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Modification of the electronic properties of the π-spacer of chromophores linked to calix[4]arene platform for DSSCs applications
摘要： We have developed two novel dyes based on p-tert-butyl-calix[4]arene in order to evaluate their behavior as sensitizer in photovoltaic devices. These dyes consist in a difunctionalized calix[4]arene with triphenylamine (TPA)-donor, a heteroaromatic π-conjugated spacer, thiophene and benzothiadiazole-phenyl ring, respectively and cyanoacetic acid as acceptor group. The effect of the p -spacer has been studied by UV-vis spectroscopy and Differential Pulse Voltammetry and the models compounds have been theoretically investigated. The dye bearing phenylbenzothiadiazole results in a bathochromic shifted absorption and an adequate efficiency to transfer charge from D to A. The considerable increase of the photocurrent density results in a better efficiency of the devices prepared with these novel dyes with respect to the p-tert-butyl-calix[4]arene derivatives bearing TPA dye. In particular, p-tert-butyl-calix[4]arene derivative based on phenylbenzothiadiazole has reached an efficiency value of 5.84 % which means an increase of 33 % of the efficiency over those calix[4]arene derivatives with TPA dye.
关键词： aggregation,calix[4]arene,multichromophore,benzothiadiazole,metal-free sensitizer
更新于2025-09-23 15:23:52
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An Eco-friendly Flexible Piezoelectric Energy Harvester That Delivers High Output Performance is Based on Lead-Free MASnI3 Films and MASnI3-PVDF Composite Films
摘要： An environmentally-friendly lead-free methylammonium tin iodide (MASnI3) perovskite is successfully synthesized using a facile approach of an antisolvent-assisted collision technique under room ambient conditions, which results stability within 24 h under ambient room conditions. The phase transition of MASnI3 from tetragonal to cubic is first observed at ~ 30 °C. Polycrystalline MASnI3 films reveal a high dielectric constant of ~ 65 at 100 kHz, a low-leakage current density of 7 × 10-7 A cm-2 at 50 kV cm-1, well-developed P-E hysteresis loops, and a high piezoelectric coefficient (d33) of 20.8 pm V-1. The MASnI3 piezoelectric energy nanogenerator (PENG) shows an output voltage of ~ 3.8 V and an output current density of 0.35 μA cm-2. To enhance the piezoelectric output performance, the MASnI3 films are composited with an environmentally friendly PVDF polymer that had a porous structure. The PVDF-MASnI3 composite based-PENG reveals a maximum output voltage of ~ 12.0 V and current density of ~ 4.0 μA cm-2. A green light-emitting diode (LED) using the PVDF-MASnI3 PENGs is instantly lighted without need of a storage device, and long-term stability of the composite PENGs is validated for 90 days. This simple and cost-effective solution process is feasible for the fabrication of large-scale, high-performance, and environmental-friendly PENGs based on lead-free organic-inorganic perovskites to extensively implicate in medical and biomechanical applications.
关键词： Dielectric property,Lead-free MASnI3,PVDF-MASnI3 composite PENGs,Piezoelectric energy,Antisolvent-assisted collision technique
更新于2025-09-23 15:23:52
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The sintering behavior and physical properties of Li <sub/>2</sub> CO <sub/>3</sub> -doped Bi <sub/>0.5</sub> (Na <sub/>0.8</sub> K <sub/>0.2</sub> ) <sub/>0.5</sub> TiO <sub/>3</sub> lead-free ceramics
摘要： In this study, Li2CO3-doped Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) ceramics were fabricated via the conventional solid-state reaction using ultrasound waves for preliminary milling. The milling time was shortened from 20 h to 1 h with ball milling. The phase structure of BNKT investigated by X-ray diffraction showed a single perovskite phase. With increasing Li2CO3 content, the phase structure of the ceramics changed from rhombohedral to tetragonal. At a sintering temperature of 1 100 8C and Li2CO3 content of 0.4 wt.%, the best physical properties of the ceramics, such as density (q), 5.9 g cm–3; electromechanical coupling factors (kp), 0.32; (kt), 0.29; remanent polarization (Pr), 12.0 lC cm–2; dielectric constant (er), 1 191; and highest dielectric constant (emax), 5 800, were obtained.
