镧掺杂硫酸钛的酸性及催化缩酮活性

以La2O3为镧源,硫酸钛掺杂镧后经高温焙烧制得一类稀土改性固体酸.用DTA,XRD表征催化剂结构,用吸附吡啶的FT-IR表征其表面酸性,由Hammett指示剂来测定酸强度,以正丁胺定量分析催化剂表面Bronsted酸和Lewis酸酸量;用环己酮与乙二醇缩酮化反应表征其酸催化性能.结果表明:催化剂表面同时存在B酸和L酸中心,且B/L酸量比与焙烧温度、镧的含量呈现较好的线性关系;在缩酮化反应中具有良好的催化活性,在300～600℃的实验范围内,催化活性随灼烧温度的升高而降低,随镧含量的增加而升高,兼有B酸和L酸的催化剂具有更好的催化活性.催化剂易回收和再生,反应后处理简单,无废酸排放,可重复使用多次,该固体酸是一种环境友好催化剂.     

Self-disproportionation of enantiomers of α-trifluoromethyl lactic acid amides via sublimation

Preparation of racemic and enantiomerically enriched α-trifluoromethyl lactic acid amide [NHPh, NH(4-Cl-C₆H₅), NHBn, NHt-Bu] derivatives have been developed. Ph, 4-Cl-C₆H₅, and tert-Bu derivatives were found to have substantial magnitude of the self-disproportionation of enantiomers (SDE) via sublimation. For example, when the optically enriched Ph, 4-Cl-C₆H₅, and tert-Bu amide derivatives were subjected to sublimation under kinetic conditions (Petri dish in open air), the enantiomeric excess of the remainder has noticeably increased. On the other hand, the SDE of Bn amide derivative by sublimation resulted in almost no change in the optical purity of the remainder. These preliminary results on the SDE of the compounds under study, as well as their excellent chemical and physico-chemical characteristics, render these amide derivatives as readily available and very promising substrates for systematic study of SDE via sublimation.     

Organocatalysis in aqueous micellar medium: a new protocol for the synthesis of [1,2,4]-triazolyl-thiazolidinones

A new environmentally friendly methodology for the efficient synthesis of biologically significant triazole thiazolidinone hybrids in aqueous medium, using acetic acid as an organocatalyst in the presence of cetyltrimethylammonium bromide (CTAB) surfactant has been developed for the first time. The effect of several surfactants on the yield and completion time of the reaction was investigated and it was found that the use of CTAB at 60 °C gave the best results (79–96% in 20 min–35 min) for the synthesis of the target compounds.     

Large‐scale Two‐dimensional MoSx Catalyst Prepared under Mild Conditions for Enhancing Electrocatalytic Hydrogen Evolution Reaction

As an electrocatalyst with abundant resources and great potential, molybdenum disulfide is regarded as one of the most likely alternatives to expensive noble‐metals catalysts. However, it is still a challenge to achieve large scale production of few‐layer MoS₂ with enhancing activity of electrocatalytic hydrogen reaction at ambient conditions. Herein, we developed a simple environmentally friendly two‐step method, which included intercalation reaction and a subsequent electrochemical reduction reaction for mass preparation of defect‐rich desulfurized MoS_x (D?MoS_x) nanosheets with plentiful sulfur vacancies. The ratio of sulfur‐molybdenum atoms can be adjusted from 2 : 1 to 1.4 : 1 by regulating the desulfurization voltage. It was found that the HER catalytic activity of the D?MoS_x was enhanced compared with that of pristine MoS₂ (P?MoS₂), the current density of D?MoS_x (desulfurization at ?1.0 V) at ?0.3 V versus RHE was about 169% of the P?MoS₂, and the Tafel slope decreased to 136 mV dec^?1. This method can be widely applied to large‐scale preparation of other two‐dimensional materials.     

硼砂-对苯二甲酸电解液中AZ91D镁合金的阳极氧化处理

研究了硼砂-对苯二甲酸环保型电解液中AZ91D镁合金的阳极氧化.考察了对苯二甲酸对镁合金阳极氧化过程及其氧化膜性能的影响,并利用扫描电镜(SEM)、X射线衍射(XRD)、能量散射谱(EDS)、动电化极化和电化学交流阻抗谱(EIS)等进行了分析表征.结果表明,对苯二甲酸的浓度对阳极氧化成膜过程、氧化膜的表面形貌、厚度、相结构和耐腐蚀性能都有重要影响.在硼酸盐电解液中加入适量的对苯二甲酸后,氧化电流密度降低,过度放电现象受到了明显的抑制,所制得的阳极氧化膜的质量也有了显著改善.氧化膜表面变得光滑、致密,膜厚度略有降低.氧化膜与镁合金基底的结合更紧密,而且其耐腐蚀性能也得到了明显增强.该研究对于镁合金阳极氧化处理工艺的环保化及阳极氧化膜质量的提高都具有积极意义.     

