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Pyranopterin Related Dithiolene Molybdenum Complexes as Homogeneous Catalysts for CO <sub/>2</sub> Photoreduction
摘要： Two original dithiolenes, with a pyrazine ring fused with a pyran ring carrying the dithiolene chelate, mimicking molybdopterin (MPT) present in the active site of formate dehydrogenases (FDHs), have been synthesized. The first one mimicks MPT in the dihydropyrazine form while the second mimicks MPT in the more biologically relevant tetrahydropyrazine form. Both have been structurally characterized as a ligand within a cobalt(cyclopentadienyl)(dithiolene) complex. The corresponding MoO(dithiolene)2 complexes have been also prepared and are reported as the first functional and stable catalysts inspired by the Mo center of FDHs so far: they indeed catalyze the photoreduction of CO2 into formic acid, as the major product, and carbon monoxide, achieving more than 100 turnover numbers in about 8 h.
关键词： CO2 reduction,homogeneous catalysis,molybdenum complex,dithiolene ligands
更新于2025-09-23 15:22:29
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White-light emissive upconversion nanoparticles for visual and colorimetric determination of the pesticide thiram
摘要： The authors describe the use of white-light emitting upconversion nanoparticles (WL-UCNPs) for visual detection of the pesticide thiram. The method is demonstrated to undergo a better discernable color change upon target binding. The WL-UCNPs are modified with the lead(II)-dithizone complex which acts as the energy acceptor and recognition unit. This leads to quenching of the blue (475 nm) and green (545 nm) emissions of the WL-UCNPs, while the red emission (650 nm) remains unaffected. Upon addition of thiram, the quenched emissions are recovered, with a linear signal increase in the range from 2 nM to 20 nM of thiram and a limit of detection of 0.26 nM. The nanoprobe was further integrated into a test paper for visual detection. The concentration-dependent color change that varies from red to cyan and bluish violet and then to white can be visually distinguished.
关键词： Lead-dithizone complex,Color-differentiation,Upconversional nanoprobe,Test paper,Energy transfer
更新于2025-09-23 15:22:29
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Bond theory, Terahertz spectra and dielectric studies in donor-acceptor (Nb-Al) substituted ZnTiNb <sub/>2</sub> O <sub/>8</sub> system
摘要： As a donor and acceptor separately, Nb5+ and Al3+ are used to substitute Ti4+ in the ixiolite ZnTiNb2O8 system for the first time. The dielectric responses in the terahertz range of this system are initially studied based on the data from terahertz time-domain transmitted spectroscopy. Combined with ligand field theory, the formation of a secondary phase of ZnAl2O4 is reasonably explicated. Then, the origins of the lower dielectric loss and the terahertz wave absorption coefficient are determined to be the high chemical bond covalency and effective phase control. For the composition of ZnTi0.85(Al0.5Nb0.5)0.15Nb2O8 sintered at 1180 °C, a low dielectric loss (< 5×10-3 @ 0.5 THz) and absorption coefficient (< 10 cm-1 @ 0.5 THz) are obtained, which make this kind of material propitious for developing terahertz dielectric devices.
