Surface Hovering of Probe on Cyclodextrin Nanoparticle that is Otherwise Sequestered in Isolated Cyclodextrin Cavity

Abstract Experimental evidence of hovering of probe on the surface of β‐cyclodextrin nanoparticles (β‐CDNPs) is given in the present work. A special double proton transfer (DPT) probe was used for this purpose. 2,2′‐bipyridine‐3,3′‐diol (BP(OH) 2 ) shows excited state intramolecular DPT (ESIDPT) in different solvents. In water, this process takes place through two mechanisms: (i) normal intramolecular proton transfer and (ii) unconventional DPT through “water‐wire” formation between the prototropic centers. The second mechanism is favoured at low availability of water around the probe. This concept was exploited in the present case to propose possible existence of BP(OH) 2 on the surface of the β‐CDNPs due to uncertainty in occupying the host cavity as all are similar and cluttered together. The probe would otherwise is completely sequestered within isolated CD nanocavity in aqueous medium. Spectroscopy has been used as a tool to establish the proposition.