Papers by Keyword: Electrochromism

Abstract: The technology of producing stable electrochromic anode nanocomposite thin film coatings based on nickel oxide (II) has been developed, which are used as active layers for modulating light flux in the manufacture of various technical devices. The method involves introduction of carbon nanoparticles (carbon-containing particles) into outer layers of nickel oxide (II) thin films obtained by gas-phase deposition under conditions of cathodic polarization in potentiostatic mode in aqueous media containing water-soluble hydroxylated fullerene derivatives - fullerenol С₆₀(ОН)₂₄, without change of their optical density in the initial state. The technology of the method realization allows to effectively change electrochromic properties of nickel oxide (II) thin films and to obtain a nanocomposite, which is a matrix of a thin layer of nickel oxide (II), doped with carbon nanoparticles, with increased contrast and having the ability to maintain a colored state after switching off polarization under open chain conditions for a long time without energy consumption in solution and in air, i.e., characterized by an “optical memory effect”.

Abstract: In this work, we report the role of structure on electrochromic behavior of nickel oxide thin coatings deposited via chemical vapor deposition on ITO-coated glass in (EtCp)₂Ni–O₂–Ar and (EtCp)₂Ni–O₃–O₂–Ar reaction systems. The structure and chemical composition were analyzed and then correlated with electrochemical response and transmittance modulation when immersed in 1 M KOH electrolyte. The NiO exhibits an anodic coloration, reaching an optical density modulation of 0.66 between colored and bleached state at 550 nm, with a color efficiency of 30.7 cm²C^-1. Very fast switching between states was obtained, the coloration and bleaching time did not exceed 0.05 sec.

Abstract: Polyamic acid (PAA) thin films were prepared by electrodepositing PAA onto indium tin oxide (ITO) electrode and characterized using electrochemical methods (cyclic voltammetry, square wave voltammetry), Ultraviolet Visible spectroscopy and Ultraviolet Visible/Spectro-electrochemistry (UV/vis Spectro-electrochemistry). The electrodeposited PAA thin films were observed to have two redox couples with a formal of 118 mV and 274 mV. The diffusion coefficient (D_e) determined from cyclic voltammetry was found to be 7.9x10^-6 cm²/s and provide a measure of how fast charge is transported through the thin film. PAA showed a broad absorption peak at 214 nm due to the carbonyl chromophores within the polymer and shoulder peak at 293 nm from a quinoid-type chromophore. The calculated band gap of 4.23 eV suggested the polymer was optically transparent between 300 nm to 800 nm. This indicated that the PAA thin films has emerged as a very promising and cost effective alternative material to ITO with good transparent and conductive properties. PAA thin films were further applied for the detection of anthracene. The analytical response of anthracene was studied at the ITO/PAA using spectro-electrochemistry. The characteristic analytical absorbance signal for anthracene was clearly identified at 375 nm when ITO/PAA electrode was polarised at -800 mV (vs Ag/AgCl). The calibration curve for anthracene showed a linear response from 4.95x10^-4 to 1.15x10^-2 M. The ITO/PAA showed a low detection limit of (0.0068 g/L) and high sensitivity for anthracene, making it a suitable platform for spectro-electrochemical analysis of polycyclic aromatic hydrocarbons.

Abstract: Nanoscale material world attracted researchers because of their outstanding properties and prospective novel applications. Tungsten trioxide semiconductor is one of the fundamental functional materials due to its versatile application as gas sensors, solar cells, and smart windows. Confined growth of the metal oxide nanostructures can tune the electrical and optical properties for modern device application. The management of morphology is a challenge to investigate the ultimate performance. In this paper, self-assembled growth of four different tungsten trioxide nanostructures were carried using a different structure directing agents through either co-precipitation or hydrothermal techniques. The monoclinic spherical and rod-like WO₃ nanostructures were obtained by acid precipitation method. WO₃ nanocuboids and nanofibers were synthesized hydrothermally using HBF₄ and NaCl as structure directing reagents to attain monoclinic and hexagonal crystal phases, respectively. Analytical techniques like XRD, TEM, and FESEM imaging methods were used to confirm the phase and morphology. All the nanopowders were calculated to have similar band gap energy at visible wavelength. A simple dip coated WO₃/ITO fabricated electrode was used as a reference electrode to carry out the electrochemical measurements for all nanopowders. The evaluated properties suggested the plausible use of WO₃ nanofibers for high efficient electrochromic device.

