An updated version of the computational package SIMPRE that uses the standard conventions for Stevens crystal field parameters

The crystal field approach used by SIMPRE is analyzed, verifying the exactness of the results concerning energy levels and magnetic properties calculated by the package. To coincide with the prevailing conventions, we reformulate the presentation of the crystal field parameters, so that the results are now, also from a formal point of view, strictly correct. New calculations are presented to test the influence of neglecting the excited J states, a common but critical approximation employed by SIMPRE. For that, we examine the case of Er(trensal) complex (H₃trensal = 2,2′,2″‐tris(salicylideneimino)triethylamine) where the influence of this approximation is found to be minimal. A patched version of the code, SIMPRE 1.1, and an updated version of the user manual are now available. Finally, we comment on “Software package SIMPRE – revisited,” which apparently revisits a software package without inspecting or using the code. © 2014 Wiley Periodicals, Inc.     

Kinetics of radical‐molecule reactions in aqueous solution: A benchmark study of the performance of density functional methods

The performance of 18 density functional approximations has been tested for a very challenging task, the calculations of rate constants for radical‐molecule reactions in aqueous solution. Despite of the many difficulties involved in such an enterprise, six of them provide high quality results, and are recommended to that purpose. They are LC‐ωPBE, M06‐2X, BMK, B2PLYP, M05‐2X, and MN12SX, in that order. This trend was obtained using experimental data as reference. The other relevant aspects used in this benchmark are: (i) the SMD model for mimicking the solvent; (ii) the conventional transition state, the zero‐curvature tunneling correction, and the limit imposed by diffusion for the calculation of the rate constants. Even though changing any of these aspects might alter the trend in performance, at least, when using them, the aforementioned functionals can be successfully used to obtain high quality kinetic data for the kind of reactions investigated in this work. © 2014 Wiley Periodicals, Inc.     

Significant nonlinear‐optical switching capacity in atomic clusters built from silicon and lithium: A combined ab initio and density functional study

Starting from a hypothetical but fundamental charge/discharge sequence, the topic of nonlinear optical switching in atomic clusters built from silicon and alkali metals is opened up. The outcomes presented in this work, obtained with ab initio methods of exceptional predictive capabilities, offer strong evidences that sizable hyperpolarizability contrasts between neutral and charged alkali metal doped cluster forms might be simultaneously accomplished. The observed switching procedure involves redox polyatomic clusters formed by Si atoms. These centers function as electron acceptors at the ground state and as electron donors at the excited states facilitating low energy charge transfer transitions upon electronic excitation. © 2014 Wiley Periodicals, Inc.     

基于纳米氧化铜修饰的异戊巴比妥的新型电化学传感器的制备与应用

在纳米氧化铜修饰的玻碳电极表面电聚合一种能够快速检测尿液中异戊巴比妥(AMB)的分子印迹敏感膜,研究了该敏感膜的最佳成膜条件及最佳工作条件.通过扫描电子显微镜(SEM)、循环伏安(CV)和电化学交流阻抗法(EIS)研究了印迹膜的表面形貌及性能.电化学实验结果表明,纳米氧化铜能提高传感器对AMB的灵敏度.在最佳实验条件下,铁氰化钾分子探针的差分脉冲伏安(DPV)峰电流响应值与AMB的浓度在1.0×10-7~1.4×10-4mol/L范围内呈现良好的线性关系(线性相关系数R=0.9966);检出限为2.1×10-9mol/L(S/N=3).此印迹传感器可用于尿液中AMB的检测,加标回收率为94.00%~104.67%.     

ZnO纳米管有序阵列与Cu2O纳米晶核壳结构的光电化学性能及全固态纳米结构太阳电池研究简

采用电化学方法在铟锡氧化物(ITO)导电玻璃基底上制备了高度有序的ZnO纳米管阵列,然后在ZnO纳米管阵列上电化学沉积Cu2O纳米晶颗粒,获得了一维有序Cu2O/ZnO核壳式纳米阵列结构,通过控制Cu2O纳米晶的沉积电量得到不同厚度的Cu2O壳层,并对该核壳式纳米阵列的形貌和结构进行了分析. 以Cu2O/ZnO一维核壳式纳米阵列结构为光电极组装全固态纳米结构太阳电池,研究了Cu2O壳层厚度对光电极光吸收性能、光电性能以及组装电池光伏性能的影响,优化了电池中对电极材料的喷金厚度. 结果表明,以Cu2O沉积电量为1.5 C的Cu2O/ZnO为光活性层,以4 mA电流下真空镀金20~25 min的铜基底为对电极组装的简易太阳电池最高可获得0.013%的光电转换效率.     

