Applied Physics A最新文献

Based on the tailorable nature of two-dimensional (2D) materials, we fabricated stepped Fe₃GeTe₂ (FGT) nanosheets devices with inhomogeneous thickness and investigated their angular magnetoresistance (AMR) behavior. Our measurements reveal a distinct antisymmetric AMR dependence on field orientation (0-360°) under low magnetic fields, exhibiting anomalous peaks at ~ 90° and ~ 270°. We suggest that this anomalous phenomenon may arise from local symmetry breaking induced by thickness inhomogeneity, which modifies the electronic structure of the topological nodal-line semimetal FGT and substantially alters the coupling between its topological band features and magnetic textures. This work offers novel experimental insights into the interaction mechanisms between topological electronic states and magnetic properties.

Pure and cobalt-doped CdS thin films (Co = 1–10 wt%) were synthesized via aerosol-assisted chemical vapor deposition (AACVD) at 250 °C. Single-source xanthate precursors were used. X-ray diffraction confirmed phase-pure wurtzite CdS. Cobalt incorporation reduced the crystallite size from approximately 27 nm (pure) to 15 nm at 5 wt% and increased microstrain. X-ray photoelectron spectroscopy verified the presence of Cd²⁺/S²⁻ and Co in mixed Co²⁺/Co³⁺ states without secondary phases. Optical analysis revealed a slight narrowing of the direct band gap with Co doping, from approximately 2.56 eV (pure) to 2.49–2.50 eV (doped films). Additionally, refractive-index dispersion and Spitzer–Fan modeling indicated a decrease in the high-frequency dielectric constant with cobalt content, consistent with reduced polarizability. Steady-state PL showed bands at ~ 485, 548, and 725 nm, all quenched with increasing Co, consistent with added non-radiative centers. Time-resolved PL (TRPL) decays were bi-exponential in the microsecond regime. At 1 wt% Co, lifetimes dropped to τ₁ ≈ 0.21 µs and τ₂≈ 1.68 µs; at higher Co, the slow component partially recovered (τ₂≈2.6–3.3 µs). The photosensing capabilities of both pure and 10 wt% cobalt-doped films were tested across temperatures from 50 °C to 150 °C. The Co-10 wt% film delivered the fastest dynamics near 80 °C, with rise and decay times of approximately 1.73 s and 1.22 s, respectively. In contrast, the pure film exhibited a slower rise time of around 3.4 s. Responsivity, detectivity, and sensitivity decreased with temperature due to increased dark current. Co doping by AACVD offers a simple way to tune CdS defects and optoelectronic properties for thermally robust photodetection.

In this work, the potential of Ni_1 − xCo_xFe₂O₄ (x = 0.0, 0.3, 0.5, 0.7, 1) bifunctional nanocomposites as nanocarriers in drug delivery systems and electrode material in supercapacitors was investigated. The nanocomposites were successfully synthesized by a simple and eco-friendly thermal treatment method using rosemary leaf extract, avoiding the need for harmful reducing or capping agents. The investigation into the cytotoxicity of ternary blended transition nanoferrite, employed as quercetin (Que) nanocarriers (NCs) in drug delivery systems, was conducted using the MTT assay. The cell viability ranged from 20% to 37% at the highest concentration (60 µg/ml) against cancer cells and resulting in a cytotoxicity of 35% to 43% against HEK 293-T cell line. By cyclic voltammetry (CV) characterizations, we also demonstrated the excellent performance as electrode material for supercapacitors of the as-prepared mixed ternary-transition-metal ferrites. The NiCF73 sample (Ni_0.7Co_0.3Fe₂O₄) had a better specific capacitance value at 2 mV/s scan rate equal to 2014 F/g. The results showed that by controlling the biocompatibility and electrochemical properties of Ni_1 − xCo_xFe₂O₄ nanocomposites, their performance in various practical applications in the biomedical field, as well as in wastewater treatment and water desalination applications, can be improved.

