Steady state, time-resolved spectroscopic measurements and theoretical computations on a photoswitchable organic dyad, 1-(4-bromo-phenyl)-3-(2-methoxy-naphthalen-1-yl)-propenone demonstrate the formations of the two different isomers in the excited singlet state though NMR study reveals the presence of only one isomer in the ground state. The present Letter describes how by combining with semiconductor TiO2 nanoparticles the presence of two different isomers of the photoswitchable dyad could be recognized in the form of various yields. (C) 2009 Elsevier B. V. All rights reserved.