Poly(phenylenevinylene) (PPV) is one of the most efficient electroluminescent conjugated polymers and has the potential to be commercialized as important components in full-color flat panel displays. Here, we report an alternative synthetic route to the commercially available PPV derivative Super Yellow PPV (SY PPV) using 2-bromo-1,4-xylylene diacetate as a novel starting material. The intermediates, monomers, and the polymer were fully characterized by nuclear magnetic resonance (NMR) and elemental analysis. The SY PPV film shows an absorption maximum at 434 nm and an absorption onset at 510 nm with an optical bandgap of ca 2.44 eV. The photoluminescent and electroluminescent maximum of SY PPV are around 516 and 552 nm, respectively. The SY PPV obtained via this new synthetic route exhibits improved electroluminescent properties, a turn on voltage of over 2.4 V, a luminance maximum exceeding 49000 cd•m -2 , and a maximum luminous efficiency (LE) of 21 cd•A -1 compared with the SY PPV prepared by the traditional route (16-18 cd•A -1 ).

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Luminescent nanospheres (EuPHS, dav=45 nm) containing 40% (w) of Eu(tta)3dpbt (tta= thenoyltrifluoroacetonato;dpbt=2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine) were prepared by encapsulating Eu(tta)3dpbt in a hybrid matrix formed in situ from poly(styrene-co-methyl methacrylate), octyltrimethoxysilane, and poly(octylsiloxane). The EuPHS are promising luminescent markers for bioanalysis because of their good dispersibility in aqueous solutions, high photostability, low cytotoxicity, and bright Eu 3+ luminescence under excitation at long wavelengths. EuPHS exhibited excellent visible light-sensitized and near-infrared two-photon-sensitized Eu 3 + luminescence properties, with a visible-light excitation peak at 415 nm and an excitation window extending up to 475 nm. The quantum yield for Eu 3 + luminescence was 0.31 (λex=415 nm, T=23 °C), and the two-photon excitation (TPE) action cross section was 5.0×10 5 GM (1 GM=10 -50 cm 4 •s•photon -1 •particle -1 ) at 830 nm. Bionanoprobes prepared 2480 FU Xiao-Yi et al.: Two-Photon-Sensitized Eu 3+ Luminescence Nanoprobes for Live Cell ImagingNo.10 by adsorbing transferrin on the surfaces of EuPHS were successfully applied in target-specific labeling and two-photon-excitation imaging of live HeLa cells.

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