Threshold switching memristors (TSMs) are crucial components in emulating neuronal functions in neuromorphic computing. However, the inherent randomness of localized resistive switching behavior in current TSM devices, coupled with excessive Ag+ accumulation in the dielectric layer, leads to performance variability and limited endurance, significantly impeding their stability and reliability for practical applications. To address these challenges, we fabricated a Pt/HfOx:Ag/Pt NIs/Pt TSM device utilizing a homogeneous nanoscale mixture of HfOx with Ag achieved via co-sputtering. By meticulously controlling the Ag doping concentration in HfOx:Ag films through co-sputtering, the formation of stable Ag CFs was suppressed, thereby extending the volatile device endurance. Simultaneously, the uniform Ag distribution promoted consistent ionization and reduced Ag⁺ migration distance, leading to electroforming-free operation and ultra-low switching voltages. The electric field concentration effect of Pt nano-islands (Pt NIs) localizes Ag conductive filament growth, which minimizes parameter variability and contributes to electroforming-free operation, ultra-low switching voltages, and improved device endurance. Pt/HfOx:Ag/Pt NIs/Pt TSM exhibits several key advantages: electroforming-free, prolonged endurance, the bidirectional threshold switching behavior, low threshold voltage (< 0.02 V), and low performance variability. This work provides innovative strategies for developing high-performance TSM devices.
Various radiology technologies, such as computed tomography, mammography and intraoral radiography utilize X-ray sensors. Using X-ray stimulated scintillating materials, ionizing radiation can be transformed into light. The gadolinium (Gd)-doped praseodymium dioxide (PrO2) nanoparticles were synthesized via a combustion method and annealed at varying temperatures. This work explores the influence of thermal treatment on the structural, optical, and photonic properties of Gd-doped PrO2 nanoparticles for indirect conversion. X-ray diffraction (XRD) and Rietveld refinement confirmed the cubic structure of Gd-doped PrO2, with enhanced crystallinity and reduced lattice strain at higher annealing temperatures. High-resolution transmission electron microscopy (HRTEM) and Grain size distribution (GSD) revealed uniform grain sizes ranging from 7 to 39 nm at 400 to 1000 °C, producing optimal surface morphology for X-ray sensing applications. Photocurrent studies conducted using BPW34 photodiodes coated with Gd-doped PrO2 nanoparticles revealed a significant sensitivity to low-dose X-rays, with the 600 °C sample achieving the highest sensitivity of 51 μC/mGy/cm3 at a dose of 7.97 mGy. The results demonstrate that Gd-doped PrO2 nanoparticles show promise for developing X-ray sensing systems that use commercial photodiode arrays.
Two new helicenes based on carbazole and anthracene units were designed, namely 15-hexyl-15 H-tetrapheno [1,2-b] carbazole (6) and 15-hexyl-12- (thiophen-2-yl)-15 H-tetrapheno [1,2-b] carbazole (11) and successfully synthesized by photocyclization reaction. Their structures were characterized by (^1)H NMR, (^{13})C NMR, mass spectrometry, and single-crystal X-ray diffraction analysis. Compounds 6 and 11 had good solubility and relatively high thermal stability with thermal decomposition at 237 and 217 (^circ ) C, respectively. They had absorption maximum peaks at 295 nm for 6 and 245 nm for 11, and emitted blue light with the peaks at 469 nm for 6 and 478 nm for 11 in dichloromethane. Especially, the fluorescence quantum yields of compound 6 in different solvents were measured ranging over 3–6% while those of compound 11 are in the range of 27–50%. The introduction of functional substituents like thiophene on the backbone of compound 6 could increase the fluorescence quantum yields by about eight times. In contrast to compound 11, compound 6 exhibited remarkable two-photon absorption performance. It particularly showed stronger absorption at excitation wavelengths ranging from 730 to 870 nm, reaching a maximum (delta ) value of 24.1 GM at 730 nm. The synthetic concept would provide a useful approach to enhance specific physicochemical performances in the field of organic optoelectronic materials.
Using pulsed laser deposition (PLD) technology, a p–n junction UV photodetector was fabricated on a porous silicon substrate. Thin films with different ratios, 40% indium oxide (In2O3) and 60% tungsten oxide (WO3) and vice versa, were successfully created using modest local facilities. After deposition, the crystal structure and general characteristics were greatly improved by a thermal annealing procedure carried out for three hours at 400 °C. The material’s polycrystalline nature was clearly shown by X-ray diffraction (XRD) analysis, which showed distinctive peaks linked to both the In2O3 and WO3 phases. Accurate information about the surface roughness, crystal size, and outer surface was obtained using high-resolution scanning electron microscopy (FE-SEM). In order to thoroughly investigate optical transmittance and optical power, ultraviolet–visible (UV–Vis) spectroscopy was utilized. Comprehensive cross-sectional and final analyses were also carried out. The findings unequivocally show that the In2O3 and WO3 films have exceptional optical and structural characteristics that guarantee their optical stability and sensitivity.
