Electrofluorochromism based on the valence change of europium complexes in electrochemical devices with Prussian blue as the counter electrode

The electrofluorochromism of Eu complexes based on the valence change between Eu3+ and Eu2+ is demonstrated in a two-electrode electrochemical device consisting of Prussian blue (PB) as the counter electrode. This study aims to improve the electrofluorochromic (EFC) performance of luminescence switching between Eu3+ and Eu2+ by enhancing the electrochemical reactivity of the EFC device. By introducing a PB film as a counter electrode in a two-electrode device, the redox reaction of Eu3+/2+ is promoted because of charge compensation by the counter PB film. The increase in the reaction charge enables faster changes in the photoluminescence from Eu3+ to Eu2+ and an increase in the blue luminescence intensity from the Eu2+ state. This approach achieves a lowered driving voltage, accelerates the electrochemical redox reaction of the Eu complex, and enhances the reversibility of the valence change of the Eu ion.

Triphenylamine-Based Covalent Organic Framework Films for Dopamine-Responsive Electrofluorochromism

Covalent organic framework (COF) film with electrofluorochromic (EFC) and electrochromic (EC) properties has been synthesized by using triphenylamine-based monomers. The film exhibited a high maximum fluorescence contrast of 151 when subjected to a drive voltage of 0.75 V vs the Ag/AgCl electrode, causing the fluorescence to be quenched, which resulted in the EFC process's "fluorescence off" state. The switching times for the fluorescence on and off states were 0.51 and 7.79 s, respectively. Over the same voltage range, the COF film also displayed EC properties, achieving a contrast of 50.23% and a coloration efficiency of 297.4 cm2 C-1 at 532 nm, with switching times of 18.6 s for coloration and 0.7 s for bleaching. Notably, the quenched fluorescence of the COF film could be restored by adding dopamine as a reductant. This phenomenon enabled the implementation of a NAND logic gate using the applied potential as a physical input and dopamine addition as a chemical input. This study demonstrates the successful development of COF films with bifunctional EFC and EC properties, showcasing their potential for use in constructing advanced optoelectronic devices.

Research Progress in Special Engineering Plastic-Based Electrochromic Polymers

SPECPs are electrochromic polymers that contain special engineering plastic structural characteristic groups (SPECPs). Due to their high thermal stability, mechanical properties, and weather resistance, they are also known as high-performance electrochromic polymer (HPEP or HPP). Meanwhile, due to the structural characteristics of their long polymer chains, these materials have natural advantages in the application of flexible electrochromic devices. According to the structure of special engineering plastic groups, SPECPs are divided into five categories: polyamide, polyimide, polyamide imide, polyarylsulfone, and polyarylketone. This article mainly introduces the latest research on SPECPs. The structural design, electrochromic properties, and applications of these materials are also introduced in this article, and the challenges and future development trends of SPECPs are prospected.

Electrochemically regulated luminescence of europium complexes with β-diketone in polyether matrices

This study investigates the electrochemical modulation of luminescence color, i.e., electrofluorochromism, of an Eu complex in a polyether solvent. The electrofluorochromic (EFC) reaction of the Eu complex occurred via a reversible redox reaction between Eu3+ and Eu2+. Initially, the intrinsically stable Eu3+ complex showed intense red photoluminescence (PL) induced by f-f transitions. After the electrochemical reduction of Eu3+ to Eu2+, broad blue PL was observed attributed to the d-f transitions in the Eu2+ complex. This distinct blue luminescence from the Eu2+ complex was attributed to the effective stabilization of the Eu2+ state by the polyether solvent. The dynamic EFC reaction that changes the valence state of the Eu ion can be potentially applied to novel chemical sensors, security devices, and display devices.

Synthesis and electrochromic properties of polyamines containing a 4,4′-diaminotriphenylamine-N,N′-diyl unit in the polymer backbone: Ru-catalyzed N–H insertion polycondensation of 1,4-phenylenebis(diazoacetate) with 4,4′-diaminotriphenylamine derivatives

Polycondensation of a bis(diazocarbonyl) compound and diaminotriphenylamine derivatization via Ru-catalyzed N–H insertion to afford electroactive polyamine.

Anthracene-based fluorescent probe: Synthesis, characterization, aggregation-induced emission, mechanochromism, and sensing of nitroaromatics in aqueous media

The sensitive and selective detection of nitroexplosive molecules thorough a simple methodology has received a significant field of research affecting global security and public safety. In the present study, the synthesis of anthracene-based chalcone (S1) was conducted using a simple condensation method. S1 was found to exhibit unique properties, such as aggregation-induced emission in solution and mechanochromic behavior in solid state. A fluorescent aggregate was applied to sense electron-deficient picric acid (PA) and 2,4-dinitrophenol (2,4-DNP) in an aqueous solution. Notably, the developed test strip-based sensor (S1) could be used to effectively detect PA and 2,4-DNP, which were visualized by the naked eye. Photophysical analysis revealed the occurrence of an electron transfer from electron-rich S1 to the electron-deficient nitro compounds, which was confirmed using density functional theory and ¹H-nuclear magnetic resonance studies. In addition, the observed results confirmed the simple synthesis of S1 as a promising material for the development of test strip-based sensor devices for the detection of toxic and explosive aromatic nitro molecules.

