Applied Physics A最新文献

This research investigates the electronic and optical properties of Cu₂O nanostructures deposited under different pH conditions and their implications for semiconductor applications. We performed a comprehensive electrochemical characterization using Mott-Schottky (M-S) analysis to determine the type of conductivity, charge carrier density, and flat-band potential of Cu₂O thin films. The results indicated that Cu₂O deposited at pH 5.4 exhibited n-type conductivity with a peak charge carrier density of 1.01 × 10¹⁵ cm^− 3, while Cu₂O deposited at pH 10 showed p-type conductivity with a carrier density of 2.07 × 10¹⁷ cm^− 3. Results showed that the prepared Cu₂O thin films were influenced by the pH and displayed different semiconductor, crystal, and morphological properties. The optical absorption edge appeared around 459 nm which indicates the formation of Cu₂O and the band gap energy was estimated using Tauc plot. Photoluminescence (PL) spectroscopy was utilized to identify and characterize defect states within the band gap, revealing significant peaks related to copper and oxygen vacancies, as well as metastable defects. The energy band diagrams and Schottky barrier potential calculations provided insights into the charge transfer mechanisms at the semiconductor-electrolyte interface. Finally, the performance of p-Cu₂O/n-Cu₂O homojunctions was evaluated through I-V characterization, demonstrating typical p-n junction behavior and a conversion efficiency of 0.374%. This study highlights the influence of deposition conditions on the electronic properties of Cu₂O and underscores the importance of optimizing these parameters for enhanced performance in photoelectrochemical devices.

The development of technology for modifying polymer materials using cold plasma is an urgent task, as traditional chemical etching leaves a toxic trace that can harm cell viability. The purpose of this work is to modify the surface of composite films composed of chitosan and hydroxyapatite, using direct current (DC) plasma, to enhance the proliferation activity of human fibroblasts on these materials. The film modifications were evaluated using scanning electron microscopy (SEM), contact angle wetting (WCA), infrared spectroscopy (IR) and mass loss analysis. Biocompatibility of the composite films was assessed by the MTT method. Plasma treatment of films in air and argon for 1 min increases the free surface energy. After plasma treatment, the main characteristic oscillation bands change, which indicates the simultaneous destruction of the chitosan polymer chain with the rupture of the O-glycoside bond and the formation of new C-OH bonds. Approximately 1.5-2% of the mass of the initial film is etched in 1 min, after 1 min the etching rate slows down and reaches 3-3.5% for air and 1.8–2.1% for argon during 4-minute processing. The results of the SEM show that after treatment in air and argon plasma, the morphology of the studied films changes and resembles cells. DC plasma modification of the CS + HA composite film increased the proliferation activity fibroblast by 23% within 2 min in air and by 4 min in argon atmosphere.

In this research, tungsten oxide nanocrystals with polymerized spherical, rod, and sheet structures were synthesized using a solvothermal method with WCl₆ as the tungsten source in three different solvent environments: ethanol, an ethanol/water mixture, and pure water. The size and morphology of the tungsten oxide nanocrystals were tuned in a cost-effective manner. Polymerized spherical tungsten oxide synthesized in ethanol consisted of nanorods with diameters of 6–10 nm; rod-shaped tungsten oxide with diameters of 150–260 nm was obtained in the ethanol/water mixture; and sheet-like tungsten oxide synthesized in pure water had dimensions of 50–100 nm × 40–200 nm. Gas sensitivity tests revealed that the synthesized materials were highly selective for acetone, with the polymerized spherical tungsten oxide showing a sensitivity as high as 25.4 at 100 ppm acetone concentration. This difference in gas-sensing properties is attributed to variations in the microstructure and crystal properties of tungsten oxide nanocrystals formed under different solvent conditions. This research provides a new perspective for the design and optimization of gas sensor materials, demonstrating that modulating the solvent type can optimize gas-sensitive performance, which is of significant research importance.

