Probing pH difference between micellar solution and nanoscale water within common black film by fluorescent dye

摘要: Abstract The protonation/deprotonation equilibrium of a fluorescent pH probe (carboxy-seminaphthorhodafluor-1, SNARF-1) within the nanoscale water layer confined in common black films (CBFs) has been studied. We find that SNARF-1 molecules feel more acidic environment CBFs than when they are bulk micellar solution, using base/acid peak area ratio dye to indicate its microenvironment pH. Three surfactants used study dependence drop versus charge: cationic (cetyltrimethylammonium bromide, CTAB), anionic (sodium dodecylsulphate, SDS) and nonionic (Triton X-100) species. decrease solution is following: ΔpH ≈ 1.5 for CTAB (pH: 7.0–9.0), ΔpH ≈ 0.8 SDS, ΔpH ≈ 0.4 Triton X-100. With addition electrolyte CBFs, we observe large amplitude anomaly, thus suggesting an electrostatic origin change at environment.