Condensed-phase absorption spectroscopy study of dye molecules at nanomolar concentrations by ultra-sensitive detection

Broadband cavity-enhanced absorption spectroscopy (BBCEAS) was used for ultra-sensitive detection of the absorption characteristics of the dye Coumarin 334 in the condensed phase at nanomolar concentrations. To provide a more detailed understanding of the spectral features, the Edgeworth–Cramer series model was used to fit the absorption spectra of the liquid and solid phases of Coumarin 334. In the fitting results of the ECS model, spectral shifts for the liquid and solid phases were observed, both bathochromic and hypsochromic, strongly indicating the effects of solvation or changes in molecular interactions, the quenching effect, strain effects, molecular aggregation, and quantum yield.