Composite films of poly(3,4‐ethylenedioxythiophene) (PEDOT)‐coated over functionalized multiwalled coiled and linear carbon nanotubes (CNTs) have been fabricated by a simple oxidative electropolymerization route. The nanotubular morphology of the polymer–CNT composite is responsible for the lower charge transfer impedance, lower internal resistance, and superior capacitive response in comparison to that shown by the control PEDOT film doped by trifluoromethanesulfonate ions. This facile electrochemistry exhibited by the PEDOT–CNT composite film ensues in a remarkably high coloration efficiency of 367 cm2 · C−1 at 550 nm, hitherto unrealized for PEDOT; thus demonstrating the huge potential the PEDOT–CNT composite film has as cathode for the entire spectrum of electrochromic devices.
We report the successful synthesis of transparent thin film of conducting poly(3,4‐ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS) coated monodisperse polystyrene (PS) microspheres via a simple physical adsorption route in an aqueous media and their electrorheological (ER) application under an applied electric field. Due to the insulating PS core, the PEDOT/PSS wrapped PS (PEDOT/PSS/PS) particles possess a low volume conductivity appropriately applied as ER active materials. Tested by a rotational rheometer under an applied electric field, the PEDOT/PSS/PS based ER fluid dispersed in a silicone oil shows a typical Bingham‐fluid behavior with increased yield stresses according to the increase of electric field strength.
Summary: The photo‐crosslinking of carbazole dendrimers was analyzed by UV and IR spectroscopic methods. Photoirradiation results in the formation of a film that is insoluble in toluene and benzene. Time‐of‐flight mass spectrometry studies revealed that the photoirradiation lead to an oligomerization of the dendrimer through crosslinking. The resulting insoluble dendrimer film could be applied as a hole‐transport layer in efficient polymer electroluminescence devices (PLEDs).
Luminance‐voltage characteristics for PLEDs wherein PEDOT:PSS and CbzG3 complex with SnCl2 were employed as the hole transport layer (ITO/HTL/EML/Ca/Ag). 相似文献
The mean diameter of poly[2‐(dimethylamino)ethyl methacrylate]‐block‐poly[2‐(diisopropylamino)ethyl methacrylate] (PDMA‐PDPA) diblock copolymer micelles can be easily adjusted from 27–155 nm (as measured by DLS) by either selective quaternisation of the PDMA block or by adding PDPA homopolymer prior to micellisation; these self‐assembled nanostructures can be shell crosslinked with 1,2‐bis‐(2‐iodoethoxy)ethane and subsequently used as templates for the preparation of silica‐coated nanoparticles and, ultimately, hollow silica nanoparticles.
We report that poly(3,4‐ethylenedioxythiophene) derived from poly(ionic liquid) (PEDOT:PIL) constitutes a unique polymeric hole‐injecting material capable of improving device lifetime in organic light‐emitting diodes (OLEDs). Imidazolium‐based poly(ionic liquid)s were engineered to impart non‐acidic and non‐aqueous properties to PEDOT without compromising any other properties of PEDOT. A fluorescent OLED was fabricated using PEDOT:PIL as a hole‐injection layer and subjected to a performance evaluation test. In comparison with a control device using a conventional PEDOT‐based material, the device with PEDOT:PIL was found to achieve a significant improvement in terms of device lifetime. This improvement was attributed to a lower indium content in the PEDOT:PIL layer, which can be also interpreted as the effective protection characteristics of PEDOT:PIL for indium extraction from the electrodes.
The synthesis of high conductivity poly(3,4‐ethylenedioxythiophene) (PEDOT) films using vacuum vapour phase polymerisation is reported. Water vapour is introduced into the chamber and results suggest that it acts as a proton scavenger during polymerisation. Process optimisation leads to PEDOT films that have high conductivity and a blue‐black appearance. Poor quality films have lower conductivity and a characteristic greenish colour. UV‐vis‐NIR spectra show that poor PEDOT films are characterised by higher absorption in the UV‐vis region and an absorption plateau in the NIR region, which suggests an increased level of disrupted conjugation along the polymer backbone or higher oligomer content. Conversely, high quality PEDOT is characterised by an extended NIR absorption tail and lower absorption in the UV‐vis region.
