Electrochromic responses of low-temperature-annealed tungsten oxide thin films in contact with a liquid and a polymeric gel electrolyte

Thin films of tungsten trioxide (WO₃) for electrochromic application were synthesized by potentiostatic method by using a peroxytungstic acid as a solution precursor. The morphology of the films with and without postthermal annealing was analyzed by atomic force microscopy. When they were in contact with the liquid electrolyte (LiI in propylene carbonate, PC) and under alternatively applied negative (−1.5 V) and positive (+1.0 V) potentials, the transient optical transmittance modulations at wavelength of 650 nm of the as-deposited and 60 °C annealed WO₃ samples were higher than that of 100 °C annealed WO₃ films, and the switching times between the colored and bleached states were related to the surface morphology of the WO₃ films. In polymeric gel electrolyte (LiI and polymethyl methacrylate in PC) devices, longer time was required for complete coloration as well as bleaching process compared with the liquid one. A parametric analysis was made for each of the transient optical transmittance curves of WO₃-based electrochromic devices to extract the values of the response time in coloration (reduction) and bleaching (oxidation) processes. It concludes that the coloration process was determined by the exchange of current density at the electrolyte–WO₃ interface and a possible inhomogeneous interfacial potential for ion intercalation retards the effective coloration time. The bleaching process seems to be controlled by the space charge-limited lithium ion diffusion in WO₃ electrode and the ionic conductivity of the electrolyte as well.     

Electrochromic properties of polythiophene polyrotaxane film

The electrochromic properties of a polythiophene polyrotaxane film consisting of a polythiophene backbone wrapped by the tetra-cationic cyclophane, cyclobis(paraquat-p-phenylene), were characterized. A naked reference polythiophene film, i.e., polythiophene without tetra-cationic cyclophane, was also characterized. The surface morphology and thickness of the film (L) were observed by atomic force microscopy. The surface of the naked reference polythiophene film has micrometer-scale polythiophene aggregates, which causes the darker color of the film and smaller color contrast in the electrochromic process. The polythiophene polyrotaxane gives a more homogeneous and brighter colored film owing to the suppression of molecular interactions between the polythiophene chains by the tetra-cationic cyclophanes. Potential-step chronoamperometric measurement provided the area density of the oxidizable sites (Γ) and the apparent diffusion coefficient of the charge transport in the film. From linear relationship between L and Γ, the concentrations of the oxidizable sites in the polythiophene polyrotaxane and naked reference polythiophene films were calculated to be 1.3 and 2.4 mmol cm(-3), respectively. Interestingly, the polythiophene polyrotaxane film afforded a significantly larger apparent diffusion coefficient than the naked reference polythiophene film. This result suggests that the rate-determining step of the charge transport is not the electron hopping between the polythiophene chains but the transport of charge-compensating counterions from the solvent into the polythiophene. We believe that the counteranions of the tetra-cationic cyclophane provide a pathway allowing the charge-compensating counteranions to migrate from the solvent to polythiophene. The polythiophene polyrotaxane film showed faster color change than the naked reference polythiophene film in the electrochromic reaction. These results indicate that our polythiophene polyrotaxane is a better electrochromic material than the naked reference polythiophene.     

Microfiltration of protein solutions at thin film composite membranes

An experimental study of the interaction of the enzyme yeast alcohol dehydrogenase (YADH) with polysulfone thin film composite microfiltration membranes (Dow-Danmark) has been carried out. It was found that the membranes adsorbed only 3/4 of a monolayer of the enzyme under the conditions studied. Even so, under filtration conditions, the membrane permeation rate decreased continuously with time. This decrease in permeation rate was due neither to concentration polarisation nor to protein adsorption alone. However, it could be quantified using the standard blocking filtration law, which describes a decrease in pore volume due to deposition of protein in the interior structure of the membrane. Reversal of the membrane, so that the supporting matrix faced the feed solution, gave more stable permeation rates. Implications for the microfiltration of industrial fermentation broths are discussed.     

