查看更多>>摘要：A mechanically induced artificial potential barrier (MIAPB) is set up in the paper by a pair of tensile/compressive stresses acted on a piezoelectric PN junction. The action mechanism of MIAPB on the electric characteristics is investigated via a full-coupled model between multi-physical fields and charge carriers. A MIAPB tuning methodology is put forward and the interaction between MIAPB and the interface potential barrier is analyzed in depth. Influences of loading locations of MIAPB on barrier configuration, carrier concentrations and recombi-nation rate are carefully illustrated and the improved I-V characteristics of a ZnO PN junction subjected to MIAPB are obtained. It is found that the tensile-stress mode of MIAPB improves performance of PN junctions by reconstructing the interface potential barrier and the compressive-stress mode by stimulating strong interaction with the interface barrier. Thus, a tensile-stress MIAPB should be applied inside the interface barrier region and a compressive-stress one outside the interface region. Numerical results show that the maximal output current can be increased by 7.16 times via a tensile-stress MIAPB and 5.18 times via a compressive-stress one, compared to the one without MIAPB, when the doping concentrations are set as 1 x 10(21) m(-3) with the loading spacing same as the width of the depletion-layer. Obviously, our study possesses referential significance to the mechanical tuning on the performance of piezoelectric PN junctions and piezotronic devices.
查看更多>>摘要：Rolling bearing is the core component of rotating machinery and its operation status greatly affects the stability of equipment. In this paper, a non-contact triboelectric bearing sensor (NC-TEBS) was proposed for monitoring the speed and skidding of rolling bearing. The NC-TEBS adopts the coupling electrode structure of non-contact induction and sweeping. It is composed of PTFE ring, grid electrode, and sweeping charge supplement device. The charge supplement device can increase the surface charge density and ensure the strength of the output signal. When the bearing runs, the PTFE ring rotates with the cage and moves relative to the grid electrode, generating periodic electrical signals via electrostatic induction. The bearing speed can be monitored in lowspeed conditions, while the bearing skidding rate can be monitored in high-speed and light-load conditions. The experimental results have shown that the NC-TEBS has an ultra-wide working speed range of 10-5000 rpm. Its maximum working speed is more than twice that of the reported triboelectric speed sensor. The maximum NCTEBS error value regarding the detection speed is less than 1.8 rpm, with the maximum error rate below 0.25%. After 5 000 000 revolutions under continuous operation, the open-circuit voltage amplitude did not decay, indicating that NC-TEBS has an ultra-long service life. Finally, the NC-TEBS developed in this paper can monitor the operation status of rolling bearing in real-time, with the characteristics of miniaturization and integration. As such, it provides a theoretical and experimental basis for the development of new self-driven and self-sensing smart bearings.
查看更多>>摘要：A long-standing hurdle in triboelectric nanogenerator (TENG) is to boost the output performances, which is a prerequisite for practical applications in portable or distributed power sources. Dielectric modulation of the triboelectric materials has proved as an efficient strategy to tackle this challenge by optimizing their charge trapping capacity and surface charge density. Herein, we introduce two kinds of typical two-dimensional transition metal carbide (Ti3C2Tx) and carbonitride (Ti3CNTx) MXene into poly(vinylidene difluoride) (PVDF) ferroelectric polymers to achieve efficient dielectric modulation. Surprisingly, the nitrogen atoms partially and randomly substituting carbon atoms in Ti3C2Tx endow Ti3CNTx with more abundant surface terminating groups (-OH and -F) and additional -NH groups, providing strong interfacial interactions, enhanced compatibility with PVDF matrix and dielectric polarization locking. These unique characteristics enable efficient dielectric modulation of PVDF/Ti3C2Tx and PVDF/Ti3CNTx films, significantly enhancing their charge trapping capacity and surface charge density. The optimized TENG device based on PVDF/Ti3CNTx exhibits higher maximum instantaneous power density of 2.5 W/m(2) than the devices based on PVDF/Ti3C2Tx (1.6 W/m(2)) and pristine PVDF (0.4 W/m(2)). This finding provides guidance for designing advanced triboelectric materials but also call for more exploration for fundamental mechanisms behind dielectric modulation.
