Filling the Charge–Discharge Voltage Gap in Flexible Hybrid Zinc-Based Batteries by Utilizing a Pseudocapacitive Material

The high charge–discharge voltage gap is one of the main bottlenecks of zinc–air batteries (ZABs) because of the kinetically sluggish oxygen reduction/evolution reactions (ORR/OER) on the oxygen electrode side. Thus, an efficient bifunctional catalyst for ORR and OER is highly desired. Herein, honeycomb-like MnCo₂O_4.5 spheres were used as an efficient bifunctional electrocatalyst. It was demonstrated that both ORR and OER catalytic activity are promoted by Mn^IV-induced oxygen vacancy defects and multiple active sites. Importantly, the multivalent ions present in the material and its defect structure endow stable pseudocapacitance within the inactive region of ORR and OER; as a result, a low charge–discharge voltage gap (0.43 V at 10 mA cm⁻²) was achieved when it was employed in a flexible hybrid Zn-based battery. This mechanism provides unprecedented and valuable insights for the development of next-generation metal–air batteries.     

A Novel BODIPY‐Based Low‐Band‐Gap Small‐Molecule Acceptor for Efficient Non‐fullerene Polymer Solar Cells

We report herein an efficient A¹‐C≡C‐A²‐C≡C‐A¹ type small‐molecule 4,4'‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐ indacene (BODIPY) acceptor (A¹=BODIPY and A²=diketopyrrolopyrrole (DPP)) by following the A‐to‐A excited electron delocalization via the BODIPY meso ‐position, the inherent directionality for the excited electron delocalization. The lowest unoccupied molecular orbital (LUMO) delocalizes across over whole the two flanking A¹ and the central A², and the highest occupied molecular orbital (HOMO) localizes dominantly on the ‐C≡C‐DPP‐C≡C‐ segment. The excited electron upon light excitation of the DPP segment delocalizes over both the BODIPY and DPP segments. The acceptor in chloroform shows an unprecedented plateau‐like broad absorption between 550 and 700 nm with a large FWHM value of 195 nm. Upon transition into solid film, the acceptor shows absorption in the whole near ultraviolet‐visible‐near infrared wavelength region (300‐830 nm) with a low band gap of 1.5 eV and a maximum absorptivity of 0.85×10⁵ cm^‐1. Introduction of the ethynyl spacer between the A¹ and A² and the close BODIPY‐to‐DPP LUMO energy levels are crucial for the excited π−electron delocalization across over whole the conjugation backbone. A power conversion efficiency of 6.60% was obtained from the ternary non‐fullerene solar cell with PTB7‐Th:p ‐DTS(FBTTh₂)₂ (0.5 : 0.5) as the donor materials, which is the highest value among the non‐fullerene organic solar cells with BODIPY as the electron acceptor material.     

Photophysics of ruthenium(II) complexes with 2-(2′-pyridyl) pyrimidine and 2,2′-bipyridine ligands in fluid solution

The photophysics of three complexes of the form Ru(bpy)₃₋(pypm)²⁺ (where bpy2,2′-bipyridine, pypm 2-(2′-pyridyl)pyrimidine and P=1, 2 or 3) was examined in H₂O, propylene carbonate, CH₃CN and 4:1 (v/v) C₂H₅OH---CH₃OH; comparison was made with the well-known photophysical behavior of Ru(bpy)₃²⁺. The lifetimes of the luminescent metal-to-ligand charge transfer (MLCT) excited states were determined as a function of temperature (between −103 and 90 °C, depending on the solvent), from which were extracted the rate constants for radiative and non-radiative decay and ΔE, the energy gap between the MLCT and metal-centered (MC) excited states. The results indicate that ^*Ru(bpy)₂(pypm)²⁺ decays via a higher lying MLCT state, whereas ^*Ru(pypm)₃²⁺ and ^*Ru(pypm)₂(bpy)²⁺ decay predominantly via the MC state.     

Novel spatial solitons in light-induced photonic bandgap structures

The study of wave propagation in periodic systems is at the frontiers of physics, from fluids to condensed matter physics, and from photonic crystals to Bose-Einstein condensates. In optics, a typical example of periodic system is a closely-spaced waveguide array, in which collective behavior of wave propagation exhibits many intriguing phenomena that have no counterpart in homogeneous media. Even in a linear waveguide array, the diffraction property of a light beam changes due to evanescent coupling between nearby waveguide sites, leading to normal and anomalous discrete diffraction. In a nonlinear waveguide array, a balance between diffraction and self-action gives rise to novel localized states such as spatial “discrete solitons” in the semi-infinite (or total-internal-reflection) gap or spatial “gap solitons” in the Bragg reflection gaps. Recently, in a series of experiments, we have “fabricated” closely-spaced waveguide arrays (photonic lattices) by optical induction. Such photonic structures have attracted great interest due to their novel physics, link to photonic crystals, as well as potential applications in optical switching and navigation. In this review article, we present a brief overview on our experimental demonstrations of a number of novel spatial soliton phenomena in light-induced photonic bandgap structures, including self-trapping of fundamental discrete solitons and more sophisticated lattice gap solitons. Much of our work has direct impact on the study of similar discrete phenomena in systems beyond optics, including sound waves, water waves, and matter waves (Bose-Einstein condensates) propagating in periodic potentials.      

