溶剂诱导翻转Pickering乳液用于原位循环使用酶催化剂

Separation and recycling of catalysts are crucial for realizing the objectives of sustainable and green chemistry but remain a great challenge, especially for enzyme biocatalysts. In this work, we report a new solvent-induced reversible inversion of Pickering emulsions stabilized by Janus mesosilica nanosheets (JMSNs), which is then utilized as a strategy for the in situ separation and recycling of enzymes. The interfacial active solid particle JMSNs is carefully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption experiments, Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA).The JMSNs are demonstrated to show order-oriented mesochannels with a large specific surface area, and the hydrophobic octylgroup is selectively modified on one side of the nanosheets. Furthermore, the inversion is found to be a fast process that is strongly dependent on the interfacial activity of the solid emulsifier JMSNs. Such a phase inversion is also a general process that can be realized in various oil/water phasic systems, including ethyl acetate-water, octane-water, and cyclohexane-water systems. By carefully analyzing the capacity of JMSNs with different surface wettabilities for phase inversion, a triphase contact angle (θ) close to 90° and a critical oil-water ratio of 1 : 2 are identified as the key factors to achieve solvent-induced phase inversion via a catastrophic phase inversion mechanism. Importantly, this reversible phase inversion is suitable for the separation and recycling of enzyme biocatalysts that are sensitive to changes in the reaction medium. Specifically, during the reaction, the organic substrates are dissolved in the oil droplets and the water-soluble catalysts are dispersed in the water phase, while a majority of the product is released into the upper oil phase and the enzyme catalyst is confined inside the water droplets in the bottom layer after phase inversion. The perpendicular mesochannels of JMSNs provide a highly accessible reaction interface, and their excellent interfacial activity allows for more than 10 rounds of consecutive phase inversions by simply adjusting the ratio of oil to water in the system. Using the enzymatic hydrolysis kinetic resolution of racemic acetate as an example, our Pickering emulsion system shows not only a 3-fold enhanced activity but also excellent recyclability. Because no sensitive chemical reagents are used in this phase inversion process, the intrinsic activities of the catalysts can be preserved even after seven cycles. The current study provides an alternative strategy for the separation and recycling of enzymes, in addition to revealing a new innovative application for Janus-type nanoparticles.     

气相色谱-串联质谱法测定蔬菜和水果中三氯生及甲基三氯生的含量

提出了应用气相色谱-串联质谱法测定蔬菜(西红柿、黄瓜等)和水果(橙子、苹果等)中潜在的污染物三氯生(TCS)和甲基三氯生(MTCS)的含量的方法,以期有助于对此污染物在蔬菜、水果等食品中的污染问题的研究,并应用于农产品质量的安全监测之中。将样品分别去皮后切块,匀浆后于-22℃保存。称取样品5.00g,先后2次用乙酸乙酯(每次10mL)超声提取10min后离心10min,合并2次的提取液。将提取液吹氮蒸发至近干。加入衍生试剂体积比为99∶1的N,O-双(三甲基硅烷基)三氟乙酰胺-三甲基氯硅烷混合溶液100μL,在60℃下进行衍生化反应40min。反应结束后,将溶液吹氮至近干,用乙酸乙酯1.0mL溶解残渣。所得溶液供气相色谱-串联质谱法分析。用DB-17MS毛细管色谱柱(30m×0.25mm,0.25μm)在150~290℃区间按程序升温条件进行分离,在电子轰击离子源及多反应监测模式下进行质谱测定。经试验确定,用两种扫描程序分别扫描,TCS衍生物的母离子和子离子依次为m/z 362,347和m/z 360,345,MTCS的母离子和子离子则均为m/z 304,254。测得TCS衍生物和MTCS的标准曲线的线性范围均为0.4~20.0μg·L^-1,其检出限(3S/N)为4~6ng·kg^-1。按标准加入法进行回收试验,测得TCS衍生物和MTCS在4种蔬菜、水果中的回收率为91.5%~107%和94.7%~111%。     