Design Rules for Improving the Cycling Stability of High-Performance Donor-Acceptor-Type Electrochromic Polymers

Although high-performance donor-acceptor (D-A)-type polymers have received much attention as an important class of electrochromic (EC) materials, the related studies have mostly focused on the influence of D and A units on the band gap, onset potential, and switching time, leaving the effect of D-A structures on cycling lifetime underexplored. Herein, we design and synthesize a series of poly(aryl amino sulfone)s (PAASs) as D-A polymers with triphenylamine-based donor units and the sulfone moiety as the acceptor unit. As a result, we present new rules to design and develop D-A structure polymers with high EC cycling stability: (1) the electron-donating and -withdrawing abilities of the donor and acceptor should be balanced during the electrochemical cycle process, and this balance can be measured by the ratio of J_red/J_ox; (2) the D-A structure should benefit to generate lower E_onset. By these design rules, the best-performing polymer PAAS-TPPA-OMe exhibits an excellent long-term cycling stability (over 3,900 cycles), low onset potential (0.26 V), fast switching time (6.0/4.3 s for the EC process), high contrast (87% at 688 nm and 94% at 928 nm), and high coloration efficiency (500 cm² C^-1 at 688 nm and 1131 cm² C^-1 at 928 nm).

Substituent effects of AIE-active α-cyanostilbene-containing triphenylamine derivatives on electrofluorochromic behavior

Four aggregation-induced emission (AIE)- and electro-active cyanostilbene-based triphenylamine-containing derivatives with different substituents were synthesized to investigate their effects on the photoluminescence properties and electrochromic (EC) and electrofluorochromic (EFC) behavior of gel-type electrochromic devices (ECDs). The optical and photoluminescence properties of the obtained materials were influenced by the substituents, and revealed AIE-active characteristics, exhibiting stronger fluorescence intensity in the aggregated state than in solution. Consequently, the EFC devices could be fabricated by combining these AIE- and electro-active materials with cathodic EC heptyl viologen HV into the gel-type electrolyte system to enhance the emission intensity, on/off contrast ratio, and response capability.

Electroluminochromic Materials: From Molecules to Polymers

Electroluminochromism is an interesting property found in certain classes of molecules and polymers whose photoluminescence can be modulated through the application of an external electrical bias. Unlike electrochromic materials, electroluminochromic counterparts and their applications are comparatively fewer in quantity and are less established. Nonetheless, there prevails an increasing interest in this class of electro-active materials due to their potential applications in optoelectronics, such as smart-displays, and chemical and biological sensing. This review seeks to showcase the different classes of electroluminochromic materials with focus on (i) organic molecules, (ii) transition metal complexes, and (iii) organic polymers. The mechanisms and electroluminochromic performance of these classes of materials are summarized. This review should allow scientists to have a better and deeper understanding of materials design strategies and, more importantly, structure-property relationships and, thus, develops electroluminochromic materials with desired performance in the future.

Cyanotriphenylamine-based polyimidothioethers as multifunctional materials for ambipolar electrochromic and electrofluorochromic devices, and fluorescent electrospun fibers

New luminescent and electrochromic polyimidothioethers were synthesized and fabricated as ambipolar electrochromic and electrofluorochromic devices, and fluorescent electrospun fibers.

High-performance electrofluorochromic devices based on aromatic polyamides with AIE-active tetraphenylethene and electro-active triphenylamine moieties

Novel electrochromic (EC) and aggregation-enhanced emission (AEE)-active triphenylamine (TPA)-based polyamides were prepared and fabricated into electrofluorochromic (EFC) devices.

Recent advances in triphenylamine-based electrochromic derivatives and polymers

Triphenylamine-containing electrochromic materials with great potential applications in low energy-consumption displays, light-adapting mirrors in vehicles, and smart windows have experienced an exponential growth of research interests. In this review, the newly developed triphenylamine-based derivatives and polymers are reviewed and elaborated.

