Integrating-Sphere-Assisted Resonance Synchronous Spectroscopy for the Quantification of Material Double-Beam UV-Vis Absorption and Scattering Extinction.

Integrating spheres (IS) have been used extensively for the characterization of light absorption in turbid samples. However, converting the IS-based sample absorption coefficient to the UV-vis absorbance quantified with a double-beam UV-vis spectrophotometer is challenging. Herein, we report an integrating-sphere-assisted resonance synchronous (ISARS) spectroscopy method performed with conventional spectrofluorometers equipped with an integrating-sphere accessory. Mathematical models and experimental procedures for quantifying the sample, solvent, and instrument-baseline ISARS intensity spectra were provided. A three-parameter analytical model has been developed for correlating the ISARS-based UV-vis absorbance and the absorbance measured with double-beam instruments. This ISARS method enables the quantitative separation of light absorption and scattering contribution to the sample UV-vis extinction spectrum measured with double-beam UV-vis spectrophotometers. Example applications of this ISARS technique are demonstrated with a series of representative samples differing significantly in their optical complexities, from approximately pure absorbers, pure scatterers, to simultaneous light absorbers, scatterers, and emitters under resonance excitation and detection conditions.