Brazilian Journal of Physics最新文献

This research investigates the structural, morphological, and optical properties of SnO₂ and Cu-doped SnO₂ films deposited on glass and FTO substrates using the RF sputtering technique. The Cu-doped samples were subsequently annealed in an oxygen flow at temperatures of 400 and 500 °C. X-ray diffraction (XRD) analysis revealed that pure SnO₂ thin films exhibited an amorphous structure on both substrates. In contrast, the Cu-doped SnO₂ sample on the glass substrate maintained its amorphous state, while the sample on the FTO substrate transitioned to a tetragonal rutile structure. Thermal annealing further induced a transformation to a tetragonal rutile structure for samples on both substrates. Energy dispersive spectroscopy (EDS) confirmed the incorporation of Cu into the SnO₂ films. The estimated crystallite sizes ranged from 16 to 20 nm for the glass substrate and from 20 to 31 nm for the FTO substrate. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) analyses demonstrated uniform surface morphology with a smooth texture and strong adhesion to the substrates. The band gap energy (Eg) values for the unannealed samples were found to be 3.52, 3.40, 3.50, and 3.29 eV. Notably, Cu doping and the deposition of SnO₂ films on FTO substrates resulted in a reduction of the band gap. These findings provide valuable insights into the effects of Cu doping, annealing, and substrate type on the structural and optical properties of SnO₂, paving the way for advanced optoelectronic applications.

The collisionless, unmagnetized relativistic dusty plasma system comprising relativistic positively charged ions, energetic ion beams, and Maxwellian electrons is considered to study the fundamental properties of dust ion-acoustic waves (DIAWs) and formation of rogue waves (RWs). The Korteweg-de Vries (KdV) equation and nonlinear Schrödinger equation (NLSE) are derived using the well-known reductive perturbation and derivative expansion approaches, respectively. The concerned parameters play a crucial role in the fundamental properties (such as phase velocity, nonlinearity, dispersion, production, and propagation) of DIAWs. In addition, the rational solution of rogue waves (RWs) exists due to the effect of concerned parameters except the ion beam for argon.

The cylindrical dust-acoustic (DA) solitary structures in an unmagnetized four-component dusty plasma medium whose constituents are negatively charged dust particles, electrons, ions, and positrons are investigated. A set of equations has been considered to describe the plasma system in a cylindrical geometry and reduced those equations into a nonlinear partial differential equation so-called ((3+1))-dimensional cylindrical Kadomstev-Petviashvili (cKP) equation with the help of reductive perturbation method. The analytical solitary wave solution of the cKP equation has been reported. The existence and non-existence of solitary wave solution with the plasma parameters have been discussed. The effects of the dust grains and the nonthermality of other particles on the amplitude and width of solitary waves are examined. It is found that our plasma system supports both the positive and negative solitary waves. These results may improve our understanding of DA solitary structures in space and laboratory plasma devices in non-thermal dusty plasma medium.

The self-organization of a four-component partially ionized dusty plasma consisting of mobile electrons, positive ions, neutrals, and negatively charged static dust particles into a non-force-free double Beltrami (DB) state is explored. The DB state is a linear superposition of two distinct single Beltrami fields, characterized by two self-organized vortices. By considering the plasma species densities typical to earth’s ionosphere, the analysis of the relaxed state shows that densities and invariant helicities of plasma species can control the nature as well as the size of self-organized vortices. Additionally, the potential implications of these DB states are highlighted.

This study introduces a highly sensitive one-dimensional (1D) photonic crystal (PC)-based biosensor for detecting urea concentrations using a defect layer approach. The sensor is designed with alternating layers of BaF₂ and TiO₂, featuring a central defect layer filled with urea samples. Using the transfer matrix method (TMM), the transmission spectra were analyzed to detect urea concentrations ranging from 50 to 800 mM. This study examines the effects of varying layer thicknesses on key performance parameters, including sensitivity, Q-factor, FWHM, FoM, and LoD, successfully optimizing the sensor design. The results demonstrate a redshift in the defect mode wavelength with increasing urea concentrations, achieving sensitivities as high as 212.75 nm/RIU. Unlike conventional methods that require extensive sample preparation and lengthy analysis times, this sensor provides a rapid, cost-effective, and scalable solution. Its capability to operate near the pathophysiological range of urea in human blood makes it particularly suitable for medical diagnostics.

