A complementary electrochromic system based on Prussian blue and indium hexacyanoferrate

A new complementary electrochromic device (ECD) based on Prussian blue (PB), indium hexacyanoferrate (InHCF), and KCl-saturated poly(2-acrylamido-2-methylpropanesulfonic acid) (K-PAMPS) was proposed and studied in this work. This novel PB-InHCF ECD (PIECD) exhibits blue-to-yellowish electrochromism with a high coloration efficiency of ca. 103 cm²/C at 690 nm. Although the operating voltages for the fully bleached and fully colored states were determined to be 1.2 V and 0 V (InHCF vs. PB), respectively, the major transmittance modulation occurs within a much narrower voltage window (0.9 V↔0.5 V). That is, the PIECD is energetically favorable. Furthermore, it is unnecessary to precolor either electrochromic (EC) electrode during the cell assembly so that the charge balance between two electrochromic films becomes much easier. In addition to the above performance, the compatibility between the K-PAMPS electrolyte and EC electrodes was also demonstrated. In short, this work proposes another promising PB-based ECD and provides a new choice in the EC field. Electronic Publication     

Tracking the optical mass centroid of single electroactive nanoparticles reveals the electrochemically inactive zone

The inevitable microstructural defects, including cracks, grain boundaries and cavities, make a portion of the material inaccessible to electrons and ions, becoming the incentives for electrochemically inactive zones in single entity. Herein, we introduced dark field microscopy to study the variation of scattering spectrum and optical mass centroid (OMC) of single Prussian blue nanoparticles during electrochemical reaction. The “dark zone” embedded in a single electroactive nanoparticle resulted in the incomplete reaction, and consequently led to the misalignment of OMC for different electrochemical intermediate states. We further revealed the dark zones such as lattice defects in the same entity, which were externally manifested as the fixed pathway for OMC for the migration of potassium ions. This method opens up enormous potentiality to optically access the heterogeneous intraparticle dark zones, with implications for evaluating the crystallinity and electrochemical recyclability of single electroactive nano-objects.

The schematic of single cubic-shaped Prussian blue (PB) mesocrystals formed by the oriented aggregation of small nanocrystals. The dark-field images of single PB nanoparticle at PB and Prussian white (PW) states, respectively.     

An Electrochemical Study of Prussian Blue Microcrystalines Mixed in PEO_400 Polymer Electrolyte by Solid-state Voltammetry

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One‐step Electrodeposition of Tris(hydroxymethyl) Aminomethane – Prussian Blue on Screen‐printed Electrode for Highly Efficient Detection of Glycosylated Hemoglobin

In this work, the modified Prussian blue (PB) film showed more stable performance in alkaline solution by one‐step electrodepositon of PB with tris(hydroxymethyl) aminomethane (Tris) on screen‐printed electrode (SPE). The morphology and structure of the modified Tris‐PB/SPE was characterized by scanning electronic microscopy, infra spectroscopy, Raman spectroscopy and X‐ray diffraction. It was inferred that the Tris particles embedded in the PB deposit layer resulted in the change of PB structure and improve its stability in alkaline solution. And then, the modified Tris‐PB/SPE was applied in the detection of Glycosylated hemoglobin (HbA1c). The optimum experimental conditions are pH 7.5, 100 mV/s, 4 μL FAOD and 5 min reaction time. The linearship of HbA1c is i=22.90 C+101.9 in the range of 0.1–2 mmol/L. Comparing with PB/SPE, Tris‐PB/SPE shows better sensitivity and recovery.     

A Free‐standing electrochromic material of poly(5,7‐bis(2‐(3,4‐ethylenedioxy)thienyl)‐indole) and its application in electrochromic device

Free‐standing poly(5,7‐bis(2‐(3,4‐ethylenedioxy)thienyl)‐indole) (PETI) was electrochemically obtained from 5,7‐bis(2‐(3,4‐ethylenedioxy)thienyl)‐indole (ETI) prepared by Stille coupling reaction of 5,7‐dibromoindole and 3,4‐ethylenedioxythiophene. For comparison, poly(5,7‐bis(2‐thiophene)‐indole) was also electrosynthesized from 5,7‐bis(2‐thiophene)‐indole (BTI) which was prepared from the 5,7‐dibromoindole and thiophene. Characterizations of ETI and BTI were performed by cyclic voltammetry, scanning electron microscopy, ¹H NMR, and ¹³C NMR spectroscopy. Spectroelectrochemical studies showed PETI had better electrochromic properties and showed two different colors (brown and blue‐violet) under various potentials with better maximum contrast (ΔT%) and coloration efficiency (CE). An electrochromic device (ECD) based on PETI and poly(3,4‐ethylenedioxythiophene) (PEDOT) was also constructed and characterized. This ECD had fast response time, high CE, better optical memory, and long‐term stability. These results indicated that PETI had potential applications for ECD. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2356–2364     

