Spectroelectrochemical Studies on Silicate Sol‐Gel Matrix‐supported Sub‐10 nm Prussian Blue Nanostructures‐based Electrochromic Device

In this study, spectroelectrochemical (SPE) studies to monitor the electrochromic properties of electrochemically synthesized sub‐10 nm sized Prussian blue (PB) nanostructures (NSs) are employed. At the beginning the dark blue coloured device, shifts reversibly between translucent and dark‐blue while applying an applied bias between +1 to ?1 V with an opposite polarization. Amine functionalized silicate sol‐gel matrix (SSG) is used as a solid support and stabilizer for electrodepositing highly uniform sub‐10 nm PB NSs. The SSG's film thickness is suitably optimized through suitable controlled experiments. It is found that the SPE behaviour of sub‐10 nm sized PB NSs, suitably followed a colour modulation of PB into Prussian white (PW) and vice‐versa. SPE studies are used to investigate the redox switching between the PB and PW and which are responsible for an electrochromic function of a fabricated electrochromic device (ECD). Fabricated ECD has demonstrated an optical modulation at 680 nm with the moderate coloration efficiency of 115.8 cm²/C. Present study validates the SPE feature of sub‐10 nm PB NSs as an active electrochromic nanomaterial and demonstrating the applicability of SPE technique to investigate the variety of electrochromic nanomaterials, with consequences in both spectral and electrochemically active nanomaterials for electrochromic device applications.     

Urea Biosensor Based on Electrochromic Properties of Prussian Blue

Prussian blue (PB) is an electrochromic material, which can be used as a signal transducer in the formation of optical urea biosensors. The previous researches in electrochromic properties of PB demonstrated the optical PB response to ammonium ions, which occurs when ammonium ions are interacting with PB layer at a constant 0.2 V vs Ag|AgCl|KCl_sat potential. In this work PB optical dependence on ammonium ions concentration was applied in the formation of electrochromic urea biosensor. Biosensor was formed by modifying the optically transparent indium tin oxide (ITO) coated glass electrode (glass/ITO) with Prussian blue layer and immobilizing urease (glass/ITO/PB‐urease). Calibration curve showed the linear dependency (R²=0.995) between the change of maximal absorbance (ΔA) and urea concentration in concentration range varying from 3 mM to 30 mM. The highest sensitivity (4 ΔA M^?1) of glass/ITO/PB‐urease biosensor is in the concentration range from 7 mM to 30 mM. It was determined that working principle of the glass/ITO/PB‐urease biosensor is not related to pH changes occurring during enzymatic hydrolysis of urea.     

Photoelectrochemistry of indium hexacyanoferrate–titania composite films

The voltammetric and electrochromic behavior of two types of indium(III) hexacyanoferrate(II/III) (InHCF) films, potentiodynamically grown either on polycrystalline Au or on tin-doped indium oxide (ITO) support electrodes, are described. A new spectral feature was seen at ca. 475 nm for the InHCF films grown on Au under extended potential window (EPW) conditions, in addition to the dominant 420 nm feature described by previous authors. The 420 nm band is the sole electrochromic feature in films grown under restricted potential window (RPW) conditions. The InHCF films were also grown in the presence of TiO₂ particles in the deposition bath. The resultant InHCF–TiO₂ composite films showed distinctly different photoelectrochemical responses for the EPW and the RPW counterparts. X-ray phoelectron spectroscopy data showed a higher TiO₂ particle uptake for the EPW films relative to their RPW counterparts, under otherwise identical growth conditions. A second film configuration built up by InHCF derivatization of a pre-formed In–TiO₂ film, yielded decidedly inferior photoresponses. Mechanistic reasons for this are presented as is evidence for the dominance of two distinct forms of InHCF under the EPW growth conditions.     

