Functionalization of Zirconium‐Based Metal–Organic Layers with Tailored Pore Environments for Heterogeneous Catalysis

Intriguing properties and functions are expected to implant into metal–organic layers (MOLs) to achieve tailored pore environments and multiple functionalities owing to the synergies among multiple components. Herein, we demonstrate a facile one‐pot synthetic strategy to incorporate multiple functionalities into stable zirconium MOLs via secondary ligand pillaring. Through the combination of Zr₆‐BTB (BTB=benzene‐1,3,5‐tribenzoate) layers and diverse secondary ligands (including ditopic and tetratopic linkers), 31 MOFs with multi‐functionalities were systematically prepared. Notably, a metal–phthalocyanine fragment was successfully incorporated into this Zr‐MOL system, giving rise to an ideal platform for the selective oxidation of anthracene. The organic functionalization of two‐dimensional MOLs can generate tunable porous structures and environments, which may facilitate the excellent catalytic performance of as‐synthesized materials.     

Flame retardancy and smoke suppression of molybdenum trioxide doped magnesium hydrate in flexible polyvinyl chloride

In this paper, an effective flame retardant consisting of hierarchical magnesium hydrate (MH) nanosheets doped with molybdenum trioxide nanoparticles (MO@MH) was successfully synthesized via a hydrothermal process. Then, MO@MH, MH, and MH/MO were respectively incorporated into flexible polyvinyl chloride (fPVC) to prepare a series of composites via melt blending. The results of limiting oxygen index (LOI), UL‐94, and cone calorimetry test showed that MO@MH exhibited better flame retardancy and smoke suppression than MH and MH/MO due to the synergistic effect of MO and MH, and the hierarchical structure of MO@MH. With the addition of 20 phr MO@MH, LOI value of fPVC was increased from 23.9% to 33.8% , and UL‐94 reached V0 rating. The peak heat release rate, total heat release, peak smoke production rate, and total smoke production were decreased to 143.0 kW/m², 44.9 MJ/m², 0.0093 m²/s and 29.4 m², respectively. The thermogravimetric analysis results suggested that MO@MH greatly promoted the dehydrochlorination of fPVC at lower temperature, so that more compact and continuous char residues were formed. The Fourier transform infrared spectroscopy results indicated that MO@MH can prevent chain scission and oxidation of fPVC carbonaceous backbone, and as a result less smoke was released.     

Efficient purification of high‐purity compounds from the stem of Lonicera japonica Thunb using two‐dimensional preparative chromatography

Purification of high‐purity compounds from traditional Chinese medicines (TCMs) plays an important role in investigating their bioactivity. Nevertheless, it is often quite difficult to isolate compounds with high purity because of the complexity of TCMs in chemical composition. In this work, a two‐dimensional preparation method was successfully developed for the preparation of high‐purity compounds from the stem of Lonicera japonica Thunb, based on two novel polar copolymerized RP stationary phases, XAqua C3 and XAqua C18. An XAqua C3 prep column was used to separate the sample in the first‐dimensional preparation, and 14 g of sample was fractionated into eight fractions with a recovery of 82%. An XAqua C18 prep column was selected to prepare high‐purity compounds in the second‐dimensional preparation for its good orthogonality with the XAqua C3 stationary phase. As a result, major compounds in the sample were isolated with more than 99% purity. This method is a potent method to realize the efficient purification of compounds with high purity from the stem of L. japonica Thunb and it shows great potential in the separation of high‐purity compounds from complex samples.     

Effects of coherence and polarization on the beam spreading and direction through atmospheric turbulence

Based on extended Huygens-Fresnel principle, analytical expressions of beam width and far-field angular spreading for electromagnetic Gaussian Schell-model (EGSM) beams propagating in atmospheric turbulence are obtained. The effects of coherence and polarization on beam spreading and directionality in atmospheric turbulence are investigated in detail. A condition is obtained under which beams with different degrees of spatial coherence and polarization will generate the same far-field angular spreading in atmospheric turbulence. Our results have potential application in long-distance free space optical communications.     

Femtosecond stimulated Raman scattering picosecond molecular thermometry in condensed phases

We demonstrate the capability of femtosecond stimulated Raman scattering (FSRS) data to measure the temperature of condensed matter at the molecular vibrational level. We report the temperature dependence of Raman loss to Raman gain ratios for low frequency modes (<300 cm(-1)) in a CaCO3 single crystal from cryogenic to room temperature, which is shown to be in agreement with theoretical predictions. We also report the measurements of nonequilibrium time evolution of mode specific vibrational temperatures in the CaCO3 single crystal to demonstrate that FSRS can measure temperature on picosecond time scales. Finally, we point out the unique origin of this temperature dependent anti-Stokes to Stokes ratio in stimulated Raman, which is not present in other coherent Raman spectroscopies. These measurements require no material dependent parameters or prior calibration.     

