International Journal of Physics | Vol. 3, No. 2, February 2012 | pp. 10–18
DOI: 10.46882/2012/IJP/000026
Article Type: Original Research Paper
Title: Synthesis and Upconversion Luminescence Enhancement of Erbium-Ytterbium Co-Doped Sodium Yttrium Fluoride Core-Shell Nanoparticles
Names of Authors: P. C. Nwosu¹, L. E. Martinez²
Authors’ Affiliations: ¹Department of Physics, University of Port Harcourt, Port Harcourt, Nigeria; ²Department of Chemistry and Materials Science, Autonomous University of Madrid, Madrid, Spain
Abstract: Lanthanide-doped upconversion nanoparticles are highly attractive for deep-tissue biological imaging and solar cell efficiency enhancement because they convert near-infrared excitation into visible light emissions. This study describes a hydrothermal synthesis route for creating highly crystalline core-shell sodium yttrium fluoride (NaYF₄) nanoparticles co-doped with trivalent erbium (Er³⁺) and ytterbium (Yb³⁺) ions. To suppress surface quenching channels, an undoped passive NaYF₄ shell layer was grew epitaxially over the active core structures. The core size and shell thickness were verified using transmission electron microscopy (TEM), which revealed uniform spherical particles with an average core diameter of 22 nm and a shell thickness of 4.5 nm. Under continuous-wave laser excitation at 980 nm, the core-shell architecture demonstrated a 35-fold enhancement in upconversion luminescence intensity compared to bare core structures. The emission spectrum exhibited strong green peaks at 525 nm and 542 nm, alongside a red peak at 660 nm, corresponding to the radiative transitions of the Er³⁺ ion. Power-dependent luminescence measurements confirmed a two-photon upconversion mechanism driving both emissions. These findings outline a method for producing bright fluorescent probes suitable for targeted bio-imaging applications.
Keywords: Upconversion nanoparticles; Hydrothermal synthesis; Core-shell structures; Luminescence enhancement; Lanthanide ions; Surface quenching; Two-photon mechanism; Biological imaging.
Manuscript Timeline: Received: November 12, 2011; Revised: December 22, 2011; Accepted: January 14, 2012; Published: February 07, 2012.
Citation: Nwosu, P. C., & Martinez, L. E. (2012). Synthesis and Upconversion Luminescence Enhancement of Erbium-Ytterbium Co-Doped Sodium Yttrium Fluoride Core-Shell Nanoparticles. International Journal of Physics, 3(2), 10–18.
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