荧光法研究二对甲基苯磺酸1,4-苯二酚酯与铁离子(Ⅲ)的分子识别作用

利用荧光光谱法考察了化合物二对甲基苯磺酸1,4-苯二酚酯对阳离子Fe3 、Mn2 、Nd2 、Ni2 、Hg2 、Zn2 、Cu2 、Co3 和阴离子F-、Cl-、Br-、I-、ClO4-、H2PO4-、AcO-、PhCOO-的识别性能。结果表明,该化合物对阴离子没有识别效果,对Fe3 具有很好的识别能力,其络合常数K值达到1.98×108L/mol。二对甲基苯磺酸1,4-苯二酚酯与Fe3 基本形成1∶2型的络合物。本文从主客体的大小形状匹配及配位识别原子等方面对受体的识别能力进行了讨论,发现了一个独特有趣的夹心三明治结构。     

Quality and Metabolomics Analysis of Houttuynia cordata Based on HS-SPME/GC-MS

Houttuynia cordata is a medicinal and edible plant with a wide biological interest. Many parts were discarded due to various modes of consumption, resulting in resource waste. In this study, a comprehensive study was conducted on various edible indicators and medicinal components of Houttuynia cordata to understand its edible and medicinal value. The edible indexes of each root, stem, and leaf were determined, and the metabolites of different parts were investigated using the headspace solid-phase micro-extraction technique (HS-SPME-GC-MS). The differential metabolites were screened by orthogonal partial least squares discriminant analysis (OPLS-DA) and clustering analysis. The results of the study showed that the parts of Houttuynia cordata with high edibility values as a vegetable were mainly the roots and leaves, with the highest vitamin C content in the roots and the highest total flavonoids, soluble sugars, and total protein in the leaves. The nutrient content of all the stems of Houttuynia cordata was lower and significantly different from the roots and leaves (p < 0.05). In addition, 209 metabolites were isolated from Houttuynia cordata, 135 in the roots, 146 in the stems, 158 in the leaves, and 91 shared metabolites. The clustering analysis and OPLS-DA found that the parts of Houttuynia cordata can be mainly divided into above-ground parts (leaves and stems) and underground parts (roots). When comparing the differential metabolites between the above-ground parts and underground parts, it was found that the most important medicinal component of Houttuynia cordata, 2-undecanone, was mainly concentrated in the underground parts. The cluster analysis resulted in 28 metabolites with up-regulation and 17 metabolites with down-regulation in the underground parts. Most of the main components of the underground part have pharmacological effects such as anti-inflammatory, anti-bacterial and antiviral, which are more suitable for drug development. Furthermore, the above-ground part has more spice components and good antioxidant capacity, which is suitable for the extraction of edible flavors. Therefore, by comparing and analyzing the differences between the edible and medicinal uses of different parts of Houttuynia cordata as a medicinal and food plant, good insights can be obtained into food development, pharmaceutical applications, agricultural development, and the hygiene and cosmetic industries. This paper provides a scientific basis for quality control and clinical use.     

The Jackson Inequality for the Best L2-Approximation of Functions on [0, 1] with the Weight x

Let L^2（[0, 1], x） be the space of the real valued, measurable, square summable functions on [0, 1] with weight x, and let n be the subspace of L2（[0, 1], x） defined by a linear combination of Jo（μkX）, where Jo is the Bessel function of order 0 and {μk} is the strictly increasing sequence of all positive zeros of Jo. For f ∈ L^2（[0, 1], x）, let E（f, n） be the error of the best L2（[0, 1], x）, i.e., approximation of f by elements of n. The shift operator off at point x ∈[0, 1] with step t ∈[0, 1] is defined by T（t）f（x）=1/π∫0^π f（√x^2 ＋t^2-2xtcosO）dθ The differences （I- T（t））^r/2f = ∑j=0^∞（-1）^j（j^r/2）T^j（t）f of order r ∈ （0, ∞） and the L^2（[0, 1],x）- modulus of continuity ωr（f,τ） = sup{｜｜（I- T（t））^r/2f｜｜：0≤ t ≤τ] of order r are defined in the standard way, where T^0（t） = I is the identity operator. In this paper, we establish the sharp Jackson inequality between E（f, n） and ωr（f, τ） for some cases of r and τ. More precisely, we will find the smallest constant n（τ, r） which depends only on n, r, and % such that the inequality E（f, n）≤ n（τ, r）ωr（f, τ） is valid.     

