We develop a novel photo-responsive supramolecular system in which the aggregation and disaggregation of polydiacetylene/silver (PDA/Ag) composite vesicles is mediated by a reversible photo-responsive molecular recognition process. The PDA/Ag composite vesicles provide necessary nonlinear optical (NLO) properties, the host-guest interaction between azobenzene and beta-cyclodextrin get PDA/Ag composite vesicles sufficiently close to each other for providing the enhanced surface plasmon resonance and a corresponding NLO effect. NLO switching of PDA/Ag composite vesicles based on reversible host-guest interactions is realized by alternating visible and UV light irradiation, which may introduce a new way for preparation of smart NLO materials. (C) 2012 Elsevier B.V. All rights reserved.