Spectroscopical investigation on colloidal suspensions of diacetylene-capped gold nanoparticles

Self-assembled monolayers containing disulfide-functionalized diacetylenes are of particular interest for applications in photonics and sensor devices. To this purpose a diacetylene derivative, the henicosa-10,12-diyn-1-yl (DS9) disulfide, was synthesized and employed to prepare gold nanoclusters capped with this monomer. The nanohybrids were obtained through a direct synthesis in toluene. The preparative conditions were varied in order to modulate the nanoparticle size and shape. The resulting organic-protected gold nanoassemblies were spectroscopically studied as colloidal suspensions. TEM analysis allowed the determination of the average dimensions in the range from 1.6 to 7.5 nm. DS9 monomer chemisorbed onto the gold nanoclusters was photopolymerized in colloidal suspension by exposure to UV radiation for variable time intervals. The polymerization process was monitored step by step through UV–vis, Raman and FT-IR spectroscopies. These data showed that the polymerization occurs with the dominant polydiacetylene phase critically depending on the nanoparticle diameter.