and 6 s. Our findings confirms that the 3% Fe doped MoO3 films suitability for ammonia gas sensing application. [ABSTRACT FROM AUTHOR]

Summary: The hot phonon bottleneck effect and the reduced carrier‐phonon interactions in quantum‐confined systems would lead to long‐lived excitonic carrier. Importantly, these phenomena prevent the carrier energy dissipation, and consequently improve the efficiency of optoelectronic devices like solar cells. Aiming this, the excellent sensitizing properties of bismuth modified lead sulphide (Bi:PbS) quantum dots (QDs) with reduced carrier‐phonon interactions are demonstrated. Further, the multiple excitonic transition states are probed from the derivatives of absorbance spectra. In the final section, both Fano interaction analysis and Huang‐Rhys factor confirms the minimum carrier‐phonon coupling in Bi:PbS QDs. The phonon lifetime is calculated by the Cuscó equation and the obtained results endorse that Bi:PbS QDs are excellent sensitizers for solar cell applications. [ABSTRACT FROM AUTHOR]

Summary: Exploring new polymorphs of groups III to V compounds of evolved physical properties has recently received substantial interest from researchers. Accordingly, we explored new pressure‐driven polymorphs of gallium nitride (GaN) and investigated their physical properties using density functional theory (DFT)‐based full‐potential (FP) linearized‐augmented‐plus‐local‐orbital (L[APW + lo]) approach. Our analysis shows the transition of ground‐state wurtzite (wz) structure to beryllium oxide (β‐BeO)‐type structure at a tensile stress of ~−6.82 GPa and to silicon carbide (SiC)‐type structure by applying moderate compressive stress of magnitude 0.27 GPa. Similarly, the transition of wz‐GaN to nickle arsenide (NiAs) and titanium arsenide (TiAs)‐type structures has been realized at 43.78 and 45.72 GPa, respectively. These new polymorphs of GaN exhibited comparable cohesive energies with wz‐structure and the phonon dispersions free of imaginary frequencies, which indicate them as stable as the ground‐state wz‐phase. Investigations of the electronic structures show the wz‐, β‐BeO‐, and SiC‐phases of GaN as semiconductors of direct bandgap of energy 3.10, 3.15, and 2.97 eV, whereas the NiAs‐ and TiAs‐ phases of GaN exhibited indirect bandgap of energy 2.59 and 2.82 eV. All the GaN polymorphs demonstrated transparent behavior for the incident light photon of energy less than 13 eV. They exhibited optical absorption as high as 3.02 × 106 cm−1, 2.23 × 106 cm−1, 2.62 × 106 cm−1, 2.67 × 106 cm−1, and 2.67 × 106 cm−1 in the case of wz‐, β‐BeO‐, NiAs‐, SiC‐, and TiAs‐structured GaN, respectively. These interesting features of the novel polymorphs of GaN indicate them promising for electronic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

Abstract: High‐end nonlinear optical devices demand superior quality KH2PO4 crystal and to meet this necessity slow solvent evaporation technique is employed to grow optical quality potassium dihydrogen orthophosphate (KH2PO4, KDOP) crystal by doping tartaric acid (TA) and special attention is devoted to optimize the defect influenced properties of KDOP crystal. The incorporation of TA in KDOP crystal matrix is evaluated by employing energy dispersive spectroscopic technique. The crystalline phase and structural dimensions of pure and TA doped KDOP crystal is evaluated by means of powder X‐ray diffraction analysis. The luminescence behavior of TA doped KDOP crystal is examined in visible region and violet colored emission is evidenced at 408 nm. The Vickers microhardness studies are carried out to uncover the constructive influence of TA on hardness and elastic stiffness coefficient of KDOP crystal. Impressive role of TA in minimizing defect density and improving the surface growth mechanism of KDOP crystal is explored by chemical etching analysis. The thermogravimetric analysis curve is traced within 30–650 °C and TA doped KDOP crystal is found thermally stale up to 233 °C. The results are appraised to propose the suitability of TA doped KDOP crystal for distinct applications. [ABSTRACT FROM AUTHOR]

The crystal structures, electronic, elastic and optical properties of the ternary compounds CuSbS 2 and CuBiS 2 have been investigated by using the full-potential linear augmented plane wave (FP-LAPW) method. From this study, it is found that the compounds CuSbS 2 and CuBiS 2 have indirect band gap energies which are calculated with the mBJ potential as 1.28 and 1.05 eV, respectively. CuSbS 2 crystallizes in an orthorhombic structure, with the Pnma space group, the lattice parameters are a = 6.018 Å, b = 3.795 Å and c = 14.495 Å, CuBiS 2 has also an orthorhombic structure, with the space group Pnma and the lattice parameters a = 6.134 Å, b = 3.911 Å and c = 14.548 Å, which are used in our calculations. Optical parameters, such as dielectric constant, refractive index and reflectivity are calculated and analyzed. Elastic properties are also investigated for the first time. The results demonstrated that the compounds CuSbS 2 and CuBiS 2 have the potential to be used for photovoltaic applications. [ABSTRACT FROM AUTHOR]

This study spotlights the fundamental insights about the structure and static first hyperpolarizability ( β) of a series of 2,4-dinitrophenol derivatives (1-5), which are designed by novel bridging core modifications. The central bridging core modifications show noteworthy effects to modulate the optical and nonlinear optical properties in these derivatives. The derivative systems show significantly large amplitudes of first hyperpolarizability as compared to parent system 1, which are 4, 46, 66, and 90% larger for systems 2, 3, 4, and 5, respectively, at Moller-Plesset (MP2)/6-31G* level of theory. The static first hyperpolarizability and frequency dependent coupled-perturbed Kohn-Sham first hyperpolarizability are calculated by means of MP2 and density functional theory methods and compared with respective experimental values wherever possible. Using two-level model with full-set of parameters dependence of transition energy (Δ Ε), transition dipole moment ( μ0) as well as change in dipole moment from ground to excited state (Δ μ), the origin of increase in β amplitudes is traced from the change in dipole moment from ground to excited state. The causes of change in dipole moments are further discovered through sum of Mulliken atomic charges and intermolecular charge transfer spotted in frontier molecular orbitals analysis. Additionally, analysis of conformational isomers and UV-Visible spectra has been also performed for all designed derivatives. Thus, our present investigation provides novel and explanatory insights on the chemical nature and origin of intrinsic nonlinear optical (NLO) properties of 2,4-dinitrophenol derivatives. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]