查看更多>>摘要：Promoting the quality of surface-enhanced Raman spectra (SERS) holds immense significance in various research fields, such as high-sensitive detection or real-time in situ monitoring. However, obtaining rich molecular information from the vibration modes in SERS remains difficult due to the surface selection rules. Herein, we develop an electrically enhanced, composite SERS substrate by combining flower-like Ag nanostructures with a piezoelectric-dielectric polymeric film. The piezoelectricity generated in the polymeric film transforms into combined quasi-static electrical fields with multi-directional distributions and intensified plasmonic hotspots in the Ag nanoflowers. Molecules adsorbed on the Ag nanoflowers are propelled by the quasi-static electrical fields and deviate from the absorption equilibrium states, a key criterion to present additional SERS peaks. In addition, the intensified hotpots generate SERS peaks with higher intensities (> similar to 2 times). Dual-enhanced SERS in both the intensity and the number of vibration peaks e.g., 3 peaks more for 4-Mpy, are obtained from a variety of widely used molecular Raman probes as well as pesticide contaminants. The universality of the dual enhancement effects from our SERS design with increasing detection sensitivity demonstrates high applicability in the rapid and on-site detection of real samples. The changes to SERS spectra, and thus the molecular vibrational fingerprints, in the combined static and plasmonic electrical fields may also inspire scientific understanding in photoelectrical catalytic processes.
查看更多>>摘要：The wireless sensor networks (WSNs) play an important and essential role in modern society. However, the requirement for huge distributed energy for sensors and wireless transmission modules has become a bottleneck in the development of WSNs. Various energy harvesting technologies have been explored for developing selfpowered sensors, however they either need a long duration for energy collection and storage, leading to not real-time sensing, or require additional power sources to run the WSNs. Here we report a novel triboelectric nanogenerator (TENG)-based fully self-powered instantaneous wireless sensor system. TENG is integrated with an RLC sensing circuit, enabling spontaneous generation of oscillating signal with encoded sensing information. Additionally, by using an electronic switch, the frequency and amplitude of the signal become extremely stable and immune to the environmental variations. An innovative impedance-modulated signal analysis method is also developed to extract the sensing information for resistive, capacitive as well as inductive types of sensors. The sensor system is then applied for real-time tire pressure and speed monitoring for a bicycle. Results showed that the self-powered wireless tire pressure sensor system is able to monitor tire pressure and speed of the bicycle, with a resolution of 5.5 kPa and a precision of about 97% respectively, demonstrating its excellent potential for general applications.
查看更多>>摘要：As the basic hydrological parameters, the concentration and type of suspended sediment particles greatly influence the aquatic ecological environment and the water conservancy infrastructure. However, because of the various composition and changing concentration, challenges still remain in low-cost and real-time sediment monitoring. Herein, we report a potential method to realize real-time monitoring of sediment particles parameters by introducing a particles-laden droplet-driven triboelectric nanogenerator (PLDD-TENG) combined with deep learning method. The mechanism of PLDD-TENG was proved to be induced by the liquid-PTFE electrification and particles-electrode electrostatic induction. The output signals of PLDD-TENG were measured under different particles types and mass fractions. The results indicated that the output signals were sensitive to the particles type and mass fraction. A convolutional neural network (CNN) deep learning model was adopted to identify the particles parameters based on the output signals of PLDD-TENG and high identifying accuracy was achieved. Meanwhile, this model can identify particles types in the mixed solution. An intelligent system was finally developed to realize visualization of real-time monitoring for sediment particles. These findings are crucial in both fundamental understanding and application prospect of triboelectric effect in two-phase flow.
Maity, KuntalPal, UttamMishra, Hari KrishnaMaji, Prasenjit...
13页
查看更多>>摘要：All inorganic cesium lead iodide (CsPbI3) is highly emerging in the fabrication of self-powered nanogenerators (NGs) and photodetectors (PDs) beyond the excellent performance in photovoltaic cells if it is used as one of the component in composite when engineering polymer such as PVDF is selected as an another component. In addition, the coupling of photoexcitation, semiconductor functionality and piezoelectric effect in CsPbI3 (CPI) and PVDF composite may advance the fields in piezo-phototronics which is explored in this work. Here, we report the preparation of CPI embedded PVDF composite (CPIP) film turns into excellent material for NG and PD fabrication. Notably, the utilization of PVDF as stabilizing layer of CPI protects the CPI from degradation in ambient environment and enhances the overall electroactive phase (F-EA similar to 96%) in CPIP film owing to its intrinsic piezoelectric nature (beta - and gamma - phase). Moreover, we aim at unraveling the atomistic details of the interaction between CPI mainly driven by PbI2 and CsI terminated surfaces and PVDF by first-principle density functional theory (DFT) calculations. In a step further, we exclusively investigate the interfacial interactions in most of the probable directions for strain-engineered bound system leading in the significant bandgap decrement. The CPIP made NG exhibits superior piezoelectric output voltage (V-oc) of 20 V and short circuit current (I-SC) of 6 mu A which is significantly higher than Neat PVDF based NG under compressive pressure. Besides, the CPIP based PD is highly sensitive to trace the visible light illumination as evidenced from response time (t(ON) as similar to 2.4 s and t(OFF) as 1.1 s), photo responsivity similar to 0.3 mAW(-1) and maximum detectivity 0.122 x 10(10) Jones. Finally, the piezo-phototronic effect is realized in CPIP composite by fabricating a self-powered PD which exhibits a significant enhancement of Delta I-sc similar to 57% that offers a promising potential in next generation piezotronic and optoelectronic application.
