Design,preparation, and characterization of Fe3O4 nanoparticles encapsulating β-cyclodextrin-bearing guanidine as a highly efficient and reusable heterogeneous base catalyst for synthesis of 3,4-dihydropyrano[3,2-c]chromenes

Chromene substructure is an important structural motif present in a variety of medicines, natural products, and materials showing biological activities. Here, a simple and convenient procedure for the synthesis of 3,4-dihydropyrano[3,2-c]chromene derivatives is described. For this purpose, Fe₃O₄ nanoparticles supported on β-cyclodextrin-guanidine were successfully prepared and used as catalyst. The structure of this catalyst was assigned by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermal gravimetric analysis, and vibrating sample magnetometer techniques. The prepared nanocomposites were used as a highly active, heterogeneous, and reusable nanocatalyst for the one-pot, three-component reaction of 4-hydroxycoumarin, aromatic aldehydes, and ethyl cyanoacetate. This method has advantages such as mild conditions, high yields, easy workup and simple purification of products, little catalyst loading, cost efficiency, and reusability of the catalyst.     

Quantification of fenoprofen in human plasma using UHPLC–tandem mass spectrometry for pharmacokinetic study in healthy subjects

A rapid, simple and sensitive ultra-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method has been developed to quantify fenoprofen, a nonsteroidal anti-inflammatory drug in human plasma for a pharmacokinetic study in healthy subjects. Owing to high levels of protein binding, protein precipitation followed by solid-phase extraction was employed for the extraction of fenoprofen and fenoprofen-d3 (used as internal standard) from 200 μL human plasma. Separation was performed on a BEH C₁₈ (50 × 2.1 mm, 1.7 μm) column using methanol−0.2% acetic acid in water (75:25, v/v) under isocratic elution. Electrospray ionization was operated in the negative mode for sample ionization. Ion transitions used for quantification in the selected reaction monitoring mode were m/z 241/197 and m/z 244/200 for fenoprofen and fenoprofen-d3, respectively. Under the optimized conditions, fenoprofen showed excellent linearity in the concentration range 0.02–20 μg/mL (r² ≥ 0.9996), adequate sensitivity, favorable accuracy (96.4–103.7%) and precision (percentage coefficient of variation ≤4.3) with negligible matrix effect. The validated method was successfully applied to a pharmacokinetic study of fenoprofen in healthy subjects. The significant features of the method include higher sensitivity, small plasma volume for processing and a short analysis time.     

Quantitative determination of potential genotoxic impurity 3-aminopyridine in linagliptin active pharmaceutical ingredient using HILIC–UV

This study aimed to develop an analytical method to determine the quantity of the impurity 3-aminopyridine (3AP). 3-Aminopyridine is a reactive reagent in the synthesis of linagliptin. The method was sensitive at level of 30.0 ppm of 3AP relative to linagliptin. The analysis was carried out using hydrophilic interaction liquid chromatography. The analytical column was Tracer Extrasil Silica (150 × 4.0 mm, 3 μm). A mobile phase of water–acetonitrile (10:90, v/v) containing 10.0 mM ammonium acetate was prepared and adjusted to pH 6.0. A UV detector was used to detect the amount of 3AP at a wavelength of 298 nm. Validation of the method was performed as per the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use in terms of detection limit, quantitation limit, linearity, accuracy, precision, specificity and robustness. The calibration curve was linear (r² = 0.999) for 3AP concentration in the range of 30.0–450.0 ppm. This method showed a good sensitivity with a detection limit and a quantitation limit of 7.5 and 25.0 ppm, respectively.     

Micro/Nanoengineered α-Fe2O3 Nanoaggregate Conformably Enclosed by Ultrathin N-Doped Carbon Shell for Ultrastable Lithium Storage and Insight into Phase Evolution Mechanism

The Fe-based transition metal oxides are promising anode candidates for lithium storage considering their high specific capacity, low cost, and environmental compatibility. However, the poor electron/ion conductivity and significant volume stress limit their cycle and rate performances. Furthermore, the phenomena of capacity rise and sudden decay for α-Fe₂O₃ have appeared in most reports. Here, a uniform micro/nano α-Fe₂O₃ nanoaggregate conformably enclosed in an ultrathin N-doped carbon network (denoted as M/N-α-Fe₂O₃@NC) is designed. The M/N porous balls combine the merits of secondary nanoparticles to shorten the Li⁺ transportation pathways as well as alleviating volume expansion, and primary microballs to stabilize the electrode/electrolyte interface. Furthermore, the ultrathin carbon shell favors fast electron transfer and protects the electrode from electrolyte corrosion. Therefore, the M/N-α-Fe₂O₃@NC electrode delivers an excellent reversible capacity of 901 mA h g⁻¹ with capacity retention up to 94.0 % after 200 cycles at 0.2 A g⁻¹. Notably, the capacity rise does not happen during cycling. Moreover, the lithium storage mechanism is elucidated by ex situ XRD and HRTEM experiments. It is verified that the reversible phase transformation of α↔γ occurs during the first cycle, whereas only the α-Fe₂O₃ phase is reversibly transformed during subsequent cycles. This study offers a simple and scalable strategy for the practical application of high-performance Fe₂O₃ electrodes.     