Graphical abstract

This article introduces a simple yet highly effective wideband microwave absorber, leveraging a resistive ink Frequency Selective Surface (FSS) in conjunction with Equivalent Circuit Modeling (ECM) and Deep Neural Network (DNN) techniques. This absorber design addresses critical challenges in the field by offering a versatile and efficient solution for wideband absorption while remaining lightweight and polarization-insensitive. The presented resistive FSS unit cell has an electrical length of 0.31 λ. The proposed square-loop FSS-based microwave absorber is designed and fabricated using Y-Shield HSF 64 resistive ink having a conductivity of 640 S/m. Experimental measurements are meticulously executed using the WR90 rectangular waveguide method, utilizing 1 × 2-unit cells. This configuration allows for broad bandwidth absorption with minimal weight and polarization sensitivity. Results indicate an impressive − 10 dB absorption bandwidth spanning 3.5 GHz (8.9–12.4 GHz) within the X-band of microwave frequencies. Beyond its wideband prowess, this absorber champions the attributes of simplicity and lightweight construction, rendering it an attractive candidate for diverse applications. Moreover, it showcases an inherent indifference to polarization, a pivotal feature for stealth applications.

Transient thermoreflectance (TTR) signal generated from delaminated films of Al, TiN and ZnO upon incidence of nanosecond pulsed laser beam and creation of oscillations is used to investigate the damping mechanism. The thermal and acoustic components of the TTR signal are evaluated and the decay in the acoustic component with time is related to the energy dissipated during damping. The damping of acoustic oscillations in MHz frequency range is explained by the dissipation of energy when the mobile dislocations oscillate in the presence of a drag force created by electron and phonon scattering. The variation of dislocation density with the size of the oscillating films in Al, TiN and ZnO is consistent with the Granato-Lṻcke theory of energy loss from mobile dislocations. TiN films with lower phonon scattering and higher transverse velocity of sound show lower energy loss during damping provided the dislocation density is not high. Al and ZnO films with higher phonon scattering and lower transverse velocity of sound show higher energy loss. The results indicate the necessity of maintaining lower dislocation density to minimize energy loss during damping.

A Nanocomposite filled flexible compact circular shaped multiband antenna proposed for improving radiation characteristics of various wireless bands. A Yagi shaped radiator modified to a coplanar waveguide fed circular ring patch and ground that cover six bands with good isolation and its radiation is enhanced by nanocomposite filled slots in feed line that corresponds to the position of circular ring radiator. Polyaniline (PANI) a conducting polymers exhibits numerous benefits. Its conductivity greatly varies through redox reactions by adjusting proton levels. The combination of carbon coated cobalt (CCo) and dichloroacetic acid (DCAA) creates a homogeneous solution with magnetic properties from the ferromagnetic nature of CCo. This magnetodielectric nanocomposite antenna is formed by homogenizing a mixture encased with CCo solution. The electromagnetic radiation of antenna is increased by modulation of magnetic properties of CCo with electric properties of PANI and this proposed nanocomposite material CCo_PANI suitable for different bending conditions. The flexibility of antenna evaluated by different bending conditions, results are matched to rigid antenna and covers 1.80–2.45 GHz PCS, 2.5/3.5 GHz WiMAX, 5G NR 78, 5G sub 6 GHz, Lower 6 GHz 5G, 5.80 GHz WLAN and 5.80 GHz ISM bands.

This study investigates the electrical transport properties of gadolinium-doped cobalt ferrite (Gd-doped CoFe₂O₄) which is prepared by a high-temperature solid-state synthesis method. The study mainly focuses on the sensitivity of the material for different in temperature and frequency, exploring its potential application as a negative temperature coefficient (NTC) thermistor. X-ray diffraction analysis is used to verify the crystal structure and phase purity. Scanning electron microscopy (SEM) was used to characterize the surface microstructure. Particle size distribution analysis revealed that increasing the gadolinium (Gd) doping concentration has resulted in a decrease in average grain size. Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the chemical composition of the Gd-doped cobalt ferrite (CoFe₂O₄) compounds. The dielectric properties of these compounds were examined as functions of temperature and frequency. The impact of grains on the overall electrical response of all the prepared samples was observed by analyzing the Nyquist (Cole-Cole) plots at various temperatures. The NTCR characteristics of the prepared materials were determined from the temperature response of DC conductivity. The grain resistance at various temperatures is used to evaluate the thermistor parameters by considering the strong temperature dependence of resistivity. This indicates the potential use of grain resistance in thermistor-based devices. The frequency-dependent conductivity agrees well with Jonscher’s proposed universal power law. Temperature-dependent spectroscopic plots of the conductivity provide the activation energy, which exhibits that the charge carriers influence the transport characteristics of the compound.