关键词： complex chemical bond theory,covalency,microwave and terahertz,dielectric properties,donor-acceptor substituted
更新于2025-09-23 15:22:29
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Inkjet-printed phosphorescent Iridium(III) complex based paper sensor for highly selective detection of Hg2+
摘要： First of its kind inkjet-printed phosphorescent Iridium(III) complex [Ir(TPQ)2(4-EO2-pic)] paper based chemosensor has been developed for Hg2+ ions. The probe is highly selective towards mercury analyte over other metal ions (Cu2+, Ca2+, Co2+, Cd2+, Pb2+, Zn2+, Ni2+, Mg2+, Mn2+, Al3+, Fe3+, La3+, Ag+, K+, Na+ and Li+). [Ir(TPQ)2(4-EO2-pic)] complex solution gave a visible color change from orange to yellow and significant phosphorescence quenching. Upon addition of aqueous Hg2+, the [Ir(TPQ)2(4-EO2-pic)] inkjet-printed paper gave a significant color change in both normal and UV light. The detection limit was found out as 1.78 × 10-8 M. Cyclic voltammetry (CV) studies were conducted to explore the further utility of [Ir(TPQ)2(4-EO2-pic)] as electrochemical sensor for Hg2+ ions in CH3CN / H2O (v/v = 1/1). The oxidation wave intensity of [Ir(TPQ)2(4-EO2-pic)] at 0.98 V decreased and new reversible oxidation wave was appeared at 0.91 V The binding ratio of the [Ir(TPQ)2(4-EO2-pic)]-Hg2+ complex was determined to be 1:1 according to the Job’s Plot. The probable binding modes of these [Ir(TPQ)2(4-EO2-pic)] with Hg2+ have also been suggested on the basis of the 1H-NMR titration, absorption and luminescence studies.
关键词： Phosphorescent,Iridium(III) complex,Inkjet-printed,Paper sensor,Hg2+ detection
更新于2025-09-23 15:21:21
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Characterization of the lossy dielectric materials using contour mapping
摘要： The imaginary part of the complex permittivity of a lossy dielectric material is large and couples with its real part. The resonant frequency of a cavity with the sample depends not only on the real part of the complex permittivity of the sample but also the imaginary part, resulting in serious ambiguity in determining the sample’s complex permittivity. This work proposes a contour mapping method to determine the complex permittivity. The full-wave simulation gives us the contours of the resonant frequency and the quality factor, which are functions of the relative dielectric constant and the loss tangent. By mapping the measured resonant frequency and the measured quality factor, one can uniquely determine the complex permittivity of the sample. Five liquids were examined, including three low-loss materials for benchmarking and two lossy materials. The measured complex permittivities of the three low-loss materials agree very well with the other methods. As for the lossy materials, the measured relative dielectric constant and the loss tangent of alcohol are 6.786 and 0.895, respectively. Besides, the measured dielectric constant of glycerin is 6.811, and its loss tangent is 0.562. The proposed contour mapping technique can be employed to measure the complex permittivity of liquids and solids from lossless to lossy materials.
关键词： lossy dielectric materials,resonant frequency,contour mapping,complex permittivity,quality factor
更新于2025-09-23 15:21:21
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Introducing a quantum kinetic model using the generalized Boltzmann equation in the complex phase space
摘要： In the present work, using the generalized Boltzmann equation of the ?rst author [Phys. Rev. E 94, 023316 (2016)], a quantum kinetic model in the complex phase space is proposed. Employing the Chapman-Enskog analysis and applying the Wick rotation (using complex-valued relaxation time), it is shown that the present model recovers the time-dependent Schr?edinger equation, while preserving the main features of the conventional lattice Boltzmann models, e.g., simplicity of implementation, second-order accuracy (in space), and convenience in parallel programming. The present results are numerically veri?ed by simulating three benchmark problems.
关键词： quantum kinetic model,Schr?dinger equation,Wick rotation,lattice Boltzmann models,generalized Boltzmann equation,Chapman-Enskog analysis,complex phase space
更新于2025-09-23 15:21:21
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ELECTRODELESS MEASUREMENT TECHNIQUE OF COMPLEX DIELECTRIC PERMITTIVITY OF HIGH-K DIELECTRIC FILMS IN THE MILLIMETER WAVELENGTH RANGE
摘要： An electrodeless measurement technique of complex dielectric permittivity of high-K dielectric ?lms is described. The technique is based on a quasi-optic Fabry-Perot resonator and modi?ed for investigation of two-layer dielectric structures — substrate/K-?lm. This procedure is destined to be used for providing a simple intermediate control of parameters of high-K ?lms before the following technological process. Regimes of measurements providing the most sensitive conditions for de?nition of ?lm parameters are considered. The proposed method is tested on two-layer structures with well-known parameters and is used for characterization of ferroelectric (Ba,Sr)TiO3 ?lms in the millimeter wavelength range (～ 50 GHz).
