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Silica‐Coated Ln 3+ ‐Doped LaF 3 Nanoparticles as Robust Down‐ and Upconverting Biolabels
Author(s) -
Sivakumar Sri,
Diamente Peter R.,
van Veggel Frank C. J. M.
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600224
Subject(s) - bioconjugation , photon upconversion , materials science , nanoparticle , photoluminescence , analytical chemistry (journal) , ion , luminescence , nanotechnology , chemistry , optoelectronics , organic chemistry
The preparation of nearly monodisperse (40 nm), silica‐coated LaF 3 :Ln 3+ nanoparticles and their bioconjugation to FITC–avidin (FITC=fluorescein isothiocyanate) is described in this report. Doping of the LaF 3 core with selected luminescent Ln 3+ ions allows the particles to display a range of emission lines from the visible to the near‐infrared region ( λ =450–1650 nm). First, the use of Tb 3+ and Eu 3+ ions resulted in green ( λ =541 nm) and red ( λ =591 and 612 nm) emissions, respectively, by energy downconversion processes. Second, the use of Nd 3+ gave emission lines at λ =870, 1070 and 1350 nm and Er 3+ gave an emission line at λ =1540 nm by energy downconversion processes. Additionally, the Er 3+ ions gave green and red emissions and Tm 3+ ions gave an emission at λ =800 nm by upconversion processes when codoped with Yb 3+ ( λ ex =980 nm). Bioconjugation of avidin, which has a bound fluorophore (FITC) as the reporter, was carried out by means of surface modification of the silica particles with 3‐aminopropyltrimethoxysilane, followed by reaction with the biotin– N ‐hydroxysuccinimide activated ester to form an amide bond, imparting biological activity to the particles. A 25‐fold or better increase in the FITC signal relative to the non‐biotinylated silica particles indicated that there is minimal nonspecific binding of FITC–avidin to the silica particles.