关键词： Lead-free ceramics,Electromechanical coupling factor,BNKT,Sintering temperature,Dielectric constant
更新于2025-09-23 15:23:52
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Structural and electrical properties of copper doped In<sub>2</sub>O<sub>3</sub> nanostructures prepared by citrate gel processes
摘要： Copper doped indium oxide (In2?xCuxO3) nanostructures were prepared by a simple citrate gel process using indium nitrate and copper nitrate as precursors. The influence of the dopant concentration (x = 0, 0.03, 0.05 and 0.07) on the structural, morphological and the electrical properties of indium oxide was studied. The crystallite size and the surface roughness (root mean square roughness and the mean roughness) of the prepared samples increased as a function of the dopant concentration. However, the copper (Cu) concentration did not affect the basic host crystal structure. The prepared samples showed an n-type semiconducting behavior and a variation in the electrical parameters, which might be due to the confinement of the electronic states of the dopants to small volumes (less than 100 nm). Implication of the degenerate electron gas model to the experimental electrical data revealed the role of the different scattering centers in conduction electron scattering.
关键词： Indium oxide,Mean free path,Electron gas model,Citrate gel route
更新于2025-09-23 15:23:52
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Uniform Cs2SnI6 Thin Films for Lead-Free and Stable Perovskite Optoelectronics via Hybrid Deposition Approaches
摘要： Herein, we synthesized uniform Cs2SnI6 films by two kinds of hybrid deposition methods by considering volume expansion involved during phase transformations. First, oblique thermal evaporation for CsI followed by SnI4 spin-coating resulted in uniform Cs2SnI6 films free of impurity phases. The rapid expansion (within 10 s of spin-coating) from CsI to Cs2SnI6 (ΔV = 106%) was accommodated by porous CsI films inhibiting crack formation. Excess SnI4 on the Cs2SnI6 after spin-coating was effectively removed by toluene washing without any damages to Cs2SnI6, and optimum deposition parameters were suggested in terms of carrier mobility. Second, annealing CsI with SnI4 vapor at 250 °C and post-annealing in the SnI4 and I2 vapor at 300 °C produced Cs2SnI6 film with complete coverage. The slow reaction (70 min for a complete conversion) provided sufficient time for complete diffusion of SnI4 into CsI without crack formation even with compact CsI. The nonradiative recombination path in Cs2SnI6 was suppressed by post-annealing in the SnI4- and I2-atmosphere, as confirmed from the enhanced photoluminescence.
关键词： Lead-free perovskite,Cs2SnI6,Electrical mobility,Oblique thermal deposition
更新于2025-09-23 15:23:52
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Effect of processing conditions on (Ba1-xCax)(Ti0.9Sn0.1)O3 lead-free ceramics for the enhancement of structural, humidity sensing and dielectric properties
摘要： The present study reports detailed guidelines for the preparation of high-quality perovskite (Ba1-xCax)(Ti0.9Sn0.1)O3 (BCTS) (x = 0.0–0.1) lead-free ceramics by solid state reaction. The compositions (x = 0.0–0.04) exhibit orthorhombic–tetragonal phase transition (TO-T), except x ≥ 0.06 that shows a pure tetragonal structure phase which conformed by X-ray diffraction (XRD). The microstructure and purity of the sintered ceramics were examined using scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS). Some pores existing in the grain boundary were observed at high concentrations of Ca content. Field emission scanning electron microscope (FE-SEM) was used to examine the morphology of sensing film of the calcined powder and it was prepared as a humidity sensor using screen-printing technique. All the compositions exhibited poor sensitivity toward the humidity sensing in the range of 0–98% RH at room temperature. Hot-stage microscope (HSM) has been used to investigate the sintering curve of the pure calcined powder and it was found that the suitable sintering temperature for obtaining a fully dense microstructure is 1400 °C. The highest values of permittivity (εr = 46,515, at 10 kHz) and piezoelectric coefficient (d33 = 510 pC/N) were achieved in the composition x = 0.02. The difference between alumina and platinum crucibles for the processing of the powders has been introduced, and by the aid of dispersive spectrometer analysis and it was indicated that use of alumina crucibles leads to the undesired presence of Al in the ceramics, which can be prevented by using a capped platinum crucibles.
关键词： Lead-free ceramics,Humidity sensing,Phase formation,Processing,Dielectric properties
更新于2025-09-23 15:23:52
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Label-free immunosensors based on a novel multi-amplification signal strategy of TiO2-NGO/Au@Pd hetero-nanostructures
摘要： A label-free electrochemical immunosensor for quantitative detection of human epididymis specific protein 4 antigen (HE4 Ag) was developed by a novel multi-amplification signal system. The multi-amplification signal system was formed by loading bimetallic Au@Pd holothurian-shaped nanoparticles (Au@Pd HSs) on titanium oxide nanoclusters functionalized nitrogen-doped reduced graphene oxide (TiO2-NGO). The Au@Pd HSs were obtained via seed-mediated approach with in-situ grown palladium nanoarms on gold nanorods (Au NRs) surfaces, which possessed good electrocatalysis for hydrogen peroxide (H2O2) reduction and excellent biocompatibility. The TiO2-NGO with the high catalytic activity and large specific surface area was synthesized by hydrothermal method. Using H2O2 as an electrochemically active substrate, the prepared label-free electrochemical immunosensor based on the TiO2-NGO/Au@Pd HSs hetero-nanostructures as the signal amplification platform exhibited excellent selectivity, reproducibility and stability for the detection of HE4 Ag. Meanwhile, the linear range from 40 fM to 60 nM with the detection limit of 13.33 fM (S/N = 3) was obtained, indicating the immunosensor offers a promising method for clinical detection of HE4 Ag.
