Intrinsically Stretchable Integrated Passive Matrix Electrochromic Display Using PEDOT:PSS Ionic Liquid Composite.

The low power consumption of electrochromism makes it widely used in actively shaded windows and mirrors, while flexible versions are attractive for use in wearable devices. Initial demonstration of stretchable electrochromic elements promises good conformability to complex surfaces. Here, fully integrated intrinsically stretchable electrochromic devices are demonstrated as single elements and 3 × 3 displays. Conductive and electrochromic ionic liquid-doped poly(3,4-ethylenedioxythiophene) polystyrene sulfonate is combined with poly(vinyl alcohol)-based electrolyte to form complete cells. A transmission change of 15% is demonstrated, along with a reflectance change of 25% for opaque reflective devices, with <7 s switching time, even under 30% strain. Stability under both electrochemical and mechanical strain cycling is demonstrated. A passive matrix display exhibits addressability and low cross-talk under strain. Comparable optical performance to flexible electrochromics and higher deformability provide attractive qualities for use in wearable, biometric monitoring, and robotic skin devices.

Synthesis, Photophysics, and Langmuir Films of Polyfluorene/Permodified Cyclodextrin Polyrotaxanes.

In the present study, we investigated the effect of permodified 2,3,6-tri-O-trimethylsilyl ß- and γ-cyclodextrin (TMS·ß-CD, TMS·Î³-CD) encapsulation on the optical, electrochemical, morphological, and supramolecular arrangements of a poly[2,7'-(9,9-dioctylfluorene-alt-2',7-fluorene)] PF copolymer. For this purpose, the photophysical properties and Langmuir monolayer formation of PF·TMS·ß-CD and PF·TMS·Î³-CD polyrotaxanes were investigated and compared with those of the reference PF. Surface pressure-area isotherms and Brewster angle microscopy studies indicated the capability of both polyrotaxanes to organize into larger and homogeneous 2D supramolecular assemblies at the air-water interface. The obtained results suggest that the presence of the surrounding TMS·ß-CD and TMS·Î³-CD macrocycles on the PF backbones leads to changes in the conformation and hydrophobicity of the film surfaces. Our investigation offers a method to assess the impact of TMS-CD encapsulation on the control of 2D monolayer formation, with particular attention on the generation of stable PF monolayers for organic electronic devices.

A simple label-free electrochemical sensor for sensitive detection of alpha-fetoprotein based on specific aptamer immobilized platinum nanoparticles/carboxylated-graphene oxide.

A label-free electrochemical aptamer-based sensor has been fabricated for alpha-fetoprotein (AFP) detection. Platinum nanoparticles on carboxylated-graphene oxide (PtNPs/GO-COOH) modified screen-printed graphene-carbon paste electrode (SPGE) was utilized as an immobilization platform, and the AFP aptamer was employed as a bio-recognition element. The synthesized GO-COOH helps to increase the surface area and amounts of the immobilized aptamer. Subsequently, PtNPs are decorated on GO-COOH to enhance electrical conductivity and an oxidation current of the hydroquinone electrochemical probe. The aptamer selectively interacts with AFP, causing a decrease in the peak current of the hydroquinone because the binding biomolecules on the electrode surface hinder the electron transfer of the redox probe. Effects of aptamer concentration and AFP incubation time were studied, and the current changes of the redox probe before and after AFP binding were investigated by square wave voltammetry. The developed aptasensor provides a linear range from 3.0-30 ng mL-1 with a detection limit of 1.22 ng mL-1. Moreover, the aptamer immobilized electrode offers high selectivity to AFP molecules, good stability, and sensitive determination of AFP in human serum samples with high recoveries.

Highly sensitive voltammetric immunosensor for the detection of prostate specific antigen based on silver nanoprobe assisted graphene oxide modified screen printed carbon electrode.

In this work, we developed an effective voltammetric immunosensing platform for the sensitive detection of prostate specific antigen (PSA) utilizing a graphene oxide (GO) modified screen-printed carbon electrode (SPCE) hybridized with the ex-situ prepared silver nanoparticles (AgNPs) as a probe and signal transducer. The sensing platform comprises a direct-type immunoassay involving the selective interaction of PSA with anti-PSA. The surface morphology and analytical performance of the modified SPCE were characterized through relevant instrumentations. The changes in the voltammetric reduction current of AgNPs at 0.11 V in the sensor electrode was correlated to the PSA concentration. Under optimum conditions, the fabricated immunosensor exhibited a sensitive response to PSA with a limit of detection (LOD) of 0.27 ng mL-1 and a dynamic calibration range of 0.75-100.0 ng mL-1. We demonstrated that the participation of AgNPs along with GO modification contribute to the desired signal amplification and sensitive detection of PSA. It is anticipated that the proposed immunosensor can serve as a biomarker and potentially be utilized for the real sample quantification of PSA.