Dopamine (DA) plays a critical role in neurological processes, and its accurate monitoring is essential for clinical diagnostics. In this work, a ternary Cu–Zn–Fe-layered double hydroxide (LDH) was integrated with multi-walled carbon nanotubes (MWCNTs) to form a conductive hybrid nanocomposite for electrochemical dopamine sensing. The structural and morphological characteristics of the composite were examined using FTIR, XRD, EDX, and FE-SEM. The prepared material was employed to modify a carbon paste electrode (CPE), where the synergistic interaction between the trimetallic LDH and MWCNTs significantly enhanced electron-transfer efficiency and electrocatalytic activity. Cyclic voltammetry (CV) analysis demonstrated a wide linear detection range of 0.211–23 µM and a low detection limit of 0.09 ± 0.01 µM, calculated using the LOD = 3SDa/s method. The anodic and cathodic peak currents increased proportionally with dopamine concentration following the regression equations: Ipa (µA) = 9.6591C (µM) + 51.007 (R2 = 0.9903) and Ipc (µA) = − 8.197C (µM)–85.15 (R2 = 0.9894). The sensor exhibited good selectivity toward dopamine in the presence of common interfering species, along with acceptable repeatability and stability during storage. Practical applicability was validated through real-sample analysis, yielding recovery values of 95.1–113% with RSD < 4%. These results demonstrate that the Cu–Zn–Fe LDH/MWCNT composite is a promising, low-cost, and efficient electrode modifier for sensitive dopamine detection in biomedical and analytical applications.
In this study, we present a novel and chemically symmetric form of nanoscale rectification arising at the interfacial contact between yttria stabilized zirconia (YSZ) nanoparticles of identical composition but deliberately differentiated crystallite sizes. Using 8 mol% Y2O3-doped YSZ synthesized via co-precipitation and thermally annealed at 400–800°C, we obtained crystallite sizes from ~ 7.5 to ~ 16 nm while retaining the cubic fluorite phase, compositional homogeneity, and controlled microstructural evolution, confirmed by TEM, XRD, and Raman spectroscopy. Electrical properties of these heterojunctions were probed via current–voltage measurements under relative humidity (RH) of 65%, 75%, and 85% in H2O- and D2O-enriched atmospheres. Junctions with size disparity exhibited pronounced rectification, increasing with humidity. Replacement of H2O with D2O consistently reduced current, indicating hydrated proton dominance in interfacial ionic transport. A symmetric 400 °C–400 °C junction served as a control, confirming that rectification arose from crystallite size differences rather than compositional variation. Dynamic electrical measurements, including I–V hysteresis cycling and chronoamperometry, revealed humidity-dependent memory effects and relaxation dynamics. The findings establish microstructural heterogeneity and interfacial hydration as powerful, intrinsic drivers of rectification in compositionally homogeneous oxides. Our findings in this study open new directions for the design of solid state nanoionic rectifiers, proton conducting interfaces, and memory enabled oxide electronics, where ionic transport can be precisely modulated by environmental conditions and nanoscale structural control.
Bi2WO6 has been extensively utilized in water treatment; however, the photocatalytic efficiency of Bi2WO6 has been found to vary significantly depending on the synthesis method employed. In this study, Bi2WO6 photocatalysts were synthesized using two distinct methods: hydrothermal synthesis and dilute nitric acid synthesis. The synthesized Bi2WO6 samples were subjected to comprehensive characterization, and their photocatalytic performances were evaluated through the degradation of tetracycline as a model reaction. The experimental results demonstrated that the Bi2WO6 prepared via the hydrothermal method exhibited a more complete crystalline structure and a more regular morphology, which contributed to its superior photocatalytic activity. Further optimization revealed that the ideal conditions for the hydrothermal synthesis were a reaction time of 12 h at a temperature of 180 ℃. The enhanced photocatalytic performance of the hydrothermally synthesized Bi2WO6, compared to that prepared by the dilute nitric acid method, was attributed to its more optimized pore structure, narrower band gap, and increased mobility of photogenerated electron–hole pairs. This research provides valuable insights for the effective design and construction of high-performance Bi-based photocatalytic materials.
This research clearly illustrates the importance of optimizing anodization time for improving the electrochemical property of TiO2/CuO heterojunction electrodes used for the construction of non-enzymatic glucose sensors. The electrodes were synthesized through electrochemical anodization of copper oxide (CuO) and hydro-thermal treatment of titanium dioxide (TiO2). The electrode synthesized under an anodization time of 15 min showed the best electrochemical property, with a high sensitivity of 4559μA mM−1 cm−2, detection limits of 0.05 mM, a wide linear range 0.05–6 mM, and high responder times of 10 s. However, the sensor showed high reproducibility and high electrochemical stability. The electrocede exhibited high electrochemical properties due to nanoscopic morphology, a highly increased CuO crystal structure, and highly reduced charge transfer resistance at the TiO2/CuO interfaces. This clearly demonstrates the high importance of anodization time for improving the property and capability of the TiO2/CuO-constructed non-enzymatic glucose sensors.
As the transition to clean energy accelerates, hydrogen (H2) has attracted significant attention due to its clean and efficient properties. Rapid detection of H2 leaks is crucial for the safe and widespread adoption of H2 energy in the energy sector. In this study, a high-performance, long-term stable room-temperature resistive microelectromechanical systems (MEMS) H2 gas sensor was fabricated by exploiting microstructural changes in palladium nanofilms(Pd NFs) induced by varying annealing temperatures. The surface morphology and microstructural evolution under different annealing conditions were systematically characterized using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The sensing mechanisms of the Pd NFs annealed at various annealing temperatures were systematically analyzed with a focus on microstructural morphology. The results showed that the microstructure induced by annealing at 300 °C effectively reduced the response time of the H2 sensor to low-concentration gases and improved long-term performance. Furthermore, the sensor achieved a detection limit as low as 20 ppm. The sensor’s response time for H2 at a concentration of 20 ppm was 16 s, which was reduced to 10 s at 40 °C. After continuous operation for 50 days, the sensor maintained stable responsiveness to H2. When exposed to 2% of H2, the Pd NFs annealed at 300 °C exhibited a 63.46% higher response compared to the unannealed Pd NFs. These findings provide an effective strategy for effectively optimizing the sensing performance of Pd NFs based H2 sensors.
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