Rapid qualitative profiling and quantitative analysis of Juglandis Mandshuricae Cortex and seven flavonoids by ultra-high performance liquid chromatography–quadrupole/orbitrap high-resolution mass spectrometry

Juglandis Mandshuricae Cortex is the bark of Juglans mandshurica Maxim., which has been used as a folk medicine plant in China and India. In this study, an ultra-high performance liquid chromatography–quadrupole/orbitrap high-resolution mass spectrometry method was developed to clarify and quantify the chemical profiling of Juglandis Mandshuricae Cortex rapidly. A total of 113 compounds were characterized. Among them, seven flavonoids were simultaneously quantified in 15 min, including myricetin, myricetrin, taxifolin, kaempferol, quercetin, quercitrin, and naringenin. The method was validated for accuracy, precision, and the limits of detection and quantification. All calibration curves showed a good linear relationship (r > 0.9990) within test ranges. The intra- and inter-day relative standard deviations were less than 2.16%. Accuracy validation showed that the recovery was between 95.6 and 101.3% with relative standard deviation values below 2.85%. The validated method was successfully applied to determine the contents of seven flavones in Juglandis Mandshuricae Cortex from seven sources and the contents of these places were calculated respectively. This method provides a theoretical basis for further developing the medicinal value of Juglandis Mandshuricae Cortex.     

Enhanced thermoelectric performance of PEDOT:PSS films via ionic liquid post-treatment

Thermoelectric(TE)energy harvesting can effectively convert waste heat into electricity,which is a crucial technology to solve energy concerns.As a promising candidate for energy conversion,poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)has gained significant attention owing to its easy doping,high transparency,and solution processability.However,the TE performance of PEDOT:PSS still needs to be further enhanced.Herein,different approaches have been applied for tuning the TE properties:(i)direct dipping PEDOT:PSS thin films in ionic liquid;(ii)post-treatment of the films with concentrated sulfuric acid(H₂SO₄),and then dipping in ionic liquid.Besides,the same bis(trifluoromethanesulfonyl)amide(TFSI)anion and different cation salts,including 1-ethyl-3-methylimidazolium(EMIM+)and lithium(Li+),are selected to study the influence of varying cation types on the TE properties of PEDOT:PSS.The Seebeck coefficient and electrical conductivity of the PEDOT:PSS film treated with H2SO4EMIM:TFSI increase simultaneously,and the resulting maximum power factor is 46.7μW·m^-1·K^-2,which may be attributed to the ionic liquid facilitating the rearrangement of the molecular chain of PEDOT.The work provides a reference for the development of organic films with high TE properties.     

Dynamic Modeling of the Feed Drive System of a CNC Metal Cutting Machine

Studying the vibrational behavior of feed drive systems is important for enhancing the structural performance of computer numerical control (CNC) machines. The preload on the screw and nut position have a great influence on the vibration characteristics of the feed drive as two very important operational conditions. Rotational acceleration of the screw also affects the performance of the CNC feed drive when machining small parts. This paper investigates the influence of preload and nut position on the vibration characteristics of the feed drive system of a CNC metal cutting machine in order to be able to eliminate an observed resonance occurred at high rotational speeds of the screw, corresponding to high feed rates. Additionally, rational structural parameters of the feed drive system are selected in order to increase the rotational acceleration for improving the performance of the CNC machine. Experiments and analyses showed that by selecting specific parameters of feed drive system and simultaneously applying a certain value of preload, a 97% increase in rotational acceleration and 30% time reduction considering the vibration resistance at high rotational speeds can be achieved.     

水热法制备二氧化锡/钨酸铋复合光催化材料及其催化活性研究

本文用水热法制备了正交晶系的纳米球状结构的二氧化锡和正交晶系的由片状聚集成球状结构的钨酸铋,并且对二者进行了复合,制备出了二氧化锡/钨酸铋复合光催化材料。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、比表面积测试仪(BET)、紫外可见分光光度计等技术对复合样品的结构、形貌、比表面积、孔容孔径和光学性质进行了表征。用碘钨灯模拟太阳光,分别以二氧化锡、钨酸铋和二氧化锡/钨酸铋复合材料为催化剂降解罗丹明B(RhB),研究所制备的二氧化锡/钨酸铋复合材料的光催化活性。光催化90 min时二氧化锡、钨酸铋和二氧化锡/钨酸铋对罗丹明B的降解率分别是9%、22%和30%。实验结果表明,在可见光下,二氧化锡/钨酸铋复合材料的光催化活性要高于单一的二氧化锡和钨酸铋。     