固态聚苯胺电致变色器件的制备和性能

采用CeO2-TiO2复合物薄膜作为聚苯胺电致变色器件的对电极, 选用聚合物固态电解质(PE: PMMA-PC-EC-LiClO4), 构筑了新型双层结构(Dual-type)聚苯胺(PANI)固态电致变色(EC)器件. 用电化学现场紫外-可见光谱法表征了该EC器件(ITO|PANI||PE||CeO2-TiO2|ITO)的电致变色性能, 并与单层结构(Single-type)EC器件(ITO|PANI||PE|| ITO)进行了比较. 研究结果表明, 双层结构EC器件比单层结构EC器件的电致变色性能好, 如响应速度快, 循环寿命长. 同时, 考察了电解质组分对聚苯胺电致变色稳定性的影响. EC器件(ITO|PANI||PE||CeO2-TiO2|ITO)的颜色呈现由透明的黄色(-1.5 V, PANI vs. CeO2-TiO2)到蓝色(1.0 V)的可逆变化, 在700 nm处的透射率由42.19%变到13.35%, 经过150个循环, 其透射率差仍保持不变, 着色效率为152.1 cm2/C.     

Screen‐printable Electrochromic Polymer Inks and Ion Gel Electrolytes for the Design of Low‐power,Flexible Electrochromic Devices

We have developed electrochromic inks and electrolyte materials to enable mass production of flexible electrochromic displays (ECDs) and other optoelectronic devices by screen printing. Here we present a new screen‐printable ink incorporating electrochromic polymer, poly(3,4‐propylenedioxythiophene)bis(ethylhexyloxy), referred to here as ECP‐Magenta, and antimony‐doped tin oxide (ATO/TiO₂) particles to facilitate electron transport. Their dispersion in a P(VDF‐co‐HFP) binder leads to the formation of a new electrochromic ink that is suitable for screen printing. This strategy opens the door to the preparation of similar electrochromic inks based on other organic or polymeric compounds. This approach is scalable and can applied to different fields. Ion gels (IGs) composed of P(VDF‐co‐HFP) and room temperature ionic liquids (RTILs) are promising solid‐state electrolytes with high ionic conductivity, flexibility, elasticity and eco‐friendliness. The electrochemical features of different ion gels were analyzed as a function of composition and nature of the ionic liquid. Hence, new formulations of IGs were developed, evaluated by Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, before being incorporated into ECDs. The electrochromic performance of ECP‐Magenta ink combined with the RTIL‐based IG was evaluated by terms of spectroelectrochemistry showing that fully flexible ECD operating at voltages below 1 V can be screen‐printed.     

A new electrochromic material from an indole derivative and its application in high-quality electrochromic devices

A novel electrochromic material, poly(indole-6-carboxylic acid) (PIn), and its application in electrochromic devices (ECDs) are discussed. PIn was switched between yellow in the reduced state and green in the oxidized state. Electrochromic switching of PIn film shows that it has fast switching time and high optical contrast. ECD based on PIn and poly(3,4-ethylenedioxythiophene) (PEDOT) was also fabricated and characterized. The response time of this device was found to be 1.0 s and the optical contrast was 45%. The coloration efficiency (CE) was calculated to be 510 cm² C^?1. Clear change from green (neutral) to blue-violet color (oxidized) of ECD is demonstrated with robust cycle life. These results provide an avenue for applications of polyindole family in electrochromic devices.     

Synthesis and electropolymerization of 5,12-dihydrothieno[3′,4′:2,3][1,4]dioxocino[6,7-b]quinoxaline and its electrochromic properties

Synthesis of a new thiophene-based monomer; 5,12-dihydrothieno[3′,4′:2,3][1,4]dioxocino[6,7-b]quinoxaline (DDQ), was realized. The chemical structure of the monomer was characterized by ¹H NMR, FTIR and mass spectroscopy techniques. Electrochemical polymerization of DDQ and characterization of the resulting polymer [P(DDQ)] was performed. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. P(DDQ) has a low oxidation potential (0.9 V) and low band gap (1.73 eV) compared to polythiophene. In addition, dual-type polymer electrochromic device (ECD) based on P(DDQ) with poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed. Spectroelectrochemistry, electrochromic switching, stability and open-circuit stability of the device were studied. It was observed that polymer have good switching time, reasonable contrast and optical memory.     