Frequency dependence of hysteresis associated with the electromechanical performance of PVDF film

The thickness strains, the electric displacements, and the hysteresis exhibited by poly(vinylidene fluoride) films under sinusoidal applied electric fields were measured over a range of frequencies from 0.05 to 100 Hz. The loops of strain‐ and electric displacement versus electric field exhibit a shape and hysteresis that undergoes a continuous and reversible change with frequency. At lower frequencies (<5 Hz), the shape and large hysteresis are characteristic of a ferroelectric with degrees of remanent polarization. At higher frequencies (>5 Hz), the shape and slight hysteresis of the loops are representative of a nonremanently polarized ferroelectric. This dependence of shape and hysteresis on frequency is attributed to the difference in rates between the rapid rate by which the polarization of domains of aligned dipoles is reversed in a periodic field and the slower rate by which the polarization is made remanent. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3207–3214, 2007     

Ratchet composite thin film for low-temperature self-propelled Leidenfrost droplet

The droplet control, especially for the self-propelled Leidenfrost droplet, has attracted many researchers' attention in applied and fundamental fields. In this paper, the ratchet thin film was fabricated by magnetron sputtering and hybrid ion beams deposition. The micro- and nanoscale structure of the film was characterized by field emission scanning electron microscope. This study reports an interesting phenomenon that the self-propelled Leidenfrost water droplet was initiated at low temperature. The Leidenfrost point of droplets was controlled by the surface wettability and parameters of the asymmetric ratchet substrate. This novel self-propelled interfacial material and preparation technology can be expanded to the manufacture process and constructed a temperature-dependent tubule for microfluidic systems.     

多硫电解质对CdS薄膜电池光电性能影响研究

在CdS薄膜的光电化学电池中,多硫电解质起着促进电子传递,减少电子空穴复合几率,从而提高电池光电转换效率的作用;但多硫电解质又会阻碍CdS薄膜对光的吸收。本文通过对CdS纳米管薄膜电池在含硫量不同的电解质中光电性能的考察,证明了0.5 mol/L Na2S、0.5 mol/L NaOH和0.5 mol/L S的液态电解质成分组合为本实验中制得的CdS纳米管薄膜光电化学电池的最佳电解质。     

Zinc oxide-potassium ferricyanide composite thin film matrix for biosensing applications

Thin film of zinc oxide-potassium ferricyanide (ZnO-KFCN) composite has been deposited on indium tin oxide (ITO) coated corning glass using pulsed laser deposition (PLD). The composite thin film electrode has been exploited for amperometric biosensing in a mediator-free electrolyte. The composite matrix has the advantages of high iso-electric point of ZnO along with enhanced electron communication due to the presence of a redox species in the matrix itself. Glucose oxidase (GOx) has been chosen as the model enzyme for studying the application of the developed matrix to biosensing. The sensing response of the bio-electrode, GOx/ZnO-KFCN/ITO/glass, towards glucose was studied using cylic voltammetry (CV) and photometric assay. The bio-electrode exhibits good linearity from 2.78 mM to 11.11 mM glucose concentration. The low value of Michaelis-Menten constant (1.69 mM) indicates an enhanced affinity of the immobilized enzyme towards its substrate. A quassireversible system is obtained with the composite matrix. The results confirm promising application of the ZnO-KFCN composite matrix for amperometric biosensing applications in a mediator-less electrolyte that could lead to the realization of an integrated lab-on-chip device.     

