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Resonance enhanced multiphoton ionisation (REMPI) detection of Cl( <sup>2</sup> P <sub/>j</sub> ) atom in the photodissociation of halogenated pyrimidines at 235 nm: role of triplet states
摘要： The dynamics of chlorine atom (2Pj) formation in the photodissociation process of halogen substituted pyrimidines, namely, 2,4,6-trichloropyrimidine and 5-chloro-2,4,6-trifluoropyrimidine have been studied around 235 nm using Resonance Enhanced Multiphoton Ionisation Time-of-Flight Mass Spectrometry technique. For the chlorine atom dissociation channel, we have determined the translational energy distribution, the recoil anisotropy parameter, β, and the spin–orbit branching ratio. In both the molecules, the TOF profiles for Cl (2P3/2) and Cl* (2P1/2) are found to be independent of laser polarisation suggesting a zero value for β, within the experimental uncertainties. For 2,4,6-trichloropyrimidine, the average translational energies for Cl and Cl* elimination channels are determined to be 6.0 ± 1.2 and 7.0 ± 1.5 kcal/mol, respectively. Similarly, for 5-chloro-2,4,6-trifluoropyrimidine, the average translational energies for Cl and Cl* elimination channels are determined to be 6.5 ± 1.2 and 7.9 ± 1.6 kcal/mol, respectively. Computational calculations are performed to generate the potential energy curves along the dissociating C-Cl bond using equation of motion coupled cluster with single and double excitations (EOM-CCSD) method. Computational studies suggest the role of triplet states in the photodissociation process forming the Cl atom.
关键词： REMPI-TOF,halogenated pyrimidines,translational energy,spin-orbit ratio,Photodissociation dynamics
更新于2025-09-23 15:23:52
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Scalable modulation of reduced graphene oxide properties via regulating graphite oxide precursors
摘要： Here we demonstrate the scalable modulation of reduced graphene oxide (RGO) properties by regulating graphite oxide (GtO) precursors. Our findings show the thickness and loose degree of GtO precursors act as key roles in flame activation process. Interestingly, the looser GtO transforms into RGO with a lower specific surface area (SSA); RGO from the thinner GtO paper shows a higher SSA. By regulating GtO precursors, SSA from 1030.5 to 335.3 m2 g?1, defect degree, oxidation degree, and pore volume from 4.61 to 1.36 cm3 g?1 can be tuned. The corresponding structural properties are translated into unique supercapacitor (SC) performances such as high specific capacitance (the highest value of 576 F g?1) and coulombic efficiency. Additionally, this method indicates great potential to prepare RGO-based metal oxide composites with good homogeneity and good SC behaviors.
关键词： Flame,Energy efficiency,Reduced graphene oxide,Precursor,Supercapacitor
更新于2025-09-23 15:23:52
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Internal-field-dependent low-frequency piezoelectric energy harvesting characteristics of in situ processed Nb-doped Pb(Zr,Ti)O3 thin-film cantilevers
摘要： Piezoelectric thin-film-based cantilevers have been investigated for higher energy-harvesting performance with simplified processing steps. Here, a simple in situ film deposition process of heavily Nb-doped lead zirconate titanate (PZT) films, which does not require annealing and poling, has been demonstrated to verify the possibility of use of the resultant films as energy-harvesters specifically for low frequency vibrating sources. The in situ domain formation of the films during the deposition was demonstrated from the apparent shifts of the capacitance-electric field curves, indicating the presence of internal electric fields. The so-called imprint behavior was found to be directly related to the performance of piezoelectric energy harvesting. As an optimal example, 12 mol% Nb-doped cantilever harvesters that showed the largest imprint behavior exhibited the best values of ~19.1 GPa figure-of-merit and ~1436 mWcm?3g?2 power density, which are competitive compared to other reported values.