Visible-to-NIR Electrochromic Device Prepared from a Thermally Polymerizable Electroactive Organic Monomer

A monomer (1) consisting of a benzothiadiazole core flanked by two triphenylamines and two styrene pendant moieties was prepared. The monomer was fluorescent with its emission spanning 145 nm in the visible, contingent on the organic solvent used for the measurement. In addition to its positive solvatochromism, the absolute fluorescence quantum yield (Φ_fl) was consistently >20% with values >80% being measured in hexane, toluene, diethyl ether, and toluene. 1 could be reversibly oxidized with an oxidation potential of 880 mV vs SCE. The monomer could be immobilized on ITO-coated glass substrates. The resulting 425 nm thick immobilized film (poly-1) was 15% thinner than the monomer coating deposited by spray- and spin-coating. The electroactive film did not delaminate from the electrode upon either washing or cycling electrochemically between its oxidized and neutral states. Its absorption at 460 nm bleached upon electrochemical oxidation with the formation of a strong absorption at 880 nm and in the NIR, similar to 1. The perceived reversible color change with applied potential switched between yellow and gray. The fluorescence intensity of poly-1 could be switched with applied potentials. A passive transmissive device prepared from poly-1 was both electrochromic and fluorochromic, exhibiting reversible color change and fluorescence quenching.

An RGB color-tunable turn-on electrofluorochromic device and its potential for information encryption

RGB color-tunable electrofluorochromic devices with a turn-on mode were fabricated successfully and applied for the first time in encrypted information storage and display.

Electrochromic and electrofluorochromic polyimides with fluorene-based triphenylamine

A series of novel polyimides (PIs) based on N,N-di(4-aminophenyl)-2-amino-9,9-dimethylfluorene and various dianhydrides were synthesized. These PIs were amorphous and readily soluble in many solvents. They displayed outstanding thermal stability and high glass transition temperatures (269–374°C). The polymer films showed reversible electrochemical redox and satisfactory electrochromic performance with long-term stability, high coloration efficiency, and acceptable switching times. The PI derived from 1,2,4,5-cyclohexanetetracarboxylic dianhydride exhibited maximum fluorescence at 400 nm with quantum yields up to 28.1%. Furthermore, the fluorescence can be effectively electroswitched between “on” and “off” states, exhibiting a high contrast ratio of 75.

Structural effects of dibromocarbazoles on direct arylation polycondensation with 3,4-ethylenedioxythiophene

Microwave-assisted direct arylation polycondensation of 3,4-ethylenedioxythiophene produced a solution processable and electrochromic polymer when 3,6-dibromocarbazole was employed as a comonomer.

Design of triphenylamine appended anthracene derivatives: electro-polymerization and their electro-chromic behaviour

Three derivatives of anthracene as a core interior with terminal one or two triphenylamine sides have been designed and developed to achieve a smart metal free electrochromic materials.

Immobilized polyazomethines containing triphenylamine groups on ITO: synthesis and acidochromic, electrochemical, electrochromic and photoelectronic properties

A new series of polyazomethines (PAMs) containing triphenylamine (TPA) as easily-oxidized units were synthesized as highly soluble materials with electrochromism.

Highly stable electrochromic and electrofluorescent dual-switching polyamide containing bis(diphenylamino)-fluorene moieties

A novel semi-aromatic polyamide with bis(diphenylamino)-fluorene moieties was designed and synthesized, which exhibited highly stable electrochromic/electrofluorescent dual-switching properties.

Electrochemical synthesis of electrochromic polycarbazole films from N-phenyl-3,6-bis(N-carbazolyl)carbazoles

Electroactive and electrochromic polycarbazole films were directly prepared on electrodes from N-phenyl-3,6-bis(N-carbazolyl)carbazoles by carbazole-based electrochemical oxidative coupling.

High-contrast electrochromic and electrofluorescent dual-switching materials based on 2-diphenylamine-(9,9-diphenylfluorene)-functionalized semi-aromatic polymers

Two kinds of 2-diphenylamine-(9,9-diphenylfluorene)-functionalized semi-aromatic polymers were prepared and they exhibited stable and high-contrast electroswitching in both coloration and emission.

High-efficiency fluorescent polyimides based on locally excited triarylamine-containing dianhydride moieties

Three fluorescent polyimides (PIs) were readily synthesized from the polycondensation of triarylamine-based tetracarboxylic dianhydride monomers with aliphatic diamine. The PL intensity of solid films and nanofibers revealed high PL quantum yields of up to 32% and 35%, respectively.

Tunable electrofluorochromic device from electrochemically controlled complementary fluorescent conjugated polymer films

The fluorescent behavior of the electrofluorochromic devices (Type I) of greenish-yellow emitting P1 and blue emitting P2 can be reversibly switched between the nonfluorescent (oxidized) state and the fluorescent (neutral) state with a superb on/off ratio of 23.8 and 21.9, respectively. Moreover, a tunable electrofluorochromic device (Type II) based on two P1 and P2 polymeric layers that are coated individually on two independent ITO electrodes shows switchable blue-white-(greenish-yellow) multifluorescence states.

Facile preparation of electrochromic poly(amine–imide) films from diimide compounds with terminal triphenylamino groups via electrochemical oxidative coupling reactions

Electroactive and electrochromic poly(amine–imide) films could be directly prepared on electrodes from diimide compounds TPA6F-DI and TPASO2-DI with triphenylamino end groups by electrochemical oxidative coupling.