Tethering inorganic luminous upconverting nanoparticles with macromolecular chppendixains using silica functionalized with RAFT agent

Abstract

Upconversion nanoparticles (UCNPs) are superior next-generation nanomaterials due to their exclusive features, such as tunable emission, high quantum yield, and excellent stability against photo-blinking/bleaching/degradation. One can compel these UCNPs to target selective applications by surface functionalization of these nanocrystals with functional groups or polymers to make them chemically active, possessing colloidal stability, better biocompatibility as well as tunable emission region. Herein, we report the preparation of rare earth (Er 3+ , 0.5% mmol) doped upconversion nanoparticles (UCNPs) and their surface functionalization using RAFT agent primed silica followed by polymer functionalization. The polymer functionalization was performed using photo-induced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization in the presence of Eosin Y (EY) which act as a photocatalyst when exposed to blue light at room temperature. The polymer functionalization of UCNPs was performed with different types of polymers, for example, poly( N -isopropyl acrylamide), poly(acrylic acid), poly(ethylene glycol)methacrylate, and poly(methyl methacrylate) via “grafting-from” approach. Numerous characterizations were performed which confirm the successful grafting of polymers via PET-RAFT polymerization. The enhancement of photoluminescent efficiency towards the red region/window was observed after the grafting of polymers. The emission in the red region is marked as suitable for biological applications. Thus, indicating the potential use of the as-synthesized core@shell@shell system for various biological platforms. Interestingly, the cytocompatibility studies render the polymer functionalized UCNPs’ potential to be used in a variety of biological applications.