分子动力学模拟研究点突变(Met108→Leu108)对树胶醛糖结合蛋白与配体作用的影响

为了研究点突变(Met108→Leu108)对树胶醛糖结合蛋白(ABP)与配体结合能力的影响,对ABP、ABP结合树胶醛糖复合物及ABP结合半乳糖复合物以及它们各自的突变体分别进行60 ns的分子动力学模拟.模拟结果表明,108号残基突变前后,电子等排体的两个氨基酸残基,使蛋白与配体间的范德华相互作用发生明显变化,同时导致蛋白的内部运动也发生变化,进而影响蛋白与配体的相互作用.进一步分析表明,突变前后的蛋白构象变化都趋向于两个结构域张开,而与配体的结合可减缓张开程度.     

磺酰化修饰聚苯乙烯的合成及芳香烃萃取性能简

利用自由基聚合反应合成了低分子量聚苯乙烯,经过端基氧化和磺酰化反应,制备出一系列极性砜基修饰的低分子量聚苯乙烯. 通过红外光谱(FTIR)、核磁共振谱(NMR)、差示扫描量热分析(DSC)以及热重分析(TGA)等手段对聚合物的结构和性能进行了表征,并通过混合烃萃取分离实验对其芳香烃选择性进行了测试. 结果表明,随着磺化比例的增加,甲苯的选择系数和分布系数均显著提高,表明极性修饰聚苯乙烯对多种芳香烃/链烷烃混合物均具有明显的芳香烃选择性.     

固定床中纤维素热解及其焦油裂解机理研究

研究了500~900℃条件下微晶纤维素在固定床中的热解过程;分别采用气质联用(GC-MS)和气相色谱分析了热解过程中生成的焦油和不可凝气体。结果表明,随热解温度升高,焦油产率减少、气体产率升高、焦产率略微下降,同时CO、CH4和H2的产率明显升高,而CO2的产率变化不明显。焦油主要由二次反应产生,不可凝气体则由一次热解产物和二次热解产物共同产生。使用Gaussian 09软件对热解过程进行了模拟,发现纤维素分子在热解过程中首先分解为纤维素单体,然后纤维素单体上的羟基官能团优先脱除,生成的中间产物重组生成焦油。随热解温度升高,焦油中醚、醇、酸等化合物分解成自由基,自由基间发生重组、结合,导致烯烃和炔烃增多以及不可凝气体含量的升高。     

FT-IR和SEM用于煤阶对煤催化加氢气化影响的研究

基于加压固定床反应器研究了不同煤阶的煤催化加氢气化效果,对比了煤阶对催化剂添加量、甲烷释放速率以及产品气组成的影响。原煤及气化残渣采用FT-IR和SEM进行表征分析。研究结果表明,不添加催化剂情况下,随着煤阶的升高原煤气化反应性降低,低阶煤的甲烷释放分为两个阶段;加入催化剂之后,3种煤中以神府烟煤的反应性最好,遵义无烟煤和云南褐煤反应性较差。SEM和FT-IR表征结果表明,高阶煤颗粒表面更加光滑、煤结构致密,而煤中的脂肪族结构以及芳香结构振动峰强度随煤阶的降低而升高,催化剂的加入使得脂肪结构吸收峰明显加强。这些差异导致不同煤样催化加氢气化反应活性不同。     

Comprehensive two‐dimensional gas chromatography coupled with static headspace sampling to analyze volatile compounds: Application to almonds

The hyphenation of static headspace sampling with comprehensive 2D GC equipped with a modulator based on capillary flow technology and a flame ionization detector was used to separate and identify 43 representative target volatile compounds (light hydrocarbons, carbonyls, pyrazines, alcohols, furans, and benzenes) frequently detected in the roasting process of nuts. Five column combinations with differing degrees of orthogonality (one conventional and four inverted phase sets) were tested in order to obtain the best conditions for analyzing these volatile compounds. Optimization of the working conditions for each of the different column combinations was performed by means of a central composite design. The best results in terms of separation and differentiation among the different chemical groups were achieved with a combination of inverted phase columns (first dimension: highly polar, INNOWax; second dimension: mid‐polar, ZB‐35). Additionally, a reference template was developed to provide an effective and rapid analysis of the target compounds. Finally, the proposed method was successfully employed to identify volatile compounds in raw and roasted almond samples from the Spanish cultivar Largueta.