Smartphone-Identifiable Photoluminescent Nanoparticle-Based Multilevel Secured Tags by Electrical Microcontact Printing

Abstract

To fight the boom in counterfeiting and especially the fraud of official documents, we propose herein original multilevel integrated security features: photoluminescent nanoparticle-based tags (PL tags). Using the electrical microcontact printing technique, PL tags are fabricated at large scale and are successfully integrated in the production line of plastic cards. We introduce COC-based stamps in the fabrication process to meet industrial constraints in terms of speed, cost and robustness. Depending on the resolution of security features, from several millimeters down to several micrometers, PL tags can also combine several degrees of reading and so security. Indeed, using a simple blue LED, they could be quickly identifiable by naked eye or a simple smartphone camera. In addition, they could also embed smaller features only readable with an optical microscope.

Core/Shell Metal Halide Perovskite Nanocrystals for Optoelectronic Applications

“…Hence these structures are considered as suitable luminescent phosphors for applications in lighting, displays, ink‐jet printing, etc. [ 54–56 ] The strategy of using one of the perovskite derivatives with larger bandgap, such as Cs 4 PbX 6 , as the shell material was proposed and demonstrated by Kaur et al. [ 52 ] ( Figure a).…”

“…Hence these structures are considered as suitable luminescent phosphors for applications in lighting, displays, ink-jet printing, etc. [54][55][56] The strategy of using one of the perovskite derivatives with larger bandgap, such as Cs 4 PbX 6 , as the shell material was proposed and demonstrated by Kaur et al [52] (Figure 2a). In such structures, the protective Cs 4 PbBr 6 shell is used to prevent degradation of the perovskite core and to ensure ample large-band offsets, enabling the excitons to follow the carrier dynamics as in the type I core/shell system.…”

“…The perovskite NCs have nonlinear absorption coefficients of up to 0.085 cm GW −1 , and can be made stable in aqueous environment and at elevated temperatures, making them potential interest for anti-counterfeiting applications. [44,56,180] Xu et al [44] utilized the double-shell CsPbBr 3 /Cs 4 PbBr 6 /SiO 2 perovskite NCs to prepare anti-counterfeiting inks. The designed NC ink .…”

Synthesis of hybrid colloidal nanoparticles for a generic approach to 3D electrostatic directed assembly: Application to anti-counterfeiting

“…[20] Its capability to realize 3D assembly was demonstrated with photoluminescent NPs which enabled a tuning of the photoluminescent signal that depends on the assembly thickness. [21] These technique potentialities were successfully applied to fabricate anti-counterfeiting markers considering multi security levels, [21] the biocompatible aspect, [22,23] the reading equipment (smartphone [24] or a dedicated optical setup [21]) and their industrial scaling up fabrication. [22,24,25] Unfortunately, 3D assembly by nanoxerography is limited to polarizable NPs with "large" diameter above 20-25 nm, [26] which represents a severe restriction.…”

“…[21] These technique potentialities were successfully applied to fabricate anti-counterfeiting markers considering multi security levels, [21] the biocompatible aspect, [22,23] the reading equipment (smartphone [24] or a dedicated optical setup [21]) and their industrial scaling up fabrication. [22,24,25] Unfortunately, 3D assembly by nanoxerography is limited to polarizable NPs with "large" diameter above 20-25 nm, [26] which represents a severe restriction. Indeed, in the case of quantum dots (QDs) for instance, the lack (or the weakness) of quantum confinement effect in NPs larger than 10 nm makes them less desirable, their synthesis with narrow size distribution being in addition often very challenging like for example in the case of the strategic InP QDs.…”