Ion conductivity of poly(ethylene oxide)-based polyurethane networks containing alkali metal salts

Ion conductivity of poly(ethylene oxide) (PEO)-based polyurethane networks containing alkali metal salts has been investigated. Consequently, it has been revealed that the conductivity is dependent on the following parameters: lattice energy of the alkali metal salt, concentration of alkali metal salt, and the cross-linking density of the network polymer (which is a function both of the amount of cross-linking agent and the molecular weight of PEO). Under optimal conditions, the conductivity at ambient temperature corresponded to 2.51 × 10^?5 Scm^?1, which is greater than that of a typical alkali metal-PEO system by a factor of about 10² to 10³. Moreover, from the standpoint of the application to electrochromic displays (ECD), tensile bond strength between the polymer electrolytes and tungsten trioxide (WO₃), which is the most promising electrochromic material, has been evaluated. The bonding strength of the bond of WO₃ with the present electrolyte has been found to be much larger than that of the alkali metal-PEO system.     

A greener electrochromic liquid crystal based on ionic liquid electrolytes

An electrochromic liquid crystal (ECLC) material composed of only liquid crystal (LC) and ionic liquid (IL) was developed. The LC containing the substituted diphenylacetylene serves as electrochromic (EC) material to realise transmittance and colour change under the direct current (DC) field, while the IL with the designable cation and anion served as electrolyte. Herein, a series of IL electrolytes was screened to investigate how IL tunes the electro-optic performance of the ECLC cell. By testing the electrochemistry window of ILs in EC cells, IL with the [NTf₂]^? anion shows adequate electrochemical stability when the EC material undergoes oxidation and reduction. The electro-optic performance of ECLC containing 1-ethoxy-4-[2-(4-pentylphenyl) ethynyl]-benzene (PEB) and IL was then evaluated by UV-vis spectrometry under the control of an electrochemical work station. Compared with other PEB-IL, PEB-[Bmim][NTf₂] with [Bmim][NTf₂] electrolyte shows a satisfactory transmittance at low operating voltage. Furthermore, Pd NPs in situ formed in [Bmim][NTf₂] reduced the EC potential and improved the light scattering of the ECLC cell. In this work, we also designed a bifunctional device based on polymer dispersed liquid crystal (PDLC) that hosts electrochromic guest molecules, and analysed the electro-optical and electrochromic properties of LC electrolyte mixtures, in order to gain control of the incident daylight and glare in building and automotive applications.     

Fluorene-based donor-acceptor-type multifunctional polymer with bicarbazole pendant moiety for optoelectronic applications

Since limited examples are in the literature in which both organic light-emitting diodes (OLEDs) and electrochromic (EC) applications were performed using the same conjugated polymer, we presented comprehensive EC and electroluminescence (EL) studies of fluorene-based electroactive polymer (e.g., CFP6) consisting of a bicarbazole pendant moiety with quinoxaline as an acceptor bridge. CFP6 was synthesized by a Suzuki cross-coupling polymerization reaction and utilized as an active and emissive layers of the electrochromic device (ECD) and OLED, respectively, due to its high photoluminescence quantum yield intensity and fine thin film forming capability. The optical, electrochemical, cyclic voltammetry measurements, and density functional theory calculations were realized. Electrochemical cross-linking process was applied over the electroactive carbazole subunit of the CFP6 polymer. After the crosslinking process, EC performance was greatly improved. On the other hand, light emission and EL characteristics of OLEDs based on CFP6 emissive layer were realized in detail with six different device architectures to understand light output profile behavior. As a result, CFP6 emitted bright greenish yellow emission with a maximum brightness of 1777 cd/m² at 215 mA/cm² in the indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/CFP6:%10 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP)/Alq3/LiF/Al device architecture.     

