Research work of the latest physical and chemical dynamic interface design of Professor Hou Xu's research group of Xiamen University: responsive liquid gating of dipole induced interface molecular reconstruction for non electric visual chemical detection

The author of the paper: the interface behavior in the confined space of Professor Hou Xu's research group is different from the relatively independent interface behavior in the macro scale because of the size effect of the space The research of dynamic interface in confined space will bring new opportunities for the development and application of interface science Based on the dynamic interface design, the concept of liquid gating is that the small holes can be sealed in the closed state reversibly by the fluid which is stable in the confined pore space, and can be reconfigured rapidly under pressure to generate the open small holes with fluid on the inner wall At the same time, the chemical structure at the molecular level determines the surface and interface properties of substances In recent years, with the development of micro characterization technology, researchers pay more and more attention to the interface molecular configuration, such as heterogeneous catalysis, electrode interface electronic transport, superhydrophobic and interface chemical reaction and other micro molecular interface mechanism, and pay more attention to the influence of interface molecular configuration on the interface properties and the way of action In recent years, Professor Hou Xu's research group of Xiamen University proposed a series of responsive liquid gating mechanisms (adv mater 2016, 28, 7049; NAT Rev Mater 2017, 2, 17016; science 2017, 69, 18; ACS appl Mater Inter 2017, 9, 35483; SCI Adv 2018, 4, eaao6724; small 2018, 14, 1703283; NAT Commun 2018, 9 , 733 ）。 Recently, based on the research of surfactant, the research group designed the physical and chemical interface of the parent molecules in the gated liquid, A new mechanism of responsive gated liquid for chemical detection is proposed A new method of liquid gated chemical detection is developed and its application in chemical detection is explored by using the dynamic rearrangement process of the interface molecules induced by dipoles of the parent molecules at the interface (Figure 1) Different from the traditional detection system, the gated liquid response liquid gated detection system is based on a special way of information transmission It uses the dipole induced interaction between the substance to be detected and the functional molecule in the system gated liquid to cause the functional molecule to rearrange the information on the interface configuration (the information on the change of the interface tension on the macro level), which is further converted into the gas transmembrane criticality Pressure threshold change information Relevant research results were published in angelw Chem Int ed (DOI: 10.1002 / anie 201814752) Figure 1 Responsive liquid gating system of dipole induced interface molecular reconstruction and its application in non electric visual chemical detection (source: angelw Chem Int ed.) In this work, the author introduces parent molecules into the gating liquid interface of responsive liquid gating system to obtain responsive liquid gating system with dynamic interface (Figure 2) With the addition of amphiphilic molecules, the arrangement of amphiphilic molecules on the interface of the gated liquid is rearranged, which shows the change of the surface tension of the gated liquid macroscopically The surface tension changes with the change of the concentration of amphiphilic molecules, and the critical pressure of the gas transmembrane of the system changes accordingly This change is different from that of inorganic and organic solutions The critical pressure threshold of gas transmembrane changes nonlinearly with the increase of the concentration of amphiphilic molecules The construction of the system provides the premise for the application of the visualized chemical detection without electricity Figure 2 The dynamic interface of the responsive liquid gating system and its threshold characteristics of gas transmembrane critical pressure (source: angelw Chem Int ed.) show that the change of threshold value of gas transmembrane critical pressure presents different characteristics with the difference of the type of substance to be measured (Figure 3) For metal ions, the threshold of gas transmembrane pressure decreases linearly with the increase of the concentration of the detector The critical pressure threshold of high valence metal ions is significantly higher than that of monovalent ions For organic solvents, the critical pressure threshold increases first and then decreases with the increase of concentration These phenomena are due to the dipole induced interaction between the substance to be detected and the functional molecule in the gated liquid, which results in the rearrangement of the functional parent molecule on the interface, and the change of the interface tension on the macro level, which finally affects the critical pressure threshold of gas transmembrane Figure 3 Responsiveness of the responsive liquid gating system to different objects to be tested (source: angelw Chem Int ed.) Further, taking divalent metal ion Ca2 + as an example, the author discusses the sensitivity and detection limit of detection by designing a visual chemical detection device (Figure 4) The results show that the critical pressure threshold of the system gas transmembrane can be significantly changed by the trace of the substance to be measured Among them, the concentration of amphiphilic molecules and the pore size of membrane materials in the system are important factors affecting the detection limit In the actual chemical detection process, the detection signal of the responsive liquid gating detection system can be realized by the visual movement of the labeled liquid drop, and the process does not need power consumption Figure 4 Application of responsive liquid gating system in non electric visual chemical detection (source: angelw Chem Int ed.) Conclusion: the author constructs a new mechanism of responsive liquid gating based on surfactant research and liquid gating system Through intuitively monitoring the critical pressure threshold of gas transmembrane, the chemical detection can be realized, and the composition, concentration and other information of the detected substance can be obtained The application of the liquid gated chemical detection system shows the broad prospect of the responsive liquid gated system This achievement was recently published in angelw Chem Int ed (DOI: 10.1002 / anie 201814752) Fan Yi and Sheng Zhizhi, Ph.D students of the school of chemistry and chemical engineering of Xiamen University, and Hou Xu, Professor, are independent correspondents The above research work is supported by national key R & D plan, National Natural Science Fund, 111 talent introduction plan, Fujian Natural Science Fund, Fujian strategic emerging industry special project and China Postdoctoral Science Fund Review of previous reports: research group of Professor Hou Xu of Xiamen University: anomalous ion transport behavior and dynamic regulation of ion rectification in curvature driven dynamic nano confined space