Non-toxic, water-soluble photocalorimetric reference compounds for UV and visible excitation

A set of non-toxic, water-soluble photocalorimetric reference compounds has been characterized. These compounds are brilliant blue G, brilliant black BN, new coccine, indigo carmine, and tartrazine. Neutral aqueous solutions of all compounds are photochemically stable under UV–visible excitation (λ>300 nm). None of these dyes are fluorescent or show optical transients detectable by laser flash photolysis on the nano- to microsecond time scale. The relationship between the amplitude of the photoacoustic signal and the laser fluence is linear up to at least 350 J/m2. The fraction of absorbed energy delivered to the medium as heat within the integration time of the instrument (α) is equal to 1 for all of the samples, within the experimental error (±0.05). With the exception of tartrazine, no photoinduced structural volume changes were detected for any of the dyes.