Influence of Organic Additive on the Morphological, Electrical and Electrochromic Properties of Sol-Gel Derived WO3 Coatings

The WO₃ electrode is ubiquitous in an electrochromic device (ECD) and is a common choice as the electrochromic (EC) layer. EC films were deposited on different substrates by spin coating using peroxotungstic acid based precursor solutions followed by appropriate thermal treatment. Many properties of the films, including some of the EC properties dependant on microstructure of the films, were found to be modified by the addition of small amounts of organic acid to the precursor solution. A study of structural, electrical and electrochromic properties of films cast by using precursor solution comprising 0 to 10 wt% of oxalic acid dihydrate (OAD) was carried out in terms of surface morphology, electrical resistance, structure and EC response. The important findings are that the addition of oxalic acid to the precursor solution results in films with excellent EC properties, devoid of cracks and decreases their dc electrical resistance.     

Electrochemical synthesis and investigation of poly(1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene) and its application in an electrochromic device

1,4-Bis(2-(3,4-ethylenedioxy)thienyl)benzene, prepared by Stille cross-coupling reaction was successfully electrochemically polymerized to give polymer 1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene (PEBE). Characterizations of the resulting polymer PEBE were performed by cyclic voltammetry (CV), UV–vis, Fourier transform infrared spectroscopy and scanning electron microscopy. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. The resulting polymer film has distinct electrochromic properties and shows three different colors (deep red, gray, and light blue) under various potentials. At the dedoped state of the polymer, the π–π* transition absorption peak is located at 510?nm and the optical band gap (E _g) was calculated as 1.92?eV. The PEBE film shows a maximum optical contrast (ΔT%) of 31.0?% at 500?nm with a response time of 0.85?s. The coloration efficiency of PEBE film was calculated to be 182.2?cm²C^?1. An electrochromic device (ECD) based on PEBE and poly(3,4-ethylenedioxythiophene) was also constructed and characterized. The response time was measured as 0.4?s, and the coloration efficiency of the device was calculated to be 225.4?cm²C^?1. Furthermore, this ECD exhibited satisfactory optical memories and redox stability.     

Enhanced electrodeposition of indium hexacyanoferrate thin films through improved plating solution stability

An ordinary plating solution for indium hexacyanoferrate (InHCF) thin film deposition, mainly composed of equal concentrations of In³⁺ and [Fe(CN)₆]^3–, usually forms precipitates rapidly when either concentration is higher than few millimolar. This contributes to the plating solution's instability. Moreover, electrodeposited capacities are limited accordingly. In this work, the plating solution's stability and the electrodeposition of InHCF were greatly enhanced by adding a large amount of K⁺ and/or H⁺. It was found that a 10-mM plating solution added with 1 M HCl and 1 M KCl could be stored as fresh over a one-week period, whereas an unmodified plating solution became useless within a couple of minutes. Also, such cationic additions, especially adding H⁺, increased the electrodeposited capacity ca. 18 times at least, as compared with that obtained from the unmodified plating solution. Furthermore, related enhancing mechanisms were proposed and verified. To sum up, this study offers a means for better InHCF electrodeposition and should promote the applications of InHCF films. Electronic Publication     

A newly-designed self-powered electrochromic window

By converting incident light into electric power, self-powered electrochromic window (SP-ECW) can achieve color change in electrochromic layer with no need for external voltage. In this work, a newly-designed SP-ECW is proposed for altering its color between deep blue and colorless state according to on/off state of incident light. The device consists of a working electrode with planar integration of photovoltaic (PV) and electrochromic (EC) elements on one electrode, a platinum counter electrode and a redox electrolyte comprising Br^–/Br ₃ ^– couple. A high transmittance modulation of 41% at 582 nm is obtained. Electrical energy converted from light is not only sufficient to drive the device, but also can be outputted to the external circuit.     