风险型多属性群决策的综合集成方法

对一类权重信息未知,并且属性值为区间灰数的风险型多属性群决策问题进行了探讨,提出了在理想状态下(即决策者群体的理想意见趋于一致时)各属性的客观权重的计算方法.构建了以组内偏差最小、组间偏差最大为目标函数的综合集成优化模型,求解出理想状态下各属性的客观权重.然后综合考虑各决策者的主观偏好,借助每一方案与理想最优方案组、理想最劣方案组综合偏离度的大小对方案的优劣进行排序.应用实例说明了该方法的可行性和有效性.     

Optical polariton properties in ZnSe-based planar and pillar structured microcavities

Strong coupling is demonstrated in monolithic ZnSe-based microcavities. Under nonresonant excitation the polariton dispersion has been investigated in dependence on the photon-exciton detuning for different excitation densities at low temperatures. For zero detuning indications of a polariton lasing threshold are observed like a k-space and energy dispersion narrowing of the lower polariton branch with increasing excitation density. Furthermore, it is observed that this effect is hampered for measurements at negative detunings as a result of the less effective polariton relaxation to the ground state. Latter results in the formation of a discrete polariton distribution at finite k values as known for the polariton bottleneck. In order to investigate the influence of a three-dimensional optical confinement on the polariton relaxation, pillar structured microcavities were fabricated. The formation of discrete polariton states in the k-space distribution is observed. Furthermore, indications for a softening of the k-conservation arising from the structural confinement are found leading to a more effective polariton relaxation. This process would be beneficial for the realization of efficient polariton lasing processes.     

Alternative adsorption-desorption of C3H6 on nanotube-like silver titanate

A novel material—nanotube-like silver titanate (NST) was prepared from nanotube H₂Ti₂O₄(OH)₂ and characterized by means of TEM, XRD, XPS and DRS. Two kinds of alternative adsorption-desorption of C₃H₆ on NST were observed under visible light irradiation and in the dark. The deconvoluted alternative adsorption-desorption curve of C₃H₆ indicated that there exist two kinds of active sites on the surface of NST with quite different rates of adsorption and desorption. This phenomenon was discussed and explained.     

New method to induce 2D–3D transition of strained CdSe/ZnSe layers

We present new growth conditions for growing high-quality CdSe/ZnSe quantum dots with photoluminescence emission measurable up to room temperature. The surface morphology is characterized in situ by Reflective High Energy Electron Diffraction (RHEED). The key point is the introduction of a new step in the growth process using amorphous selenium to induce a 2D–3D transition of a CdSe strained layer on ZnSe to form the dots. Optical characterizations by photoluminescence of CdSe/ZnSe quantum dots obtained that way, as well as X-ray diffraction results are also discussed here.     

Construction of direct Z-scheme g-C3N4/TiO2 nanorod composites for promoting photocatalytic activity

Direct Z-scheme g-C₃N₄/TiO₂ nanorod composites were prepared for enhancing photocatalytic activity for pollutant removal. The characterization revealed that the g-C₃N₄/TiO₂ nanorod composite formed a close interface contact between g-C₃N₄ and TiO₂ nanorods, which was of benefit for the charge transfer and resulted in its high photocatalytic activity. The g-C₃N₄/TiO₂ nanorod composites exhibited higher photocatalytic activity for degradation of Rhodamine B (RHB) than bare g-C₃N₄ and TiO₂ nanorods. The high photocatalytic activity of g-C₃N₄/TiO₂ nanorod composites is attributed to the formation of the direct Z-scheme system, in which the electrons from the conduction band (CB) of TiO₂ combine with the holes from the valence band (VB) of C₃N₄ while the electrons from the CB of C₃N₄ and holes from the VB of TiO₂ with stronger redox ability are used to reduce and oxidize pollutants. Based on the radical-trapping experiments, the main reactive species for RHB degradation are O₂⁻ and · OH, which are produced by photoinduced electrons and holes with high redox ability. This work provides insights into the photocatalytic mechanism of composite materials for the photocatalytic removal of organic pollutants.