关键词： Thin films,Cantilevers,Piezoelectric energy harvesting,Nb-doping,PZT
更新于2025-09-23 15:23:52
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Fabrication of PAN/ZnO Nanofibers by Electrospinning as Piezoelectric Nanogenerator
摘要： Piezoelectric nanogenerator is a material that is used for converting mechanical energy to electrical energy. This research aimed to study the piezoelectric nanogenerator properties in PAN/ZnO nanofibers layered on the stainless-steel substrate. ZnO nanoparticles that were used in this work were synthesized by coprecipitation method. The ZnO nanoparticles were mixed with PAN dissolved with DMF. Fabrication of PAN-ZnO nanofibers was done using the electrospinning method on the stainless-steel substrate. The formed PAN/ZnO nanofibers were then characterized using XRD, SEM, and FTIR. To test the piezoelectric nanogenerator properties, PAN/ZnO nanofibers were combined to PAN nanofibers and coated on the stainless-steel substrate to form piezoelectric nanogenerator device. This device was then connected to an electrometer and an oscilloscope to measure the current and voltage resulted after bending. The results of XRD of ZnO nanoparticles had the wurtzite crystal structure with the size of about 46 nm. Meanwhile, the PAN/ZnO had an amorphous structure. The test results of piezoelectric nanogenerator properties showed the value of voltage and current of 7.22 V and 47.48 μA, respectively. PAN/ZnO nanofibers on the stainless-steel substrate are potential to be the material of piezoelectric nanogenerators in general.
关键词： electrospinning,PAN/ZnO nanofiber,energy harvesting,piezoelectric nanogenerator
更新于2025-09-23 15:23:52
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Near-infrared quantum cutting via energy transfer in Bi3+, Yb3+ co-doped Lu2GeO5 down-converting phosphor
摘要： In recent years, down-converting phosphors have grown rapidly and been still growing for their potential to significantly improve the photoelectric conversion efficiency of silicon-based solar cells. However, the discovery of new optical materials with optimized properties (in terms of emission intensity, chemical and thermal stability and quantum yield) would still be of the utmost importance. Herein, we report a novel down-converting phosphor Lu2GeO5: Bi3+, Yb3+. Our research results show that the energy transfer efficiency from Bi3+ to Yb3+ in Lu2GeO5 is as high as 65%. Via such an energy transfer from Bi3+ to Yb3+, an absorbed ultraviolet photon gives rise to almost two emitted infrared photons. The theoretical quantum yield of Lu2GeO5: Bi3+, Yb3+ system is calculated to reach up to 165%. The mechanism of the energy transfer from Bi3+ to Yb3+ is proved to be an electric dipole-dipole interaction. Meanwhile, Lu1.87GeO5: 0.03Bi3+, 0.10 Yb3+ phosphor exhibits an excellent resistance against thermal quenching. The present investigation provides people a new down-converting phosphor Bi3+, Yb3+ co-doped Lu2GeO5 with near-infrared quantum cutting to achieve high photoelectric conversion efficiency of silicon-based solar cells.