Use of Screen‐printed Electrodes Modified by Prussian Blue and Analogues in Sensing of Cysteine

The utilisation of screen‐printing technology allows for a mass scalable approach for the production of electrochemical screen‐printed electrodes (SPEs) and the presence of a redox mediator can add new possibilities to the electrochemical properties of the SPEs. Among the materials used as redox mediators, cyanidoferrates polymers can be used for electro‐oxidation of cysteine. In this work, two monomers, namely, [Fe(CN)₆]⁴⁻ and [Fe(CN)₅NH₃]³⁻ were used to produce Prussian blue (PB) and Prussian blue‐Ammine (PB‐Ammine), respectively. In addition, two modification methods were compared, firstly via a drop‐casting and secondly by the incorporation of these materials into a printable ink. The SPE modified by PB‐Ammine (drop‐casting) exhibits the highest electroactive area, however the highest heterogeneous rate constant was found with the SPE modified by PB‐Ammine that was incorporated into the ink. The highest value of the constant of electro‐oxidation of cysteine and lowest limit of detection was also observed in the SPE modified by PB incorporated into the ink. These studies suggest that the electrocatalytic properties of SPE modified by PB and PB‐Ammine are dependent upon the availability of Fe³⁺ catalytic sites and the increased kinetics of the chemical reaction between the catalytic sites and the analyte.     

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.     

Self‐Assembling of Hybrid Prussian Blue Units in Cinder Matrix: Characterization and Electrocatalysis

Industrial waste cinder (CFe*) has been utilized as a stable anchoring matrix for self‐assembling of Fe(CN)₆^3? as hybrid Prussian blue units (PB, *Fe³⁺Fe^II(CN)₆) on a screen‐printed carbon electrode (SPE) for efficient catalytic applications. The waste cinder was found to be a composite of calcium and iron silicates similar to glass matrix by X‐ray photoelectron spectroscopic (XPS) study. The hybrid PB formations were confirmed by both FT‐IR and electrochemical methods. Most importantly, the free iron (Fe*) ion bound to the non‐bridging oxygen terminals of the silicates was found to play a key role in the PB formation. The self‐assembled PB hybrid on the cinder‐modified screen‐printed electrodes (designated as PBCFe*‐SPE) improved linear detection range and sensitivity for H₂O₂ mediated oxidation than those obtained at a classical PB‐SPE in 0.1 M, pH 2 KCl/HCl base electrolyte at 0.0 V (vs. Ag/AgCl) by amperometric batch analysis.     

A novel high‐contrast ratio electrochromic material from spiro[cyclododecane‐1,9′‐fluorene]bicarbazole

A novel electroactive spirocyclododecylfluorene monomer named 2,7‐bis(carbazol‐9‐yl)‐9,9′‐spiro[cyclododecane‐1,9′‐fluorene] (SFC) was synthesized and electrochemically polymerized to give a very stable multi‐electrochromic polymer (poly‐SFC). Two separate oxidation processes were observed for both SFC monomer and poly‐SFC that carries two carbazole units. The polymeric film of poly‐SFC was coated onto ITO/glass surface, and it shows different colors (transparent, yellowish green, green, and dark green) upon stepwise oxidations. An electrochromic device based on poly‐SFC was assembled in the sandwich cell configuration of ITO/poly‐SFC//gel electrolyte//PEDOT/ITO. Poly‐SFC exhibits 90% of transparency at neutral state and a high contrast ratio (ΔT = 58% at 800 nm). This device constructed from it represents a response time of about 1 s, high coloration efficiency (1377 cm² C^–1) and retained its performance by 96.4% even after 1000 cycles. Exhibiting high transparency at neutral state, reversible redox behavior, resistance to overoxidation, and especially high contrast ratio at near IR region can make poly‐SFC be useful and promising candidate for electrochromic applications despite having a relatively slow response time. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Fast,Direct, Low‐Cost Route to Scalable,Conductive, and Multipurpose Poly(3,4‐ethylenedixoythiophene)‐Coated Plastic Electrodes