Multilayered gold-nanoparticle/polyimide composite thin film through layer-by-layer assembly

A novel type of composite thin film consisting of gold nanoparticles (AuNPs) and polymide (PI) was fabricated through layer-by-layer (LBL) assembly. To fabricate such films, bare AuNPs and a poly (amic acid) bearing pendant amine groups, namely, amino poly (amic acid) or APAA, were synthesized and assembled in an LBL fashion. Without any organic encapsulation layer on their surface, AuNPs were bound directly to APAA chains at the amine sites; X-ray photoelectron spectroscopy study suggested that the binding was based on a combined effect of metal-ligand coordination and electrostatic interaction, with the former dominating over the latter. An approximately linear growth of the film started from the second layer of AuNP as revealed by the UV-vis spectroscopy, and the degree of particle aggregation was higher in the first AuNP layer than in the subsequent layers due to the differences in the density of binding sites. The resultant assembly was heated to imidize the APAA, thereby creating a robust composite structure.     

Interfacially synthesized thin film composite RO membranes for seawater desalination

A composite RO membrane with high salt rejection and high flux for the desalination of seawater was prepared by treating a porous polysulfone (PS) support sequentially with a di-amine and then with a polyfunctional acid chloride, thereby forming a thin film of polyamide (PA) on the PS support. In order to establish conditions for the development of suitable thin film composite (TFC) membranes on a coating machine, various parametric studies were carried out which included varying the concentration of reactants, reaction time, curing temperature and curing time for thin film formation by the interfacial polymerization technique. By suitable combination of these factors,a desired thin film of polyamide with improved performance for seawater desalination could be obtained. Moreover, the product water fluxes were considerably enhanced by post-treatment of the TFC membrane. Continuous sheets of TFCs were developed on the mechanical coating unit and tested for RO performance in a plate-and-frame configuration with synthetic seawater. The performance of these composite membranes was also determined for the separation of organics and compared with cellulose acetate (CA) membranes.     

Electrochemical study of Azathioprine at thin carbon nanoparticle composite film electrode

Thin carbon nanoparticle/Nafion film (CNP/N), as a novel electrode material, is formed on the surface of the glassy carbon electrode in a simple solvent evaporation process. The electrochemical behavior of Azathioprine (Aza) at the CNP/N-modified electrode is investigated in detail by the means of cyclic voltammetry. During the electrochemical reduction of Aza, an irreversible cathodic peak is appeared. Cyclic voltammetric studies indicated that the reduction process has an irreversible and adsorption-like behavior. The observed reduction peak is attributed to a four-electron process referring to the reduction of nitro group to the corresponding hydroxylamine. The prepared electrode showed an excellent catalytic activity toward the electro-reduction of Aza leading to a significant improvement in sensitivity as compared to the bare glassy carbon electrode where the electrochemical activity for this compound is very weak.     

Analytical performance characteristics of thin and thick film amperometric microcells

The analytical performance of amperometric microcells with different electrode geometries is compared for enzyme activity measurements. The microcells were fabricated with thin film photolithography or thick film screen-printing in four different designs. The cells made with the thin film process used flexible substrate with microelectrode array or a circular, disk-shaped working electrode. The screen-printed working electrodes had semicircle or disk shape on ceramic chips. Putrescine oxidase (PUO) activity measurement was used as a model. The determination of PUO activity is important in the clinical diagnosis of premature rupture of the amniotic membrane. An electropolymerized m-phenylenediamine size-exclusion layer was used to eliminate common interferences. The size exclusion layer revealed also to be advantageous in protecting the electrodes from fouling by putrescine (enzyme substrate). The electrode fouling of bare electrodes was insignificant for screen-printed electrodes, but very severe for electroplated platinum working electrodes. The microelectrode array electrodes demonstrated smaller RSD and higher normalized sensitivities for hydrogen peroxide and PUO activity. All the other electrodes were demonstrating comparable analytical performances.     

不同含钴阴极在YSZ薄膜电解质固体氧化物燃料电池中的性能

固体氧化物燃料电池阴极材料的阻抗对固体氧化物燃料电池的性能有较大影响.我们通过XRD、对称电池以及单电池性能测试等方法比较系统地研究了4种最为常用的含钴阴极材料直接用于钇稳定化氧化锆（YSZ）电解质薄膜与通过引入SDC夹层后用于YSZ电解质薄膜后的性能.我们发现,不同的含钴阴极材料与YSZ材料之间都不同程度地发生相反应,在应用于YSZ电解质薄膜上时,相反应大大降低了含钴阴极材料的性能,在使用了SDC夹层后,单电池的功率输出显著提高.     

