Dual-Color Photoluminescent Functionalized Nanoparticles for Static-Dynamic Anticounterfeiting and Encryption: First Collaboration of Spiropyran and Coumarin

Abstract

Increasing the security of anticounterfeiting materials has been the most important challenge in recent years, and the development of dual-color photoluminescent inks with multi-level security, static/dynamic emission, and dynamic color change is an important solution to overcome this problem. In this study, the multi-functionalized copolymer nanoparticles containing different functional groups (with a concentration of 20 wt %), including ester, carboxylic acid, hydroxyl, epoxide, amide, and amine groups were synthesized successfully by the emulsion polymerization method. The results showed that the particle size and morphology of nanoparticles are affected by the polarity of functional groups. The prepared multi-functionalized copolymer nanoparticles were modified physically with spiropyran (photochromic and red fluorescence emission) and coumarin (cyan emission) derivatives to develop dual-color photoluminescent polymer nanoparticles with application in static−dynamic photoluminescent anticounterfeiting inks, which have multi-level security. The investigation of optical properties indicates that the kinetics of photochromism and photoluminescence properties of samples containing spiropyran is dependent on the local polarity on the surface of polymer nanoparticles. Hence, an increase in the polarity (functionalization with amide, carboxylic acid, and hydroxyl groups) has resulted in fast photochromism, high-intensity photoluminescence emission and increased the efficiency of the photoswitchable color change of emission from cyan to pink. Dual-color photoluminescent anticounterfeiting inks were prepared by mixing polymer nanoparticles containing spiropyran with polymer nanoparticles containing coumarin, in different ratios (1:1, 1:3, 1:5, 1:8, and 1:10). Obtained results showed that prepared samples have cyan emission under UV light of 254 nm (static mode), and a dynamic photoswitching of fluorescence emission from cyan to pink (as a function of irradiation time) was also observed under UV-light irradiation of 365 nm, which is well known as a dynamic mode of emission. The responsivity and intensity of dynamic photoluminescence emission are dependent on the local polarity of the surface functional groups, in which the samples based on amide functionalized copolymer nanoparticles displayed high-intensity emission in the static mode and high-intensity photoswitchable dual-color emission in the dynamic mode, in the case of all ratios of colloid solution mixtures. Printing security tags on cellulose paper by dual-color photoluminescent inks indicates advantages such as maximum printability, resolution, brightness, and static−dynamic photoluminescence emission with high intensity for inks based on amide functionalized nanoparticles. The static−dynamic dual-color photoluminescent anticounterfeiting ink with unique properties and multi-level security was reported for the first time by the collaboration of spiropyran and coumarin. This study can open a new approach and window to the future of advanced and high-security an...

Chameleon-like Photoluminescent Janus Nanoparticles as Full-Color Multicomponent Organic Nanoinks: Combination of Förster Resonance Energy Transfer and Photochromism for Encryption and Anticounterfeiting with Multilevel Authentication

“…As expected, the fluorescence emission of the FL-PMAHM-15% sample displays remarkable overlap with the SP-PMAHM-15% sample and also with CU-PMAHM-15% in which this sample has the potential for acting as a bridge to connect a relation between SP-PMAHM-15% and CU-PMAHM-15%. According to our recent work, the polymer nanoparticles containing SPOH do not have photoswitchable emission based on FRET when mixed with polymer nanoparticles containing CU, in which the color of the mixture under UV-light irradiation of 254 nm is blue, and its color under UV-light irradiation of 365 nm converted dynamically to red emission as a function of irradiation time . Therefore, the FL-PMAHM-15% nanoparticles can display very complex optical properties when mixed with SP-PMAHM-15% or CU-PMAHM-15% samples or even in a more complex state when we have a mixture of three samples.…”

“…The solid product was filtered and washed with very cold ethanol and then recrystallized in ethanol to afford final products as SPOH. The chemical structures of SPOH were characterized by 1 HNMR analysis (CDCl 3 as the solvent), and the corresponding spectra are presented in our previous studies. − …”

“…A yield of about 86% was obtained for the synthesis of the CU derivative. The chemical structure of CU was characterized by 1 HNMR spectroscopy using CDCl 3 as the solvent, and the obtained spectra were presented in our previous studies …”

“…The color of the developed photoresponsive composite nanomaterials can be reversibly switched between purple and colorless upon irradiation of UV-light and visible-light irradiation by the FRET mechanism. Our recent study has focused on dual-color photoluminescent polymer nanoparticles containing spiropyran (as a red-emissive photoluminescent molecule) and coumarin (as a blue-emissive luminescent molecule), in which the blue emission was observed under UV-light irradiation of 254 nm and dynamic red emission was observed under UV-light irradiation of 365 nm. ,, Developed nanoparticles do not display the FRET mechanism between spiropyran and coumarin, and each of them was excited by a specific wavelength of UV-light irradiation.…”

UV Irradiation-Induced Cyclic-to-Linear Topological Changes of a Light/pH Dual-Sensitive Cyclic Copolymer for Enhanced Drug Delivery

“…Exogenous photoreactive stimuli are easier to control than endogenous ones . The common photoreactive groups include azobenzene, coumarin, cinnamic acid, and o-nitrobenzyl ester . O-nitrobenzyl (ONB) ester has attracted considerable interest due to the ease of synthesis and prompt breakage properties .…”