Hybrid nanorattles of metal core and stimuli-responsive polymer shell for confined catalytic reactions

Narrowly-dispersed silver@silica@poly(methacrylic acid) (Ag@SiO2@PMAA) core–double shell hybrid nanoparticles (NPs) were first synthesized by distillation–precipitation polymerization, using silver@silica core–shell NPs from the sol–gel reaction as templates. Selective removal of the inorganic silica inner-shell from the Ag@SiO2@PMAA core–double shell hybrid NPs by HF etching produces the Ag@air@PMAA hybrid nanorattles with a Ag nanocore, PMAA shell and free space in between. The Ag nanocores, Ag@SiO2 core–shell NPs, Ag@SiO2@PMAA core–double shell NPs and Ag@air@PMAA hybrid nanorattles were characterized by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy and energy-dispersive X-ray (EDX) analysis. The as-synthesized Ag@air@PMAA hybrid nanorattles were explored as a nanoreactor system for confined catalytic reaction. The rate of catalytic reaction can be further regulated by controlling molecule diffusion in and out of the stimuli-responsive PMAA shell through the simple variation of environmental stimuli, such as salt (NaCl) concentration of the medium.