查看更多>>摘要：Electrocatalytic nitrogen reduction reaction (NRR), which can produce ammonia from N2 and H2O under ambient conditions, has emerged as a promising sustainable alternative to the Haber-Bosch (H-B) process. However, their unsatisfied conversion efficiency and selectivity severely restrict the real utilization of NRR, owing to the stubborn triple bond in the N2 molecule and the competitive hydrogen evolution reaction (HER). Here, inspired from the local microenvironment of the nitrogenase, we report for the first time a facile and general strategy to boost the NRR selectivity and activity through the self-assembled monolayer (SAM) of hexanethiol (HEX) on a series of metal electrocatalysts (Cu, Au, Pt, Pd and Ni). Molecular dynamics (MD) simulations suggest that the HEX SAM provides a hydrophobic microenvironment to impede the diffusion and adsorption of water molecules and promote that of N2 molecules, thus inhibiting HER and simultaneously improving the NRR performance. Notably, among all the prepared samples, the highest Faradic efficiency (FE) of 50.5% is achieved on Cu-HEX with NH3 formation rate (R) of 1.2 mu g h-1 cm- 2. Remarkably, for the HER-favored Pt catalyst, the highest R of 26.4 mu g h-1 cm-2 is also achieved on Pt-HEX with FE of 1.8% under 1 cm2 of electrode area. The present strategy not only represents a general diffusion-controlled method to engineer highperformance NRR electrocatalysts, but also provides a new insight into the effect of surface chemistry of catalysts on the NRR process and kinetics.
查看更多>>摘要：Lithium-rich layered oxides (LLOs) are one of the most promising cathodes for next-generation Li-ion batteries owing to their extraordinary energy density and low cost. However, the anionic redox reactions inevitably destabilize the oxygen framework and lead to oxygen release, which incurs voltage fading and capacity decay. Although less voltage fading can be realized in the cobalt-free iron-substituted materials, they still suffer from severe transition metal (TM) dissolution and poor kinetics. Herein, to ameliorate these drawbacks, we develop a novel eutectic melting salt treatment strategy. By controlling the melt and solidification of a LiF-MgF2-CaF2 ternary salt, the robust fluoride coating layer and functional doping were synchronously conducted in a Co-free Fe-substituted Li-rich cathode Li1.2Ni0.13Fe0.13Mn0.54O2. The outer fluoride layer effectively suppresses the oxygen release and prevents TM ion dissolution, while the inner doping elements improve the Li+ diffusion kinetics and further stabilize the bulk crystal structure. Benefiting from these, the modified cathode exhibits significantly enhanced electrochemical performance, with negligible capacity loss from the 35th to the 120th cycles at 0.2 C, mitigated voltage fading, improved rate capability and better thermal stability as well.
Shin, Min JeongLee, AhreumPark, Joo HyungCho, Ara...
9页
查看更多>>摘要：Transparent photovoltaic (TPV) devices using very thin absorbers, which are sandwiched by transparent conducting front and rear contacts, provide efficient solar energy yields and partially visible transparency. These characteristics allow such devices to be used in applications including building-integrated photovoltaics (BIPV), solar vehicles, and wearable devices. In this study, we developed the TPVs with tunable power conversion efficiencies (PCEs) and average visible transmittance (AVT) values using ultrathin Cu(In,Ga)Se-2 (CIGS) absorber layers with thicknesses ranging from 30 to 300 nm, prepared using a single-stage coevaporation process. The PCE and AVT values of these devices could be easily tuned by controlling the absorber thickness; the TPV devices exhibited respective PCEs ranging from 11.0% to 2.1% (front illumination) and 6.6-1.7% (rear illumination), as well as AVTs ranging from 9.1% to 47.8% as the absorber thickness was varied from 300 to 30 nm. The TPV device prepared with a 100 nm-thick fully depleted CIGS absorber layer exhibited an enhanced bifaciality factor close to unity owing to the field-driven charge transport and reduced recombination at the rear contact and/or in the bulk of this device. Similar PCEs of similar to 5% under front and the rear illumination at an AVT of similar to 35% were achieved. This TPV device demonstrated constant PCEs under low-light irradiance (10-100 mW cm -2 ) irrespective of the illumination direction, as well as an enhanced bifacial performance as J(SC) linearly increased from 11.4 to 19.3 mA cm(-2) as the rear illumination intensity was increased from 0 to 60 mW cm(-2). It also exhibited high light-soaking stability.
NSTL
Elsevier