Responsive Janus emulsion as an unconventional indicator for a traditional argentometric titration

Argentometric titrations are traditional and widely recognized methods for detecting halide ions. However, their practical application is often constrained by challenges such as pH control and reliance on specific indicators. In this study, we introduce a novel optical indicator for argentometric titration, based on previously reported Janus droplet systems and employing cetyltrimethylammonium bromide (CTAB) and Zonyl as surfactants. Furthermore, Janus droplets were utilized to explore the impact of various cations on the efficiency of the CTAB surfactant, revealing that contact angle values are influenced by the cations' positions within the Hofmeister series. • Impact of Ions on Droplets: Morphological transitions in complex droplets are driven by ion-specific interactions. • Halide Ion Effects: Halide ions, removed via argentometric precipitation, restore droplet contact angles. • Innovative Optical Indicator: A novel argentometric titration uses droplet morphology for real-time halide ion detection.