The Asymmetric One-Dimensional Constrained Ising Model: Rigorous Results

We study a one-dimensional spin (interacting particle) system, with product Bernoulli (p) stationary distribution, in which a site can flip only when its left neighbor is in state +1. Such models have been studied in physics as simple exemplars of systems exhibiting slow relaxation. In our East model the natural conjecture is that the relaxation time (p), that is 1/(spectral gap), satisfies log (p) as p0. We prove this up to a factor of 2. The upper bound uses the Poincaré comparison argument applied to a wave (long-range) comparison process, which we analyze by probabilistic techniques. Such comparison arguments go back to Holley (1984, 1985). The lower bound, which atypically is not easy, involves construction and analysis of a certain coalescing random jumps process.     

光子晶体的带隙破缺随插入介质层变化规律的研究

采用文中图1所示的一维光子晶体的缺陷模,应用光学传输矩阵法,证明了由光子晶体的缺陷结构引起的光子禁带破缺,得出:"f"(禁带破缺处对应的入射光频率)随"nc"(插入介质层的折射率)的增加线性下降,数值模拟了它们的几何图形.并根据f-nc的对应关系提出了一种测量介质折射率的方法.     

ESR spectrometer with a loop-gap resonator for cw and time resolved studies in a superconducting magnet

The design and performance of an electron spin resonance spectrometer operating at 3 and 9 GHz microwave frequencies combined with a 9-T superconducting magnet are described. The probehead contains a compact two-loop, one gap resonator, and is inside the variable temperature insert of the magnet enabling measurements in the 0-9T magnetic field and 1.5-400 K temperature range. The spectrometer allows studies on systems where resonance occurs at fields far above the g approximately 2 paramagnetic condition such as in antiferromagnets. The low quality factor of the resonator allows time resolved experiments such as, e.g., longitudinally detected ESR. We demonstrate the performance of the spectrometer on the NaNiO2 antiferromagnet, the MgB2 superconductor, and the RbC60 conducting alkaline fulleride polymer.     

Ergodicity of transition semigroups for stochastic fast diffusion equations

In this paper, we first show the uniqueness of invariant measures for the stochastic fast diffusion equation, which follows from an obtained new decay estimate. Then we establish the Harnack inequality for the stochastic fast diffusion equation with nonlinear perturbation in the drift and derive the heat kernel estimate and ultrabounded property for the associated transition semigroup. Moreover, the exponential ergodicity and the existence of a spectral gap are also investigated.     

Non‐centrosymmetric plasmonic crystals for second‐harmonic generation with controlled anisotropy and enhancement

Rectangular arrays of pyramidal recesses coated by silver film are investigated by means of polarization‐resolved nonlinear microscopy at 900 nm fundamental wavelength, demonstrating strong dependence of the dipole‐allowed SHG upon the lattice parameters. The plasmonic band gap causes nearly complete SHG suppression in arrays of 650 nm periodicity, whereas a sharp resonance at 550 nm periodicity is observed due to excitation of band edge Bloch states at fundamental frequency, accompanied by symmetry‐constrained interactions with similar modes at the second‐harmonic frequency. Additionally, coupling with modes at the bottom side of the silver film may lead to extraordinary optical transmission, opening a channel for SHG from the highly nonlinear GaAs substrate. Changing the lattice geometry enables SHG intensity modulation over three orders of magnitude, while the effective nonlinear anisotropy can be continuously switched between the two lattice directions, reaching values as high as ±0.96.

     

CdS纳米晶颗粒薄膜的制备及其光学特性研究

采用化学浴沉积法,以CdCl2·H2O、CS(NH2)2、NH4Cl、NH3·H2O和去离子水作为反应前驱物,在不同的氨水浓度下制备CdS纳米晶颗粒薄膜.通过扫描电镜、X射线衍射、X射线能量色散谱、紫外-可见光透射光谱、椭圆偏振光谱等方法,研究了反应前驱物中氨水浓度对CdS纳米晶颗粒薄膜的表面形貌、晶体结构、S/Cd原子比、光透过率、光学带隙、折射率、消光系数和光学吸收边等物理性能的影响.结果表明:反应前驱物中氨水浓度在0.4～1.0mol/L范围内,可以在衬底上形成均匀致密的CdS纳米晶颗粒薄膜.随着氨水浓度的增加,CdS纳米晶的平均晶粒尺寸逐渐减少,S/Cd原子比逐渐增加,由富Cd型转变为富S型,禁带宽度逐渐增加.在500～1000 nm波段内,折射率的平均值为1.75;消光系数k小于0.07.