Chemical composition of bioactive pressurized extracts of Romanian aromatic plants

In this contribution, pressurized liquid extraction (PLE) has been employed to isolate bioactive compounds from three native Romanian plants, oregano (Origanum vulgare), tarragon (Artemisia dracunculus) and wild thyme (Thymus serpyllum). Different PLE conditions have been tested including extraction with water, ethanol and their mixtures in a wide range of extraction temperatures (50-200°C), and the antioxidant capacity of the extracts was measured using different assays (DPPH radical scavenging, TEAC assay and Folin-Ciocalteau assay to measure total phenols). Moreover, a complete chemical characterization by using LC-MS/MS was carried out to be able to correlate the bioactivity with the particular chemical composition of each extract and plant. The use of PLE with water as a solvent at the highest temperature tested (200°C) always provided the highest extraction yields for the three studied plants, being maximum for oregano (>60%). Besides, oregano's pressurized water extracts at lower temperatures (50°C) presented the highest content on total phenols (184.9 mg gallic acid/g extract) and the best antioxidant activities (EC(50) 6.98 μg/ml). In general, oregano extracts were the most active, followed by wild thyme extracts. The antioxidant capacity measured by DPPH assay was highly correlated with the amount of total phenols. Moreover, the use of a LC-MS/MS method allowed the identification of 30 different phenolic compounds in the different extracts, including phenolic acids, flavones, flavanones and flavonols, which have an important influence on the total antioxidant capacity of the different extracts.     

One‐Step Synthesis of Natural Silk Sericin‐Based Microcapsules with Bionic Structures

Different techniques are being developed for fabricating microcapsules; it is still a challenge to fabricate them in an efficient and environment‐friendly process. Here, a one‐step green route to synthesize silk protein sericin‐based microcapsules without any assistance of organic solvents is reported. By carefully changing the concentration of calcium ions accompanied with stirring, the morphology of the microcapsules can easily be regulated to form either discoidal, biconcave, cocoon‐like, or tubular structures. The chelation of Ca²⁺ and shearing force from agitation may induce the conformational transformation of sericin, which possibly results in the formation of microcapsules through the self‐assembly of the protein subsequently. The as‐prepared cocoon‐like microcapsules exhibit pH‐dependent stability. A potential application of microcapsules being fabricated from natural water‐soluble silk protein sericin for controlled bioactive molecules loading and release system by a pH‐triggered manner is quite feasible.

     

Targeted Multiresidue Method for the Analysis of Different Classes of Pesticides in Agro-Food Industrial Sludge by Liquid Chromatography Tandem Mass Spectrometry

Sludge generated after washing of fruits and vegetables during agro-food processes is a complex matrix and selective methods for the identification and quantification of pesticides’ residues are necessary in order to achieve a sustainable and effective management of the total sewage. The present work describes the development and validation of a reliable, simple and fast analytical method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the determination of 47 pesticides of different chemical classes, including organosphosphates, pyrethroids, neonicotinoids, triazoles and others, in sludge samples after QuEChERS sample preparation. The necessity of the individual steps of QuEChERS was investigated and the LC-ESI-MS/MS conditions were optimized to achieve maximum sensitivity of the target analytes. The method limits of detection (LODs) ranged between 0.0005 mg/kg (imidacloprid) and 0.05 mg/kg (beta cyfluthrin). The recoveries ranged between 71–120% and the repeatability of the method was ≤25% expressed as relative standard deviation. The method was applied to sludge samples generated after washing of fruits in an agro-fruit-packaging unit in Greece. The results showed the presence of 37 pesticides’ active substances with concentrations ranging from low ppbs, such as fludioxinil (5 μg/kg) up to low ppms such as beta cyfluthrin (3.5 mg/kg) and with their sum concentration reaching up to 19 mg/kg.     

Ultrasound and microwave assisted synthesis of dihydroxyacetophenone derivatives with or without 1,2-diazine skeleton

A thorough study concerning O-alkylation and α-bromination of dihydroxyacetophenone (DA) and N-alkylation of 1,2-diazine, under ultrasound (US) and microwave (MW) irradiation as well as under conventional thermal heating (TH) is presented. Under US and MW irradiation the yields are higher, the amount of used solvent decreases substantially, the reaction time decreases considerable (from hours or days to minutes) and the consumed energy decreases, consequently the O-alkylation, α-bromination and N-alkylation methods could be considered environmentally friendly. A selective and efficient way to either bis-O-alkylation or mono-O-alkylation of DA has been found, the relative position of the two hydroxyl groups on the phenyl moiety being compulsory. A selective and efficient way for α-bromination in heterogeneous catalysis of DA derivatives under US irradiation is presented. The N-alkylation reaction of DA under US and MW irradiation proved to be the most convenient setup procedure for these types of reactions. Overall, the use of US proved to be more efficient than MW or TH.     

Self-disproportionation of enantiomers of isopropyl 3,3,3-(trifluoro)lactate via sublimation: Sublimation rates vs. enantiomeric composition

The presented results convincingly demonstrate that self-disproportionation of enantiomers via sublimation is substantially more complex phenomenon then was previously believed. We demonstrate that the racemic form of isopropyl 3,3,3-trifluoro-2-hydroxypropanoate (1) sublimed faster regardless of the starting enantiomeric composition of the enantiomerically enriched mixtures studied in the range from 20.8, 36.8, 58.7 to 79.4% ee. This preferential sublimation of the racemic form allowed for, the most possibly simple, preparation of optically pure samples of compound 1. In this work we also suggest some general experimental procedures, which may be easily used to facilitate the interpretation of the data collected in different laboratories.