Fluorescence studies on the photophysical properties and encapsulation behavior of acetaminophen in different environments

A systematic study on the spectroscopy and photophysical properties of widely used analgesic and anti-pyretic drug acetaminophen (NAPAP) was presented using steady state and time-resolved fluorescence spectroscopy. The results in homogeneous solvents were compared with those in bio-mimicking environments of cyclodextrin and micellar cavities. Extensive theoretical calculations using time dependent density functional theory (TDDFT) were also done to substantiate the spectral assignment as well as to compare the structure and stability of possible hydrogen bonded conformations of NAPAP in aqueous medium. Facile proton dissociation occurs due to extensive charge redistribution in the excited state. The variation in fluorescence yield and the life time of excited state species in cyclodextrin cavities and micellar medium is due to shift in acid-base dissociation equilibrium in these environments.