title: Spectroscopic evidence of monomeric aluminium phthalocyanine tetrasulphonate in aqueous solutions.
abstract: Aqueous solutions of aluminium phthalocyanine tetrasulphonate (AlPcS(4)) were investigated by means of absorption and fluorescence spectroscopy. The absorption spectrum of AlPcS(4) is independent of concentration in a wide range (from 10(-8) to 10(-4) M). The fluorescence spectrum measured with a standard setup is strongly dependent on AlPcS(4) concentration, and the fluorescence maximum is gradually red-shifted with increasing concentration. Calculations that take into account reabsorption of fluorescence (inner-filter effect) fit the experimental observations at low concentrations (up to 10(-6) M). Disagreement between the calculations and spectra recorded at higher concentrations (above 10(-5) M) shows that the reabsorbed light may be reemitted as fluorescence. The influence of inner-filter effects on the spectral shape was demonstrated by the experiments where a fibre-optic front-face fluorescence setup was applied: Under such conditions the shape of the fluorescence spectra for a high concentration (10(-3) M) coincided with that of a low concentration (10(-8) M). In conclusion, the present spectroscopic results show that AlPcS(4) does not form aggregates and is a very stable compound in aqueous solutions.
authors.affiliation: Institute for Cancer Research, Department of Radiation Biology, The Norwegian Radium Hospital, Oslo, Norway. petras.juzenas@labmed.uio.no
authors.forename: Petras
authors.initials: P
authors.lastname: Juzenas
authors.forename: Asta
authors.initials: A
authors.lastname: Juzeniene
authors.forename: Ricardas
authors.initials: R
authors.lastname: Rotomskis
authors.forename: Johan
authors.initials: J
authors.lastname: Moan
mesh_terms: D005456:Fluorescent Dyes / Q000032:analysis* / Q000737:chemistry; D007211:Indoles / Q000032:analysis* / Q000737:chemistry; D009942:Organometallic Compounds / Q000032:analysis* / Q000737:chemistry; D012996:Solutions / Q000032:analysis; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D005456:Fluorescent Dyes; D007211:Indoles; D009942:Organometallic Compounds; D012996:Solutions; C048577:aluminum tetrasulfophthalocyanine