Silica‐Coated Ln³⁺‐Doped LaF₃ Nanoparticles as Robust Down‐ and Upconverting Biolabels

Abstract

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 (lambda=450-1650 nm). First, the use of Tb(3+) and Eu(3+) ions resulted in green (lambda=541 nm) and red (lambda=591 and 612 nm) emissions, respectively, by energy downconversion processes. Second, the use of Nd(3+) gave emission lines at lambda=870, 1070 and 1350 nm and Er(3+) gave an emission line at lambda=1540 nm by energy downconversion processes. Additionally, the Er(3+) ions gave green and red emissions and Tm(3+) ions gave an emission at lambda=800 nm by upconversion processes when codoped with Yb(3+) (lambda(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.

One-pot synthesis and strong near-infrared upconversion luminescence of poly(acrylic acid)-functionalized YF3:Yb3+/Er3+ nanocrystals

“…During the past decades, magnetic nanoparticles [1,2], noble metal nanocrystals [3], quantum dots (QDs) [4][5][6][7], and other kinds of luminescent nanomaterials [8][9][10] have been successfully prepared and widely used in the biological and medical fields. Due to their novel optical properties, QDs are preferable to organic dyes for biotagging applications.…”

“…Photon upconversion is an alternative process for the generation of visible emission (blue-green-red) by near-infrared (NIR) excitation. It is based on sequential photon absorption and energy transfer steps involving real metastable excited states of the chromophore [8,[18][19][20][21][22]. The unique luminescence properties of lanthanide ions incorporated in fluoride matrices have long been recognized and attracted great attention.…”

“…The unique luminescence properties of lanthanide ions incorporated in fluoride matrices have long been recognized and attracted great attention. Recent studies suggest that lanthanide fluorides, including YF 3 , LaF 3 , NaLaF 4 , NaGaF 4 , and NaYF 4 nanocrystals are useful upconversion matrices [8,16,19,20,23,24]. After doping with Yb 3+ /Er 3+ or Yb 3+ /Tm 3+ ion-pairs, the resulting nanocrystals possess novel visible upconversion fluorescence.…”

Luminescent and hydrophilic LaF3–polymer nanocomposite for DNA detection

“…Therefore, it is still challenging chemists to find more efficient probes. Among these luminescent biomaterials, luminescent lanthanide ion-doped nanocrystals have become attractive due to their unique luminescence properties, such as high quantum yields, low photobleaching, narrow emission bands and especially longer luminiscent lifetimes (μs-ms range), allowing for gated time-resolved fluorescence (15)(16)(17)(18)(19)(20)(21)(22)(23). Hence, lanthanide ion-doped nanocrystals are promising as alternative materials for biolabels.…”

Improvement of dispersion stability and characterization of upconversion nanophosphors covalently modified with PEG as a fluorescence bioimaging probe

“…Recently, upconverting (UC) phosphors (UCPs) have been used for bioimaging [7][8][9][10]. UC phosphors are ceramic materials in which rare earth ions are embedded in an inorganic host.…”