Effects of hydroxyethyl methyl cellulose ether on the hydration and compressive strength of calcium aluminate cement

Journal of Thermal Analysis and Calorimetry - Aluminate containing phases such as tricalcium aluminate (C3A) and dodecacalcium heptaaluminate (C12A7) play a key role in the reaction between...     

六方相LaOF∶Er,Yb的上转换发光及温度传感特性

氟氧化物兼有氧化物优异的稳定性和氟化物的低声子能量,是上转换发光材料的一种热点基质材料,因而研究六方相LaOF∶Er,Yb的上转换发光性能及其温度特性具有重要意义。本文采用水热法制备了六方相LaOF∶Er,Yb荧光材料,通过X射线衍射(XRD)、扫描电镜(SEM)和荧光光谱对其结构和上转换荧光性能进行表征。实验结果表明,水热法120℃得到六方相LaF3,经800℃和1000℃退火后分别形成四方相LaOF和六方相LaOF。980 nm激发下,六方相LaOF∶Er,Yb中Yb3+与Er3+存在能量传递,通过双光子吸收产生绿光和红光的上转换荧光,并且Yb3+与Er3+的最佳浓度分别为3%和1%。最后研究了六方相LaOF∶Er,Yb在温度传感方面的应用,其在150~400 K温度范围的相对灵敏度和绝对灵敏度分别为0.037 K-1和0.0043 K-1。该材料具有优异的温度传感特性,对荧光温度传感器件的设计和应用具有指导意义。     

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.     

HPLC-DAD分析金线莲中天麻素和天麻苷元

研究超声-微波协同法提取金线莲中的天麻素和天麻苷元,并对提取条件进行了优化.应用高效液相-二极管阵列检测法分析提取物中的天麻素和天麻苷元.研究结果表明:金线莲中天麻素、天麻苷元和其他杂质成分能够很好的分离,且两者的含量分别为1.430及0.562 mg/g,相对标准偏差为0.94%和0.25%.方法准确、快速、灵敏度高、重现性好.     

Identification of metabolites of Ginkgolide B in vivo and in vitro using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry

Ginkgolide B is a dietary diterpene with multiple pharmacological activities. However, current research on ginkgolide B is not comprehensive. The current study analyzed the metabolic profile of ginkgolide B in vivo and in vitro using ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry. To detect and identify the different metabolites in ginkgolide B, a novel data processing method was used as an assistant tool. A total of 53 different metabolites of ginkgolide B (38 phase I metabolites and 15 phase II metabolites) were detected relative to blank samples. The biotransformation route of ginkgolide B was identified as oxidation, dehydroxylation, hydrogenation, decarbonylation, demethylation, sulfate conjugation, glucose conjugation, methylation, and acetylation. The current study demonstrated a method for rapidly detecting and identifying metabolites and provided useful information to further characterize the pharmacology and mechanism of ginkgolide B. A method for the analysis of other diterpene metabolic components in vivo and in vitro was also established.     

Magnetic Multi-Walled Carbon Nanotubes Matrix Solid-Phase Dispersion with Dispersive Liquid–Liquid Microextraction for the Determination of Ultra Trace Bisphenol A in Water Samples

Magnetic nanoparticle-assisted solid-phase dispersion (MMSPD) combined with dispersive liquid–liquid microextraction (DLLME) prior to high performance liquid chromatography with fluorescence detector (HPLC–FLU) is presented for determination of ultra trace Bisphenol A (BPA) in water. Magnetic multi-walled carbon nanotubes (MMWCNTs) were synthesized for the adsorption of BPA in water. Ultra trace BPA in water was transferred into the elute solvent by the MMSPD and further concentrated into trace volume extraction solvent by the DLLME. The limit of detection and limit of quantitation were 0.003 and 0.01 µg L^?1, respectively. Good linearity of BPA was found, ranging from 0.01 to 10 µg L^?1, with good squared regression coefficient (R ²) of 0.9999. Additionally, relative recoveries were 83.1 and 95.9% for two environmental water samples spiked with 0.20 µg L^?1 BPA, respectively. All results showed that the MMWCNTs nanoparticle-assisted MMSPD–DLLME–HPLC–FLU method was simple and reliable for the determination of ultra trace BPA in environmental water.     

Visible light induced decomposition of sulfonyl hydrazides using Pd/ZrO2 nanocomposite photocatalyst

A new approach to synthesis of thiosulfonates has been developed under mild conditions without any oxidants and promoting reagents through a Pd/ZrO₂ nanocomposite photocatalyst catalyzed decomposition of sulfonyl hydrazides. This protocol gave the products in moderate yields, comparable to the best results reported so far. Finally, a plausible reaction mechanism was proposed.     

Mixing of Racemic Poly(L-lactide)/Poly(D-lactide) Blend with Miscible Poly(D,L-lactide):Toward All Stereocomplex-type Polylactide with Strikingly Enhanced SC Crystallizability

Stereocomplex-type polylactide (SC-PLA) consisting of alternatively arranged poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) chains has gained a good reputation as a sustainable engineering plastic with outstanding heat resistance and durability,however its practical applications have been considerably hindered by the weak SC crystallizability.Current methods used to enhance the SC crystallizability are generally achieved at the expense of the precious bio-renewability and/or bio-degradability of PLAs.Herein,we demonstrate a feasible method to address these challenges by incorporating small amounts of poly(D,L-lactide) (PDLLA) into linear high-molecular-weight PLLA/PDLA blends.The results show that the incorporation of the atactic PDLLA leads to a significant enhancement in the SC crystallizability because its good miscibility with the isotactic PLAs makes it possible to greatly improve the chain mixing between PLLA and PDLA as an effective compatibilizer.Meanwhile,the melt stability (i.e.,the stability of PLLA/PDLA chain assemblies upon melting) could also be improved substantially.Very intriguingly,SC crystallites are predominantly formed with increasing content and molecular weight of PDLLA.More notably,exclusive SC crystallization can be obtained in the racemic blends with 20 wt％ PDLLA having weight-average molecular weight of above 1 ×10s g/mol,where the chain mixing level and intermolecular interactions between the PLA enantiomers could be strikingly enhanced.Overall,our work could not only open a promising horizon for the development of all SC-PLA-based engineering plastic with exceptional SC crystallizability but also give a fundamental insight into the crucial role of PDLLA in improving the SC crystallizability of PLLA/PDLA blends.