Title: Synthesis and properties of Y₂O₃:Eu³⁺ nanoflakes for security labels application using inkjet ink with electrohydrodynamic printing technique

Authors: Dung Chinh Trinh; Hieu Thi Pham; Phuong Hau Thi Pham; Dung My Thi Dang; Chien Mau Dang

Addresses: Institute for Nanotechnology, Vietnam National University, Ho Chi Minh City, 700000, Vietnam; The University of Science, Vietnam National University, Ho Chi Minh City, 700000, Vietnam ' The University of Science, Vietnam National University, Ho Chi Minh City, 700000, Vietnam ' Institute for Nanotechnology, Vietnam National University, Ho Chi Minh City, 700000, Vietnam ' Institute for Nanotechnology, Vietnam National University, Ho Chi Minh City, 700000, Vietnam ' Institute for Nanotechnology, Vietnam National University, Ho Chi Minh City, 700000, Vietnam

Abstract: Y₂O₃:Eu³⁺ nanoflakes are successfully synthesised by hydrothermal method with trisodium citrate as surfactant. The doping ratio of Eu³⁺ ion affects the luminescent intensity of the product. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and Raman spectroscopy are used for the characterisation of size, structure and morphology of the samples prepared at different conditions. The corresponding patterns of Y₂O₃:Eu³⁺ nanoflakes can be indexed to the cubic phase of Y₂O₃ (JCPDS 43-1036). The flake morphology of Y₂O₃:Eu³⁺ attains 98% when the molar ratio of citrate/yttrium is 0.6. Y₂O₃:Eu³⁺ nanoflakes have well-organised flake morphology with the average width around ~90-100 nm and the thickness around ~20 nm. The Y₂O₃:Eu³⁺ nanoflakes synthesised with 5-h reaction time are flower-like nanocrystals composed of numerous contorted nanoflakes linked together by edge-to-surface. The photoluminescence results show the strongest emissivity at wavelength of 618 nm due to ⁵D₀→⁷F₂ transition and the sample synthesised at 5-h hydrothermal reaction time has the best luminescent intensity. The crystallinity level, luminescent intensity and size of nanoparticles are elevated under annealing process. The ink for inkjet, containing synthesised Y₂O₃:Eu³⁺ nanoflakes, disperses in ethyl cellulose and other necessary solvents. The experimental security labels are printed by inkjet which uses electrohydrodynamic printing technique. The lines printed by inkjet device are solid and even, with the width at 138-170 µm in PET substrate and the smallest distance of two adjacent lines at 300 µm. The experiment security labels are nearly invisible under daylight and red under UV mercury lamps with wavelength of around 254 nm.

Keywords: luminescent material; nanoparticles; Y₂O₃:Eu³⁺; security label.

DOI: 10.1504/IJNT.2018.099933

International Journal of Nanotechnology, 2018 Vol.15 No.11/12, pp.936 - 951

Published online: 28 May 2019 *

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