Poly(3,4‐ethylenedioxythiophene) (PEDOT) films are deposited, using an electroless method, onto flexible plastic poly(ethylene terephthalate) (PET) substrates of approximately 20×6 cm². The sheet resistance of a PEDOT–PET film is approximately 600 Ω per square, and the nanoscale conductivity is 0.103 S cm^?1. A plastic electrochromic PEDOT–Prussian blue device is constructed. The device undergoes a color change of pale blue to deep violet–blue reversibly over 1000 cycles, thus demonstrating its use as a light‐modulating smart window. The PEDOT–PET film is also used in a quantum dot solar cell, and the resulting photoelectrochemical performance and work function indicate that it is also promising for photovoltaic cells. The high homogeneity of the PEDOT deposit on PET, the optimal balance between conductivity and optical transparency, and the demonstration of its use in an electro‐optical device and a solar cell, offer the opportunity to use this electrode material in a variety of low‐cost optoelectronic devices.     

Effects of Supporting Electrolytes on Spectroelectrochemical and Electrochromic Properties of Polyaniline‐poly(styrene sulfonic acid) and Poly(ethylenedioxythiophene)‐poly(styrene sulfonic acid)‐based Electrochromic Device

Electrochromic devices are fabricated by using polyaniline (PANI) doped with poly(styrene sulfonic acid) (PSS) as coloring electrodes, poly(ethylenedioxythiophene)‐poly(styrene sulfonic acid) (PEDOT‐PSS) as complementary electrodes, and hybrid polymer electrolytes as gel electrolytes. The device based on LiClO₄‐based electrolyte (weight ratio of PMMA:PC:LiClO₄ = 0.7:1.1:0.3) shows the highest optical contrast and coloration efficiency (333 cm²/C) after 1200 cycles in these devices, and the color changes from pale yellow (?0.5 V) to dark blue (+2.5 V). The spectroelectrochemical and electrochromic switching properties of electrochromic devices are investigated, the maximum optical contrast (ΔT%) of electrochromic device for ITO|PANI‐PSS‖PMMA‐PC‐LiClO₄‐SiO₂‖PEDOT‐PSS|ITO are 31.5% at 640 nm, and electrochromic device based on LiClO₄‐based electrolyte with SiO₂ shows faster response time than that based on LiClO₄‐based electrolyte without SiO₂.     

A Robust,Precious‐Metal‐Free Dye‐Sensitized Photoanode for Water Oxidation: A Nanosecond‐Long Excited‐State Lifetime through a Prussian Blue Analogue

Herein, we establish a simple synthetic strategy affording a heterogeneous, precious metal‐free, dye‐sensitized photoelectrode for water oxidation, which incorporates a Prussian blue (PB) structure for the sensitization of TiO₂ and water oxidation catalysis. Our approach involves the use of a Fe(CN)₅ bridging group not only as a cyanide precursor for the formation of a PB‐type structure but also as an electron shuttle between an organic chromophore and the catalytic center. The resulting hetero‐functional PB‐modified TiO₂ electrode demonstrates a low‐cost and easy‐to‐construct photoanode, which exhibits favorable electron transfers with a remarkable excited state lifetime on the order of nanoseconds and an extended light absorption capacity of up to 500 nm. Our approach paves the way for a new family of precious metal‐free robust dye‐sensitized photoelectrodes for water oxidation, in which a variety of common organic chromophores can be employed in conjunction with CoFe PB structures.     

Electroanalytical Properties of ITO Electrodes Modified with Environment‐Sensitive Poly(N‐isopropylacrylamide) Gel and Prussian Blue

It has been shown that ITO electrodes could be modified with a volume‐phase‐transition gel based on poly(N‐isopropylacrylamide) cross‐linked with N,N′‐methylenebisacrylamide. Prussian blue (PB) was deposited electrochemically inside the gel while glucose oxidase was added at the time of electropolymerization. The electrocatalytic activity of glucose oxidase towards the oxidation of glucose (measured as the reduction current of hydrogen peroxide) was strongly depressed by the shrinking process. Since the volume phase transition triggered by the temperature change is reversible the obtained change in the enzyme activity may be useful for getting a switchable system.     