关键词： Fabry-Perot resonator,complex dielectric permittivity,electrodeless measurement,millimeter wavelength range,high-K dielectric films
更新于2025-09-23 15:21:21
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Multisoliton interactions for the Manakov system under composite external potentials
摘要： The soliton interactions of Manakov soliton trains subjected to composite external potentials are modelled by the perturbed complex Toda chain (PCTC). The model is applied to several classes of potentials, such as: (i) harmonic, (ii) periodic, (iii) ‘wide well’-type potentials, and (iv) inter-channel interactions. We demonstrate that the potentials can change the asymptotic regimes of the soliton trains. Our results can be implemented, e.g., in experiments on Bose–Einstein condensates and can be used to control the soliton motion. In general, our numerical experiments demonstrate that the predictions of complex Toda chain (CTC) (respectively PCTC) match very well the Manakov (respectively perturbed Manakov) model numerics for long-time evolution, often much longer than expected. This means that both CTC and PCTC are reliable dynamical models for predicting the dynamics of the multisoliton trains of the Manakov model in adiabatic approximation. This extends our previous results on scalar soliton trains to the Manakov trains with compatible initial parameters.
关键词： adiabatic interaction,perturbed complex Toda chain,Manakov system,breathing of multisoliton trains
更新于2025-09-23 15:21:21
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Complex Permittivity Measurement of Paraffin Phase-Change Material at 26 GHz–1.1 THz Using Time-Domain Spectroscopy
摘要： We report complex permittivity measurement of hexatriacontane films at the frequency range of 26 GHz–1.1 THz. Hexatriacontane (C36H74) has a melting point of 75 ?C that exhibits a 15% volumetric change which is crucial in developing low-loss RF microactuators with large displacement. In this work, we employ time-domain spectroscopy to measure the transmission coefficient of the paraffin samples in the frequency range of 0.3–1.1 THz. In order to extract the dielectric constant and accurately estimate the small values of loss tangent, we developed a propagation model which measured data are fitted to through a new least-squares minimization method. A Debye relaxation model is used to model the frequency dependence of the permittivity. Described method is rapidly convergent with minimum amount of signal processing. This method can be used to determine the complex permittivity of the materials by devising an appropriate function for the frequency dependence of the complex permittivity. Transmission through 20 samples of paraffin with various thicknesses is measured and the average permittivity is found to be 2.25 with standard deviation of 0.028. The loss tangent is monotonically increasing with frequency and the maximum value is 6.32×10?3 at 1.1 THz. Our study demonstrates that paraffin is a low-loss dielectric which makes it an attractive candidate for development of electro-thermo-mechanical actuators for sub-millimeter- and millimeter wave (mmW) variable capacitors, low-loss reconfigurable antennas, and phase shifters.
关键词： Terahertz,Time-domain spectroscopy,Loss tangent,Millimeter wave,Alkane,Paraffin,Complex permittivity
更新于2025-09-23 15:21:21
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Microstructure and properties of honeycomb composite films containing Eu and Sn
摘要： Honeycomb composite films were prepared by breath figure method via a straightforward, one-step process by doping complex containing Eu or Sn into polystyrene-b-poly(acrylic acid) (PS-b-PAA) solution. Several influencing factors, such as the concentration of the block polymer solution, the relative humidity of the environment and the amount of complexes, were investigated to control micropore size and tune film surface properties. The characteristics of the composite films were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), ultraviolet and emission spectra. Results indicate that composite films containing Eu have excellent optical performance, and micro-patterned bowl-like SnO2 microparticles could be fabricated from composite films containing Sn after being calcined at 600 °C for 5 h. This general approach for the fabrication of honeycomb composite films opens a convenient and effective route to the functional modification of honeycomb films and offers new prospects for the application in miniaturized sensors, micro-reactor and catalysis.
关键词： Complex containing Eu,Breath figure method,Honeycomb composite film,Tin dioxide,Microstructure
更新于2025-09-23 15:21:21