SWNT was functionalized with N-(1-pyrenylmethyl)-1,5-diaminopentane and the resulting PYalphaSWNT sample characterized by optical and IR spectroscopy. The photochemical properties of PYalphaSWNT were studied by dispersing the insoluble solid in silica and applying diffuse reflectance techniques. From the emission decay kinetics (quenching of pyrenyl singlet excited state by the SWNT walls) and laser flash photolysis (detection of pyrenyl radical cation) evidence in support of occurrence of an intramolecular quenching from pyrenyl singlet excited state to the SWNT walls has been obtained. (C) 2003 Elsevier B.V. All rights reserved.