Synthesis of Hexagonal Yb³⁺,Er³⁺‐Doped NaYF₄ Nanocrystals at Low Temperature

Abstract

Nanocrystals of NaYF4 doped with Yb3+ and Er3+ are synthesized in oleylamine using Y2(CO3)3, Yb2(CO3)3, Er2(CO3)3, Na2CO3, and NH4F as precursors. In contrast to other starting materials normally used for such syntheses, these precursors react even at room temperature to form hexagonal‐phase (β‐phase) NaYF4:Er,Yb nanoparticles. Cubic‐phase (α‐phase) NaYF4:Yb,Er particles are formed only at elevated temperatures (>250 °C). The formation of the cubic phase at high temperatures can be suppressed by replacing pure oleylamine with oleic acid/oleylamine mixtures. Under optimized reaction conditions, particles with an average particle size of about 7 nm are generated in 84% yield. Heat treatment (30 min, 280 °C) of the particles significantly increases the luminescence efficiency. A transparent solution of the heat‐treated, nanometer‐sized phosphor in toluene shows intense visible light emission upon excitation in the near infrared.

Nanopartikel für die Aufwärtskonversion

“…Im Unterschied dazu entsteht bei der einfachen Festkörperreaktion von NH 4 F, Na 2 CO 3 und Seltenerdcarbonaten die nanokristalline b-Phase von NaYF 4 schon bei Raumtemperatur. [228] …”

“…[59,69,175,214,228,259,411,416] [59,214,259,411] Die ermittelten Intensitätsverhältnisse zwischen Referenz und nanopartikulären UC-Leuchtstoffproben zeigen eine starke Abhängigkeit von der Laserleistung, dem Zustand und der Größe der Nanopartikel und bewegen sich im Bereich von 100 bis 150 000. [59,214,259,411] -Nanopartikeln bestimmt; abhängig von der Partikelgröße wurden Werte von 0.005 bis 0.3 ermittelt.…”

Magnetic-luminescent YbPO4:Er,Dy microspheres designed for tumor theranostics with synergistic effect of photodynamic therapy and chemotherapy

“…Moreover, they are superior to downconversion materials in that they: have deeper light penetration depth without tissue autofluorescence; have an absence of photobleaching and photoblinking; and cause less harm to biological specimens. [3][4][5]7 The reported matrix material examples include NaYF 4 nanocrystals, [8][9][10] zinc sulfide nanoparticles, 11 zinc oxide nanoparticles, 12,13 lanthanide oxides, 14,15 and so on. Phosphate compounds are also an appropriate matrix for RE ions because they are stable at high temperatures and hence can overcome the drawbacks of poor thermal stability and mechanical properties of other RE compounds.…”

Effect of Er3+ Concentration on Upconversion in Hexagonal-Phase NaYF4:Er3+ Nanocrystals

“…The NaYF 4 :Er 3+ NCs were synthesized in oleic acid (OA) and 1-octadecene (ODE) with Y 2 (CO 3 ) 3 ·xH 2 O, Er 2 (CO 3 ) 3 ·xH 2 O, Na 2 CO 3 and NH 4 F as precursors [3]. During the reaction process, small NaYF 4 :Er 3+ crystal nucleation was progressed at low temperature and the discharged gas was mainly ammonia.…”