基于NiCo2O4纳米片电极的非对称混合电容器

The looming global energy crisis and ever-increasing energy demands have catalyzed the development of renewable energy storage systems. In this regard, supercapacitors (SCs) have attracted widespread attention because of their advantageous attributes such as high power density, excellent cycle stability, and environmental friendliness. However, SCs exhibit low energy density and it is important to optimize electrode materials to improve the overall performance of these devices. Among the various electrode materials available, spinel nickel cobaltate (NiCo₂O₄) is particularly interesting because of its excellent theoretical capacitance. Based on the understanding that the performances of the electrode materials strongly depend on their morphologies and structures, in this study, we successfully synthesized NiCo₂O₄ nanosheets on Ni foam via a simple hydrothermal route followed by calcination. The structures and morphologies of the as-synthesized products were characterized by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller (BET) surface area analysis, and the results showed that they were uniformly distributed on the Ni foam support. The surface chemical states of the elements in the samples were identified by X-ray photoelectron spectroscopy. The as-synthesized NiCo₂O₄ products were then tested as cathode materials for supercapacitors in a traditional three-electrode system. The electrochemical performances of the NiCo₂O₄ electrode materials were studied and the area capacitance was found to be 1.26 C·cm^-2 at a current density of 1 mA·cm^-2. Furthermore, outstanding cycling stability with 97.6% retention of the initial discharge capacitance after 10000 cycles and excellent rate performance (67.5% capacitance retention with the current density from 1 to 14 mA·cm^-2) were achieved. It was found that the Ni foam supporting the NiCo₂O₄ nanosheets increased the conductivity of the electrode materials. However, it is worth noting that the contribution of nickel foam to the areal capacitance of the electrode materials was almost zero during the charge and discharge processes. To further investigate the practical application of the as-synthesized NiCo₂O₄ nanosheets-based electrode, a device was assembled with the as-prepared samples as the positive electrode and active carbon (AC) as the negative electrode. The assembled supercapacitor showed energy densities of 0.14 and 0.09 Wh·cm^-3 at 1.56 and 4.5 W·cm^-3, respectively. Furthermore, it was able to maintain 95% of its initial specific capacitance after 10000 cycles. The excellent electrochemical performance of the NiCo₂O₄ nanosheets could be ascribed to their unique spatial structure composed of interconnected ultrathin nanosheets, which facilitated electron transportation and ion penetration, suggesting their potential applications as electrode materials for high performance supercapacitors. The present synthetic route can be extended to other ternary transition metal oxides/sulfides for future energy storage devices and systems.     

电磁场作用下菜籽油的摩擦学性能研究

使用改进后的四球摩擦磨损试验机考察了不同电磁场强度和不同载荷条件下菜籽油的摩擦学性能,结合扫描电子显微镜(SEM)、X射线能谱仪(EDS)和X射线光电子能谱仪(XPS)分析了磨斑的表面形貌及表面典型元素的化学状态,并对摩擦学机理进行了初步探讨.结果表明:在所考察的工况下,电磁场有利于改善菜籽油的抗磨减摩性能,其强度越大,对菜籽油抗磨减摩性能的改善效果越好;电磁场通过促进吸附膜的吸附作用和O元素与金属表面作用,有利于在磨斑表面生成更厚、更致密的摩擦化学反应膜,从而增强了菜籽油的抗磨减摩性能;不同强度的电磁场可能会改变长链菜籽油分子在摩擦界面的吸附形态而影响其减摩性能.     

Coupling nanoliter high‐performance liquid chromatography to inductively coupled plasma mass spectrometry for arsenic speciation

Nanoliter high‐performance liquid chromatography shows low consumption of solvents and samples, offering one of the best choices for arsenic speciation in precious samples in combination with inuctively coupled plasma mass spectrometry. A systematic investigation on coupling nanoliter high‐performance liquid chromatography to inductively coupled plasma mass spectrometry from instrument design to injected sample volume and mobile phase was performed in this study. Nanoflow mobile phase was delivered by flow splitting using a conventional high‐pressure pump with reuse of mobile phase waste. Dead volume was minimized to 60 nL for the sheathless interface based on the previously developed nanonebulizer. Capillary columns for nanoliter high‐performance liquid chromatography were found to be sensitive to sample loading volume. An apparent difference was also found between the mobile phases for nanoliter and conventional high‐performance liquid chromatography. Baseline separation of arsenite, arsenate, monomethylarsenic, and dimethylarsenic was achieved within 11 min on a 15 cm C₁₈ capillary column and within 12 min on a 25 cm strong anion exchange column. Detection limits of 0.9–1.8 μg/L were obtained with precisions variable in the range of 1.6–4.2%. A good agreement between determined and certified values of a certified reference material of human urine (GBW 09115) validated its accuracy along with good recoveries (87–102%).     

