Pressure-Induced Ultralow Critical Micelle Concentration of Surfactant for Encapsulating Dye

Achieving the ultralow critical micelle concentration (CMC) of the surfactant encapsulating the dye has spawned a vital pathway to boost the efficiency and stability of dye-sensitized solar cells (DSSCs). The attainment of ultralow CMC while sustaining the constant micelle presents a significant challenge. Here, by an ingenious pressurizing strategy, the ultralow CMC is obtained for the immobilized micelle. The ultralow CMC of cetyl trimethyl ammonium bromide (CTAB) is performed under pressure by the detection of encapsulated coumarin 35 (C35) attractively. At 0.80 GPa, the CMC of CTAB is decreased ≈111-fold to 8.3 ± 0.1 µm compared to 917.2 ± 8.7 µm at 0.10 MPa. The ultralow CMC under pressure is probed relying on the quenched fluorescence background of C35. Femtosecond transient absorption spectra confer a clear picture that the pressure-induced fluorescence quenching is ascribed to the reinforced competition for the twisted intramolecular charge transfer process of the C35. This study provides a robust strategy for achieving ultralow CMC, laying the groundwork for the efficient application of DSSCs.