Visualization of air-water gas exchange using novel fluorescent dyes

Laser-Induced Fluorescence (LIF) techniques are applied to visualize air-water gas exchange across the aqueous mass boundary layer in wind/wave facilities. Dissolved oxygen is made visible by quenching of the fluorescence of an organic ruthenium complex (tris(4,7-diphenyl-1,10-phenanthroline disulfonic acid) ruthenium(II) dichloride, Ru(dpp ds)3), and acid or alkaline volatile species such as CO2, HCl or diethylamine by the fluorescent pH indicator 1-hydroxy-pyrene-3,6,8-trisulfonic acid (HPTS). Fluorescence of both dyes can be stimulated by a 473 nm DPSS laser. The spectral peaks of the fluorescence emission (510 nm for HPTS and 610 nm for Ru(dpp ds)3) are different enough, so that the concentration
fields of both dyes can be measured simultaneously using two cameras with different bandpass filters. The paper details the properties of the two dyes and demonstrates their usage with some preliminary visualization experiments.