Mechanofluorochromic Carbon Nanodots: Controllable Pressure‐Triggered Blue‐ and Red‐Shifted Photoluminescence

Mechanofluorochromic materials, which change their photoluminescence (PL) colors in responding to mechanical stimuli, can be used as mechanosensors, security papers, and photoelectronic devices. However, traditional mechanofluorochromic materials can only be adjusted to a monotone direction upon the external stimuli. Controllable pressure‐triggered blue‐ and red‐shifted PL is reported for C‐dots. The origin of mechanofluorochromism (MFC) in C‐dots is interpreted based on structure–property relationships. The carbonyl group and the π‐conjugated system play key roles in the PL change of C‐dots under high pressure. As the pressure increases, the enhanced π–π stacking of the π‐conjugated system causes the red‐shift of PL, while the conversion of carbonyl groups eventually induces a blue‐shift. Together with their low toxicity, good hydrophilicity, and small size, the tunable MFC property would boost various potential applications of C‐dots.     

饱和蒸气压测定实验中气流量调控装置的改进

In the static method of saturated vapor pressure measurements, the key operation is to adjust the pressure of the system. Because of the invisibility of the gas, it is difficult to control the air flow, which often results in air pouring into the system due to excessive air flow in the constant pressure adjustment process. By designing a mini gas flow control device, the control operation is visualized; thus, problems associated with controlling the air flow can be avoided. Furthermore, frequent adjustment of the air flow becomes unnecessary, greatly reducing the lab hour.     

Pressure Dependence of the Lattice Distortion in Perovskite La0.5−xBixCa0.5MnO3 (x=0.1, 0.15, 0.2)

The in situ behavior of distorted perovskite La_0.5−xBi_xCa_0.5MnO₃ (x=0.1, 0.15, 0.2) under high pressure has been studied by energy-dispersive X-ray diffraction in a diamond anvil cell. An abnormal change of the 202–040 d-spacing ascribed to the disappearance of the distortion mode Q₂ in the MnO₆ octahedra is observed at 1.2, 1.4, and 1.6 GPa, respectively, and it results in a reduction of the Jahn–Teller distortion commonly existing in the manganites. Effect of the unique 6s² long-pair character of the Bi³⁺ ion on the pressure dependence of the lattice distortion is discussed.     

Na3RuD7 – Synthese und Struktur

Na₃RuD₇ – Synthesis and Structure Na₃RuD₇ was synthesized by the reaction of sodium deuteride with ruthenium powder under a hydrogen pressure of 6000 bar at 900 K. X‐ray investigations on powdered samples and elastic neutron diffraction experiments led to the atomic arrangement (space group: P4₂/mnm), which is characterized by isolated [RuD₇]‐anions. The coordination polyhedron formed by the seven deuterium ligands can be described as a distorted pentagonal bipyramide.     

Effect of pressure on the solubilities ofo-,m- andp-xylene in water

The solubilities of o-, m- and p-xylene in water were measured at 25.0°C up to 250, 385, and 50 MPa, respectively. The solubility increased with increasing pressure up to 120 MPa (50 MPa for p-xylene) and then decreased. The reaction volumes, V^o accompanying the dissolution at 0.1 MPa were estimated as –3.6±0.5, –3.4±0.5, and –4.1±0.5 cm³-mol^–1 for o-, m-, and p-xylene, respectively, from the pressure dependences of the solubilities. The limiting partial molar volumes, of p- and o-xylene in water under high pressure were estimated from V^o and the molar volume of the xylene. The partial molar volumes decreased with increasing pressure. The reaction volume for the formation of intra-molecular pairwise hydrophobic interaction between the methyl groups, as proposed by Ben-Naim, is discussed for the V^o of p- and o-xylene at 0.1 MPa.     

高压下轻元素单质的结构相变

压力是物质独立于温度和化学组分的一个重要维度,能够有效改变物质内部原子间的相互作用,诱导形成具有新结构和新性质的高压新相,可以揭示许多常压下不曾有过的新现象和新规律,为制备出常压条件下无法得到的新材料提供了创新性源泉。元素单质在常压下大多具有简单的晶体结构,但在高压下却发生了非常复杂的结构相变,形成了多种新颖的高压相,产生了超导、超硬、金属-绝缘体相变等奇异现象,吸引了科学界的广泛关注。本文针对元素周期表中前12种轻元素单质的高压结构相变、高压相的新奇物理特性及相变产生的物理机制进行了探讨和论述,并对实验和理论高压结构相变的研究方法进行了展望。     

Atmospheric pressure photoionization mass spectrometry as a tool for the investigation of the hydrolysis reaction mechanisms of phosphite antioxidants

The hydrolysis reaction mechanism of phosphite antioxidants is investigated by liquid chromatography-mass spectrometry (LC/MS). The phosphites were chosen because they differed in chemical structure and phosphorus content. Dopant assisted-atmospheric pressure photoionization (DA-APPI) is chosen as the ion source for the ionization of the compounds. In our previous work, DA-APPI was shown to offer an attractive alternative to atmospheric pressure chemical ionization (APCI) since it provided background-ion free mass spectra and higher sensitivity [M. Papanastasiou, et al., Polymer Degradation and Stability 91 (11) (2006) 2675–2682]. In positive ion mode, the molecules are generally detected in their protonated form. In negative ion mode, the phosphites are unstable and only fragment ions are observed; these however, are characteristic of each phosphite and may be used for the identification of the analytes in complex mixtures.The analytes under investigation are exposed to accelerated humid ageing conditions and their hydrolytic pathway and stability is investigated. Different substituents around the phosphorus atom are shown to have a significant effect on the stability of the phosphites, with phenol substituents producing very hydrolytically stable structures. Alkanox P24 and PEP-36 follow a similar hydrolytic pathway via the scission of the first and then the second PO_phenol bonds, eventually leading to the formation of phenol, phosphorous acid and pentaerythritol as end products. HP-10 exhibits a rather different structure and the products detected suggest scission of either the PO_hydrocarbon or one of the PO_phenol bonds. A phenomenon similar to that of autocatalysis is observed for all phosphites and is attributed to the formation of dialkyl phosphites as intermediate products.     

Coherent thermodynamic model for solid,liquid and gas phases of elements and simple compounds in wide ranges of pressure and temperature

Thermodynamic modeling of fluids (liquids and gases) uses mostly series expansions which diverge at low temperatures and do not fit to the behavior of metastable quenched fluids (amorphous, glass like solids). These divergences are removed in the present approach by the use of reasonable forms for the “cold” potential energy and for the thermal pressure of the fluid system. Both terms are related to the potential energy and to the thermal pressure of the crystalline phase in a coherent way, which leads to simpler and non diverging series expansions for the thermal pressure and thermal energy of the fluid system. Data for solid and fluid argon are used to illustrate the potential of the present approach.     

SCL教学法在中职卫校化学课程中的探索与实践

以溶液渗透压教学为例,介绍了SCL教学法在中职卫校“医用化学基础”课程中的应用。具体实施过程包括创设情境,导入新课,借助小组活动引导新知,通过层层讲授推导新知以及在实践应用中拓展思维。结果表明SCL教学法能明显活跃课堂气氛,改变学生学习习惯。