The photophysical behaviour of 1-nitrocarbazole, 3-nitrocarbazole, 1,6-dinitrocarbazole and 3,6-dinitrocarbazole in acetonitrile was studied by using spectroscopic, luminescence and photoacoustic techniques. Absorption spectra and triplet state transient spectra were recorded and the phi(T) and tau(T) values were determined. Phosphorescence emission at 77 K and the dynamic properties in terms of phi(P), k(o)(p) and k(nr) for the mono and dinitrocarbazoles were derived. Results are discussed in terms of the optimised structure of 1-nitrocarbazole, 3-nitrocarbazole, 1,6-dinitrocarbazole and 3,6-dinitrocarbazole and are compared with that of carbazole. The nitro group attached to the carbazole moiety induces important changes in the photophysical behaviour of these compounds. (C) 2007 Elsevier B.V. All rights reserved.