Up-conversion FRET from Er³⁺/Yb³⁺:NaYF₄ Nanophosphor to CdSe Quantum Dots

Abstract

Förster resonance energy transfer (FRET) between nanoparticles of up-conversion lanthanide phosphor as donors and quantum dots as acceptors is demonstrated. Fluoride (NaYF4) nanocrystals (ca. 30 nm size) codoped with the Er3+ and Yb3+ ions were synthesized with a high-pressure solvothermal microwave assisted technique and dispersed in organic solvent. Up-converted luminescence from the rare-earth ions doped into fluoride nanomatrix was achieved with optical pumping in NIR (976 nm) region. The green erbium upconversion emission at 540 nm is efficiently quenched by quantum dots (QDs) leading to color change of the mixture for different relative concentrations. Simultaneously, orange emission from quantum dots appears due to energy transfer from Er3+/Yb3+:NPs donors to QDs acceptors. The concomitant decrease of the average lifetime of donor emission at 540 nm (from ∼153 to ∼130 μs) indicates that the excitation of CdSe QDs occurs not only through reabsorption but also through Förster Resonance Energy Transfer. Acceptor luminescence lifetime mimics that of the donor and reaches hundreds of microseconds. The Förster radius (R 0) was calculated to be short (∼15 Å), mostly due to low quantum yield of the multilevel emitting donor. This short-range interaction proves that in our system the FRET occurs mostly through Er3+ ions proximate to the surface, resulting in efficiency of energy transfer equal to η = 14.8%.

Fluorescent Nanocomposites

“…In addition, no acceptor can be excited directly because the excitation is in the near-IR. The FRET from up-converting phosphors to QDs (Bednarkiewicz et al 2010 ) and carbon nanoparticles ) was demonstrated. The energy transfer to small-molecular dye was used for diagnostics directly in serum (Kuningas et al 2006 ).…”

Materials for FRET Analysis: Beyond Traditional Dye–Dye Combinations

“…However, fully exploiting the UC properties is more common and UCNPs have a wide range of applications, including display devices, solar cells, optoelectronics, lasers, catalysis, and biolabeling, such as bioassays, imaging, and therapy, which have been the topic of recent reviews [374,377,380,385,386,391,392]. In most cases the UCNPs donors are coupled with the traditional organic fluorophore acceptors, although there have been reports of UCNPs coupling with QD [393] or Au NP [394] acceptor NMs. LRET-based in vitro sensors using UCNPs have been successfully developed for small molecules, such as ammonia [395] and glucose [394], nucleic acid hybridization [396], and protein detection, such as caspase-3 [397] and avidin [392].…”

Photonen aufkonvertierende Nanopartikel zur optischen Codierung und zum Multiplexing von Zellen, Biomolekülen und Mikrosphären

“…[211][212][213] Für diese Art von Assay ist es notwendig, dass die Emissionsintensität der UCNPs ausschließlich durch den Analyten verändert wird. Dies wird meistens durch LRET erreicht, wobei die UCNPs als Donor und ein organischer Farbstoff, [214] Goldnanopartikel, [149,215,216] Quantenpunkt, [217] Kohlenstoffnanopartikel, [218,219] Graphenoxid, [220] Mangandioxid [221] oder Phycobiliprotein [222] als Akzeptor wirken. Goldnanopartikel haben sich als die effizientesten Akzeptoren für UCNPs herausgestellt (Abbildung 10), doch ihr großer Durchmesser (gegenüber denen organischer Farbstoffe) kann zur sterischen Hinderung während der Analyterkennung führen.…”