Fabrication of Photoswitchable and Thermotunable Multicolor Fluorescent Hybrid Silica Nanoparticles Coated with Dye-Labeled Poly(N-isopropylacrylamide) Brushes

• DOI: 10.1021/cm901072g
• Publication Date: 2009-07-29T13:03:32Z
• Authors: Tao Wu; Gang Zou; Jinming Hu; Shiyong Liu
• Keywords: Spiropyran; Merocyanine; Atom-transfer radical-polymerization; Poly(N-isopropylacrylamide)

We report on the fabrication of hybrid silica nanoparticles densely grafted with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) brushes inner and outer layers selectively labeled fluorescence resonance energy transfer (FRET) donors, 4-(2-acryloyloxyethylamino)-7-nitro-2,1,3-benzoxadiazole (NBDAE), photoswitchable acceptors, 1′-(2-methacryloxyethyl)-3′,3′-dimethyl-6-nitro-spiro(2H-1-benzo-pyran-2,2′-indoline) (SPMA), respectively, via surface-initiated sequential atom radical polymerization (ATRP). P(NIPAM-co-NBDAE)-b-P(NIPAM-co-SPMA) at surface core exhibit collapse in broad temperature range 20−37 °C. UV irradiation aqueous dispersion induces transformation SPMA moieties layer polymer from nonfluorescent spiropyran (SP) form to fluorescent merocyanine (MC) form, leading occurrence FRET process between NBDAE residues. Most importantly, efficiency can be facilely tuned thermo-induced collapse/swelling by changing relative distance donor acceptor species located within brushes, respectively. Thus, coated serve as a sensitive ratiometric thermometer. On other hand, when nanoparticle was irradiated visible light again after irradiation, MC reverts back SP turn-off process. Overall, this novel type is capable emitting multicolor fluorescence, which light, temperatures or proper combination these factors.