物理化学学报 >> 2020, Vol. 36 >> Issue (10): 1910006.doi: 10.3866/PKU.WHXB201910006

所属专题: 胶体与界面化学前沿

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溶剂诱导翻转Pickering乳液用于原位循环使用酶催化剂

邹后兵1, Ettelaie Rammile2,*(), 闫帅1, 薛楠1, 杨恒权1,*()   

  1. 1 山西大学化学化工学院,太原 030006
    2 Food Colloids Group, School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, United Kingdom
  • 收稿日期:2019-10-07 发布日期:2020-06-11
  • 通讯作者: Ettelaie Rammile,杨恒权 E-mail:R.Ettelaie@food.leeds.ac.uk;hqyang@sxu.edu.cn
  • 基金资助:
    国家自然科学基金(21703128);国家自然科学基金(U1510105);国家自然科学基金(21733009);国家自然科学基金(21573136)

Solvent-Induced Inversion of Pickering Emulsions for In Situ Recycling of Enzyme Biocatalysts

Houbing Zou1, Rammile Ettelaie2,*(), Shuai Yan1, Nan Xue1, Hengquan Yang1,*()   

  1. 1 School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan 030006, P. R. China
    2 Food Colloids Group, School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, United Kingdom
  • Received:2019-10-07 Published:2020-06-11
  • Contact: Rammile Ettelaie,Hengquan Yang E-mail:R.Ettelaie@food.leeds.ac.uk;hqyang@sxu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21703128);the National Natural Science Foundation of China(U1510105);the National Natural Science Foundation of China(21733009);the National Natural Science Foundation of China(21573136)

摘要:

催化剂特别是酶的高效分离与循环利用是实现绿色催化合成的关键。本文发展了一种溶剂诱导的Pickering乳液可逆翻转的策略,实现了酶的原位分离和高效循环利用。首先,本文利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外(FT-IR)光谱、氮气吸附以及热重分析(TGA)等手段,详细表征所使用的固体纳米颗粒Janus型介孔氧化硅纳米片(JMSNs)。结果表明JMSNs样品具有有序垂直介孔孔道和较高的比表面积,并且疏水性有机基团辛基选择性的修饰在纳米片的一端。然后,我们发现这种溶剂诱导的转相是一个快速的过程,且具有良好的普适性,可以适用于乙酸乙酯-水、正辛烷-水、环己烷-水等多种油-水双相体系,同时,这种翻转与固体乳化剂JMSNs的界面活性息息相关。通过仔细分析具有不同浸润性JMSNs样品的转相能力,接近于90°三相接触角和合适的油水比被认为是实现溶剂诱导转相的关键因素,这一结果说明该翻转可能是一种突变转相机制。最后,本文将这种可逆的溶剂诱导转相过程成功的应用于原位分离、循环利用对反应环境敏感的酶催化剂。具体地说,在反应时,反应底物溶解在油滴中而酶催化剂分散在水相(连续相)中,在反应结束并转相后,绝大多数产物从油滴中释放到上层油相(连续相)中,而酶催化剂被稳定地限域在水滴中,这不仅保证反应平稳进行,而且防止在移走产物时酶催化剂的损失。更为重要的是,在该乳液体系中,JMSNs平躺吸附在乳液的油水界面,其垂直的介孔孔道有利于反应物分子扩散,合适的JMSNs界面活性确保这种翻转过程仅通过调控油水比即可实现连续操作。因此,在酶(CALB)催化的酯水解动力学拆分反应中,该Pickering乳液反应体系不仅表现出3倍加强的活性,而且可以实现酶的原位分离与循环利用。得益于整个过程并不涉及任何敏感性化学试剂,在连续使用七次后,酶催化剂的本征活性依然可以很好的保持。本文不仅发展了一种新的方法用于催化剂的原位分离与循环利用,而且报道了Janus纳米材料的一种新的应用领域。

关键词: Janus纳米片, 乳液翻转, 介孔氧化硅, 催化剂循环, 酶催化, 动力学拆分反应

Abstract:

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.

Key words: Janus nanosheet, Emulsion inversion, Mesoporous silica, Catalyst recycling, Enzyme catalysis, Kinetic resolution reaction

MSC2000: 

  • O648