A novel organic hyperbranched copper phthalocyanine was synthesized for use as a hole injection nanolayer on ITO in organic light‐emitting diodes (OLEDs). This material is soluble in organic solvents which allows for processing under anhydrous conditions, unlike water based conventional polymer hole injection layer materials such as poly(3,4‐ethylenedioxythiophene)(PEDOT)/polystyrene sulfonate (PSS). The hyperbranched layer increased the luminous efficiency and brightness of single layer OLED devices, in addition to reducing current leakage which causes crosstalk in panel devices, compared to devices prepared from PEDOT/PSS. Therefore, this material is more suitable for OLED applications due to its processing and performance advantages over conventional commercial conducting polymer compositions.
Langmuir‐Blodgett films of a cellulose derivative containing porphyrins, porphyrin‐cellulose, were fabricated in order to construct a cellulose‐based molecular photocurrent generation system. On visible light illumination of the LB monolayer film deposited on an ITO electrode, anodic photocurrents were observed with a quantum yield of 1.6% at an applied potential of 0 V versus SCE, and 3.8–4.6% at 0.2–0.3 V versus SCE. These values indicate that the self‐quenching of the photoexcited porphyrins in the cellulose LB film was suppressed, while porphyrin moieties in the LB film had a densely packed structure. This is because the porphyrins are located at a distance of approximately 1.0 nm along the cellulose backbone.
Summary: In this paper, PEDOT/PSS‐ZnO coaxial nanocables with diverse inner core sizes are prepared by a new and facile method that involves two‐steps: the synthesis of ZnO nanoparticles through a sol‐gel process, followed by dewetting‐controlled self‐assembly of the nanoparticles and charged polymers to generate a cable‐like nanostructure with the aid of a vacuum. The nanocables have an outer diameter of ca. 100 nm with a polycrystalline ZnO inner core of 7–25 nm in diameter. The length and morphology of the nanocables are determined by external vacuum conditions as well as the ZnO concentration in the composite. A photoluminescence study shows an enhanced green light emission arising from ZnO with a size‐dependence feature.
TEM image of a PEDOT/PSS‐ZnO nanocable at high magnification. 相似文献
The carbon nitride poly(triazine imide) with intercalated bromide ions is a layered, graphitic material of 2D covalently bonded molecular sheets with an exceptionally large gallery height of 3.52 Å due to the intercalated bromide anions. The material can be cleaved both mechanically and chemically into thin sheets and scrolls analogous to the carbon‐only systems graphite and graphene.
The Michael reaction of chitosan with acrylic acid was carried out successfully, even in water alone as the reaction medium. As a consequence of its good solubility in water, the reaction product, N‐carboxyethylchitosan, showed excellent biodegradable properties with standard activated sludge.
Summary: Efficient engineering of solid dispersions stagnates by the current inability to establish the mode of drug distribution on a molecular level at a low drug load. This study describes the application of fluorescence resonance energy transfer (FRET) to characterize the mode of incorporation of dispersed lipophilic molecules in a solid matrix. Two different lipophilic fluorophores (donor and acceptor) were used as model substances and were incorporated in polyvinylpyrrolidone to form solid dispersions using two different production processes: lyophilization and fusion. The efficiency of the resonance energy transfer from donor to acceptor was measured by confocal microscopy. We show that the method can be used to compare the modes of drug incorporation of solid dispersions at the nanoscale.
Absorption and emission spectra of Bodipy R6G (donor) and Bodipy 650/665 (acceptor). 相似文献
We report the use of a PTFE‐based microfluidic device for the encapsulation of living, therapeutically‐active cells within monodisperse alginate microspheres. We present a novel microfluidic platform and a flexible experimental method for the production of alginate microspheres. Cell lines HEK293, U‐2 OS and PC12 were separately encapsulated using this method, with minimal loss of cell viability.
