Monitoring hydrophilic and hydrophobic properties on membrane surface.
Inspired by the H-bond acceptor sensitive nature of HBT-DPI , we tried to sense the surficial hydrophilicity and hydrophobicity usingHBT-DPI . HBT-DPI emitted green emission upon polycarbonate (PA) membrane (hydrophilic surface) and yellow emission upon hydrophilic membranes containing poly(1,1-difluoroethylene) (PVDF), polypropylene (PP) and polytetrafluoroethylene (PTFE), demonstrating the outstanding property of our fluorophore (Figures S14 and 3A). On this basis, we tried our fluorophore to monitor the modified membranes, which showed extensive requirement and application in material science.39,51,52 We used PVDF membrane as the model surface and created hydrophilic areas using Sub-Atmospheric Microthermal Plasma (SAMP). The original PVDF membrane surface was hydrophobic with a contact angle of around 128.3° (Figure 3A), and the subsequent treatment of SAMP increased the surface hydrophilicity, rendering a contact angle of around 26.7° (Figure 3B). The oxygen contents intensified by the SAMP treatment at the membrane surface (Tables S1 and S2) increase the hydrophilicity while also acting as the H-bond acceptors. Consequently, by sensing the H-bond acceptors, the green coating of HBT-DPIon the original PVDF membrane surface (Figure 4A) turned to yellow on the modified surface (Figure 3B), demonstrating the potential ofHBT-DPI on distinguishing between hydrophilic and hydrophobic areas.