Title: Fabrication and upconversion emission processes in nanoluminophores NaYF₄: Er, Yb and NaYF₄: Tm, Yb

Authors: Lam Thi Kieu Giang; Tran Kim Anh; Nguyen Thanh Binh; Le Quoc Minh; Lukasz Marciniak; Witold Łojkowski

Addresses: Insitute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi, Vietnam ' Insitute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi, Vietnam ' Insitute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi, Vietnam ' Insitute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi, Vietnam ' Department of Excited States Spectroscopy, Institute of Low Temperature and Structure Research, Polish Academy of Sciences ul. Okolna 2, 50-422 Wroclaw, Poland ' Laboratory of Nanostructures, Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw, Poland

Abstract: In this paper we present the new results of fabrication, characterisation and upconversion emission process of NaYF₄ nanoparticles doped with Er³⁺ or Tm³⁺and Yb³⁺ as sensitiser. In order to fabricate α-, β-NaYF₄:2%Er³⁺, 19%Yb³⁺and α-, β-NaYF₄:2%Tm³⁺, 19%Yb³⁺ nanoparticles the soft template method in isopropylamine at 140C and diethylene glycol (DEG) at 180C has been used. The morphology, structures and emission properties were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and luminescence spectroscopy. The upconversion luminescence (UCL) spectra of α and β crystalline forms of NaYF₄:2%Er³⁺, 19%Yb³⁺and NaYF₄:2%Tm³⁺, 19%Yb³⁺ nanoparticles were investigated upon diode laser excitation at 976 nm. The strong emissions in the green and red spectral regions were observed upon this excitation. The spectral lines of the UCL could be assigned to the upconversion radiative transitions of the Er³⁺ or Tm³⁺ ions with Yb³⁺ sensitiser. The upconversion emission spectra dependent on laser excitation powers have been investigated in order to elucidate the upconversion emission paths which could take place. We found the significant influence of the type of nanocrystalline structure on the upconverting radiative transition mechanisms in NaYF₄:2%Er³⁺, 19%Yb³⁺and NaYF₄:2%Tm³⁺, 19%Yb³⁺ nanoparticles.

Keywords: nanoparticles; NaYF4; ytterbium; erbium; thulium; sodium yttrium fluoride; Er3+; Yb3+; Tm3+; multiphoton upconversion; soft template; upconversion luminescence; UCL nanomaterials; rare earth elements; nanotechnology; morphology; structure; emission properties.

DOI: 10.1504/IJNT.2015.067911

International Journal of Nanotechnology, 2015 Vol.12 No.5/6/7, pp.538 - 547

Published online: 08 Mar 2015 *

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