Large-scale synthesis and screen printing of upconversion hexagonal-phase NaYF₄:Yb³⁺,Tm³⁺/Er³⁺/Eu³⁺ plates for security applications

Abstract

β-NaYF 4 UCMPs are large-scale synthesized, and the UCMPs fluorescence inks-based screen printing patterns are applied for anti-counterfeit application.Abstract: Upconversion materials could be applied for anti-counterfeit fields because of their high concealment and high upconversion fluorescence efficiency. Herein, the different lanthanide ions-doped β-NaYF 4 upconversion micro-particles (UCMPs) with uniform hexagonal morphology were large-scale synthesized (more than 0.5 g) through a facile hydrothermal method. It is very interesting to find out the fluorescence intensity and the eventual morphology of UCMPs are highly dependent on the reaction conditions. Then, the optimal UCMPs with uniform morphology and strong fluorescence intensity were selected as promising candidate for preparing ink.Eventually, we successfully printed designable and multicolor fluorescent patterns on flexible substrates (common paper and polyethylene terephthalate, PET) by using the as-prepared β-NaYF 4 : Yb 3+ , Tm 3+ /Er 3+ /Eu 3+ UCMPs inks. Under ambient conditions, the printed patterns on conventional paper are invisible, while such printed patterns on PET are white color. But all the patterns could perform blue, yellow-green and green fluorescence patterns under the irradiation of 980 nm lasers, respectively, when using β-NaYF 4 : Yb 3+ , Tm 3+ /Er 3+ /Eu 3+ UCMPs inks. We envision that the UCMPs fluorescent inks-based flexible and rapid screen printing patterns have an enormous potential for anti-counterfeit and security applications.

A Novel Approach to Synthesise a Dual‐Mode Luminescent Composite Pigment for Uncloneable High‐Security Codes to Combat Counterfeiting

“…The nanorods of Gd 2− x −y Yb x Er y O 3 (0≤ x ≤0.3; 0≤ y ≤0.1) were synthesised by using a customised hydrothermal method . Gd 2 O 3 , YbCl 3 and ErCl 3 were taken as starting materials.…”

“…Initially, 200 mg of dual mode luminescent composite pigment was dispersed in 50 mL PVC gold medium by vigorous stirring with a glass rod and then mixed ultrasonically at 45 kHz for 30 mins to obtain a good dispersion. To print different patterns on a black papers, a standard screen printing technique was used . A proper selection of dispersive medium is essential because of two reasons: first the nanophosphor should be dispersed into the medium without formation of clusters or agglomerates and second, for obtaining better printing, the viscosity of the ink (≈3500 micro poise) is very important as it determines the quality of printing …”

“…The nanorods of Gd 2ÀxÀy Yb x Er y O 3 (0 x 0.3;0 y 0.1) were synthesised by using ac ustomised hydrothermal method. [52][53][54] Gd 2 O 3 , YbCl 3 and ErCl 3 were taken as starting materials. The stoichiometric amount of Gd 2 O 3 was dissolved in as olution containing 15 mL deionised (DI) water and 5mLn itric acid followed by continuous stirring at 80 8Cu ntil the solution turned into at ransparent nitrate solution.…”

“…Eur.J.2017, 23,17144 -17151 www.chemeurj.org ing technique was used. [52] Ap roper selection of dispersive medium is essential because of two reasons:f irst the nanophosphor should be dispersed into the medium without formation of clusters or agglomerates and second, for obtaining better printing, the viscosity of the ink ( % 3500 micro poise) is very important as it determines the quality of printing. [7,8]…”

Triluminescent Functional Composite Pigment for Non‐Replicable Security Codes to Combat Counterfeiting

“…Different kinds of luminescent materials; lanthanide based luminescent conventional organic dyes, nanomaterials, metal‐organic‐frameworks (MOFs), plasmonic nanomaterials, carbon based quantum dots, semiconductor quantum dots etc. have been explored up to now for the fabrication of security ink to solve the counterfeiting problems ,. Most of the above stated materials have their own pros and cons, which is well investigated in our earlier studies ,,.…”