Spectral Signatures of Organic Materials Modified by Ammonia Interaction*

Optical spectroscopy provides a sensitive probe of gas–molecule interactions through measurable shifts in emission and absorption features. In this work, we show that the conjugated organic material pyrene-4,5-dione exhibits fluorescence spectral shifts of about 100 nm when exposed to ammonia. The mechanism of this interaction was proposed and confirmed numerically using time-dependent density functional theory (TD-DFT) simulations to show that ammonia adsorption alters the electronic energy gap, thereby modifying the optical transition energies and overall photophysical response of the system.