Flexible Composite Electrochromic Device with Long-Term Bistability Based on a Viologen Derivative and Prussian Blue

Electrochromic Devices and Smart Window Applications of Near-Infrared Electrochromic Thienoviologens Polymer Properties

In recent years, with the increasing demand for building energy efficiency and comfort in daily life, electrochromic smart windows have attracted widespread attention. Electrochromic smart windows utilize electrochromic material (ECM) technology to change the color or transparency of the window under the action of an electric field, thereby regulating the light and heat entering the room and achieving energy-saving effects. A bistable electrochromic material is a material that can switch between two color states and maintain one of these states without an external electric field. Although ECMs with bistable properties can significantly reduce energy consumption, current research on their application in smart windows is limited. Therefore, three conjugated extended viologen polymers with thiophene derivative bridges, PDV-MMA, PBV-MMA, and PTV-MMA, were designed and synthesized, and electrochromic devices (ECDs) were prepared. The introduction of thiophene derivatives not only prolongs the effective conjugated chain length of viologen, but also extends the electrochromic (EC) response to the near-infrared (NIR) region. In addition, by inserting different thiophene derivatives to separate the two pyridinium moieties, viologen polymers emit strong fluorescence that can be quenched by applying a negative voltage. The electrochromic device based on PDV-MMA material has fast response time (1.8 s), low turn-on voltage (-0.9 V), high color contrast (73.7%), high coloring efficiency (550 cm2/C), and cycling stability (3300 cycles). In addition, ECD based on PDV-MMA exhibits bistable characteristics, with only a 10% transmittance decay within 221 min, displaying clear patterns even after 20 h of power outage, and significantly reducing indoor temperature (7.0 °C) in simulated indoor environments. These characteristics make the application of electrochromic smart windows highly attractive in energy-efficient buildings. The study also demonstrated an intelligent window system driven by a solar cell (SC), further validating its feasibility in practical applications.

Four multi-stimuli-responsive color-changing materials based on Anderson-viologens for erasable inkless printing, UV detectors and gradient detection of amine gases

Multi-stimuli-responsive materials have garnered widespread attention due to their exceptional potential in various applications, including optical anti-counterfeiting devices, sensor technology, and information storage materials. In this study, we demonstrate the synthesis of four polyoxometalates/viologens (POMs/Vios)-based compounds featuring remarkable color-changing performance, namely, [Zn6(HL)2(H2O)20(TeMo6O24)3]·6H2O (1), [Co6(HL)2(H2O)20(TeMo6O24)3]·4H2O (2), [Zn(TeMo6O24)(H2O)2]·L2·6H2O (3), [Co(TeMo6O24)(H2O)2]·L2·6H2O (4) (L·Cl2 = 1,1'-[1,3-phenylenebis(methylene)] bis-(4,4'-bipyridine) dichloride). Compounds 1, 3, and 4 exhibit rapid and reversible photochromic properties, making them suitable for applications in erasable inkless printing and information storage. Furthermore, hydrogels based on these compounds can act as ultraviolet detectors. An innovative electrochromic (EC) hydrogel can be prepared by incorporating compounds 1-4 into polyacrylamide (PAAm). The integrated electrochromic devices (ECDs) based on EC hydrogel can precisely switch between the coloring and fading states through the precise control of different voltages. They are characterized by simple operation, high sensitivity, and low-voltage drive (ranging from -0.21 to -0.35 V). Additionally, compounds 1-4 act as highly efficient organic amine gas sensors. This work is anticipated to provide inspiration for the systematic design and development of diverse color-changing materials that respond to multiple external stimuli.

A Tetramethyl Viologen for Aqueous Electrochromic Devices

The poor electrochemical reversibility of the dimers limits the application of viologens in aqueous electrochromic devices (ECDs). Here, we report a tetramethyl viologen, 2,2',6,6'-tetramethyl-4,4'-bipyridine hydrobromide ([MVH][Br]), in which tetramethyl substitution provides significant steric hindrance to prevent dimerization. Our experiments show that this designed viologen performs excellently in an aqueous solvent, including excellent color variation, optical modulation, cycling stability, and radical inertness. Typically, an aqueous ECD fabricated with the viologen is able to retain 95.48% of its optical modulation after 5000 cycles. Furthermore, we found that this viologen is impervious to UV polymerization. Based on this property, we demonstrate a bichromatic ECD based on a hydro-ionic hybrid gel using in situ UV polymerization. This study not only extends the application of viologens in aqueous ECDs but also paves the way for the future development of high-mechanical-performance hydrogel-based ECDs.

LAMP-visualized photofuel cell self-powered dual-mode sensing platform for detection of transmissible gastroenteritis virus

The detection of transmissible gastroenteritis virus (TGEV) is of great significance to reduce the loss of pig industry. A LAMP-visualization/PFC self-powered dual-mode output sensor platform was constructed to detect TGEV by combining a simple and intuitive photoelectrochromic material with a highly sensitive PFC self-powered sensing platform without external power supply. The PFC sensing substrate was constructed using CdS nanoparticles modified ZnO NRs (CdS/ZnO NRs) as the photoanode, which exhibited high photoactivity, and Prussian blue (PB) as the cathode. After LAMP reaction on the optical anode, visual signals caused by PB discolorimetry can be detected semi-quantitatively, or PFC power density electrical signals collected by electrochemical workstation can be used. The output power density value is logarithm of TGEV concentration. The linear relationship was good within the detection range of 0.075 fg/μL-7.5 ng/μL, with a detection limit of 0.025 fg/μL (S/N = 3). This multi-signal output sensing platform provides more choices for quantifying TGEV detection results, and the two methods can be mutually verified, which meets the needs of different scenarios and improves the reliability of detection. It has a good effect in the actual sample detection, without the use of expensive and complex instruments, and has a broad application prospect.