CH4, CO2和H2O在非金属原子修饰石墨烯表面的吸附

煤层气(矿井瓦斯)是一种有望替代传统化石燃料,如煤、石油和天然气的非常规气体. 作为可得的清洁能源,它的利用被认为是节能和经济的选择. 在本工作中,非金属原子X(X=H,O,N,S,P,Si,F,Cl)修饰的石墨烯(Gr)被用来代表具有结构异性的煤表面模型. 通过密度泛函理论系统地研究了煤层气组分Y(Y=CH₄,CO₂,H₂O)在非金属原子修饰石墨烯上的吸附作用. 结果表明Y在非金属原子修饰石墨烯上的吸附均为物理吸附. 态密度和差分电荷密度共同表明了这种弱的相互作用.其中,H和Cl对CH₄的作用较大; N、O、F、Cl对CO₂的作用较强; N,Cl对H₂O的影响不容忽视. 总的来说,吸附能大小依次为：H₂O>CO₂>CH₄. 因此,在CH₄富集的煤层里注入H₂O或CO₂可以与CH₄形成竞争吸附,进而提高煤层气采收率. 本工作提供了在分子水平下煤层气与非金属原子修饰石墨烯之间的相互作用的详情,并为煤层瓦斯的开采与分离提供了有用的信息.     

Dy3+单掺及Dy3+,Er3+共掺GdVO4纳米粒子的制备及发光性能的研究

用水热法制备了Dy3+单掺及Dy3+,Er3+双掺GdVO4纳米荧光粉,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、红外光谱仪(FTIR)和荧光(FL)光谱对合成样品的结构、形貌和发光性能进行表征;探讨了Dy3+掺杂浓度、络合剂对GdVO4:Dy3+纳米晶的结构、形貌和发光性能的影响;考察了不同波长的近红外光和紫外光激发的GdVO4:Dy3+,Er3+,得到不同颜色的上转换和下转换荧光光谱。以760~830 nm近红外光和210~380 nm紫外光激发GdVO4:Dy3+纳米晶,可获得Dy3+蓝绿色双模发光;其中蓝光来自于Dy3+离子的4F9/2→6H15/2跃迁,绿光由Dy3+离子4F9/2→6H13/2跃迁产生。     

盐析剂——氯化钠存在下稀土含量的准确测定

分光光度法(Spectrophotometry)和电感耦合等离子体发射光谱法(ICP-AES)是常用的测定单一稀土含量的方法。但是萃取稀土过程中通常会加入盐析剂NaCl,萃余水相中大量钠离子所产生的光谱背景严重干扰了稀土含量的测定。考察了NaCl对稀土含量测定的影响,实验结果表明:在基体不匹配的情况下,只有当钠盐浓度低于0.08 mol·L-1时,分光光度法可以准确测定萃余液中单一轻稀土(La,Ce,Pr,Nd)及中稀土(Sm,Eu,Gd)的含量,但不能准确测定重稀土的含量;而使用ICP-AES法,在NaCl浓度为0.001~1.0 mol·L-1条件下无法准确测定稀土含量。因此,实验室宜采用分光光度法在基体不匹配的条件下测定轻、中稀土含量,重稀土在基体匹配的条件下用电感耦合等离子体发射光谱法测定。     

TNT高温热解及含碳团簇形成的反应分子动力学模拟

ReaxFF-MD模拟三硝基甲苯(TNT)高温热解显示增加了伦敦耗散力项(E_lg)的ReaxFF/lg 势函数在含能材料平衡密度计算方面具有优越性. 产物识别分析得出TNT热解的主要产物为NO₂、NO、H₂O、N₂、CO₂、CO、OH以及HONO,且最终产物为H₂O、N₂和CO₂. 使用ReaxFF势函数模拟同样过程进行比较性分析显示,在主要产物和最终产物方面与ReaxFF/lg 作用结果具有一致性,但在化学反应动力学方面表现出一些差异. ortho-NO₂键断裂和C―NO₂→C―ONO重排布-断裂形成NO₂和NO是TNT热解的主要初级反应,且前者产生速率大于后者,NO₂和NO形成后很快参与次级反应并最终形成N₂. 高温热解中形成OH等小分子会促进H₂O的形成. 环上基团相互反应或直接脱落后,主环间C―C键才发生断裂,但温度升高会加快主环断裂,并进一步分解形成CO₂,这也是高温条件下CO₂分布产生波动的一个重要原因. 并且当晶胞中的TNT分子几乎完全分解时,系统的势能开始明显衰减. 与温度相比,密度对热解中最大含碳团簇形成的影响更明显. 并且,模拟结果显示,在TNT完全分解前已经出现含碳中间体的聚合现象. 此项工作表明使用ReaxFF/lg 反应力场研究TNT高温热解可以提供具体的动力学和化学方面的信息,并有助于理解含能材料的爆轰问题并可进行安全评估.     

