Yolk–shell nanorattles encapsulating a movable Au nanocore in electroactive polyaniline shells for flexible memory device

Abstract

Template-assisted synthesis of hairy rattle-type hybrid nanospheres, consisting of a gold nanocore and poly(4-vinylaniline) (PVAn) shell decorated with polyaniline (PANI) brushes (Au@air@PVAn-g-PANI hybrid nanorattles), was carried out. Initially monodispersed Au@SiO₂-MPS (MPS: 3-(trimethoxysilyl)propyl methacrylate) core–shell nanospheres were prepared by coating of gold nanoparticles (Au NPs) via the modified Stöber method. Narrowly dispersed Au@SiO₂@PVAn nanospheres were prepared by distillation–precipitation polymerization of 4-vinylaniline (VAn) and divinylbenzene (DVB) from the Au@SiO₂-MPS-1 template nanospheres. Surface-initiated oxidative graft copolymerization of aniline from the Au@SiO₂@PVAn nanospheres, using the aniline moieties of PVAn as the anchoring site, produced the Au@SiO₂@PVAn-g-PANI nanospheres. HF etching of the hairy Au@SiO₂@PVAn-g-PANI core–double shell nanospheres removes the inorganic silica inner-shell and gives rise to hairy Au@air@PVAn-g-PANI hybrid nanorattles. The hybrid nanorattles can be integrated into an electrically insulating poly(vinyl alcohol) (PVA) matrix. The Al/Au@air@PVAn-g-PANI + PVA/ITO-coated poly(ethylene terephthalate) (PET) flexible device, with a turn-on voltage of −2.0 V and an ON/OFF state current ratio of more than 10⁴, was fabricated. This device can be switched to the ON state under a negative electrical sweep and also can be reset to the initial OFF state by a reverse (positive) electrical sweep. The memory behaviors of the flexible device were almost unchanged under the bending test.