Preparation of Three‐Dimensional Ordered Macroporous Prussian Blue Film Electrode for Glucose Biosensor Application

Ordered 3D interconnected macroporous Prussian blue (PB) films were electrochemically fabricated by using colloidal crystals of polystyrene beads as sacrificial templates. The prepared PB film electrodes have excellent catalytic activity towards the reduction of hydrogen peroxide. The PB structure was further used as functional interface for fabricating an enzyme‐based glucose sensor by using surface modification technique based on the electrostatic interactions. The resulted sensor has higher functional density, and larger surface area. The interconnected macroporous structure allows enhanced mass transport. These characteristics of the sensor enable us to detect glucose with high sensitivity. Therefore, the present 3D ordered macroporous film sensor exhibits wide linear detection range towards glucose, acceptable reproducibility and operational and storage stability. The present approach is promising for the generation of high‐enzyme‐content thin films with tailored bioactivity.     

Physicochemical Characteristics of Polypyrrole/(Glucose oxidase)/(Prussian Blue)‐based Biosensor Modified with Ni‐ and Co‐Hexacyanoferrates

In this work, three types of electrodes suitable for amperometric glucose biosensors were designed. One type of electrode was based on bio‐selective layer of polypyrrole/(glucose oxidase)/(Prussian Blue) (Ppy/GOx/PB) and it was used as a control electrode regarding to which electrochemical properties of two other types of electrodes were compared. During the formation of Prussian blue layers graphite electrodes were additionally modified by Ni‐hexacyanoferrate (NiHCF) and by Co‐hexacyanoferrate (CoHCF) in order to design Ppy/GOx/PB‐NiHCF and Ppy/GOx/PB‐CoHCF electrodes, respectively. Some physicochemical characteristics of all three types of electrodes were evaluated and compared. The Ppy/GOx/PB‐NiHCF electrode showed wider linear range of the calibration curve than Ppy/GOx/PB and Ppy/GOx/PB‐CoHCF electrodes. The effect of temperature on analytical performance of the Ppy/GOx/PB‐NiHCF based biosensor has been evaluated and activation energy of enzyme catalysed reaction has been calculated within the temperature range of 15 °C to 30 °C.     

Characterization of polyether‐poly(methyl methacrylate)‐lithium perchlorate blend electrolytes

Solid polymer electrolyte (SPE) systems based on interpenetrating blends of poly(ethylene oxide‐co‐propylene oxide) and poly(methyl methacrylate) host matrices, with lithium perchlorate as guest salt, were prepared. These electrolytes were presented as free‐standing films, and their thermal and electrochemical properties were characterized by conductivity and electrochemical stability measurements. The properties of the interpenetrating blends of poly(ethylene oxide‐co‐propylene oxide) and poly(methyl methacrylate) host matrices as the electrolyte component of a solid‐state electrochromic device are reported and the results obtained suggest that this electrolyte provides an encouraging performance in this application. The most conducting electrolyte composition of this SPE system is the formulation designated as SPE2‐0PC (5.01 × 10^?4 S cm^?1 at about 57°C). The lowest decomposition temperature was registered with the SPE6‐15PC composition (233°C). The average transmittance in the visible region of the spectrum was above 41% for all the samples analyzed. After coloration the device assembled with 71 wt% PC presented an average transmittance of 15.71% and an optical density at 550 nm of 0.61. Copyright © 2010 John Wiley & Sons, Ltd.     

Prussian Blue Derived Nanoporous Iron Oxides as Anticancer Drug Carriers for Magnetic‐Guided Chemotherapy

New nanoporous iron oxide nanoparticles with superparamagnetic behavior were successfully synthesized from Prussian blue (PB) nanocubes through a thermal conversion method and applied to the intracellular drug‐delivery systems (DDS) of bladder cancer cells (i.e., T24) with controlled release and magnetic guiding properties. The results of the MTT assay and confocal laser scanning microscopy indicate that the synthesized iron oxide nanoparticles were successfully uptaken by T24 cells with excellent biocompatibility. An anticancer drug, that is, cisplatin, was used as a model drug, and its loading/release behavior was investigated. The intracellular drug delivery efficiency was greatly enhanced for the cisplatin‐loaded, PB‐derived, magnetic‐guided drug‐delivery system compared with the non‐drug case. The synthesized nanomaterials show great potential as drug vehicles with high biocompatibility, controlled release, and magnetic targeting features for future intracellular DDS.     