The concepts and dynamic processes related to complex financial networks (CFNs) are explored in this review article. After providing a definition of CFNs, we discuss the most important dynamic process associated with them, i.e., contagion. We then examine the relationship between interconnectedness and systemic risk in CFNs. Next, we discuss approaches to the measurement of systemic risk and the challenges associated with this task. Finally, we highlight three research avenues that, in our opinion, are crucial for a better understanding of the dynamics of the contagion process in CFNs: loss distribution regime, endogenous complex networks, and multilayer complex networks.

In this work, we investigated the electrical and dielectric properties of a new biocomposite-based vinyl resin emulsion reinforced with microparticles of green microcrystalline cellulose. We measured the electrical response of each sample by assessing AC electrical conductivity in the temperature range of 260–340 K and in the frequency range of 100 Hz–1 MHz. The electrical conductivity dispersion is well described by Jonscher’s power law. Accordingly, the associated mechanism conductivity is due to the correlated barrier-hopping conduction mechanism. Dielectric properties were performed using the electric modulus formalism and analyzed according to the Havriliak-Negami model. For the neat vinyl resin emulsion, the observed relaxation process is attributed to the α-relaxation. When the fillers are added to the vinyl resin emulsion, a water dipolar polarization is identified for temperatures below the glass transition temperature and a superposition of α-relaxation and an interfacial polarization, known as Maxwell–Wagner-Sillars, for temperatures above the glass transition point. The activation energies of these are determined according to the Arrhenius law. Dielectric analysis allowed for probing the reinforcement/matrix adhesion, which can control the electrical conductivity performance of the composite materials.

Our research explored an environmentally friendly approach for the synthesis of bimetallic zinc oxide-cerium oxide nanoparticles (ZC NP) through the utilization of Salvadora persica extract. We characterized the physicochemical properties of the synthesized nanoparticles using PXRD, Raman spectroscopy, FESEM, and EDX analyses. As a result, both main peaks of zinc oxide and cerium oxide NP appeared in the PXRD graph, which indicated the formation of bimetallic NP. Spherical morphology showed in the FESEM image which particles have a size of about 30–40 nm. The analysis of hemocompatibility indicated that the NP does not appreciably affect the integrity of erythrocytes at concentrations nearing 2000 µg mL⁻¹. The toxicity function of synthesized sample on human colon cancer (HT-29) and fibroblast (NIH/3T3) cells was considered through the results of MTT trial. The outcomes of synthesized NP displayed significant cytotoxic effects against HT-29 cells at 20.73 μg mL⁻¹ concentration as its IC50, while it was non-toxic on NIH-3T3 cells. Therefore, we suggest the applicability of our product in therapeutic applications such as drug delivery as well as industrial implementations.

The characterization of covalent interactions between atoms is controlled and modified by the analysis of the dispersion relation of surface plasmon polariton (SPP) waves. The analysis was conducted at the interface of gold and dielectric cesium medium for the generation of SPPs and to extract information on covalent bonding among the atoms. Crucial information regarding atom localization and electron sharing among atoms is reported by damping and dispersion spectrums of SPPs. The real and imaginary components of the dispersion relation of SPP waves serve as indicators for the arrangement of atoms in elongated chains of covalent interactions. It is investigated that each atom contributes two electrons to the formation of double covalent bonds with neighboring atoms. The localization of atoms and the precise sharing of electrons is governed by the higher-order Kerr nonlinearity and the superposition of standing waves of control fields. Furthermore, the investigation extends to the identification of crystal defects within the optical lattice structure, which is achieved through an examination of the dispersion relation of surface SPP waves. Quantitatively eight atoms and twenty-four double covalent bonds are reported in the position ranges of (2lambda ) in xy-plane. Our results provide useful information about material structure and nanotechnology.

We investigate the properties of a double-path Josephson junction connected to Bose-Einstein condensate reservoirs. By comparing the current in the proposed setup with that in a similar system connected to superconductors, we elucidate the key differences between the two systems. The systems are influenced by the Aharonov-Bohm effect, Rashba spin-orbit interaction, and phase difference of order parameters between left and right leads. Utilizing the Keldysh formalism, it turns out that, in the system connected to Bose-Einstein condensate reservoirs, the Josephson current includes higher frequency components of the phase difference between left and right reservoirs. Additionally, the dependence of critical current on energy level does not show the complete symmetric resonance but the Fano-type resonance with single or double peaks. These differences result from the bosonic statistics of reservoirs.