A lithium secondary battery using a thin film of polymer electrolyte as a separator

Ion-conductive polymer which shows an ionic conductivity (σ_i) of 1.4 × 10^?4S/cm at 25°C when mixed with LiClO₄ (molar ratio in Li/OE = 0.05) was used as a separator of electrodes in a lithium secondary battery. The effect of high ionic conductivity on the performance of the battery was studied. The polymer structure was and the cathode was comprised of poly(1,3,4-thiadiazole disulfide), graphite powder and the polymer electrolyte. The cell [(?)Li/polymer electrolyte/graphite–poly(disulfide) (+)] had an open circuit voltage (V_oc) of 3.25 V, a plateau voltage of 2.75 V, a discharge density (i_d) of 0.05 mA/cm² with the cathode utilization of 63%, and achieved over several tens of cycles at 25°C.     

Analytical performance characteristics of thin and thick film amperometric microcells

The analytical performance of amperometric microcells with different electrode geometries is compared for enzyme activity measurements. The microcells were fabricated with thin film photolithography or thick film screen-printing in four different designs. The cells made with the thin film process used flexible substrate with microelectrode array or a circular, disk-shaped working electrode. The screen-printed working electrodes had semicircle or disk shape on ceramic chips. Putrescine oxidase (PUO) activity measurement was used as a model. The determination of PUO activity is important in the clinical diagnosis of premature rupture of the amniotic membrane. An electropolymerized m-phenylenediamine size-exclusion layer was used to eliminate common interferences. The size exclusion layer revealed also to be advantageous in protecting the electrodes from fouling by putrescine (enzyme substrate). The electrode fouling of bare electrodes was insignificant for screen-printed electrodes, but very severe for electroplated platinum working electrodes. The microelectrode array electrodes demonstrated smaller RSD and higher normalized sensitivities for hydrogen peroxide and PUO activity. All the other electrodes were demonstrating comparable analytical performances.     

Fabrication of solid thin film electrolyte and LiCoO2 by aerosol flame pyrolysis deposition

Aerosol flame pyrolysis deposition method was applied to deposit the oxide glass electrolyte film and LiCoO₂ cathode for thin film type Li-ion secondary battery. The thicknesses of as-deposited porous LiCoO₂ and Li₂O–B₂O₃–P₂O₅ electrolyte film were about 6 μm and 15 μm, respectively. The deposited LiCoO₂ was sintered for 2 min at 700 °C to make partially densified cathode layer, and the deposited Li₂O–P₂O₅–B₂O₃ glass film completely densified by the sintering at 700 °C for 1 h. After solid state sintering process the thicknesses were reduced to approximately 4 μm and 6 μm, respectively. The cathode and electrolyte layers were deposited by continuous deposition process and integrated into a layer by co-sintering. It was demonstrated that Aerosol flame deposition is one of the good candidates for the fabrication of thin film battery.     

Electrochromic properties of sputtered TiO2 thin films

TiO₂ thin films were deposited on ITO/Glass substrates by the rf magnetron sputtering in this study. The electrochromic properties of TiO₂ films were investigated using cyclic voltammograms (CV), which were carried out on TiO₂ films immersed in an electrolyte of 1 M LiClO₄ in propylene carbonate (PC). As- deposited TiO₂ thin film was amorphous, while the films post-annealed at 300~600°C contained crystallized anatase and rutile. With the increase of the annealing temperature, the surface roughness of film increased from 1.232 nm to 1.950 nm. Experimental results reveal that the processing parameters of TiO₂ thin films will influence the electrochromic properties such as transmittance, ion-storage capacity, inserted charge, optical density change, coloration efficiency and insertion coefficient.     

