Applied Physics A Solids and Surfaces

Al-doped hexagonal ZnS monolayer (h-ZnS-2D) at different concentrations is adopted by using Density Functional Theory (DFT) to show the effect of Al doping on the optoelectronic and thermoelectric performances of h-ZnS-2D. The optimized cells give planar structures with small decrease of the lattice parameter and a n-type conductivity with a direct band gap, which increasing with Al content. An improvement of absorption and reflectivity and a decrease in transmittance are observed with doping in the visible and IR ranges. The thermoelectric properties showed a negative Seebeck coefficient justifying the n-type conduction and an enhancement of electrical conductivity and power factor for an optimum Al concentration of 12.5%. At high Al content, the formation of additional insulating phase of Al2S3 explains the degradation of the properties. This study opens the way to use these doped monolayers as a potential candidate in the optoelectronic applications and for thermoelectric power generation.

Triple perovskite Sr3CoSb2O9 was found to be orthorhombic having space group Immm from the Rietveld refinement of X-ray diffraction data. Impedance analysis of Sr3CoSb2O9 was performed to study the presence of different electro-active regions, electrical transport mechanism and origin of colossal dielectric constant in the temperature and frequency range of 273–423 K and 40 Hz–3 MHz, respectively. An equivalent circuit model (RgCg)(RgbQgb)(ReQe) was used to explain the complex impedance plane plots. The Rg and Rgb derived from Z View fitting of the impedance (Z) data reflect semiconducting behavior of Sr3CoSb2O9. Reduction in Z′ was observed as a function of temperature and frequency which indicates increase in ac conductivity and negative temperature coefficient of resistance. In order to explain the electrical conduction mechanisms in grains and grain boundaries the variable range hopping model was employed. AC conductivity as a function of frequency follows Jonscher’s power law. The ac conduction mechanism was explained from temperature dependent variation of frequency exponents n1 and n2. The modulus analysis confirmed the presence of non-Debye type multiple relaxation mechanisms. Dielectric properties of the sample were also investigated in the temperature range 273–423 K. At higher frequencies reduction in dielectric loss was observed.

Electron transport in branched semiconductor nanostructures provides many possibilities for creating fundamentally new devices. We solve the problem of its calculation using a quantum network model. The proposed scheme consists of three computational parts: S-matrix of the network junction, S-matrix of the network in terms of its junctions’ S-matrices, electric currents through the network based on its S-matrix. To calculate the S-matrix of the network junction, we propose scattering boundary conditions in a clear integro-differential form. As an alternative, we also consider the Dirichlet-to-Neumann and Neumann-to-Dirichlet map methods. To calculate the S-matrix of the network in terms of its junctions’ S-matrices, we obtain a network combining formula. We find electrical currents through the network in the framework of the Landauer–Büttiker formalism. Everywhere for calculations, we use extended scattering matrices, which allows taking into account correctly the contribution of tunnel effects between junctions. We demonstrate the proposed calculation scheme by modeling nanostructure based on two-dimensional electron gas. For this purpose we offer a model of a network formed by smooth junctions with one, two and three adjacent branches. We calculate the electrical properties of such a network (by the example of GaAs), formed by four junctions, depending on the temperature.

The attention of this note is focused on the use of an infrared imaging system to monitor the unsteady thermal response of a glass fibre-reinforced polymer material to impact load. On the monitored surface during impact, the material undergoes first a cooling down due to thermo-elastic effects and then heating up because of dissipation of the impact mechanical energy. Mainly within the elastic phase, temperature variations occur during a very short time (fractions of seconds) and, thus, their visualisation can be performed only with a high-frequency imaging device. In this work, measurements were performed essentially during the elastic phase with the FLIR ThermaCam SC3000, which allows for a frame rate up to 900 Hz.

We report the in situ synthesis and interesting optical properties of graphene oxide–CdTe (GO–CdTe) nanocomposites, as well as their potential application in solar cells. By doping GO during the synthesis process of CdTe quantum dots (QDs), the as-prepared GO–CdTe nanocomposites have layered structure and CdTe QDs are well preserved on the layer with uniform distribution and no aggregation. The effects of different experimental conditions on the optical properties of GO–CdTe nanocomposite are investigated. Interestingly, the colors of GO–CdTe nanocomposite solutions under daylight are similar to their fluorescence color observed under ultraviolet (UV) light, distinct from those of pure CdTe QDs and GO/CdTe nanocomposites prepared by direct mixing of GO and CdTe QDs. In addition, we demonstrate the application of GO–CdTe nanocomposites for sensitized solar cells, which show enhanced photoelectric performance. Our findings may provide new insight into optical properties of QDs coupled with carbon nanomaterials.

We have studied the electronic excitations of fluorinated copper phthalocyanine, CuPcF16, thin films using electron energy-loss spectroscopy in transmission. This allowed for the derivation of the dielectric function in a wide energy range. Furthermore, we have analyzed the lowest excitation feature using a Lorentz model, which enabled the determination of the dielectric background in the energy range of the gap excitation, and an analysis of the momentum dependence of the spectral intensities at low energies.

Silicon nanoparticles (SiNPs) are widely used as promising nanoplatform owing to their high specific surface area, optical properties and biocompatibility. Silicon nanoparticles find possible application in biomedical environment for their potential quantum effects and the functionalization with biomaterials, too. In this work, we propose a new approach for bio-functionalization of SiNPs and M13-engineered bacteriophage, displaying specific peptides that selectively recognize peripheral blood mononuclear cells (PBMC). The “one-step” functionalization is conducted during the laser ablation of silicon plate in buffer solution with engineered bacteriophages, to obtain SiNPs binding bacteriophages (phage–SiNPs). The interaction between SiNPs and bacteriophage is investigated. Particularly, the optical and morphological characterizations of phage–SiNPs are performed by UV–Vis spectroscopy, scanning electron microscopy operating in transmission mode (STEM) and X-ray spectroscopy (EDX). The functionality of phage–SiNPs is investigated through the photoemissive properties in recognition test on PBMC. Our results showed that phage–SiNPs maintain the capability and the activity to bind PBMC within 30 min. The fluorescence of phage–SiNPs allowed to obtain an optical signal on cell type targets. Finally, the proposed strategy demonstrated its potential use in in vitro applications and could be exploited to realize an optical biosensor to detect a specific target.