关键词： Lu2GeO5: Bi3+, Yb3+,Quantum cutting,Energy transfer,Down-converting phosphors
更新于2025-09-23 15:23:52
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Management of Conditions Associated With Aging and Older Adults Using Therapeutic Electromagnetic Energy
摘要： To assess the effectiveness of therapeutic electromagnetic energy in the management of conditions associated with an aging and older adult population. A systematic review of literature from 2008 to 2018 was completed in PubMed, CINAHL, and Science Direct. We also reviewed sources to identify additional relevant studies. Studies in this review were limited to randomized controlled trials that evaluated the effects of shortwave diathermy or pulsed electromagnetic energy units in treating conditions commonly experienced by adults older than 50 years. Study quality was determined using the Physiotherapy Evidence Database (PEDro) classification scale. Fifteen randomized controlled trials met our search criteria. Multiple pathologies were evaluated with the studies examining treatment effects of knee osteoarthritis (n = 12), frozen shoulder (n = 1), postoperative rotator cuff repair (n = 1), and postmenopausal osteoporosis (n = 1). Of the 12 studies that examined knee osteoarthritis, 2 compared pulsed electromagnetic field to placebo or sham, 2 compared the addition of shortwave diathermy to strengthening activities alone, 3 evaluated shortwave diathermy dosage, 3 compared shortwave diathermy to other modalities, and 2 reviewed the benefits of adding pulsed electromagnetic field to other modalities and exercise. Due to the high degree of variability in protocols and outcome measures among studies, meta-analysis was not appropriate. Studies on knee osteoarthritis reported that the use of pulsed electromagnetic field and shortwave diathermy provides statistically significant improvement in pain and function compared with placebo, sham, or control, although there appears to be no benefit in using either form of electromagnetic radiation in addition to or in place of another modality. It also appears that dosage does not significantly change short-term outcomes. These findings are similar to those identified in other recently published systematic reviews that focused exclusively on knee osteoarthritis. Subjects with shoulder pathologies showed improvements in pain, mobility (range of motion), function, activities of daily living, and pain medication usage with pulsed electromagnetic field or shortwave diathermy. Changes in postmenopausal bone density were similar when pulsed electromagnetic field was compared with medication. Conclusion: Shortwave diathermy and pulsed electromagnetic frequency demonstrate similar clinical benefits as other modalities for improving pain, function, and quality of life in the short-term. Further research is needed to better evaluate the parameters of electromagnetic energy and effects for other conditions commonly affecting aging and older adults and at other treatment sites on the body.
关键词： diathermy,electromagnetic energy,pulsed electromagnetic field,shortwave diathermy
更新于2025-09-23 15:23:52
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High room-temperature pyroelectric property in lead-free BNT-BZT ferroelectric ceramics for thermal energy harvesting
摘要： Pyroelectrics are attracting increasing attention because they enable pyroelectric generators to extract energy from low-gradient-temperature heat for portable electronic devices. High pyroelectric coefficient around room temperature is essential for high-performance energy harvesters, which, unfortunately, is only commonly achieved in lead-based ferroelectrics. Herein we report a high room temperature pyroelectric response of 27.2 × 10-4 C m-2 K-1 in 0.94(Bi0.5Na0.5)TiO3-0.06Ba(Ti0.75Zr0.25)O3 lead-free ceramics by modulating the Zr4+/Ti4+ ratio to tune the ferroelectric-relaxor antiferroelectric-like phase transition point to around ambient temperature, whose pyroelectric response is one order of magnitude higher than that of the sample without Zr and even comparable to those of lead-containing pyroelectrics. The theoretical analysis revealed that introduced Zr4+ could incorporate into the TiO6 octahedral lattices and break the long-range translational symmetry of BaTiO3 lattices, resulting in the reduction of B-site ion displacement activation energy and transition point of ferroelectric-relaxor antiferroelectric-like phase, giving rise to a pronounced room-temperature pyroelectric effect in BNT-BZT.
关键词： BNT-BZT ceramics,Energy harvesting,Room temperature pyroelectric property,Phase transition
更新于2025-09-23 15:23:52
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A passive SPICE model for rectennas
摘要： Purpose – This paper aims to present a SPICE model to represent antennas in receiving mode. The model can be used to evaluate the performance of the antenna when it is coupled to several different nonlinear electric circuits. The proposed methodology is particularly suitable for rectenna applications, as it allows the analysis of different configurations for a rectenna more efficiently than using full-wave analysis simulators coupled directly to each rectifier circuit. Design/methodology/approach – The model presented uses reciprocity theory to calculate the ideal voltage source of the Thevenin-equivalent circuit for an antenna. Vector fitting is then used to approximate the model to rational functions that can be converted to Resistor, Inductor and Capacitor circuits. Additional components are added to the circuit to prevent numerical instability. Findings – Two rectennas are used to illustrate the performance of the proposed model, one based on a 2.45-GHz rectangular patch antenna and another based on a planar spiral antenna. The second antenna has impedance with positive and negative real parts along the frequency range, which could lead to numerical instabilities. The proposed method is shown to be stable while working with these negative resistance values, which may appear during circuit parameterization. Research limitations/implications – The equivalent SPICE circuit model for the antenna makes it easy to simulate nonlinear circuits connected to the antenna and perform transient analyses. The computational cost of antenna analysis is reduced, being more computationally efficient than methods that involve full-wave simulation. This characteristic makes it an interesting approach for working with rectennas, or any application where the time constant of the circuit is much longer than the period of the incident wave. Originality/value – For most antenna applications, the numerical stability of the circuit can be achieved using passive enforcement. However, depending on the phase response of the antenna, the impedance that represents its far-field characteristic may present a negative real part, in which case, passive enforcement will fail. In this paper, the problem of numerical instability is solved by introducing an offset resistance and a current-controlled voltage source to the model.