Synthesis of Two‐Dimensional Transition‐Metal Phosphates with Highly Ordered Mesoporous Structures for Lithium‐Ion Battery Applications

Materials with ordered mesoporous structures have shown great potential in a wide range of applications. In particular, the combination of mesoporosity, low dimensionality, and well‐defined morphology in nanostructures may exhibit even more attractive features. However, the synthesis of such structures is still challenging in polar solvents. Herein, we report the preparation of ultrathin two‐dimensional (2D) nanoflakes of transition‐metal phosphates, including FePO₄, Mn₃(PO₄)₂, and Co₃(PO₄)₂, with highly ordered mesoporous structures in a nonpolar solvent. The as‐obtained nanoflakes with thicknesses of about 3.7 nm are constructed from a single layer of parallel‐packed pore channels. These uniquely ordered mesoporous 2D nanostructures may originate from the 2D assembly of cylindrical micelles formed by the amphiphilic precursors in the nonpolar solvent. The 2D mesoporous FePO₄ nanoflakes were used as the cathode for a lithium‐ion battery, which exhibits excellent stability and high rate capabilities.     

Oxidative Cross‐Coupling of Allenyl Ketones and Organoboronic Acids: Expeditious Synthesis of Highly Substituted Furans

Allenyl ketones are employed as coupling partners in palladium‐catalyzed oxidative cross‐coupling reactions with organoboronic acids. This reaction constitutes an efficient methodology for the synthesis of highly substituted furan derivatives. Palladium‐carbene migratory insertion is proposed as the key step in this transformation.     

Self‐Healable Electrically Conducting Wires for Wearable Microelectronics

Electrically conducting wires play a critical role in the advancement of modern electronics and in particular are an important key to the development of next‐generation wearable microelectronics. However, the thin conducting wires can easily break during use, and the whole device fails to function as a result. Herein, a new family of high‐performance conducting wires that can self‐heal after breaking has been developed by wrapping sheets of aligned carbon nanotubes around polymer fibers. The aligned carbon nanotubes offer an effective strategy for the self‐healing of the electric conductivity, whereas the polymer fiber recovers its mechanical strength. A self‐healable wire‐shaped supercapacitor fabricated from a wire electrode of this type maintained a high capacitance after breaking and self‐healing.     

Geometry‐Assisted Three‐Dimensional Superlocalization Imaging of Single‐Molecule Catalysis on Modular Multilayer Nanocatalysts

To establish the structure–catalytic property relationships of heterogeneous catalysts, a detailed characterization of the three‐dimensional (3D) distribution of active sites on a single catalyst is essential. Single‐particle catalysis of a modular multilayer catalytic platform that consists of a solid silica core, a mesoporous silica shell, and uniformly distributed Pt nanoparticles sandwiched in between these layers is presented. The first 3D high‐resolution super‐localization imaging of single fluorescent molecules produced at active sites on the core‐shell model nanocatalysts is demonstrated. The 3D mapping is aided by the well‐defined geometry and a correlation study in scanning electron microscopy and total internal reflection fluorescence and scattering microscopy. This approach can be generalized to study other nano‐ and mesoscale structures.     

Effects of Edge Oxidation on the Stability and Half‐Metallicity of Graphene Quantum Dots

A comprehensive first‐principles theoretical study of the electronic properties and half‐metallic nature of zigzag edge‐oxidized graphene quantum dots (GQDs) is carried out by using density functional theory (DFT) with the screened exchange hybrid functional of Heyd, Scuseria and Ernzerhof (HSE06). The oxidation schemes include ‐OH, ‐COOH and ‐COO groups. We identify oxidized GQDs whose opposite spins are localized at the two zigzag edges in an antiferromagnetic‐type configuration, showing a spin‐polarized ground state. Oxidized GQDs are more stable than the corresponding fully hydrogenated GQDs. The partially hydroxylated and carboxylated GQDs with the same size exhibit half‐metallic state under almost the same electric‐field intensity whereas fully oxidized GQDs behave as spin‐selective semiconductors. The electric‐field intensity inducing the half metal increases with the length of the partially oxidized GQDs, ranging from M=4 to 7.     

微芯片毛细管电泳法快速测定盐酸二甲双胍

提出用带有非接触电导检测的微芯片毛细管电泳法快速测定片剂中盐酸二甲双胍的含量。取盐酸二甲双胍片20片,剥除糖衣后混匀研细,称取0.100 0g,用水超声溶解、过滤,滤液定容至100mL供毛细管电泳分析。十字通道芯片使用前按规定进行清洗。试验中采用含5%(体积分数)乙醇和0.1mmol·L-1十二烷基磺酸钠的2.0mmol·L-1柠檬酸缓冲溶液作为分离介质,进时间为10.0s,分离电压为1.3kV,可在1min内实现分离和测定。盐酸二甲双胍的质量浓度在10.0~110.0mg·L-1范围内与相应峰高呈线性关系,检出限(3S/N)为1.0mg·L-1。应用此方法分析了3个片剂样品,并用标准加入法做回收试验,测得回收率在94.5%~103%之间,测定值的相对标准偏差(n=6)在0.63%~1.1%之间。