Abstract: The electrochromic properties of an electrochemical polymerized composite consisted of poly (3,4-ethylenedioxythiophene) doped with fluorescent yellow dye (PEDOT-FY) with different polymerization time are reported. The structures of PEDOT-FY were characterized via cycle voltammograms and spectroelectrochemistry. The PEDOT-FY films can appears orange-yellow and purple in the neutral state, and yellow-green and deep green in the oxidized state. Polymerizing for 6 min, the PEDOT-FY film comes out a new pair of oxidative and reductive peaks around 0.3V and-0.15V. In addition, the PEDOT-FY films also have short response times. It is shown that acid dye doping is an effective method to broaden the color change range of the electrochromic mateials.

Abstract: Triphenylamine derivative is one of the multifunctional materials which has attracted considerable interest of research for their unique radical properties containing triphenylamine unit with higher holes mobility, excellent photoelectric conversion capability. The three benzyl rings of triphenylamine unit can connect different functional groups which can display different activity in the fields of organic solar cells, electroluminescence, electrochromism, optical limiting and chemical sensors. Moreover， the developing prospects of triphenylamine derivative are also briefly discussed.

Abstract: A novel binuclear ruthenium alkynyl complexes with dithienylethene unit [{(MePh-tpy)(PPh₃)₂RuCl}₂(C≡C-DTE-C≡C)](ClO₄)₂ (II) has been synthesized and characterized by elemental analysis and NMR spectra. Its photochromic behaviors and redox properties have also been investigated. The results indicated that the open-ring isomers of the metal complex could be triggered, either by light or electricity, to convert to their closed forms.

Abstract: The electrochromic properties of an electrochemical polymerized composite consisted of poly (3,4-ethylenedioxythiophene) doped with fluorescent yellow dye (PEDOT-FY) are reported. The structures of PEDOT-FY were characterized via cycle voltammograms, spectroelectrochemistry and colorimetric analysis. Film of the PEDOT-FY composites with different FY concentrations appears multi-color changes, such as blue violet↔brillant blue, aubergine↔blue grey, magenta↔ aquamarine blue, orange-yellow↔grass-green, claybank↔moss green in the neutral state and the oxidized state respectively, which are different from the pure PEDOT of dark blue (-0.8V) and light blue (1.0V). The response time reaching 90% of the full optical contrast of PEDOT-FY was 3.4s for the oxidation process and 2.6s for the reverse reduction process when the [EDOT]/[FY] is 1:2, however, when the FY concentration decreased to [EDOT]/[FY] =1:0.01, the response time reduced to 1.9s and 1.7s for the oxidation and reduction process respectively, which is equal to that of the pure PEDOT. Additionally, the colorimetric analysis results show that components of yellow and red in PEDOT-FY films become stronger than pure PEDOT film at the whole electrochromic process. It is shown that acid dye doping is an effective method to broaden the color change range of the electrochromic mateials.

Abstract: 4-Phenoxy-4', 4''-diaminotriphenylamine was synthesized from N, N-diarylation of 4-amino diphenyl ether and 4-fluoro nitrobenzene, and subsequent reduction of the resultant dinitro compound. The prepared triphenylamine and 4-methoxy-4', 4''-diaminotriphenylamine were dissolved in acetone respectively as the curing agents with epoxy resins to obtain a homogeneous mixture of the reactants. The cross-linked polymer film, which was well adhered to the ITO glass were cured by gradually increasing the temperature under N₂ atmosphere. The cured epoxy resins films exhibited good thermal stability and electroactive properties. CV of the films revealed two pairs of reversible redox peaks, with coloration change from the colorless neutral state to the blue oxidized state.

Abstract: Comparative work of erbium doped vanadium pentoxide and titanium dioxide thin films were carried out via sol gel technique by dissolving erbium (III) nitrate pentahydrate in vanadium (V) oxoisopropoxide and titanium (IV) isopropoxide. Fourier Transform IR and thermogravimetric/differential thermal measurements were performed to find out erbium substitution. UV-Vis. spectroscopy indicated a blue shift upon Er doping in V₂O₅ film due to the softening of V=O bond. The similar behavior was expected in TiO₂ film and the prediction shall be shown only if annealing of the film above 600°C, resulting oxygen deficiency in anatase TiO₂ while Ti deficiency in rutile TiO₂ film. Due to such impact of erbium on structure, granule size of the films, determined by AFM, increased yielding more space for intercalation of ion in host materials and monitored through cyclic voltammetry measurements.