Silver Nanoparticles-Accelerated Photopolymerization of a Diacetylene Derivative

Abstract

We have investigated silver nanoparticles (AgNPs)-accelerated photopolymerization of a diacetylene derivative, 1,6-di(<i>N</i>-carbazolyl)-2,4-hexadiyne (DCHD), which undergoes a phase transformation of the crystal structure from monomer to polymer during the photopolymerization. We have successfully fabricated nanocomposites of AgNPs and DCHD monomer nanocrystals by means of the modified reprecipitation method, and we monitored its photopolymerization process with Raman spectroscopy upon 532 nm excitation. Although the localized surface plasmon resonance (LSPR) wavelength of AgNPs in an aqueous dispersion was located around 400 nm, that of AgNPs in the present nanocomposites was shifted to longer wavelength region. The extinction of the nanocomposites at 532 nm became significant because of the red-shift and broadening of the LSPR, and, thus, surface plasmon-enhanced photoelectric fields on the AgNP surfaces could generate upon 532 nm excitation. As compared to the Raman spectra of bare DCHD monomer nanocrystals, the nanocomposites exhibited strongly enhanced Raman intensities and 20–40 times faster photopolymerization. Because the excitation power used in the present experiments is considered to be insufficient for the thermal process, two- or multiphoton polymerization was assumed to be dominant. We have also observed a unique power dependence of the polymerization rate derived from the phase transformation behavior.