The transmission characteristics of the magnetic coupling resonance wireless power transfer (MCR-WPT) system with different loading methods of electromagnetic metamaterials (MTM) are studied in this paper. Firstly, a primitive MTM with a working frequency of 6.78 MHz is designed. Secondly, the magnetic field concentration and anti-misalignment characteristics of the MTM are analyzed. Finally, the transmission characteristics of the MCR-WPT system with different loading styles and quantities of MTMs are researched experimentally. The research results show that when the transmission distance is 400 mm and the MTMs are loaded between the transmitting coil and the receiving coil, the maximum transmission efficiencies of the MCR-WPT system loaded with one, two, and three pieces of the MTM are 28.57%, 42.27%, and 41.5%, respectively. When the MTM is 30 mm away from the transmission system, the transmission efficiency of the four-sided surround type MCR-WPT system is 38.72%, which is 6% higher than that of the two-sided MCR-WPT system. When the transmission distance changes from 200 to 500 mm, the transmission efficiency of the MCR-WPT system can be maximized by adjusting the loading method of MTMs. The results can provide a reference for further improving the transmission efficiency of the middle- and long-distance MCR-WPT systems.

The mechanical and electrical properties of strain gauge resistance alloys are intricately related to the element content of their alloys, and play a crucial role in the performance of sensors. This study delves into the effects of different Ni contents on the mechanical properties, microstructure, and electrical properties of FeCrCoWNi strain gauge alloy metals. Through comprehensive analysis of tensile testing, XRD, EDS, SEM, and TEM, the effects of different Ni contents on the mechanical and electrical properties of the alloy were discussed in detail and systematically, and the fracture mechanism was investigated. The research results indicate that with the increase of Ni content, the yield strength of FeCrCoWNi alloy shows a trend of first decreasing and then increasing, while the hardness shows a trend of first increasing and then decreasing, and the electrical resistivity gradually decreases. Transmission electron microscopy and X-ray diffraction analysis have shown that the addition of Ni results in grain refinement caused by the fcc phase, as well as excellent particle strengthening effects. The increase in grain size after Ni addition leads to a decrease in the number of grain boundaries, which is considered the main driving factor affecting the mechanical and electrical properties of the alloy.

In the present investigation, the bio-reduction of silver nitrate has been done using the extracts obtained from the leaves and flowers of Catharanthus roseus and the resultant silver nano particles were incorporated with ZnO through sonication. The ZnO was prepared via a simple soft chemical route. The characteristics of the resultant nanoparticles were analyzed using X-ray diffraction spectrometer, scanning electron microscope, Fourier Transform Infrared spectrophotometer, EDAX and elemental mapping techniques. The diffraction patterns of thus prepared ZnO nanomaterials revealed that they are crystallized with (101) plane which is the preferential orientation. The FTIR, report reveals that the phenolic compounds had played a vital role in the reduction of synthesized Ag nanoparticles. The SEM analysis revealed the coral rock like structure of the synthesized nanomaterials. The EDAX and mapping analysis confirms the presence of the elements Zn, Ag and O and C in the prepared samples. From the results, it can be concluded that the Catharanthus roseus leaves and flowers are good sources for the synthesis of silver nanoparticles. The plant mediated Ag incorporated ZnO showed better antibacterial property on Gram negative bacteria (Staphylococcus aureus and Escherichia coli) and Gram-positive bacteria (Klebsiella pneumonia).The antifungal action of Catharanthus roseus leaf and flower mediated Ag:ZnO nanoparticles were tested against three fungal strains namely Aspergillus Niger, Aspergillus flavus and Penicillium chrysogenum. Ag:ZnO:Leaf nanoparticles showed stronger antimicrobial activities when compared to the Ag:ZnO and Ag:ZnO:Flower nanoparticles. The radical scavenging activity named DPPH, was used to study antioxidant capability of the resultant nanoparticles and the related inhibition percentage of Ag:ZnO:Leaf and Ag:ZnO:Flower nanoparticles were found to be 65, 76 and 93%, respectively.