温度对AZO薄膜红外辐射性能的影响

随着全球资源的减少和环境的恶化，节能减排已成为人们关注的焦点，具有保温隔热功能的低辐射玻璃成为研究的热点。提高玻璃保温隔热性能最有效的方法就是在其表面涂覆低辐射率层。原材料丰富、导电性能好、可见光透过率高等优势使得Al掺杂ZnO (AZO)薄膜成为最具潜力的低辐射率层。系统研究了温度对AZO薄膜红外辐射性能的影响，分析了变化机理。首先研究了在一定的温度下持续一段时间后，AZO薄膜的红外比辐射率的变化情况。然后研究了在变温环境中红外比辐射率的变化情况。采用直流磁控溅射法在室温下玻璃基片上沉积500 nm厚的AZO薄膜，将薄膜放到马弗炉中进行热处理，在100～400 ℃空气气氛下保温1 h，随炉冷却。采用X射线衍射仪对AZO薄膜进行物相分析，采用扫描电子显微镜观察薄膜表面形貌变化。利用四探针测试法测量AZO薄膜的电阻率，采用红外比辐射率测试仪测试薄膜红外比辐射率, 可见分光光度计测量可见光谱。测试的结果表明，薄膜热处理前后均为六角纤锌矿结构，(002)择优取向。300 ℃及以下热处理1 h后，(002)衍射峰增强，半高宽变窄，晶粒尺寸长大。随着热处理温度的升高，薄膜的电阻率先减小后增大，200 ℃热处理后的薄膜具有最小的电阻率(0.9×10-3 Ω·cm)。热处理温度升高，晶粒长大使得薄膜电阻率降低。热处理温度过高，薄膜会从空气中吸收氧，电阻率下降。薄膜的红外比辐射率变化趋势和电阻率的一致，在200 ℃热处理后获得最小值(0.48)。自由电子对红外光子有较强的反射作用，当电阻率低，自由电子浓度高的时候，更多的红外光子被反射，红外辐射作用弱，红外比辐射率小。薄膜的可见光透过率随着热处理温度的升高先减小后增大，200 ℃热处理后的薄膜的可见光透过率最小，但仍高达82%。这种变化是由于自由电子浓度变化引起的，自由电子对可见光有很强的反射作用。选取未热处理和200 ℃热处理后的样品进行变温红外比辐射率的测量，将样品放在可加热的样品台上，位置固定，在室温到350 ℃的升温和降温过程中每隔25 ℃测量一次红外比辐射率，结果表明，在室温到350 ℃的温度范围内，AZO薄膜的红外比辐射率在升温过程中随着温度的上升而增大，在降温过程中减小，经过整个升、降温过程后，薄膜的红外比辐射率增大。     

Facile preparation of Ag/Ag2WO4/g‐C3N4 ternary plasmonic photocatalyst and its visible‐light photocatalytic activity

Introducing plasmonic metals into semiconductor materials has been proven to be an attractive strategy for enhancing photocatalytic activity in the visible region. In this work, a novel and efficient Ag/Ag₂WO₄/g‐C₃N₄ (AACN) ternary plasmonic photocatalyst was successfully synthesized using a facile one‐step in situ hydrothermal method. The composition, structure, morphology and optical absorption properties of AACN were investigated using X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and UV–visible diffuse reflectance spectroscopy, respectively. Photocatalytic performance of AACN was evaluated via rhodamine B and tetracycline degradation. The results indicated that AACN had excellent photocatalytic performance for rhodamine B degradation with a rate constant of 0.0125 min^?1, which was higher than those of Ag₂WO₄ and Ag/Ag₂WO₄. Characterization and photocatalytic tests showed that the strong coupling effect between the Ag/Ag₂WO₄ nanoparticles and the exfoliated ultrathin g‐C₃N₄ nanosheets was superior for visible‐light responsivity and reduced the recombination rate of photogenerated electrons and holes. A proposed mechanism is also discussed according to the band energy structure and the experimental results.     

Protection of Li metal anode by surface-coating of PVDF thin film to enhance the cycling performance of Li batteries

The PVDF thin film on the surface of the lithium metal can highly suppress the lithium dendrites.