基于近红外光谱技术的白酒酒醅在线监测研究

为实现白酒生产过程中出窖酒醅智能化配粮,该文开发了一套在线近红外光谱监测系统,实时在线检测出窖酒醅配粮前的水分、淀粉及酸度,实时检测结果转化为4~20 mA电控输入信号,解决酒醅智能配粮问题。通过将在线近红外分析系统与台式近红外分析仪相结合,在四川宜宾六尺巷酒厂开展酒醅在线监测与配粮智能化应用。结果表明,台式仪器检测水分、淀粉、酸度的平均误差分别为-0.25%、0.38%和0.29 mmol/10 g,检测水分、淀粉、酸度的预测标准差(SEP)分别为0.60%、0.75%和0.18 mmol/10 g;在线仪器检测酒醅水分、淀粉、酸度的平均误差分别为-0.75%、0.48%、0.29 mmol/10 g,检测水分、淀粉、酸度的SEP分别为0.66%、0.97%、0.22 mmol/10 g。相比台式近红外分析结果,在线结果的平均误差及ＳＥＰ均有所放大,但在线分析的准确度能满足酒醅在线配粮控制的精度要求。     

C5a受体拮抗剂W-54011的合成

以7-甲氧基-1-萘满酮为原料,经Wittig反应、去甲基化、烯醇互变和Jones氧化反应等制得关键中间体7-甲氧基-1,2,3,4-四氢化萘-1-羧酸(4); 4-异丙基苯胺和4-(二甲基胺基)苯甲醛经过还原胺化反应得(E)-4-{[(4-异丙基苯基)亚胺基]甲基}-N,N-二甲基苯胺(6); 4转化为相应的酰氯后与6反应合成N-[4-(二甲基氨基)苄基]-N-(4-异丙基苯基)-7-甲氧基-1,2,3,4-四氢化萘-1-甲酰胺(W-54011),总收率24%,其结构经¹H NMR, ¹³C NMR和HR-MS（ESI）表征。      

Molecular‐Sieving Membrane by Partitioning the Channels in Ultrafiltration Membrane by In Situ Polymerization

Commercial ultrafiltration membranes have proliferated globally for water treatment. However, their pore sizes are too large to sieve gases. Conjugated microporous polymers (CMPs) feature well‐developed microporosity yet are difficult to be fabricated into membranes. Herein, we report a strategy to prepare molecular‐sieving membranes by partitioning the mesoscopic channels in water ultrafiltration membrane (PSU) into ultra‐micropores by space‐confined polymerization of multi‐functionalized rigid building units. Nine CMP@PSU membranes were obtained, and their separation performance for H₂/CO₂, H₂/N₂, and H₂/CH₄ pairs surpass the Robeson upper bound and rival against the best of those reported membranes. Furthermore, highly crosslinked skeletons inside the channels result in the structural robustness and transfer into the excellent aging resistance of the CMP@PSU. This strategy may shed light on the design and fabrication of high‐performance polymeric gas separation membranes.     

One‐step synthesis of polysiloxane graft polyethylene mimic: Non‐expensive compatibilizer for polyethylene/polysiloxane blend

Polysiloxane/polyolefin copolymers have drawn much attention recently and emerged as a new group of functional polyolefin since they possess distinctive properties and find great potential applications in many areas (eg, compatibilizer, processing aid and surface modifier). However, traditional routes to synthesize polysiloxane/polyolefin copolymers generally require multi‐step labor‐consuming procedures. Herein, we report a novel one‐step synthesis of polydimethylsiloxane graft polyethylene (PDMS‐g‐PE) mimics. It was found that PDMS‐g‐PE mimics, namely vinylmethylsiloxane‐dimethylsiloxane‐(C30‐45 alkyl)methylsiloxane copolymers (short for VD‐AMS), could be formed via a one‐step synthetic procedure based on the siloxane equilibrium process between silanol‐terminated vinylmethylsiloxane‐methylsiloxane copolymer and (C30‐45 alkyl)methylsilicone. The chemical structures of VD‐AMS were characterized unambiguously using Fourier transform infrared spectroscopy, nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry. The correlation between reaction conditions and the structural parameters of VD‐AMS was established. Based on our experimental results, a plausible mechanism for the synthesis of VD‐AMS was proposed. Scanning electron microscopy micrographs showed that VD‐AMS could function as an efficient compatibilizer for immiscible PE/silicone blend. Given that the precursors of VD‐AMS are commercially available with low prices and that VD‐AMS can be easily synthesized under mild conditions, we believe VD‐AMS can represent as a competitive potential compatibilizer due to its relatively low cost.     

An Exceptional Peroxide Birefringent Material Resulting from d–π Interactions

Birefringent materials, which can modulate the polarization of light, are almost exclusively limited to oxides. Peroxides have long been overlooked as birefringent materials, because they are usually not stable in air. Now, the first peroxide birefringent material Rb₂VO(O₂)₂F is reported, the single crystals of which keep transparency after being exposed in the air for two weeks. Interestingly, Rb₂VO(O₂)₂F does not feature an optimal anisotropic structure, but its birefringence (Δn=0.189 at 546 nm) exceeds those of the majority of oxides. According to the first‐principles calculations, this exceptional birefringence should be attributed to the strong electronic interactions between localized π orbital of O₂^2? anions and V⁵⁺ 3d orbitals, which may be also favorable to the stability in the air for Rb₂VO(O₂)₂F. These findings distinguish peroxides as a brand‐new class of birefringent materials that may possess birefringence superior to the traditional oxides.     