Graphical abstract

Dielectric functions play a pivotal role in the interaction of light with nanoscale matter. They determine all optical properties, including dispersion, absorption, scattering, reflection, transmittance, and polarization. In this study, we present a method for extracting dielectric functions from UV-Vis spectra of monodisperse colloidal silver nanoparticles, offering an alternative to standard experimental techniques within the constrained wavelength range of 400 to 600 nm. The approach utilizes a developed Mie scattering fitting function, incorporating additional conditions on the dielectric function behavior at the localized surface plasmon resonance wavelength. It enables the extraction of universal dielectric functions from UV-Vis data at localized surface plasmon resonance points by knowing absorbance and wavelength as well as concentrations of colloidal nanoparticles and optical path length. The universality of dielectric functions makes them applicable for fitting of UV-Vis spectra of colloidal silver nanoparticles of an a priori unknown sizes within the diameter range of 20 to 100 nm with possible extension to bigger sizes. Once determined, these dielectric functions can be directly applied to UV-Vis spectra to ascertain the size and concentration of monodisperse silver nanoparticles’ colloidal solutions.

In this study, thin films of pure titanium dioxide (TiO₂) and titanium dioxide dual mixed with zinc oxide (ZnO) and magnesium oxide (MgO) with varying concentrations of (ZnO: MgO)_x ranging from 0 to 30 wt% undoped and doped gold nanoparticles (AuNPs) were prepared on glass using the chemical spray pyrolysis (CSP) technique. The morphological, structural, and sensing properties of the prepared thin films were examined. Atomic Force Microscopy (AFM) analysis revealed that these films exhibit a consistent structure before and after doping. Initially, the roughness of these films was observed to increase upon the introduction of impurities (ZnO: MgO)_x. This trend reversed at x = 0.20, where a decrease in roughness occurred. Interestingly, a subsequent decrease in the roughness of all films was noted after doping with AuNPs. Gas sensing measurements were carried out through resistance measurements in the absence of, and exposure to, reducing gas (H₂S) and oxidizing gas (NO₂). The results showed that sensitivity increased significantly after addition of dual oxides (ZnO: MgO)_x. The maximum sensitivity (147%) was obtained at a 2% mixing ratio and an operating temperature of 523 K for NO₂ and H₂S gases. The gas sensitivity retarded by addition of gold NPs.

Vibration energy harvesters can transform ambient mechanical vibration into electrical energy, which can then be utilized to power microelectronic devices such as IoT sensors. Inspired by the bidirectional bending mechanism of the flytrap’s blades, prestress is incorporated into the magnetostrictive harvester to transform it into a bistable structure. This enhancement aims to significantly improve the system’s output capacity. To further advance the research on prestressed magnetostrictive bistable vibration harvesters, this study proposes novelty the motion model of the magnetostrictive bistable vibration harvester and the mechanomagnetoelectric coupling model, along with their numerical solutions. A series of accurate values, such as the end displacement of the system, the stress of Galfenol and the induced voltage, were obtained. The curvature characteristics and nonlinear behaviors of the harvester system were analyzed via the finite element method. Eventually, the working capability of the prototype was tested through experiments. The results indicate that the working frequency band of the system is evidently widened. When the excitation frequency is 10 Hz and the acceleration is 3.16 g, the large-amplitude periodic inter-well vibration can persist from 8.5 Hz to 11.5 Hz, and the maximum generated power is 6.64 mW. These findings fully demonstrate the application potential of the proposed bio-inspired bistable harvester in low-frequency broadband vibration energy harvesting.

