Radioluminescent Photonic Bandgap Hydrogels: Mechanochromic Tunable Emissions

Abstract

Fully organic, radioluminescent crystalline colloidal arrays (CCAs) with covalently incorporated emitters were synthesized by using up to three organic fluorophores that were Förster resonance energy transfer (FRET) pairs with each other. The emitters were covalently incorporated into monodisperse poly­(styrene-co-propargyl acrylate) nanoparticles in various combinations, resulting in blue-, green-, and red-emitting CCAs when excited with an X-ray source. The negatively charged surfaces of the monodisperse nanoparticles caused self-assembly into a crystal-like structure, which resulted in a partial photonic bandgap (i.e., rejection wavelength) within the near-visible and visible light spectrum. When the rejection wavelength of the CCA overlapped its radioluminescence, the spontaneous emission was inhibited and the emission intensity decreased. A poly­(ethylene glycol) methacrylate-based hydrogel network was used to encapsulate the CCAs and stabilize their crystal-like structure. Within the hydrogel, coupling the photonic bandgap with the radioluminescence of the CCA films led to robust optical systems with tunable emissions. These fully organic, hydrogel-stabilized, radioluminescent CCAs possess mechanochromic tunable optical characteristics with future applications as potentially less toxic X-ray bioimaging materials.

Organic Near‐Infrared‐Emitting Nanoparticles for X‐Ray Bioimaging: A Nontoxic Alternative Harnessing Förster Resonance Energy Transfer‐Based Sequential Energy Transfer

“…Nanoparticle Preparation (P R ): Monodisperse, radioluminescent nanoparticles with three copolymerized dyes (Anth, Napth, and RhB) were prepared using a modified emulsion polymerization procedure. [44,46,47] Briefly, styrene, propargyl acrylate, and divinylbenzene were passed over alumina basic to remove inhibitors prior to use. Initially, 50 mL of deionized water was added to the round bottom flask along with 0.32 mL (2.9 mmol) propargyl acrylate and 3.68 mL of a 0.3 w w À1 % solution of AMMA/NMMA/RMMA in styrene (32.1 mmol styrene, 36.2 μmol AMMA, 25.5 μmol NMMA, and 18.0 μmol RMMA).…”

“…The Anth, Naphth, and RhB methyl methacrylate derivatives (AMMA, NMMA, and RMMA, respectively) were synthesized using previously described methods. [ 44 ] Additionally, the azSiPc [ 45 ] and azICG [ 27 ] were also synthesized according to previously described methods.…”