Polyimide polydimethylsiloxane triblock copolymers for thin film composite gas separation membranes

This article demonstrates the successful fabrication of thin‐film‐composite (TFC) membranes containing well‐defined soft‐hard‐soft triblock copolymers. Based on “hard” polyimide (PI) and “soft” polydimethylsiloxane (PDMS), these triblock copolymers (PDMS‐b‐PI‐b‐PDMS), were prepared via condensation polymerization, and end‐group allylic functionalization to prepare the polyimide component and subsequent “click” coupling with the soft azido functionalized PDMS component. The selective layer consisted of pure PDMS‐b‐PI‐b‐PDMS copolymers which were cast onto a precast crosslinked‐PDMS gutter layer which in turn was cast onto a porous polyacrylonitrile coated substrate. The TFC membranes' gas transport properties, primarily for the separation of carbon dioxide (CO₂) from nitrogen (N₂), were determined at 35 °C and at a feed pressure of 2 atm. The TFC membranes showed improvements in gas permselectivity with increasing PDMS weight fraction. These results demonstrate the ability for glassy, hard polymer components to be coated onto otherwise incompatible surfaces of highly permeable soft TFC substrates through covalent coupling. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3372–3382     

Application of thin film composite membranes to the membrane aromatic recovery system

The membrane aromatic recovery system (MARS) is a new membrane technology which recovers aromatic acids and bases. The first industrial installation has been operating at a Degussa site in the UK recovering cresols since 2002. The state of the art MARS technology employs a tubular silicone rubber membrane. However, this places some limitations on the process due to relatively low mass transfer rates and limited chemical resistance.In this paper, flat sheet composite membranes were investigated for application to the MARS process. In particular for recovery of compounds, such as 1,2-benzisothiazolin-3-one (BIT) which show low mass transfer rates through the current membrane. These composite membranes are comprised of a thin nonporous PDMS selective layer coated on a microporous support layer cast from polyacrylonitrile, polyvinylidene fluoride, polyetherimide or polyphenylenesulphone. The membranes have been characterised using SEM and gas permeation. The mass transfer of BIT through the composite membranes with no chemical reaction enhancement was an order of magnitude higher than through tubular silicone rubber membranes (10⁻⁷ m s⁻¹ versus 10⁻⁸ m s⁻¹). With chemical reaction enhancement, the mass transfer increased by another order of magnitude to 1.6 × 10⁻⁶ m s⁻¹ for BIT through a PVDF supported composite membrane. Mass transfer through the composite membrane was described well using analysis based on the resistance in series theory with chemical reaction. However, when a high osmotic pressure was applied across the membrane (molarity ∼ 3 M), significant water transport occurred across the membrane.     

Transparent electrochemical capacitor based on electrodeposited MnO2 thin film electrodes and gel-type electrolyte

A new concept for a transparent electrochemical capacitor was demonstrated. It includes two MnO₂ electrodes separated with a gel electrolyte, making the whole device less than 1 mm thick and transparent. Preliminary electrochemical experiments revealed a capacitance of 2 mF cm^?2 over more than 200 cycles. The device exhibited only a small absorbance change during repeated cycling.     

Ambipolar, high performance, acene-based organic thin film transistors

We present a high performance, ambipolar organic field-effect transistor composed of a single material. Ambipolar molecules are rare, and they can enable low-power complementary-like circuits. This low band gap, asymmetric linear acene contains electron-withdrawing fluorine atoms, which lower the molecular orbital energies, allowing the injection of electrons. While hole and electron mobilities of up to 0.071 and 0.37 cm2/V.s, respectively, are reported on devices measured in nitrogen, hole mobilities of up to 0.12 cm2/V.s were found in ambient, with electron transport quenched. These devices were fabricated on octadecyltrimethoxysilane-treated surfaces at a substrate temperature of 60 degrees C.