Creation of Nanotips on ITO Electrode by Nanoparticle Deposition: An Easy Way to Enhance the Performance of Electrically Responsive Photonic Crystal and Fabricate Electrically Triggered Anticounterfeiting Tags

Abstract

Electrically responsive photonic crystals (ERPC) are promising materials for electrophoretic displays, smart windows, and tunable optical devices. However, the high working voltage limits the application of most polar ERPCs because it damages color saturation, response stability, and reversibility. Herein, an easy but general method based on the modification of electrodes with nanoparticles is developed to improve ERPC's performance. The deposition of Au, Cu, or Cu2O nanoparticles created nanotip structures on the electrode, which enhanced the charge injection and local electric field strength, lowered 43% of the working voltage, and increased the color saturation. Meanwhile, the lowered voltage inhibited the electrodeposition of colloidal particles and the electrochemical reaction, which also improved the stability and reversibility of the electrical response. Based on the region‐selective modification of the electrode and the resulting asymmetric electrical response, an electrically triggered tag with a “pattern showing/hiding” effect is fabricated for anticounterfeiting purposes.

Repeatable Instantaneous Chromogenic and Magnetic-Responsive Hydrogels Based on an Agarose-Locust Bean Gum Network

“…They provide aesthetic value and convenience for the exchange of biological information. The sources of colors primarily include pigment, bioluminescence, and structural colors. − In recent years, structural colors have been extensively studied as an important category of optical displays and material colors, especially responsive photonic crystal structural materials based on Bragg diffraction coloration. − Due to the presence and controllability of photonic bandgaps, they have a unique responsive color-changing mechanism. The produced colors are bright and do not weaken over time, so they have become a research focus. − …”

Electrically Responsive Photonic Crystals with Enhanced Suspension Stability and Color Saturation for Electrophoretic Displays and Smart Windows

“…To solve this problem, low-polar solvents such as 1,2-dichlorobenzene and paraffinic hydrocarbon − were chosen as the dispersion medium to decrease the screening of the Coulombic interactions, where the maximum blueshift of wavelength can reach 181 nm under 1.7 V in 1,2-dichlorobenzene and 120 nm under 4 V in paraffinic hydrocarbon. Besides, electrodes modified with ion-exchange resin coating, plasma treatment, and nanoparticle depositions could further improve the performance of ERPCs, − as a result of which ERPCs based on SiO 2 particles can exhibit a blue shift of 105 nm under 1.3 V. Although many efforts have been put into ERPCs, the suspension stability of LCCs is rarely taken into consideration when improving the performance of ERPCs. The suspension stability of commonly used inorganic electrophoretic nanoparticles (such as Fe 3 O 4 , ZnS, CeO 2 , and TiO 2 ) in the dispersion medium is a key premise for achieving good color saturation, fast response speed, and cycle stability, which plays a critical role in the image quality and service life of ERPC devices.…”

3D printing of non-iridescent structural color inks for optical anti-counterfeiting

“…Structural color materials 1–3 with unique nano- or micro-scale structural arrangements provide the possibility of manipulating the propagation of light in specific photonic bandgaps (PBG), rendering vivid reflection of colors with fastness, sustainability and metallic luster for potential real-world applications, such as anti-counterfeiting encryption, 4–7 sensors, 8,9 smart windows 10 and displays. 11,12 High-throughput and scalable structural color optical devices have the potential to be finely tailored into colloidal particles 13–20 or block copolymer 21–28 assembly.…”