关键词： Antenna,SPICE model,Rectenna,Energy harvesting
更新于2025-09-23 15:23:52
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The evolution of phase structure, dielectric, strain, and energy storage density of complex-ions (Sr1/3Nb2/3)4+ doped 0.82Bi0.5Na0.5TiO3-0.18Bi0.5K0.5TiO3 ceramics
摘要： Lead-free Bi0.5(Na0.82K0.18)0.5Ti1-x(Sr1/3Nb2/3)xO3 (abbreviated as BNKT-xSN, x = 0.02–0.045) ceramics were fabricated via the conventional ceramic process, and the (Sr1/3Nb2/3)4+ complex-ions were used to modify the phase transition and multifarious electrical responses of BNKT-xSN ceramics. The SN complex-ions absolutely incorporate into the lattice of BNKT matrix to form perovskite structure. The grain morphologies and size are almost unaffected by SN complex-ions. The phase transition concerning ferroelectric type transforming into ergodic relaxor happens with increasing SN content, and the corresponding critical point is x = 0.035. The phase transformation process results in the improvement of energy storage density (W = 0.754 J/cm3) at 80 kV/cm and a high bipolar strain (S = 0.25%) with small hysteresis. The dielectric constant at Tm peaks gradually decreases with increasing SN content, and the ferroelectric-relaxor transition temperature (TF-R) is depressed to room temperature. The evolution behaviors might facilitate our cognition about the mechanism between phase structure and multiple electrical properties of BNT-based ceramics.
关键词： BNT-BKT,(Sr1/3Nb2/3)4+,Phase transition,Field-induced strain,Energy storage
更新于2025-09-23 15:23:52
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Electron transfer from photoexcited naphthalene-1,4:5,8-bis(dicarboximide) radical anion to Mn(bpy)(CO)3X and Re(bpy)(CO)3X CO2 reduction catalysts linked via a saturated methylene bridge
摘要： Supramolecular systems that connect a naphthalene-1,4:5,8-bis(dicarboximide) (NDI) radical anion donor to Mn(bpy)(CO)3Br or Re(bpy)(CO)3Cl CO2 reduction catalysts via a methylene bridge have been synthesized and studied by femtosecond transient visible, near-infrared and mid-infrared spectroscopy. The use of the methylene bridge to link NDI to the complexes does not affect the reduction potentials of the metal complexes. Selective photoexcitation of NDI?? to 2*NDI?? results in ultrafast reduction of the bipyridine (bpy) ligands on both the Mn and Re complexes to form Mn(I)(bpy??)(CO)3X and Re(I)(bpy??)(CO)3X in near unity quantum yield, respectively. The initial formation of Mn(I)(bpy??)(CO)3X is unexpected based on previous electrochemical data that indicates the Mn(I) center is reduced at a more positive potential than the bpy ligand. Moreover, the rate of forward electron transfer in the Mn complex was found to be faster than in the Re complex, while the rate of the back electron transfer in the Re complex was faster than in the Mn complex.
关键词： Electrochemistry,CO2 reduction,Electron transfer,Radical anions,Femtosecond spectroscopy,Solar energy
更新于2025-09-23 15:23:52