Shell thickness dependence of upconversion luminescence of β-NaYF4:Yb, Er/β-NaYF4 core-shell nanocrystals.

NaYF4:Yb, Er/NaYF4 core-shell nanocrystals with different thickness shells were synthesized. The correlation between shell thickness and upconversion (UC) luminescence intensity was investigated experimentally and theoretically. We found that the UC fluorescence intensity of the core-shell nanocrystals is enhanced exponentially with shell thickness (d) in the form of (1-0.9 exp(-d/d0). For our core-shell nanocrystals, the d0 was determined as about 5.5 nm, corresponding to an enhancement of about 12 times for the 540 nm emission intensity. The d0 may be treated as the optimized shell thickness, which represents a balance between the conflict requirements of strong UC fluorescence intensity and small total crystal size for bioapplications.

[1]  Wei Li,et al.  Direct imaging the upconversion nanocrystal core/shell structure at the subnanometer level: shell thickness dependence in upconverting optical properties. , 2012, Nano letters.

[2]  Maurice C. G. Aalders,et al.  Critical Shell Thickness of Core/Shell Upconversion Luminescence Nanoplatform for FRET Application , 2011 .

[3]  Guanying Chen,et al.  Ultrasmall monodisperse NaYF(4):Yb(3+)/Tm(3+) nanocrystals with enhanced near-infrared to near-infrared upconversion photoluminescence. , 2010, ACS nano.

[4]  Zhengquan Li,et al.  Seed-mediated synthesis of NaY F4:Y b, Er/NaGdF4 nanocrystals with improved upconversion fluorescence and MR relaxivity , 2010, Nanotechnology.

[5]  Zhengquan Li,et al.  An efficient and user-friendly method for the synthesis of hexagonal-phase NaYF4:Yb, Er/Tm nanocrystals with controllable shape and upconversion fluorescence , 2008, Nanotechnology.

[6]  H. Güdel,et al.  Low-temperature upconversion spectroscopy of nanosized Y2O3:Er,Yb phosphor , 2005 .

[7]  H. Güdel,et al.  Anomalous power dependence of sensitized upconversion luminescence , 2005 .

[8]  K. Krämer,et al.  Novel materials doped with trivalent lanthanides and transition metal ions showing near-infrared to visible photon upconversion , 2005 .

[9]  F. V. van Veggel,et al.  Improvement in the luminescence properties and processability of LaF3/Ln and LaPO4/Ln nanoparticles by surface modification. , 2004, Langmuir : the ACS journal of surfaces and colloids.

[10]  Nuno Moreno,et al.  Imaging plant cells by two-photon excitation , 2004, Protoplasma.

[11]  Daisuke Matsuura,et al.  Red, green, and blue upconversion luminescence of trivalent-rare-earth ion-doped Y2O3 nanocrystals , 2002 .

[12]  Ralph H. Page,et al.  Upconversion-pumped luminescence efficiency of rare-earth-doped hosts sensitized with trivalent ytterbium , 1997 .

[13]  E. Sveshnikova,et al.  The application of luminescence-kinetic methods in the study of the formation of lanthanide ion complexes in solution , 1994 .

[14]  F. Auzel.  Upconversion and anti-Stokes processes with f and d ions in solids. , 2004, Chemical reviews.