Molecular engineering tuning optoelectronic properties of thieno[3,2-<Emphasis Type="Italic">b</Emphasis>]thiophenes-based electrochromic polymers

Thieno[3,2-b]thiophene (TT) monomers end-capped with 3,4-ethylenedioxythiophene (EDOT) moieties are electropolymerized to form π-conjugated polymers with distinct electrochromic (EC) properties. Steric and electronic factors (electron donor and acceptor substituents) in the side groups of the TT core, as well as the structure of the polymer backbone strongly affect the electrochemical and optical properties of the polymers and their electrochromic characteristics. The studied polymers show low oxidation potentials, tunable from–0.78 to +0.30 V (vs. Fc/Fc⁺) and the band gaps from 1.46 to 1.92 eV and demonstrate wide variety of color palettes in polymer films in different states, finely tunable by structural variations in the polymer backbone and the side chains. EC materials of different colors in their doped/dedoped states have been developed (violet, deep blue, light blue, green, brown, purple-red, pinkish-red, orange-red, light gray, cyan and colorless transparent). High optical contrast (up to 79%), short response time (0.57–0.80 s), good cycling stability (up to 91% at 2000 cycles) and high coloration efficiency (up to 234.6 cm² C^–1) have been demonstrated and the influence of different factors on the above parameters of EC polymers have been discussed.     

Ethylene dicysteine (EC) and ethyl cysteinate dimer (ECD) complexes of Ga(III) and In(III)

Ethylene dicysteine (EC) and ethyl cysteinate dimer (ECD) complexes of⁶⁷Ga and¹¹¹In were prepared and the complexation yield and radiochemical purity estimated by paper chromatography, paper electrophoresis and solvent extraction into chloroform.¹¹¹In-EC was found to be anionic, whereas¹¹¹In-ECD was neutral. EC complexes of⁶⁷Ga and¹¹¹In were stable upto 6 hours and expectedly less lipophilic than ECD complexes. ECD complexes of⁶⁷Ga and¹¹¹In were unstable in aqueous medium, but highly stable in chloroform. The utility of the work for stabilisation of products as organic extract and the possible role and limitation for the development of new⁶⁸Ga radiopharmaceuticals and of bifunctional chelating agent (BCA) for¹¹¹In are discussed.     

High‐performance Flexible Complementary Electrochromic Device Based on Plasma Modified WO3 Nano Hybrids and V2O5 Nanofilm with Low Operation Voltages

Tungsten trioxide‐poly(3,4‐ethylenedioxythiophene) (WO₃‐PEDOT) and tungsten trioxide‐polyfuran (WO₃‐PFu) were prepared by rf rotating plasma polymerization. Electrochromic hybrid thin films were fabricated onto flexible polyethylene terephthalate (PET)/ indium tin oxide (ITO) film using electron beam evaporation method. In order to deeply characterize all films, scanning electron microscopy‐energy dispersive X‐ray spectroscopy (SEM‐EDS) and electrochemical impedance spectroscopy (EIS) techniques were used. The counter electrode effect on plasma modified WO₃ nano hybrids‐based electrochromic devices (ECDs) was evaluated. By incorporating flexible vanadium pentoxide (V₂O₅) film as counter electrode, complementary ECDs were constructed through combining the hybrid flexible films (WO₃‐PEDOT, WO₃‐PFu) as working electrodes, which exhibit highly efficient electrochromic performance with low voltage operation. Especially, WO₃‐PEDOT/V₂O₅‐based ECD owns a high optical modulation of 61.5 % at 750 nm driven by −1.0 V (coloration) and +1 V (bleaching) with fast response times (coloration time: 13.58 s, bleaching time: 8.07 s) and a high coloration efficiency of 527 cm² C⁻¹. This study can supply useful and efficient avenue for designing flexible complementary electrochromic device for energy‐saving flexible electronics.     

