Ultrabright Fluorescent Polymer Dots with Thermochromic Characteristics for Full-Color Security Marking

Abstract

Innovative and scalable security technologies are in high demand to deter increasing counterfeiting in modern society. Here, we report the first example of thermochromic–fluorescent ink based on semiconducting polymer dots (Pdots) by taking advantage of the unique optical properties of Pdots. We designed and synthesized two types of thermochromic molecules and then incorporated them with multicolor fluorescent Pdots. The resulting Pdots exhibited colorimetric and fluorescent dual-readout abilities in response to different temperatures which greatly increase the security level for anticounterfeiting applications. These multifunctional Pdots can be easily doped into flexible substrates or prepared as inks. These full-color inks can be further loaded into marker pens for handwriting or cartridges for inkjet printing with excellent signal-to-background contrast. Moreover, complex and delicate full-color images can be printed on security documents or currency for practical use. We anticipate that this first example of thermoresponsive dual-readout methodology based on Pdots will have broad use in advanced security marking technologies.

Luminescence anti‐counterfeiting: From elementary to advanced

“…Reproduced with permission: Copyright 2019, American Chemical Society. [ 95 ] (C and D) Multilevel luminescence anti‐counterfeiting co‐regulated by excitation light and chemical reagents. (C) Metal ions.…”

“…In addition to ThL, heat stimuli can also bring many interesting changes for anti‐counterfeiting labels. [ 63,93–96 ] Yang et al. [ 95 ] utilized three kinds of polymer dots solution as anti‐counterfeiting inks to write word “CHEMISTRY” on paper (Figure 7B).…”

“…[ 63,93–96 ] Yang et al. [ 95 ] utilized three kinds of polymer dots solution as anti‐counterfeiting inks to write word “CHEMISTRY” on paper (Figure 7B). At 298 K, the letters were light purple under daylight, and only part letters could emit bright fluorescence under 365 nm UV light, while the fluorescence of other letters was weaker.…”

Polymer Labelling with a Conjugated Polymer-Based Luminescence Probe for Recycling in the Circular Economy

“…A highly sophisticated example found in the literature is the use of unique fillers with spectral features specific to narrow-band visible light fluorescence for anti-counterfeiting and recycling [ 10 , 11 ]. In addition, combining various components allows us to write more than one-bit information into the label [ 12 ], and other functions can also be added to the material systems, including thermochromism for dual read tagging [ 13 ]. In turn, such particulate materials show rather intriguing chemistry, requiring rare elements for their synthesis.…”

Catalyst-Free Polymerization with 100% Atom Economy: Facile Synthesis of Polysulfonates with Multifunctionalities

“…The generation of complex fluorescent patterns by photolithography technique is of great significance in terms of the optical writing and reading, anti-counterfeiting applications, and biological sensing systems. 36 Because of the excellent solubility and film-forming ability of the present polysulfonates, their uniform films without defect can be easily fabricated on silica wafers by a simple spincoating technique. The photo-responsive behavior of the polysulfonates makes them excellent candidates for pattern generation.…”