Synthesis and nonlinear optical properties of nanometer-size silver-coated polydiacetylene composite vesicles

Two kinds of nanometer-size silver-coated polydiacetylene (PDA) composite vesicles were prepared by simple and effective approaches. Silver nanoparticles were coated onto the outer and inner surface (I) or only on the outer surface of PDA vesicles (II), respectively. UV-vis spectra and transmission electron microscopy (TEM) were used to confirm the formation of PDA/Ag nanocomposite vesicles. Nonlinear optical (NLO) properties of these PDA/Ag nanocomposite vesicles had been measured by the Z-scan technique. The value of n(2) for pure PDA vesicles was 1.2 x 10(-14) cm(2) W(-1). However, for PDA/Ag nanocomposite vesicles (on the outer surface) it was 7.3 x 10(-14) cm2 W(-1). Nearly seven times enhancement was observed as a result of local field enhancement under the surface plasmon resonance of silver nanoparticles at the interface. NLO properties of these PDA/Ag nanocomposite vesicles can be modulated by varying the size, shape and coverage of Ag nanoparticles and these PDA/Ag nanocomposite vesicles are expected to be good candidates for new optical and nonlinear devices.