As shown by Maillard et.al., sensitivity towards water content, realized via overlap of donor luminescence and water absorption band may be effectively utilized in practice (some harmonics of a set of water -OH vibrations are situated in a visible wavelength range). But unlike for fluorophores discussed elsewhere, for this molecule we have no need to shift luminescence batochromically since exciplex already possesses sufficient spectral overlap. Moreover, sensing may be considered ratiometric since we both observe concentration-related main / exciplex band ratio and distribution of radiative decay constants for exciplex. Decays at exciplex peak observed for series with varied BODIPY-C18 concentration at 50 Vol.% water / acetonitrile ratio were extracted utilizing the same technique (Figure ). At lowest concentration we observe pronounced bimodality. Here, 0.43 ns -1 -centered constant is related to ineffective waterdriven exciplex resonant quenching, whereas second distribution is also related to insignificant portion of monomeric dye, indicating incomplete aggregation at this concentration. Subsequent distributions in series are centered around 1.12 ns -1 with lower observed variance as compared to that found in high water content systems. This shows that effect of aggregation induced via antisolvent treatment and concentration increase is different. Fit results are summarized in Table (a).