Polydiacetylene-Functionalized Noble Metal Nanocages

Description

Stable chitosan-protected noble metal nanocages of relatively small size (~ 50 nm) were successfully synthesized by the galvanic replacement reaction between the corresponding silver nanoparticles and HAuCl4 in aqueous suspension. A broad surface plasmon band peaked around 700 nm and extended to the near-infrared was observed by properly changing the experimental conditions. To test the performance, the nanocages were functionalized with 10,12-pentacosadiynoic acid (PCDA) chains and then irradiated with UV light to induce monomer polymerization. A very high polymer conversion was observed. The time evolution of the electronic absorption and Raman spectra showed a variety of polydiacetylenic forms, including the unusual highly-delocalized bluish-green phase. The nanocages act as Surface-Enhanced Raman Scattering (SERS) active substrates with all our available excitation lines and show improved Raman activity in comparison with data from mixed silver-gold colloids. The shift of the plasmonic band to the NIR is expected to magnify the nonlinear response of polydiacetylene in this region.

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