Plasmon enhanced upconverting core@triple-shell nanoparticles as recyclable panchromatic initiators (blue to infrared) for radical polymerization

Abstract

With the rise of stereolithographic processes and advanced fabrication processes, photo-induced polymerization is becoming increasingly popular. The development of panchromatic radical initiators, that is to say initiators which are activated by a wide spectrum, is still in its infancy, with the near-infrared range remaining a challenge. We have reported a rationally-designed nanohybrid which can initiate photo-polymerization from ultraviolet to near-infrared wavelengths. Integration of Ag and Au plasmonic nanoparticles (NPs), upconverting (UC) materials and BiFeO₃ (BFO) semiconductors with a rational architecture design results in the formation of an Ag@SiO₂@UC@BFO–Au core@triple-shell structure. Compared to the conventional thermal radical polymerization method, this material can initiate polymerization under visible or near-infrared light at room temperature, and the initiator can easily be recycled and reused. The excellent activity of the nanohybrid photoinitiator is attributed to the combination of the optical properties of the UC material and BFO semiconductor and the surface plasmon resonance (SPR) in the core@shell configuration, where the Ag NP core demonstrates dual roles of increasing resonant VIS photon scattering as a “mirror” and improving the upconverting efficiency of the NIR-to-VIS photons as a “resonator”; the Au NPs anchored on the BFO shell further enable an efficient energy transfer of absorbed VIS photon energy from Au to BFO via a plasmon-induced resonance energy transfer (PIRET) process.