Versatile Synthetic Strategy for Coating Upconverting Nanoparticles with Polymer Shells through Localized Photopolymerization by Using the Particles as Internal Light Sources

Abstract

We present a straightforward and generic strategy for coating upconverting nanoparticles (UCPs) with polymer shells for their protection, functionalization, conjugation, and for biocompatibility. UCPs are attracting much attention for their potential use as fluorescent labels in biological applications. However, they are hydrophobic and non‐compatible with aqueous media; thus prior surface modification is essential. Our method uses the internal UV or visible light emitted from UCPs upon photoexcitation with near‐infrared radiation, to locally photopolymerize a thin polymer shell around the UCPs. In this way, a large variety of monomers with different chemical functionalities can be incorporated. If required, a second layer can be added on top of the first. Our method can provide a large spectrum of surface functional groups rapidly and in one pot, hence offering a platform for the preparation of libraries of functional polymer‐encapsulated UCPs for applications in bioassays, biosensing, optical imaging, and theranostics.

High-resolution 3D photopolymerization assisted by upconversion nanoparticles for rapid prototyping applications

“…UCNP based photoinitiator systems and radical polymerization driven by NIR-light were shown 7 , 19 . NIR light converted to the green luminescence of NaYF 4 :Yb 3+ , Er 3+ nanoparticles, has been successfully used to induce straightforward thin polymer shell formation on UCNP surface for its hydrophilization 20 and drug loading 21 . Micrometer-sized UCMs were used for NIR-induced curing of PCC 22 – 24 .…”

Thermal Polymerization on the Surface of Iron Oxide Nanoparticles Mediated by Magnetic Hyperthermia: Implications for Multishell Grafting and Environmental Applications

“…Recently, Haupt et al proposed an original strategy for coating upconverting nanoparticles (UCP) with polymer shells by using the particles as internal light sources. 30 The method used the UV or visible light emitted from UCP upon photoexcitation with near-infrared radiation, to locally photopolymerize a thin polymer shell around the UCP. Based on this work, it should be possible to initiate the polymerization from magnetic nanoparticles surface by using their heating properties under alternating magnetic field.…”

Molecularly imprinted polymers with multi-functionality

“…3). In this system, when the UCPs were irradiated with a NIR source, they emitted visible light (λ em =520-540 nm) that, in the presence of the photosensitizer eosin Y, initiated the photopolymerization [28]. Because the photopolymerization relied on the UCPs to provide the initiating visible light, it was only on the surface of the UCPs that the actual polymerization could take place.…”