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NEAR-IR TWO PHOTON MICROSCOPY IMAGING OF SILICA NANOPARTICLES FUNCTIONALIZED WITH ISOLATED SENSITIZED Yb(III) CENTERS

  • Author(s): Lapadula, Giuseppe
  • Bourdolle, Adrien
  • Allouche, Florian
  • Conley, Matthew P.
  • Maron, Laurent
  • Lukens, Wayne W.
  • Guyot, Yannick
  • Andraud, Chantal
  • Brasselet, Sophie
  • Copéret, Christophe
  • Maury, Olivier
  • Andersen, Richard A.
  • et al.
Abstract

Bright nano objects emitting in the near infrared with a maximal cross section of 41.4 x 103 GM (Goppert Mayer), were prepared by implanting ca. 180 4,4 diethylaminostyryl 2,2 bipyridine (DEAS) Yb(III) complexes on the surface of 12 nm silica nanoparticles. The surface complexes ([DEAS Ln SiO2], Ln =Y,Yb) were characterized using IR, solid state NMR, UV Vis, EXAFS spectroscopies in combination with the preparation and characterization of similar molecular analogues by analytical techniques (IR, solution NMR, UV Vis, X ray crystallography) as well as DFT calculations. Starting from the partial dehydroxylation of the silica at 700 C on high vacuum having 0.8 OH.nm 2, the grafting of Ln(N(SiMe3)2)3 generate ≤SiO Ln(N(SiMe3)2)2, which upon thermal step and coordination of the DEAS chromophore yields (≤SiO)3Ln(DEAS). Surface and molecular analogues display similar properties, in terms of DEAS binding constants absorption maxima and luminescence properties (intense emission band assigned to a ligand centered CT fluorescence and life time) in the solid state, consistent with the molecular nature of the surface species. The densely functionalized nanoparticles can be dispersed via ultra-sonication in small ca. 15-20 nm aggregates (1 to 6 elementary particles) that were detected using two photon microscopy imaging at 720 nm excitation, making them promising nano objects for bio imaging.

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