Single-Step Synthesis of Vertically Aligned Carbon Nanotube Forest on Aluminium Foils.

Vertically aligned carbon nanotube (VACNT) forests are promising for supercapacitor electrodes, but their industrialisation requires a large-scale cost-effective synthesis process suitable to commercial aluminium (Al) foils, namely by operating at a low temperature (<660 °C). We show that Aerosol-Assisted Catalytic Chemical Vapour Deposition (CCVD), a single-step roll-to-roll compatible process, can be optimised to meet this industrial requirement. With ferrocene as a catalyst precursor, acetylene as a carbon source and Ar/H2 as a carrier gas, clean and dense forests of VACNTs of about 10 nm in diameter are obtained at 615 °C with a growth rate up to 5 µm/min. Such novel potentiality of this one-step CCVD process is at the state-of-the-art of the multi-step assisted CCVD processes. To produce thick samples, long synthesis durations are required, but growth saturation occurs that is not associated with a diffusion phenomenon of iron in aluminium substrate. Sequential syntheses show that the saturation trend fits a model of catalytic nanoparticle deactivation that can be limited by decreasing acetylene flow, thus obtaining sample thickness up to 200 µm. Cyclic voltammetry measurements on binder-free VACNT/Al electrodes show that the CNT surface is fully accessible to the ionic liquid electrolyte, even in these dense VACNT forests.

Visible-light active conducting polymer nanostructures with superior photocatalytic activity.

The development of visible-light responsive photocatalysts would permit more efficient use of solar energy, and thus would bring sustainable solutions to many environmental issues. Conductive polymers appear as a new class of very active photocatalysts under visible light. Among them poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most promising conjugated polymer with a wide range of applications. PEDOT nanostructures synthesized in soft templates via chemical oxidative polymerization demonstrate unprecedented photocatalytic activities for water treatment without the assistance of sacrificial reagents or noble metal co-catalysts and turn out to be better than TiO2 as benchmark catalyst. The PEDOT nanostructures exhibit a narrow band gap (E = 1.69 eV) and are characterized by excellent ability to absorb light in visible and near infrared region. The novel PEDOT-based photocatalysts are very stable with cycling and can be reused without appreciable loss of activity. Interestingly, hollow micrometric vesicular structures of PEDOT are not effective photocatalysts as compared to nanometric spindles suggesting size and shape dependent photocatalytic properties. The visible-light active photocatalytic properties of the polymer nanostructures present promising applications in solar light harvesting and broader fields.

Conducting polymer nanostructures for photocatalysis under visible light.

Visible-light-responsive photocatalysts can directly harvest energy from solar light, offering a desirable way to solve energy and environment issues. Here, we show that one-dimensional poly(diphenylbutadiyne) nanostructures synthesized by photopolymerization using a soft templating approach have high photocatalytic activity under visible light without the assistance of sacrificial reagents or precious metal co-catalysts. These polymer nanostructures are very stable even after repeated cycling. Transmission electron microscopy and nanoscale infrared characterizations reveal that the morphology and structure of the polymer nanostructures remain unchanged after many photocatalytic cycles. These stable and cheap polymer nanofibres are easy to process and can be reused without appreciable loss of activity. Our findings may help the development of semiconducting-based polymers for applications in self-cleaning surfaces, hydrogen generation and photovoltaics.

Synthesis and photophysical characteristics of polyfluorene polyrotaxanes.

Two alternating polyfluorene polyrotaxanes (3·TM-ßCD and 3·TM-γCD) have been synthesized by the coupling of 2,7-dibromofluorene encapsulated into 2,3,6-tri-O-methyl-ß- or γ-cyclodextrin (TM-ßCD, TM-γCD) cavities with 9,9-dioctylfluorene-2,7-diboronic acid bis(1,3-propanediol) ester. Their optical, electrochemical and morphological properties have been evaluated and compared to those of the non-rotaxane counterpart 3. The influence of TM-ßCD or TM-γCD encapsulation on the thermal stability, solubility in common organic solvents, film forming ability was also investigated. Polyrotaxane 3·TM-ßCD exhibits a hypsochromic shift, while 3·TM-γCD displays a bathochromic with respect to the non-rotaxane 3 counterpart. For the diluted CHCl3 solutions the fluorescence lifetimes of all compounds follow a mono-exponential decay with a time constant of ≈0.6 ns. At higher concentration the fluorescence decay remains mono-exponential for 3·TM-ßCD and polymers 3, with a lifetime τ = 0.7 ns and 0.8 ns, whereas the 3·TM-γCD polyrotaxane shows a bi-exponential decay consisting of a main component (with a weight of 98% of the total luminescence) with a relatively short decay constant of τ1 = 0.7 ns and a minor component with a longer lifetime of τ2 = 5.4 ns (2%). The electrochemical band gap (ΔE g ) of 3·TM-ßCD polyrotaxane is smaller than that of 3·TM-γCD and 3, respectively. The lower ΔE g value for 3·TM-ßCD suggests that the encapsulation has a greater effect on the reduction process, which affects the LUMO energy level value. Based on AFM analysis, 3·TM-ßCD and 3·TM-γCD polyrotaxane compounds exhibit a granular morphology with lower dispersity and smaller roughness exponent of the film surfaces in comparison with those of the neat copolymer 3.

