Monitoring Based on Narrow‐Band Resonance Raman for “Phase‐Shifting” π‐Conjugated Polydiacetylene Vesicles upon Host–Guest Interaction and Thermal Stimuli

: The present study reports a quantified monitoring by means of in situ resonance Raman scattering that analyzes phase-shifting characteristics of π-systems upon interacting with target analytes. A chemo- and thermochromic polydiacetylene vesicular probe is evaluated with multiple-wavelength Raman scattering modes in resonance with its phases, respectively, and thus can trace the phase-shifts. This Raman scattering-based analytical quantification is also successful in monitoring host-guest recognition events by utilizing much narrower bands, compared to those in conventional absorption or photoluminescence (PL) methods. As one of the outcomes, the monitoring analysis overcomes the limitations based on widely used colorimetric response (%CR) or PL that failed in the case of interaction with a surfactant, CTAB.