Xue Huang

1,3-Dioleoyl-2-palmitoylglycerol (OPO) has been a hotspot of functional oils research in recent years, but due to the high cost of sn-1,3 specific lipase in enzymatic synthesis and the lack of biocatalyst stability, large-scale industrial application is difficult. In this study, the prepared magnetic ZnFe2O4 was functionalized with dopamine to obtain ZnFe2O4@PDA, and the nano-biocatalyst ZnFe2O4@PDA@RML was prepared by immobilizing sn-1,3 specific lipase of Rhizomucor miehei lipase (RML) via a cross-linking method. The existence of RML on ZnFe2O4@PDA was confirmed by XRD, FTIR, SEM, and TEM. This strategy proved to be simple and effective because the lipase immobilized on magnetic nanoparticles could be quickly recovered using external magnets, enabling reuse of the lipase. The activity, adaptability to a high temperature, pH value, and operational stability of immobilized RML were superior to those of free RML. After optimizing the synthesis conditions, the OPO yield was 42.78%, and the proportion of PA at the sn-2 position (PA-Sn2) was 54.63%. After the first four cycles, the activity of ZnFe2O4@PDA@RML was not significantly affected. The magnetically immobilized lipase has good thermal stability, long-term storage stability, reusability, and high catalytic activity. It can be used as a green and efficient biocatalyst to synthesize the OPO functional lipid.

In this study, anisotropic graphene/graphene oxide (GO) aerogels (AGAs) were obtained by freeze-drying after direct participation of pristine graphene in the self-assembly of anisotropic gel by the heat flow method. After vacuum microwave treatment, the physical, chemical and structural characteristics of the AGAs were investigated. The results show that AGAs, in which the internal graphene sheets are parallel to the heat flow direction, are successfully prepared. After microwave treatment, the amount of oxygen and nitrogen reduces significantly and the sp2 domain increases. However, at the same time, many fragments and holes are generated in the graphene sheets. The effects of AGAs on the phase transition of paraffin is studied, and the results show that the melting enthalpy, solidification enthalpy and initial melting temperature of AGA/paraffin composites decreases as the GO content in the AGAs increases, whereas the melting range, solidifying range and subcooling degree increases. The highest axial thermal conductivity of the AGA/paraffin composite is 1.45 W/(mK), and the thermal conductivity enhancement efficiency is 884% (AGA content was 0.53 vol %). Compared with previously investigated, similar AGA/paraffin composites, the aerogels fabricated in this study have the obvious advantages of a simple fabrication process, a low cost and a high thermal conductivity enhancement efficiency. These aerogels possess the potential for application in phase-change energy storage (PES), thermal energy management and other fields.

In this study, we investigated the directional heating of graphene oxide (GO) dispersion to generate a temperature gradient and form a simulated “ocean current” inside the dispersion so that GO sheets could be aligned in a directional manner and then reduced and self-assembled into anisotropic reduced graphene oxide (rGO) gel. After freeze-drying and varying degrees of vacuum microwave treatment, anisotropic chemically derived graphene aerogels (AGAs) were obtained. Through performance detection and the analysis of the results, it was verified that the AGAs with certain characteristics of “ocean current” were prepared in this experiment, and its axial direction has obvious directional arrangement. After being treated by vacuum microwave for a short time (1 min.), the axial thermal conductivity of the composite materials (AGA-adsorbed paraffin) was observed to be 1.074 W/mK, and the thermal conductivity enhancement efficiency was 995%; as compared with similar thermal conductivity enhancement composites that were found in previous studies, the proposed method in this paper has the advantages of simple processing, high efficiency, and energy conservation.