Summary: Due to its capability of dispensing very small volumes of different liquids in a controlled manner, ink‐jet printing is well suited for combinatorial experiments. The multi‐nozzle ink‐jet delivery system is especially advantageous for parallel chemical synthesis of different materials. We have used ink‐jet printing of an oxidizing agent to pattern a pre‐coated conducting polymer, poly(3,4‐ethylenedioxy)‐thiophene‐poly(styrene sulfonate) (PEDOT‐PSS), yielding electrodes with predefined shapes and a controlled degree of sheet resistivity for use in gray‐scale organic light‐emitting devices (OLEDs). The electrical and optical properties of the PEDOT‐PSS layer are modified via chemical interaction using the oxidizing agent. These experiments were performed using a desktop ink‐jet printer in conjunction with common graphic software which employed color functions such as CMY (cyan, magenta and yellow), HSL (hue, saturation and luminosity) and RGB (red, green and blue).
Photographs of gray‐scale OLEDs patterned on PEDOT‐PSS surfaces by an ink‐jet printer on plastic substrates. 相似文献
Polymeric core–shell microstructures have been constructed through a new method, namely sequential precipitation, which is intrinsically a self‐assembly and phase separation process. High‐quality poly(vinyldene fluoride)–polycarbonate–lithium perchlorate composite films with spherical core–shell microstructures have been prepared and determined to consist of conducting cores and insulating shells. Because of the percolation effect, the resulting materials present a dielectric constant as high as 104–107 at the threshold.
Spin‐coating a mixture solution of P3HT and PCBM on a cold substrate largely enhanced the power conversion efficiency (PCE) of the bulk heterojunction (BHJ) solar cells. This concept was based on the abrupt decrease in the solubility of P3HT as solution temperature decreased. The selective precipitation of P3HT on the PEDOT:PSS‐coated cold substrate facilitated a desirable rich composition of P3HT at the interface with the PEDOT:PSS layer. The high crystallinity of P3HT suppressed the movement of PCBM during thermal annealing, preventing aggregation of PCBM. The morphological excellence of the pristine film gave a comparable PCE to that made by the conventional fabrication process. After thermal annealing, the device made via coating on a cold substrate showed above 30% increase in PCE from the BHJ solar cells made by the conventional method.
In this paper, we report on the tunable metal‐enhanced fluorescence (MEF) of Ag nanostructures. Because of the good MEF properties of the highly dendritic Ag nanostructures, we obtained an increase of up to 25 times for the weak fluorescence of porphyrin molecules (Por4–). More importantly, by the introduction of a stimulus‐responsive PAA/PDDA multilayer film as an interlayer, the distance between the fluorophores and the Ag nanostructures could be tuned by immersing the substrates into solutions of different ionic strength or pH. The MEF behavior of the composite films could thus be tuned in a controlled manner, because of the distance dependent nature of the MEF effects.
In this work we describe the synthesis of multi‐sensitive aqueous microgel particles with incorporated conducting poly(3,4‐ethylenedioxythiophene) (PEDOT) nanorods. We demonstrate that the loaded amount of PEDOT nanorods as well as their morphology can be varied by controlling the reaction conditions such as monomer concentration and alcohol concentration in aqueous phase. Obtained microgels can be stimulated by changes in the environment temperature as well as by the repulsion/attraction forces within polymeric network due to the reversible oxidation/reduction of the conjugated polymer. Microgels with unique properties can be operated in colloidal systems or used as building blocks for the preparation of nanostructured films.
Nanofiber scaffolds of collagen have been fabricated via electrospinning using benign solvent systems as a replacement for 1,1,1,3,3,3 hexafluoro‐2‐propanol. Simple binary mixtures of phosphate‐buffered saline and ethanol have been found to be highly effective for electrospinning. FTIR spectra suggest that the triple helical structure of collagen was conserved after dissolution and electrospinning. Crosslinking of the electrospun collagen scaffolds was achieved with standard methods.
