Anomalous power dependence of sensitized upconversion luminescence

Suyver, J.F.; Aebischer, Annina; Garcı́a-Revilla, Sara; Gerner, Pascal; Güdel, Hans U.

doi:10.1103/physrevb.71.125123

Cited by 403 publications

(350 citation statements)

References 19 publications

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“…This deviation is usually observed in the case of the Yb 3þ , Er 3þ couple and can be ascribed to the presence of competing decay channels, depleting the intermediate Er 3þ -state populated after the absorption of the first photon. [38] At high excitation densities the slope of the curves is reduced further due to saturation of the upconversion process as was investigated in detail by Gü del and coworkers [56] The offset between lines A and C or lines B and D in Figure 8 clearly shows that the surface-treatment increases the upconversion efficiency by a factor of approximately 25. Unfortunately, no reference upconversion material is available that can be homogeneously dispersed in a solvent.…”

Section: Resultsmentioning

confidence: 62%

Synthesis and Optical Properties of KYF₄/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF₄

Schäfer

Ptáček

Zerzouf

et al. 2008

Adv Funct Materials

214

129

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KYF4/Yb3+, Er3+ nanocrystals with a mean diameter of approximately 13 nm were synthesized at 200 °C in the high boiling organic solvent N‐(2‐hydroxyethyl)ethylenediamine (HEEDA). The particles crystallize in the cubic phase known from α‐NaYF4 and form transparent colloidal solutions in tetraethylene glycol (TEG) or propanol. Solutions containing 1 wt % of the nanocrystals in TEG display visible upconversion emission upon continuous wave (CW) excitation at 978 nm. Growing undoped KYF4 on the surface of the KYF4/Yb3+, Er3+ nanocrystals increases the upconversion efficiency by more than a factor of 20. The XRD data of these particles, display a slight increase in the mean particle size from 13 to 15.5 nm, indicating that only a part of the subsequently added KYF4 shell material is deposited onto the particle surface. Nevertheless the performed surface modification obviously leads to core/shell structured particles.

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Section: Resultsmentioning

confidence: 62%

Synthesis and Optical Properties of KYF₄/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF₄

Schäfer

Ptáček

Zerzouf

et al. 2008

Adv Funct Materials

214

129

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“…These double logarithmic plots of the visible upconversion emission intensity versus the power density of the 980 nm excitation confirm that both the 551 and 668 nm emissions involve two-photon upconversion processes. At high excitation densities the slope of the curves is reduced due to upconversion process saturation [31]. However, for the NIR (831 nm) emission of the PAA-coated nanoparticles, the slope of the plot is 2.71, which indicates that the upconversion emission is a three-photon process.…”

Section: Upconversion Luminescence Mechanism Of the Nanocrystalsmentioning

confidence: 92%

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

2010

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This paper describes the synthesis of new upconverting luminescent nanoparticles that consist of YF 3 :Yb 3+ /Er 3+ functionalized with poly(acrylic acid) (PAA). Unlike the upconverting nanocrystals previously reported in the literature that emit visible (blue-green-red) upconversion fluorescence, these as-prepared nanoparticles emit strong near-infrared (NIR, 831 nm) upconversion luminescence under 980 nm excitation. Scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction were used to characterize the size and composition of the luminescent nanocrystals. Their average diameter was about 50 nm. The presence of the PAA coating was confirmed by infrared spectroscopy. The particles are highly dispersible in aqueous solution due to the presence of carboxylate groups in the PAA coating. By carrying out the synthesis in the absence of PAA, YF 3 :Yb 3+ /Er 3+ nanorice materials were obtained. These nanorice particles are larger (~700 nm in length) than the PAA-functionalized nanoparticles and show strong typical visible red (668 nm), rather than NIR (831 nm), upconversion fluorescence. The new PAA-coated luminescent nanoparticles have the pottential be used in a variety of bioanalytical and medical assays involving luminescence detection and fluorescence imaging, especially in vivo fluorescence imaging, due to the deep penetration of NIR radiation.

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“…[ 31,36,37 ] Theoretically, the emission intensity of traditional photoluminescent materials such as quantum dots, dyes, and lanthanide-based phosphors satisfi es the linear relationship with the square of the electric fi eld intensity ( |E| 2 ), while the UCL intensity is proportional to the 2 n -th power of the electric fi eld intensity ( |E| 2 n for a n-photon UC process). [ 38,39 ] So it is expected that more signifi cant enhancement induced by plasmonic modulation can be obtained in UCNPs, especially for those high-order multi-photon UCL processes. In previous literatures, various gold or silver nanostructures have been utilized to amplify the UCL signals of the well-known NaYF 4 : Yb 3+ , Tm 3+ (Er 3+ ) UCNPs, and the enhancement factor of the overall UCL strength usually varies from several to several ten times, which is much lower than the theoretical prediction.…”

Section: Introductionmentioning

confidence: 99%

Large Upconversion Enhancement in the “Islands” Au–Ag Alloy/NaYF₄: Yb³⁺, Tm³⁺/Er³⁺ Composite Films, and Fingerprint Identification

Chen

Zhang

et al. 2015

Adv Funct Materials

143

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The surface plasmon (SP) modulation is a promised way to highly improve the strength of upconversion luminescence (UCL) and expand its applications. In this work, the "islands" Au-Ag alloy fi lm is prepared by an organic removal template method and explored to improve the UCL of NaYF 4 : Yb3+, Tm 3+ /Er 3+ . After the optimization of Au-Ag molar ratio (Au 1.25 -Ag 0.625 ) and the size of NaYF 4 nanoparticles (NPs, ≈7 nm), an optimum enhancement as high as 180 folds is obtained (by refl ection measurement) for the overall UCL intensity of Tm 3+ . Systematic studies indicate that the UCL enhancement factor (EF) increases with the increased size of metal NPs and the increase of diffuse refl ection, with the decreased size of NaYF 4 NPs, with the decreased power density of excitation light and with improving order of multiphoton populating. The total decay rate varies only ranging of about 20% while EF changes signifi cantly. All the facts above indicate that the UCL enhancement mainly originates from coupling of SP with the excitation electromagnetic fi eld. Furthermore, the fi ngerprint identification based on SP-enhanced UCL is realized in the metal/UC system, which provides a novel insight for the application of the metal/UC device.

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Anomalous power dependence of sensitized upconversion luminescence

Cited by 403 publications

References 19 publications

Synthesis and Optical Properties of KYF₄/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF₄

Synthesis and Optical Properties of KYF₄/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF₄

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

Large Upconversion Enhancement in the “Islands” Au–Ag Alloy/NaYF₄: Yb³⁺, Tm³⁺/Er³⁺ Composite Films, and Fingerprint Identification

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Anomalous power dependence of sensitized upconversion luminescence

Cited by 403 publications

References 19 publications

Synthesis and Optical Properties of KYF4/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF4

Synthesis and Optical Properties of KYF4/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF4

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

Large Upconversion Enhancement in the “Islands” Au–Ag Alloy/NaYF4: Yb3+, Tm3+/Er3+ Composite Films, and Fingerprint Identification

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Synthesis and Optical Properties of KYF₄/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF₄

Synthesis and Optical Properties of KYF₄/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF₄

Large Upconversion Enhancement in the “Islands” Au–Ag Alloy/NaYF₄: Yb³⁺, Tm³⁺/Er³⁺ Composite Films, and Fingerprint Identification