Separation/Concentration‐signal‐amplification in‐One Method Based on Electrochemical Conversion of Magnetic Nanoparticles for Electrochemical Biosensing

We propose a separation/concentration‐signal‐amplification in‐one method based on electrochemical conversion (ECC) of magnetic nanoparticles (MNPs) to develop a facile and sensitive electrochemical biosensor for chloramphenicol (CAP) detection. Briefly, aptamer‐modified magnetic nanoparticles (MNPs‐Apt) was designed to capture CAP in sample, then the MNPs‐Apt composite was conjugated to Au electrode through the DNA hybridization between the unoccupied aptamer and a strand of complementary DNA. The ECC method was applied to transfer MNPs labels to electrochemically active Prussian blue (PB). The anodic and cathodic currents of PB were taken for signal readout. Comparing with conventional methods that require electrochemically active labels and related sophisticated labelling procedures, this method explored and integrated the magnetic and electrochemical properties of MNPs into one system, in turn realized magnetic capturing of CAP and signal generation without any additional conventional labels. Taking advantages of the high abundance of iron content in MNPs and the refreshing effect deriving from ECC process, the method significantly promoted the signal amplification. Therefore, the proposed biosensors exhibited linear detection range from 1 to 1000 ng mL⁻¹ and a limit of detection down to 1 ng mL⁻¹, which was better than or comparable with those of most analogues, as well as satisfactory specificity, storage stability and feasibility for real samples. The developed method may lead to new concept for rapid and facile biosensing in food safety, clinic diagnose/therapy and environmental monitoring fields.     

Electrochromic hysteresis performance of a prussian blue film arising from electron-transfer control by a tris(2,2'-bipyridine)ruthenium(II)-doped WO(3) film as studied by a spectrocyclic voltammetry technique

A [Ru(bpy)(3)](2+) (bpy=2,2'-bipyridine)-doped WO(3) film was prepared as a base layer on a substrate by cathodic electrodeposition from a colloidal triad solution containing peroxotungstic acid (PTA), [Ru(bpy)(3)](2+), and poly(sodium 4-styrenesulfonate) (PSS). A Prussian blue (PB; Fe(II)-Fe(III)) film was cathodically electrodeposited on the [Ru(bpy)(3)](2+)-doped WO(3) film or neat WO(3) film from an aqueous Berlin brown (BB; Fe(III)-Fe(III)) colloid solution to yield a [Ru(bpy)(3)](2+)-doped WO(3)/PB bilayer film or WO(3)/PB bilayer film. For the spectrocyclic voltammogram (SCV) of the WO(3)/PB film, a redox response of Prussian white (PW; Fe(II)-Fe(II))/PB was observed at 0.11 V, however, further oxidation of PB to BB was not allowed by the interfacial n-type Schottky barrier between the WO(3) and PB layers. For the [Ru(bpy)(3)](2+)-doped WO(3)/PB film, any electrochemical response assigned to the redox of PB was not observed in the cyclic voltammogram, however, the in situ absorption spectral change recorded simultaneously showed the significant redox reactions based on PB. The SCV revealed that PW on the [Ru(bpy)(3)](2+)-doped WO(3) film is completely oxidized to PB by a geared reaction of Ru(II)/Ru(III) at 1.05 V, and that 32 % of PB formed is further oxidized to BB by the same geared reaction in the potential scan to 1.5 V. PB was completely re-reduced to PW by a geared reaction of H(x)WO(3)/WO(3) at -0.5 V in the reductive potential scan. These geared electrochemical reactions produced an electrochromic hysteresis performance of the PB film layered on the [Ru(bpy)(3)](2+)-doped WO(3) film.     

A Solution‐processible,n‐dopable polypyrrole derivative

In this study, soluble, n‐dopable, florescent, electrochromic polypyrrole derivative was synthesized through both chemical and electrochemical polymerization of 2‐[6‐(1H‐pyrrol‐1‐yl)hexyl]‐1H‐benzo[de]isoquinoline‐1,3(2H)‐dione (PyNI). The polymer synthesized through chemical polymerization had PL emission maxima at 471 and 543 nm and exhibited two redox couples at E_1/2,p = ?1.48 V and E_1/2,p = 1.12 V due to n‐type and p‐type doping, respectively. Electrochromic properties of electrochemically synthesized poly(PyNI) (PPyNI) were investigated via spectroelectrochemistry, kinetic studies, coloration efficiency, and colorimetry measurements. The optical band gap of PPyNI was calculated as 2.99 and 2.37 eV. Spectroelectrochemistry analysis of PPyNI reflected electronic transitions at 330–418 nm and 704 nm due to π–π* transition and charge carrier band formation, respectively. The polymer exhibited a switching time of 1.63 s and an optical contrast of 33.37%. Furthermore, dual‐type, complementary‐colored polymer electrochromic device in ITO/PPyNI/PEDOT/ITO configuration was assembled and characterized. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012