Rapid Synthesis of Chiral 1,2‐Bisphosphine Derivatives through Copper(I)‐Catalyzed Asymmetric Conjugate Hydrophosphination

1,2‐Bisphosphines have been identified as one class of important and powerful chiral ligands in asymmetric catalysis with transition metals. Herein, a copper(I)‐catalyzed asymmetric hydrophosphination of α,β‐unsaturated phosphine sulfides was developed with the assistance of “soft–soft” interaction between copper(I)‐catalyst and the phosphine sulfide moiety, which afforded 1,2‐bisphosphine derivatives with diversified electronic nature and steric hindrance in high to excellent yields with high to excellent enantioselectivity. Moreover, the challenging catalytic asymmetric hydrophosphination/protonation reaction was achieved with excellent enantioselectivity. Strikingly, the dynamic kinetic resolution of racemic diarylphosphines was also successfully carried out with high to excellent diastereo‐ and enantioselectivities. Interestingly, the nucleophilic copper(I)‐diphenylphosphide species was characterized by ³¹P NMR spectrum and mass spectrum. At last, three products were transformed to chiral 1,2‐bisphosphines, which were employed as ligands in Rh‐catalyzed asymmetric hydrogenation of α‐amino‐α,β‐unsaturated ester. The α‐amino acid derivative was produced in high enantioselectivity, which demonstrated the utility of the present methodology.     

Photoinduced Copper‐Catalyzed Asymmetric Decarboxylative Alkynylation with Terminal Alkynes

We describe a photoinduced copper‐catalyzed asymmetric radical decarboxylative alkynylation of bench‐stable N‐hydroxyphthalimide(NHP)‐type esters of racemic alkyl carboxylic acids with terminal alkynes, which provides a flexible platform for the construction of chiral C(sp³)?C(sp) bonds. Critical to the success of this process are not only the use of the copper catalyst as a dual photo‐ and cross‐coupling catalyst but also tuning of the NHP‐type esters to inhibit the facile homodimerization of the alkyl radical and terminal alkyne, respectively. Owing to the use of stable and easily available NHP‐type esters, the reaction features a broader substrate scope compared with reactions using the alkyl halide counterparts, covering (hetero)benzyl‐, allyl‐, and aminocarbonyl‐substituted carboxylic acid derivatives, and (hetero)aryl and alkyl as well as silyl alkynes, thus providing a vital complementary approach to the previously reported method.     

Dynamic and wear characteristics of self-lubricating bearing cage: effects of cage pocket shape

34,354,966 active cases and 460,787 deaths because of COVID-19 pandemic were recorded on November 06, 2021, in India. To end this ongoing global COVID-19 pandemic, there is an urgent need to implement multiple population-wide policies like social distancing, testing more people and contact tracing. To predict the course of the pandemic and come up with a strategy to control it effectively, a compartmental model has been established. The following six stages of infection are taken into consideration: susceptible (S), asymptomatic infected (A), clinically ill or symptomatic infected (I), quarantine (Q), isolation (J) and recovered (R), collectively termed as SAIQJR. The qualitative behavior of the model and the stability of biologically realistic equilibrium points are investigated in terms of the basic reproduction number. We performed sensitivity analysis with respect to the basic reproduction number and obtained that the disease transmission rate has an impact in mitigating the spread of diseases. Moreover, considering the non-pharmaceutical and pharmaceutical intervention strategies as control functions, an optimal control problem is implemented to mitigate the disease fatality. To reduce the infected individuals and to minimize the cost of the controls, an objective functional has been constructed and solved with the aid of Pontryagin’s maximum principle. The implementation of optimal control strategy at the start of a pandemic tends to decrease the intensity of epidemic peaks, spreading the maximal impact of an epidemic over an extended time period. Extensive numerical simulations show that the implementation of intervention strategy has an impact in controlling the transmission dynamics of COVID-19 epidemic. Further, our numerical solutions exhibit that the combination of three controls are more influential when compared with the combination of two controls as well as single control. Therefore, the implementation of all the three control strategies may help to mitigate novel coronavirus disease transmission at this present epidemic scenario.