顶空气相色谱法测定茶多酚工业废水中的三氯甲烷

改用氢火焰离子化检测器和毛细管色谱柱,以医用100 mL输液瓶为气液平衡瓶,采用带锁定气密性注射器,利用顶空气相色谱法对茶多酚工业废水中三氯甲烷含量进行了测定,通过实验得到最佳顶空色谱条件。结果表明,以SPETM-1毛细管色谱柱,FID检测器进行顶空气相色谱测定,标准曲线相关系数为0.9997,RSD为2.73%～5.16%之间,回收率在99.28%～99.98%之间,方法精密度好,准确度高,能满足工业分析要求。     

Discovery of Two-Dimensional Quantum Spin Hall Effect in Triangular Transition-Metal Carbides

Though the quantum spin Hall effect(QSHE) in two-dimensional(2 D) crystals has been widely explored, the experimental realization of quantum transport properties is only limited to HgTe/CdTe or InAs/GaSb quantum wells. Here we employ a tight-binding model on the basis of d_(z~2), d_(xy), and d_(x~2-y~2) orbitals to propose QSHE in the triangular lattice, which are driven by a crossing of electronic bands at the Γ point. Remarkably, 2 D oxidized Mxenes W_2 M_2 C_3 are ideal materials with nontrivial gap of 0.12 eV, facilitating room-temperature observations in experiments. We also find that the nontrivially topological properties of these materials are sensitive to the cooperative effect of the electron correlation and spin-orbit coupling. Due to the feasible exfoliation from its 3 D MAX phase, our work paves a new direction towards realizing QSHE with low dissipation.