The effect of permodified cyclodextrins encapsulation on the photophysical properties of a polyfluorene with randomly distributed electron-donor and rotaxane electron-acceptor units.

We report on the synthesis as well as the optical, electrochemical and morphological properties of two polyrotaxanes (4a and 4b), which consist of electron-accepting 9,9-dicyanomethylenefluorene 1 as an inclusion complex in persilylated ß- or γ-cyclodextrin (TMS-ß-CD, TMS-γ-CD) (1a, 1b) and methyltriphenylamine as an electron-donating molecule. They are statistically distributed into the conjugated chains of 9,9-dioctylfluorene 3 and compared with those of the corresponding non-rotaxane 4 counterpart. Rotaxane formation results in improvements of the solubility, the thermal stability, and the photophysical properties. Polyrotaxanes 4a and 4b exhibited slightly red-shifted absorption bands with respect to the non-rotaxane 4 counterpart. The fluorescence lifetimes of polyrotaxanes follow a mono-exponential decay with a value of τ = 1.14 ns compared with the non-rotaxane, where a bi-exponential decay composed of a main component with a relative short time of τ1 = 0.88 (57.08%) and a minor component with a longer lifetime of τ2 = 1.56 ns (42.92%) were determined. The optical and electrochemical band gaps (ΔE g) as well as the ionization potential and electronic affinity characterized by smaller values compared to the values of any of the constituents. AFM reveals that the film surface of 4a and 4b displays a granular morphology with a lower dispersity supported by a smaller roughness exponent compared with the non-rotaxane counterpart.

A first truly all-solid state organic electrochromic device based on polymeric ionic liquids.

Using polymeric ionic liquids and PEDOT as ion conducting separators and electrodes, respectively, an all-polymer-based organic electrochromic device (ECD) has been constructed. The advantages of such an ECD are: fast switching time (3 s), high coloration efficiency (390 cm(2) C(-1) at 620 nm), optical contrast up to ΔT = 22% and the possibility of working under vacuum.

Nano rods for coloured glasses obtained by hybrid sol-gel coating.

Many new materials are now allowing new properties thanks to nanotechnology because this domain of physics gives possibilities to optimize targeted properties even if these materials react in very various influential parameters. Architectural, automotive, bone pathologies, environment, display applications are some concerned domains. The sol-gel process is a method allowing the realisation of coats at ambiant temperature, thus it is possible to realize Liquid Crystal Display (LCD), water-repellent coatings on privacy glass, antireflective coatings, hydrophobic or hydrophilic surfaces, bone tissue regeneration. In this study, the purpose is to show the thermal influence on a covered glass with a complex hybrid sol-gel solution. This coated glass is going to change color from red to orange under the heat influence. This color change effect comes from the evolution of various compounds organizations then/or from their loss during the degassing sequence. We show in spite of the complexity of the process that the responsible is mainly the organic dye. Thus the structure of the heated glass at 250 degrees C looks radically different than the heated one at 350 degrees C. SEM measurement allows to identify the surface compositions and to determine the elementary composition along the sample's cross section. TGA is used to justify a mass loss when samples are annealed. UV/Visible measurement is realized by two methods: in-line transmission to evaluate luminous flux and thus give colorimetric dot in the normalized CIE diagram and diffuse transmission to observe the size influence of the pigments. Infrared Reflectivity allows to evaluate the influence of species on the structure and to better target the nature of the lost compounds during annealing. TEM measurement proves that the obtained iron particles are nano rods for both samples.

Elaboration of nanohybrid materials by photopolymerisation of 3,4-ethylenedioxythiophene on TiO2.

A method for the elaboration of a heterojunction composed on n-type inorganic semiconducting nanoparticles, TiO(2), and a p-type organic semiconducting polymer poly(3,4-ethylene dioxythiophene) by UV illumination is described.