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.