固体氢在极端压强下的超导性能

氢元素在常压下具有最简单的晶体结构和物理性质。随着压强增加,氢单质发生相变,由绝缘体转变为金属,被称为金属氢。数值模拟表明,金属氢具有高温超导电性,因此,金属氢研究也被称为高压物理领域的“圣杯”课题。利用基于密度泛函理论的第一性原理计算方法,对固体氢在极端高压(0.5～5.0 TPa)下的结构和超导电性开展了系统研究。研究结果表明：固体氢的高压相变序列为I4₁/amd→oC12→cI16;对于同一种结构,随着压强增加,电声耦合系数减小,费米面处电子态密度减小,特征振动频率增加,超导转变温度发生小幅变化;在2.0 TPa压强下,固体氢的超导转变温度高达418 K(库伦赝势经验值μ^*=0.10)。研究工作将为金属氢及其超导电性的后续理论和实验研究提供参考。     

Syntheses and Crystal Structures of Two Copper~Ⅱ Complexes with Tetracyanonickelate~Ⅱ

Two copper-nickel complexes, {[Cu(i-Pr3TACN)][Ni(CN)4]}2·2H2O (1) and {[Cu(DACH)][Ni(CN)4]}n (2), have been synthesized by the self-assembly reactions of K2[Ni(CN)4] with CuCl2 and the corresponding chelating ligand 1,4,7-triisopropyl-1,4,7- triazacyclononane (i-Pr3TACN) or 1,4-diazacycloheptane (DACH), respectively. The complexes were structurally characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra and magnetic properties. Complex 1 presents a [2+2] type of molecular square structure and 2 features a 2D β-pucker structure. The magnetic susceptibility measurements reveal a weak antiferromagnetic interaction between the Cu(Ⅱ) ions, with the J values of-22.11 and -32.50 cm-1 for 1 and 2. Moreover, by changing the size of macrocyclic ligands we have successfully constructed two different strictures, which may provide useful information for the construction of the structure.     

Synthesis and superconductivity in yttrium superhydrides under high pressure

Flourishing rare earth superhydrides are a class of recently discovered materials that exhibit near-room-temperature superconductivity at high pressures, ushering in a new era of superconductivity research at high pressures. Yttrium superhydrides drew the most attention among these superhydrides due to their abundance of stoichiometries and excellent superconductivities. Here, we carried out a comprehensive study of yttrium superhydrides in a wide pressure range of 140 GPa—300 GPa. We successfully synthesized a series of superhydrides with the compositions of YH₄, YH₆, YH₇, and YH₉, and reported superconducting transition temperatures of 82 K at 167 GPa, 218 K at 165 GPa, 29 K at 162 GPa, and 230 K at 300 GPa, respectively, as evidenced by sharp drops in resistance. The structure and superconductivity of YH₄ were taken as a representative example and were also examined using x-ray diffraction measurements and the superconductivity suppression under external magnetic fields, respectively. Clathrate YH₁₀, a candidate for room-temperature superconductor, was not synthesized within the study pressure and temperature ranges of up to 300 GPa and 2000 K. The current study established a detailed foundation for future research into room-temperature superconductors in polynary yttrium-based superhydrides.     

QuEChERS前处理联合UPLC–MS/MS法检测花生中22种农药残留

建立了Qu ECh ERS(Quick,Easy,Cheap,Effective,Rugged,Safe)前处理联合UPLC–MS/MS法检测花生中22种农药残留的方法。样品用10 m L乙腈提取,以多壁碳纳米管、N-丙基乙二胺为吸附剂,对2 m L提取液进行净化,净化液稀释至2倍体积,以MRM扫描方式、正负离子模式同时分析。22种农药在10,20,50μg/kg 3个添加水平下,平均回收率为70.6%~121.2%,相对标准偏差小于10%(n=6);多菌灵、抗蚜威、扑草净在0.05~10μg/L,啶虫脒、氟虫腈砜、苯醚甲环唑、哒螨灵、嘧霉胺、嘧菌酯在0.5~20μg/L,烯酰吗啉、噻虫嗪、氟啶脲、灭幼脲、吡虫啉、甲维盐、除虫脲、氟虫腈、氟甲腈、氟虫腈亚砜、咪鲜胺、二甲戊灵在0.5~50μg/L之间,阿维菌素在0.5~100μg/L范围内线性良好,相关系数r2均大于0.995 0。22种农药的定量限在2μg/kg以下,远低于各待测农药最高残留限量标准(MRL)。该法适于花生中农药残留的同时快速检测。     

Pressure-induced phase transition in transition metal trifluorides

As a fundamental thermodynamic variable, pressure can alter the bonding patterns and drive phase transitions leading to the creation of new high-pressure phases with exotic properties that are inaccessible at ambient pressure. Using the swarm intelligence structural prediction method, the phase transition of TiF₃, from R—3c to the Pnma phase, was predicted at high pressure, accompanied by the destruction of TiF₆ octahedra and formation of TiF₈ square antiprismatic units. The Pnma phase of TiF₃, formed using the laser-heated diamond-anvil-cell technique was confirmed via high-pressure x-ray diffraction experiments. Furthermore, the in situ electrical measurements indicate that the newly found Pnma phase has a semiconducting character, which is also consistent with the electronic band structure calculations. Finally, it was shown that this pressure-induced phase transition is a general phenomenon in ScF₃, VF₃, CrF₃, and MnF₃, offering valuable insights into the high-pressure phases of transition metal trifluorides.     

海地瓜多糖脱色工艺研究

比较了活性炭、H2O2及大孔树脂对海地瓜多糖的脱色效果。从脱色率及多糖保留率两方面进行考察,树脂D392处理优于活性炭和H2O2,对其脱色工艺进行优化,通过响应面实验建立了数学模型,并确定树脂D392脱色的最优工艺为时间:5h,pH 10,温度:60℃,此时,脱色率达(84.2±0.6)%,多糖保留率为(82.9±1.1)%。研究工作有利于海参多糖品质的提高,为海参多糖后续研究及应用奠定了基础。