Plots of the fluorescence quantum yields determined in THF/H2O solutions by using 9,10-diphenylanthracene (F=90% in cyclohexane) as the internal standard versus the fraction of water in the solvent. Insets: photo- graphs of the TPE–Ar luminogens in the THF/water mixture (fw =99%) taken under the illumination of a 365 nm UV lamp. Excitation wavelengths [nm]: 320 for TPE–ptol and TPE–mtol, and 310 for the other six fluorophores.