Thermosensitive and pH-sensitive Au-Pd bimetallic nanocomposites.

The bimetallic nanoparticles were protected by a double stimuli-sensitive diblock copolymer, poly(N-isopropylacrylamide)-block-poly(4-vinylpyridine) (PNIPAM-b-P4VP), which was synthesized via the reversible addition-fragmentation chain transfer (RAFT) polymerization. The obtained nanocomposites were made up of bimetallic nanoparticles cross-linked P4VP core and PNIPAM shell. Energy-dispersive X-ray (EDX) spectra and UV-vis transmittance revealed the formed nanoparticles was truly bimetallic particles with incomplete core-shell structures, Au as core and Pd as shell, rather than the physical mixture of monometallic nanoparticles. Laser light scattering (LLS) demonstrated the nanocomposites exhibit both thermo and pH sensitivity. X-ray diffraction (XRD) clearly showed Au formed a high-ordered crystal while Pd fashioned amorphous aggregates. In addition, the bimetallic nanocomposites show special responsiveness for temperature and better catalytic activity than corresponding monometallic nanocomposites.