Yb3+掺杂稀土钽铌酸盐的晶体场从头计算研究

Yb³⁺掺杂晶体材料是重要的激光材料,在超短脉冲激光、大功率激光等领域有重要应用前景,但长期以来很难通过实验拟合确定Yb3+晶体场参数,尤其是低对称体系,从头计算是解决此问题的重要途经.本文介绍了适合计算稀土离子掺杂晶体的从头计算DV-Xα方法和有效哈密顿量模型,用该方法计算了Yb³⁺掺杂M型和M'型钽铌酸盐的晶场参数和旋轨耦合参数,得到的能级结构和实验能很好地符合,并发现了Yb³⁺掺杂钽铌酸盐的晶场强度参数随稀土原子序数呈现规律变化.表明结合DV-Xα计算和有效哈密顿量方法是计算Yb³⁺掺杂低对称钽铌酸盐晶体场的有效途径,结果显示Yb3+掺杂钽铌酸盐晶体有望成为新型全固态激光工作物质.     

Eu^3+激活氟氧硼酸锗酸盐闪烁玻璃的发光性能

采用传统高温熔融法合成了玻璃组成为B2O3-GeO2-15GdF3-(40-x)Gd2O3-xEu2O3(0≤x≤10)的Eu^3+激活氟氧硼酸锗酸盐闪烁玻璃。在硼锗酸盐玻璃基质中,Gd2O3和GdF3稀土试剂的总含量高达55%,从而确保其密度高于6.4 g/cm^3。闪烁玻璃的光学性能通过光学透过光谱、光致发光光谱、X射线激发发射(XEL)光谱和荧光衰减曲线来表征。玻璃中Gd^3+→Eu^3+离子的能量传递通过激发光谱、发射光谱和Gd^3+-Eu^3+离子间距得到证明,同时也确定了在紫外线和X射线激发下Eu^3+激活氟氧硼酸锗酸盐闪烁玻璃的最佳浓度。Judd-Ofelt理论分析了玻璃中Eu―O键的共价性随Eu^3+掺杂浓度增加而显著增强。Eu^3+激活氟氧硼酸锗酸盐闪烁玻璃在80~470 K温度范围内荧光衰减曲线和发射光谱的温度依赖关系最终证实了其具有较好的发光稳定性。     

激光雷达辅助驾驶道路参数计算方法研究

针对特定场景辅助驾驶的需求，构建道路场景车载激光雷达三维扫描系统，并设计基于三维激光点云的道路参数提取与计算方法，包括路面宽度、横杆或桥梁或隧道限高、拐弯半径等等，为辅助判断道路的可通过性提供决策依据。测试和对比实验表明，所设计算法效果稳定、精度良好，在效率和自动化程度上有一定优势，可为辅助驾驶提供非常有益的决策参数。     

饮用水中三氯甲烷与其他氯消毒副产物在活性炭上的吸附竞争研究

通过等温吸附实验，探究了三氯甲烷（CHCl₃）与二氯一溴甲烷（CHBrCl₂）、二氯乙酸（Cl₂CHCOOH）在活性炭上的竞争吸附关系，同时探究了在低浓度条件下CHBrCl₂和Cl₂CHCOOH浓度变化对活性炭吸附CHCl₃的影响。实验结果表明，活性炭吸附CHCl₃和CHBrCl₂符合Freundlich模型，对Cl₂CHCOOH的吸附符合Langmuir模型；活性炭对3种消毒副产物均为优先吸附，吸附能力由大到小依次为CHBrCl₂、CHCl₃、Cl₂CHCOOH；低浓度条件下，活性炭对消毒副产物的吸附效果随体系中物质种类的增加而降低；低浓度条件下，Cl₂CHCOOH的浓度变化对CHCl₃的吸附效果影响不大，但吸附效果随水体中CHBrCl₂浓度的升高而降低。     

Surface passivation in n-type silicon and its application in silicon drift detector

Based on the surface passivation of n-type silicon in a silicon drift detector(SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-silicon(NAOS)method has good compactness and simple process, the first layer film is formed by the NAOS method. The Al2O3 film is also introduced into the passivation stacks owing to exceptional advantages such as good interface characteristic and simple process. In addition, for requirements of thickness and deposition temperature, the third layer of the SiO2 film is deposited by plasma enhanced chemical vapor deposition(PECVD). The deposition of the SiO2 film by PECVD is a low-temperature process and has a high deposition rate, which causes little damage to the device and makes the SiO2 film very suitable for serving as the third passivation layer. The passivation approach of stacks can saturate dangling bonds at the interface between stacks and the silicon substrate, and provide positive charge to optimize the field passivation of the n-type substrate.The passivation method ultimately achieves a good combination of chemical and field passivations. Experimental results show that with the passivation structure of SiO2/Al2O3/SiO2, the final minority carrier lifetime reaches 5223 μs at injection of 5×10¹⁵ cm^-3. When it is applied to the passivation of SDD, the leakage current is reduced to the order of nA.     

运用三维离散元技术模拟落锤撞击下奥克托今颗粒的点火燃烧过程

炸药颗粒的点火燃烧过程一直是人们关注的热点问题。近年来，三维离散元技术在中尺度观测颗粒材料的动力学过程中拥有显著优势。炸药燃烧属于颗粒材料的反应动力学，运用三维离散元技术(DM3)可以有效地观测炸药燃烧传播的过程。以奥克托今(HMX)颗粒为例，本文成功模拟并观测到了HMX颗粒的燃烧反应程度，确定了颗粒开始燃烧反应的时间，以及燃烧反应传播的时间。同时，结合落锤冲击颗粒的三维图像以及其表观压强和放热功率，得到了HMX颗粒燃烧反应、燃烧传播的整个反应动力学过程，包括颗粒在冲击加载下碎化塑性变形的过程，颗粒燃烧反应放热的过程，落锤回弹颗粒喷射的过程等。同时，进一步说明了尖顶颗粒更利于颗粒点火，平顶颗粒有抑制颗粒点火的能力。