Synthesis, characterization and electrochromic properties of copolymer of 3-{[4-(thien-3-yl-methoxy)phenoxy]methyl}thiophene with thiophene

(3-{[4-(Thien-3-yl-methoxy)phenoxy]methyl}thiophene) (TMPMT) was synthesized via the reaction of 3-bromomethylthiophene with hydroquinone and characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). Electrochemical copolymerization of TMPMT with thiophene in acetonitrile/boron trifluoride diethyl etherate (AN/BFEE) solvent mixture was achieved using tetrabutylammonium tetrafluoroborate (TBAFB) as the supporting electrolyte. Resulting copolymer was characterized via cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), four probe technique conductivity measurement and UV-Vis spectroscopy. Spectroelectrochemical analysis of the copolymer [P(TTMT-co-Th)] revealed that π-π^∗ electronic transition occurs at 427 nm with a band gap value of 2.20 eV. Copolymer gives brown color at the fully reduced state whereas; at fully oxidized state the film has a gray-blue color. Kinetic studies were carried out at the maximum contrast wavelength upon measuring the percent transmittance, T% (7.6%) and switching time (2.0 s) to examine the switching ability of the copolymer. Dual type electrochromic device (ECD) of P(TMPMT-co-Th) and poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed. Spectroelectrochemistry, switching ability, open circuit memory and stability of the device were examined by UV-Vis spectroscopy and cyclic voltammetry. The device switches between brown and blue at switching voltages of 0.0 V and 2.8 V with a short switching time of 1.4 s.     

Manufacture and demonstration of organic photovoltaic‐powered electrochromic displays using roll coating methods and printable electrolytes

Electrochromic devices (ECDs) were prepared on flexible substrates using spray coating and slot‐die coating methods. The electrochromic materials were the conjugated electroactive polymers, poly((2,2‐bis(2‐ethylhexyloxymethyl)‐propylene‐1,3‐dioxy)‐3,4‐thiophene‐2,5‐diyl) as a vibrantly colored active material (ECP‐Magenta) and poly(N‐octadecyl‐(propylene‐1,3‐dioxy)‐3,4‐pyrrole‐2,5‐diyl) as a minimally colored, charge balancing material (MCCP). Two electrolyte systems were compared to allow development of fully printable and laminated devices on flexible substrates. Devices of various sizes, up to 7 × 8 cm², are demonstrated with pixelated devices containing pixel sizes of 4 × 4 mm² or 13 × 13 mm². The transmission contrast exhibited by the devices, when switched between the fully bleached and fully colored state, was 58% at a visible wavelength of 550 nm, and the devices exhibited switching times of <10 s. Additionally, we demonstrate the utilization of printed organic photovoltaic devices (with or without the use of a lithium‐polymer battery) to power the devices between the colored and bleached state, illustrating a self‐powered ECD. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

RP-LC-UV Determination of Proanthocyanidins in Guazuma ulmifolia

A simple, reproducible, and efficient liquid chromatographic method was developed with UV detection. Water (0.05% TFA):acetonitrile (0.05% TFA) was used as the mobile phase in a gradient system for the determination of procyanidin B2 (PB2) and epicatechin (EC) in the bark of Guazuma ulmifolia Lam. The analysis was performed using a Phenomenex Gemini RP C₁₈ column (5 μm) as stationary phase, at 30 °C, with a flow rate of 0.8 mL min⁻¹, at a wavelength of 210 nm for detection and determination. The main validation parameters of the method were also determined. Calibration curves were found to be linear, with ranges of 20.00–150.00 (PB2) and 10.00–110.00 μg mL⁻¹ (EC). The correlation coefficients of linear regression analysis were between 0.9981 and 0.9988, and the detection limits were between 2.89 and 2.54 μg mL⁻¹. The contents of PB2 and EC were successfully determined, with satisfactory reproducibility and recovery. Recoveries of the PB2 and EC were 103.00 and 104.01%, respectively. The method was successfully applied to the determination of procyanidins in the bark of G. ulmifolia.