In this study, Co_0.5Cd_0.5Fe₂O₄ (CCFO) and Ni_0.5Cd_0.5Fe₂O₄ (NCFO) spinel ferrite nanoparticles were synthesized via a sol-gel auto-combustion method and systematically investigated for their structural, morphological, elastic, and dielectric properties. X-ray diffraction analysis confirmed the formation of a cubic spinel structure with minor Fe₂O₃ impurity, attributed to thermal oxidation during annealing. Cation distribution was estimated using the Buerger intensity ratio method, revealing a strongly inverse configuration for CCFO and a partially inverse arrangement in NCFO, which influences lattice parameters and microstrain. NCFO had a slightly greater lattice constant (8.475 Å) and crystallite size (16.93 nm) than CCFO (8.395 Å and 16.14 nm), despite the smaller ionic radius of Ni²⁺. This suggests that cation redistribution and strain effects dominated ionic size trends. FESEM revealed quasi-spherical to platelet-like agglomerate nanoparticles with mean sizes of 152 nm (CCFO) and 171 nm (NCFO), consistent with XRD-derived crystallite sizes within agglomeration limits. FTIR spectroscopy confirmed the spinel framework and enabled estimation of elastic moduli, which were consistently higher in CCFO due to stronger metal–oxygen bonding. Dielectric measurements over 20 Hz–2 MHz demonstrated typical Maxwell-Wagner interfacial polarization, with CCFO exhibiting higher dielectric constant and loss, attributed to enhanced electron hopping and defect concentration. This comparative study highlights the significant impact of Co²⁺/Ni²⁺ substitution on structural and functional characteristics, offering insights for tailored design of Cd-based ferrites in microwave and magnetic applications.

This study evaluates the corrosion resistance, tribological behavior, and hardness of TiSiCN and TiCN coatings deposited via PVD on untreated and heat-treated AISI 410 stainless steel for seawater applications. Heat treatment enhanced substrate hardness and wear resistance, providing a stronger foundation for the coatings. Electrochemical analysis revealed that TiSiCN coatings offered superior corrosion protection, with the hardened sample exhibiting an Ecorr of − 710 mV, an icorr of 1.2 µA/cm², and a protection efficiency of 76.47%, compared to 64.71% for TiCN. Although heat-treated uncoated substrates showed slight improvement over untreated ones, the application of coatings was the primary factor in enhancing corrosion resistance. Tribological testing demonstrated lower coefficients of friction for TiSiCN coatings (0.32 for hardened, 0.37 for unhardened) relative to TiCN (0.36 and 0.41), along with higher microhardness values (2500 HV vs. 2200 HV). Cross-sectional microscopic analysis measured coating thickness and examined the coating–substrate interface, enabling correlation between microstructure and performance. SEM observations of wear tracks showed narrower, smoother paths with minimal delamination for TiSiCN coatings, confirming superior adhesion and wear resistance. Overall, TiSiCN coatings combine excellent corrosion resistance, enhanced tribological performance, and mechanical durability, making them highly suitable for marine and high-performance applications.

To enhance the ozone reaction activity of solution-processed indium-gallium-zinc-oxide thin-film transistors (IGZO-TFTs), we investigated two approaches for introducing additional hydroxyl (OH) groups, which are known to promote the reactions: (1) spin-coating or firing in a humid environment, and (2) increasing the indium (In) content from the conventional 60% to 72% or 80%. Both approaches enhanced ozone reaction activity, allowing for detection at concentrations as low as 1 ppm. Notably, the enhancement achieved by the second approach was attributed to electrons supplied to the conduction band, originating not only from OH groups but also from In atoms. As a results, the detection limit of a low-cost, solution-processed ozone sensor was significantly lowered from 5 ppm to 1 ppm.

An effective method of cleaning the taste sensors to remove residues is still an issue in sensor applications. Residues of taste substances can cause measurement inaccuracies and can damage the lipid membrane of the sensor, reducing its lifetime and reusability. In this study, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), as surfactants, were used for the cleaning process of the positive and negative taste sensor based on a screen-printed carbon electrode (SPCE) to detect bitter taste. Trioctylmethylammonium chloride (TOMA) and phosphoric acid di(2-ethylhexyl) ester (PAEE) were utilized as lipid membranes of positive and negative sensors, respectively. The cleaning process using CTAB and SDS took only 5 and 2 min, respectively, which is faster than cleaning using conventional solutions. Characterization tests, such as scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR), showed that utilization of surfactant solutions did not damage the lipid membrane of the taste sensor. In addition, long-term response testing of the taste sensors showed that the sensors cleaned using the surfactant solution had a longer lifetime. Therefore, cleaning the taste sensor using a surfactant solution can overcome the residue on the lipid membrane, speed up the cleaning time, and enhance the reusability of the taste sensor.