论化学学习中的能量观建构

能量观是中学化学学习中的核心观念。能量观的建构有利于学生形成核外电子运动的能量思维方式,了解从能量的角度研究物质及其转化的思维方法等。能量观建构的基本策略是:(1)在物质的微粒性认识学习中形成物质的微粒具有热能的观念;(2)在原子结构学习中形成核外电子运动的能量思维方式;(3)在元素及其化合物学习中发展高能量的最外层电子不稳定的认识;(4)在化学变化现象的积累学习中强化物质转化伴随有能量变化的认识;(5)通过化学键概念及其理论学习理解物质转化过程中伴随有能量变化;(6)在影响化学反应速率的条件讨论中深化理解有效碰撞理论;(7)在化学热力学问题研究中进一步理解能量守恒;(8)利用概念图技术帮助化学能量观的建构。     

Thermodynamic Analysis of Urea Physical Vapour Transport

The vaporisation-condensation scheme of urea has been investigated in the temperature region below the melting point, in order to establish the thermodynamic reactions on which the physical vapour transport (PVT) of urea is based. By making use of both reported data and experimental results of MS, DTA, DTG, and HPLC analysis, it was shown that PVT relevant reactions are basically molecular sublimation and partial decomposition in solid biuret and ammonia. MS analysis of urea crystals and source residues have also shown that no decomposition can be observed in the growing crystals, unless reheated during growth. The temperature dependence of the decomposition pressure has been found to be: log₁₀P_NH3 [torr] = 38 – 13840/T [K]. The use of this relation in diffusive mass transport calculations brought to linear growth rate values not in disagreement with the experimental values found in closed tube PVT grown crystals.     

Direct Catalytic Asymmetric and Regiodivergent N1- and C3-Allenylic Alkylation of Indoles

Herein we report a Pd-catalyzed asymmetric allenylic alkylation strategy for the direct functionalization of 1H-indoles by employing P-chiral BIBOP-type ligands. The regioselectivity (N1/C3) of this process can be switched efficiently. Using Cs₂CO₃ at elevated temperatures in MeCN, N1-alkylated indoles bearing axial chirality with a stereocenter non-adjacent (β) to the nitrogen are produced in good yields with high enantioselectivity and complete N1-regioselectivity regardless of the electronic properties and substitution patterns of diverse indoles. Using K₂CO₃ at room temperature in CH₂Cl₂, chiral C3-alkylated indoles can also be obtained. Notably, we introduce a new class of tri-substituted allenylic electrophiles that proceeded through different pathways from di-substituted allenylic electrophiles.     

Solution Growth and Characterisation of L‐alanine Single Crystals

Single crystals of L‐alanine have been grown from buffered aqueous solutions and characterised as to their optical quality via wavefront distortion analysis, electrooptical response and harmonic generation efficiency. Refraction indices as well as phase matching loci were found in satisfactory agreement with previously published data for crystals grown in non buffered solution. Estimates for the electro‐optical response are reported for the first time. The experimentally observed crystal habit is discussed in terms of morphological importance (M.I.), which was found to be in disagreement with the predictions of crystallographic criteria based on the interplanar distance d_hkl, on the periodic bond chains (PBC) and the attachment energy E_att. This disagreement is tentatively attributed to the presence of impurities and non‐appropriate supersaturation conditions.     

Asymmetric Coordination of Iridium Single-atom IrN3O Boosting Formic Acid Oxidation Catalysis

Rational design of the proximal coordination of an active site to achieve its optimum catalytic activity is the ultimate goal in single-atom catalysis, but still challenging. Here, we report theoretical prediction and experimental realization of an asymmetrically coordinated iridium single-atom catalyst (IrN₃O) for the formic acid oxidation reaction (FAOR). Theoretical calculations reveal that the substitution of one or two nitrogen with more electronegative oxygen in the symmetric IrN₄ motif splits and downshifts the Ir 5d orbitals with respect to the Fermi level, moderating the binding strength of key intermediates on IrN_4−xO_x (x=1, 2) sites, especially that the IrN₃O motif shows ideal activity for FAOR with a near-zero overpotential. The as-designed asymmetric Ir motifs were realized by pyrolyzing Ir precursor with oxygen-rich glucose and nitrogen-rich melamine, exhibiting a mass activity of 25 and 87 times greater than those of state-of-the-art Pd/C and Pt/C, respectively.     

Economical cobalt-free single-crystal LiNi0.6Mn0.4O2 cathodes for high-performance lithium-ion batteries

Journal of Solid State Electrochemistry - With the scarcity of cobalt resources and soaring prices, the removal of cobalt from nickel-rich layered cathodes is now a priority to reduce the material...     

Top-Seeded Solution Growth of Monomethylurea Single Crystals

It was previously reported on the growth of monomethylurea (NMU) single crystals from methanol solution by a mechanical limitation-direction (MLD) technique in which long (100) oriented seeds, capped on their extremities, were employed. The crystals obtained by this technique, in spite of their good structural and optical quality, presented their core region, in which the seed was located, with a higher density of structural defects and henceforth a reduced cross section useful for optical applications. It is here referred to a new, top-seeded growth configuration, devised on the basis of a preliminary PBC analysis for assessing the morphological importance of the crystal faces experimentally observed during crystal growth, which allows to grow NMU crystals in which the defected core region is removed for almost the entire length of the crystal.