关键词： Au@Pd nanoparticles,Titanium oxide,Label-free electrochemical immunosensor,Nitrogen-doped reduced graphene oxide,Human epididymis specific protein 4
更新于2025-09-23 15:23:52
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A Robust Parameter-free Thresholding Method for Image Segmentation
摘要： In this paper, we presented a new parameter-free thresholding method for image segmentation. In separating an image into two classes, the method employs an objective function that not only maximizes the between-class variance but also the distance between the mean of each class and the global mean of the image. The design of the objective function aims to circumvent the challenge that many existing techniques encounter when the underlying two classes have very different sizes or variances. The advantages of the new method are twofold. First, it is parameter-free, meaning that it can generate consistent results. Second, the new method has a simple form that makes it easy to adapt to different applications. We tested and compared the new method with the standard Otsu method, the maximum entropy method, and the 2D Otsu method on the simulated and real biomedical and photographic images and found that the new method can achieve a more accurate and robust performance.
关键词： histogram,parameter-free thresholding,Segmentation,objective function
更新于2025-09-23 15:23:52
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Inversion-free force tracking control of piezoelectric actuators using fast finite-time integral terminal sliding-mode
摘要： The major hurdles to control the force created by piezoelectric actuators (PEAs) are originated from its strong nonlinear behaviors which include hysteresis, creep, and vibration dynamics. To achieve an accurate, fast and robust force tracking performance without using complicated modeling and parameter identification of PEAs, this paper presents a practical direct force control scheme. The proposed controller is based on two core approaches: 1) fast finite-time integral terminal sliding mode (FFI-TSM) which allows fast convergence and high accuracy to the closed-loop system without control chattering; and 2) an inverse-model-free compensation, named force-based time-delayed estimation (FBTDE) which offers significant robustness with minimum use of plant dynamics information. The finite-time stability of the overall closed-loop system is proven through the Lyapunov's method. The proposed force tracking controller is implemented on the PEA system driving a variable physical damping actuator mechanism. The overall accuracy, convergence speed, and robustness of the proposed controller are validated under various experimental scenarios. Comparative experimental results are particularly presented to verify the effectiveness of the FFI-TSM term and the FBTDE term.
关键词： Inversion-free force control,Piezoelectric actuators (PEAs),Time-delayed control (TDC),Terminal sliding mode
更新于2025-09-23 15:23:52
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Wetting Transition from the Cassie–Baxter State to the Wenzel State on Regularly Nanostructured Surfaces Induced by an Electric Field
摘要： When droplets are placed on hydrophobic textured surfaces, different wetting state Cassie-Baxter (CB) state or Wenzel (W) state may occur depending on materials and structures of surfaces, types and sizes of droplets, thermal fluctuations, and external stimuli. The wetting transition from the CB to the W state and the opposite process have attracted a great deal of attention due to their primary importance for designing and fabricating textured surfaces. In this work, molecular dynamics (MD) simulations are employed to understand the mechanism behind the CB-to-W transition for a nanoscale water film placed on a surface decorated with a single nanogroove when an external electric field is applied. The free energy variation during the transition process is computed on the basis of the restrained MD simulations. Water intrusion into the groove is observed by simulation snapshots, which provides a direct evidence for the electric-field-induced CB-to-W transition. In the previous experiments, however, only a sharp reduction in the apparent contact angle is employed to judge whether the transition takes place. The free energy curves reveal that there are two energy barriers separating the CB and W states (?E1) as well as separating the W and CB states (?E2). Owing to the presence of ?E1, although the CB state has a higher free energy than the W state, it cannot spontaneously convert to the W state. When the external energy input exceeds ?E1, the CB-to-W transition can be triggered, otherwise the transition will stop, and the water film will return to the CB state. Moreover, it is found that the maximum of free energy always occurs after the film touches the groove bottom. Thus, the requirement of the film touching the groove bottom is responsible for the presence of the energy barrier ?E1. Finally, the dependences of the two energy barriers on the electric field strength, groove aspect ratio, and intrinsic contact angle of the groove are also discussed.
关键词： Cassie-Baxter state,wetting transition,Wenzel state,energy barrier,free energy,molecular dynamics simulations.
更新于2025-09-23 15:23:52