Synthesis and Research of Rare Earth Nanocrystal Luminescent Properties for Security Labels Using the Electrohydrodynamic Printing Technique

Chinh Dung Trinh,Phuong Hau Thi Pham,Dung My Thi Dang,Thuan Van Doan,Chien Mau Dang,Pham Van Quan

doi:10.3390/pr8020253

Abstract

YVO4:Eu3+ nanoparticles were successfully synthesized by two methods, namely the sonochemical method and hydrothermal method. The X-ray diffraction (XRD) patterns showed the tetragonal phase of YVO4 (JCPDS 17-0341) was indexed in the diffraction peaks of all samples. The samples synthesized by the sonochemical method had a highly crystalline structure (X-ray diffraction results) and luminescence intensity (photoluminescence results) than those synthesized by the hydrothermal method. According to the results of field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM), the average size of YVO4:Eu3+ nanoparticles was around 25–30 nm for the sonochemical method and 15–20 nm for the hydrothermal method. YVO4:Eu3+ nanoparticles in the case of the sonochemical method had a better crystalline structure and stronger emissivity at 618 nm. The Eu3+ ions’ average lifetime in YVO4:Eu3+ at 618 nm emission under 275 nm excitation were at 0.955 ms for the sonochemical method and 0.723 ms for the hydrothermal method. The security ink for inkjet devices contained YVO4:Eu3+ nanoparticles, the binding agent as polyethylene oxide or ethyl cellulose and other necessary solvents. The device used for security label printing was an inkjet printer with an electrohydrodynamic printing technique (EHD). In the 3D optical profilometer results, the width of the printed line was ~97–167 µm and the thickness at ~9.1–9.6 µm. The printed security label obtained a well-marked shape, with a size at 1.98 × 1.98 mm.

Highlights

Researchers have paid attention to an inkjet technique in order to produce spare parts, such as electric circuits and bio-sensors [1,2,3,4]
The purpose of this study is to provide a synthesis of strong luminescent intensity YVO4 :Eu3+
The YVO4 :Eu3+ nanoparticles size synthesized by two methods is suitable for the preparation of security ink

Summary

Introduction

Researchers have paid attention to an inkjet technique in order to produce spare parts, such as electric circuits and bio-sensors [1,2,3,4]. This technique possesses the advantages of reducing steps in preparation and the printing ability in many different substrates, such as conductive, non-conductive, solid or flexible substrates. In 2012, Meruga et al [5] researched security ink from rare earth nanoparticles using β-NaYF4 -doped Yb3+ /Er3+ and Yb3+ /Tm3+ in order to print a security QR code on a paper substrate and PET by Optomec direct-write aerosol jetting.

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Results

Conclusion