Size dependence of the upconverted luminescence of NaYF4:Er,Yb microspheres for use in ratiometric thermometry.

The size-dependent temperature sensitivity is observed on the upconversion luminescence of NaYF4:Er,Yb microspheres with sizes between 0.7 and 2 μm that are prepared by a poly(acrylic acid)-assisted hydrothermal process. It is found that the fluorescence intensity ratio (FIR) of their green upconversion emissions (with peaks at 521 and 539 nm) is strongly size-dependent at temperatures between 223 and 403 K. As the size of the spheres increases from 0.7 to 1.6 μm, the maximum sensitivity decreases from 36.8 × 10(-4) to 24.7 × 10(-4) K(-1). This effect is mainly attributed to the larger specific surface area of the smaller spheres where a relatively large number of Er(III) ions are located at the surface. This results in an increase in the efficiency of the (4)S3/2 → (2)H11/2 population process of the Er(III) ions due to stronger electron-phonon interactions with increasing T. Heating of the spheres by NIR light is also supposed to cause enhanced electron-phonon interactions in such particles.

[1]  Jun Lin,et al.  Up-conversion cell imaging and pH-induced thermally controlled drug release from NaYF4/Yb3+/Er3+@hydrogel core-shell hybrid microspheres. , 2012, ACS nano.

[2]  L. Carlos,et al.  Lanthanide-based luminescent molecular thermometers , 2011 .

[3]  V V Moshchalkov,et al.  Optical nanoheater based on the Yb3+-Er3+ co-doped nanoparticles. , 2009, Optics express.

[4]  Hans H Gorris,et al.  Photon-upconverting nanoparticles for optical encoding and multiplexing of cells, biomolecules, and microspheres. , 2013, Angewandte Chemie.

[5]  Yangyang He,et al.  Temperature Sensing and In Vivo Imaging by Molybdenum Sensitized Visible Upconversion Luminescence of Rare‐Earth Oxides , 2012, Advanced materials.

[6]  Jing Wang,et al.  Multifunctional Au@mSiO2/rhodamine B isothiocyanate nanocomposites: cell imaging, photocontrolled drug release, and photothermal therapy for cancer cells. , 2013, Small.

[7]  Francisco Sanz-Rodríguez,et al.  Temperature sensing using fluorescent nanothermometers. , 2010, ACS nano.

[8]  Hans H. Gorris,et al.  Photon upconverting nanoparticles for luminescent sensing of temperature. , 2012, Nanoscale.

[9]  Marco Pedroni,et al.  NIR-to-NIR two-photon excited CaF2:Tm3+,Yb3+ nanoparticles: multifunctional nanoprobes for highly penetrating fluorescence bio-imaging. , 2011, ACS nano.

[10]  S. Wade,et al.  Fluorescence intensity ratio technique for optical fiber point temperature sensing , 2003 .

[11]  Gilles Tessier,et al.  Back side thermal imaging of integrated circuits at high spatial resolution , 2007 .

[12]  T. Le Saux,et al.  Fluorescent thermometers for dual-emission-wavelength measurements: molecular engineering and application to thermal imaging in a microsystem. , 2009, Analytical chemistry.

[13]  Bin Dong,et al.  Optical thermometry through infrared excited green upconversion emissions in Er3+–Yb3+ codoped Al2O3 , 2007 .

[14]  Glauco S. Maciel,et al.  Er3+-doped BaTiO3 nanocrystals for thermometry: Influence of nanoenvironment on the sensitivity of a fluorescence based temperature sensor , 2004 .

[15]  O. Wolfbeis,et al.  Luminescent probes and sensors for temperature. , 2013, Chemical Society reviews.

[16]  V. K. Rai.  Temperature sensors and optical sensors , 2007 .

[17]  S. N. Baker,et al.  Noncontact two-color luminescence thermometry based on intramolecular luminophore cyclization within an ionic liquid. , 2003, Chemical communications.

[18]  O. Wolfbeis,et al.  Ratiometric fluorescent nanoparticles for sensing temperature , 2010 .

[19]  Otto S. Wolfbeis,et al.  Luminescent Europium(III) Nanoparticles for Sensing and Imaging of Temperature in the Physiological Range , 2010, Advanced materials.

[20]  Gregory S Harms,et al.  Upconverting nanoparticles for nanoscale thermometry. , 2011, Angewandte Chemie.

[21]  Louis A. Cuccia,et al.  Controlled Synthesis and Water Dispersibility of Hexagonal Phase NaGdF4:Ho3+/Yb3+ Nanoparticles , 2009 .

[22]  Guanying Chen,et al.  Sensing Using Rare-Earth-Doped Upconversion Nanoparticles , 2013, Theranostics.

[23]  Wing-Cheung Law,et al.  Core/shell NaGdF4:Nd(3+)/NaGdF4 nanocrystals with efficient near-infrared to near-infrared downconversion photoluminescence for bioimaging applications. , 2012, ACS nano.

[24]  Hong Zhang,et al.  Effect of annealing on upconversion luminescence of ZnO : Er3+ nanocrystals and high thermal sensitivity , 2007 .

[25]  Zhuang Liu,et al.  Upconversion nanophosphors for small-animal imaging. , 2012, Chemical Society reviews.