3D assembly of upconverting NaYF4 nanocrystals by AFM nanoxerography: creation of anti-counterfeiting microtags.
Formation of 3D close-packed assemblies of upconverting NaYF4 colloidal nanocrystals (NCs) on surfaces, by Atomic Force Microscopy (AFM) nanoxerography is presented. The surface potential of the charge patterns, the NC concentration, the polarizability of the NCs and the polarity of the dispersing solvent are identified as the key parameters controlling the assembly of NaYF4 NCs into micropatterns of the desired 3D architecture. This insight allowed us to fabricate micrometer sized Quick Response (QR) codes encoded in terms of upconversion luminescence intensity or color. Topographically hidden messages could also be readily incorporated within these microtags. This work demonstrates that AFM nanoxerography has enormous potential for generating high-security anti-counterfeiting microtags.
Université de Toulouse, LPCNO, INSA-CNRS-UPS, 135 Avenue de Rangueil, Toulouse, 31077, France. laurence.ressier@insa-toulouse.fr.
Neralagatta M
NM
Sangeetha
Pierre
P
Moutet
Delphine
D
Lagarde
Gregory
G
Sallen
Bernhard
B
Urbaszek
Xavier
X
Marie
Guillaume
G
Viau
Laurence
L
Ressier