Nanocomposites based on titanium dioxide and polythiophene: Structure and properties

Effect of doped H, Br, Cu, Kr, Ge, As and Fe on structural features and bandgap of poly C13H8OS-X: a DFT calculation

Structural features such as the shape, the lattice constant, the bond length, the total energy per cell, and the energy bandgap (Eg) of C13H8OS-X are studied by the calculating Partial Density Of States (PDOS), and DOS package of the Material Studio (MS) software. Calculations show that the bond length and the bond angle between atoms insignificant change as 1.316 Å to 1.514 Å for C-C, 1.211 Å for C-O, 1.077 Å to 1.105 Å for C-H; bond angle of round one changes from 118.883° to 121.107° for C-C-C, from 117.199° to 122.635° for H-C-C, from 119.554° to 123.147° for C-C-O and from 109.956° to 117.537° for C-C-H. When C13H8OS-X doped in the order of -Br, -Cu, -Kr, -Ge, -As, and -Fe then bond lengths, bond angles between atoms have a nearly constant value. Particularly for links C-X, there is a huge change in value, respectively 1.876, 1.909, 10.675, 2.025, 2.016, 2.014 Å; the total energy change from Etot = -121,794 eV to Etot = -202,859 eV, and the energy band gap decreases from Eg = 2.001 eV to Eg = 0.915 eV. The obtained results are useful and serve as a basis for future experimental research.

DFT Prediction of Factors Affecting the Structural Characteristics, the Transition Temperature and the Electronic Density of Some New Conjugated Polymers

Conjugated polymers are promising materials for various cutting-edge technologies, especially for organic conducting materials and in the energy field. In this work, we have synthesized a new conjugated polymer and investigated the effect of distance between bond layers, side-chain functional groups (H, Br, OH, OCH3 and OC2H5) on structural characteristics, phase transition temperature (T), and electrical structure of C13H8OS using Density Functional Theory (DFT). The structural characteristics were determined by the shape, network constant (a, b and c), bond length (C-C, C-H, C-O, C-S, C-Br and O-H), phase transition temperatures, and the total energy (Etot) on a base cell. Our finding shows that the increase of layer thickness (h) of C13H8OS-H has a negligible effect on the transition temperature, while the energy bandgap (Eg) increases from 1.646 eV to 1.675 eV. The calculation of bond length with different side chain groups was carried out for which C13H8OS-H has C-H = 1.09 Å; C13H8OS-Br has C-Br = 1.93 Å; C13H8OS-OH has C-O = 1.36 Å, O-H = 0.78 Å; C13H8OS-OCH3 has C-O = 1.44 Å, O-H =1.10 Å; C13H8OS-OC2H5 has C-O = 1.45 Å, C-C = 1.51Å, C-H = 1.10 Å. The transition temperature (T) for C13H8OS-H was 500 K < T < 562 K; C13H8OS-Br was 442 K < T < 512 K; C13H8OS-OH was 487 K < T < 543 K; C13H8OS-OCH3 was 492 K < T < 558 K; and C13H8OS-OC2H5 was 492 K < T < 572 K. The energy bandgap (Eg) of Br is of Eg = 1.621 eV, the doping of side chain groups H, OH, OCH3, and OC2H5, leads to an increase of Eg from 1.621 eV to 1.646, 1.697, 1.920, and 2.04 eV, respectively.

Promoter Effects of Functional Groups of Hydroxide-Conductive Membranes on Advanced CO2 Electroreduction to Formate

The electrochemical reduction of CO₂ at ambient conditions provides a latent solution of turning waste greenhouse gases into commodity chemicals or fuels; however, a satisfactory ion-conducting membrane for maximizing the performance of a CO₂ electrolyzer has not been developed. Here, we report the synthesis of a sequence of hydroxide-conductive polymer membranes, which are based on polymer composites of poly(vinyl alcohol)/Guar hydroxypropyltrimonium chloride, for use in CO₂ electrolysis. The effect of different membrane functional groups, including thiophene, hydroxybenzyl, and dimethyloctanal, on the efficiency and selectivity of CO₂ electroreduction to formate is thoroughly evaluated. The membrane incorporating thiophene groups exhibits the highest Faradaic efficiency of 71.5% at an applied potential of -1.64 V versus saturated calomel electrode (SCE) for formate. In comparison, membranes containing hydroxybenzyl and dimethyloctanal groups produced lower efficiencies of 67.6 and 68.6%, respectively, whereas the commercial Nafion 212 membrane was only 57.6% efficient. The improved efficiency and selectivity of membranes containing thiophene groups are attributed to a significantly increased hydroxide conductivity (0.105 S cm^-1), excellent physicochemical properties, and the simultaneous attenuation of formate product crossover.

Preparation and ageing-resistant properties of polyester composites modified with functional nanoscale additives

This study investigated ageing-resistant properties of carboxyl-terminated polyester (polyethylene glycol terephthalate) composites modified with nanoscale titanium dioxide particles (nano-TiO2). The nano-TiO2 was pretreated by a dry coating method, with aluminate coupling agent as a functional grafting additive. The agglomeration resistance was evaluated, which exhibited significant improvement for the modified nanoparticles. Then, the effects of the modified nano-TiO2 on the crosslinking and ageing-resistant properties of the composites were studied. With a real-time Fourier transform infrared (FT-IR) measurement, the nano-TiO2 displayed promoting effect on the crosslinking of polyester resin with triglycidyl isocyanurate (TGIC) as crosslinking agent. Moreover, the gloss retention, colour aberration and the surface morphologies of the composites during accelerated UV ageing (1500 hours) were investigated. The results demonstrated much less degree of ageing degradation for the nanocomposites, indicating an important role of the nano-TiO2 in improving the ageing-resistant properties of synthetic polymer composites.

Photovoltaic hybrid films with polythiophene growing on monoclinic WO3 semiconductor substrates

A new photovoltaic film consisting of monoclinic WO(3) semiconductor and conjugated polythiophene (PT) is prepared via an in situ polymerization which is initiated by photoexcited WO(3). It is observed that PT grows on the WO(3) substrate along with reaction time, leading to uniform and high quality PT-WO(3) composite films. Structures of the as-synthesized films are studied by using Raman and X-ray photoelectron spectroscopy (XPS) with the aim of gaining an insight into the interface. The results show that the sulfur sites of PT are bound to the semiconductor through a strong linkage and an acceptor-donor complex is formed as a result of the electron transfer from PT to WO(3). The cyclic voltammetry analysis confirms the charge-transfer reaction. Film devices are fabricated by using the PT-WO(3) composite film as the active layer and measured under AM 1.5G illumination for the photocurrents and incident photon-to-current conversion efficiency.

Polythiophene composites: a review of selected applications

Conducting polymers (CPs) provide a class of processible, film forming semiconductors and metals. Electrical and optical properties of CPs, similar to those of metals and semiconductors, and the attractive properties associated with conventional polymers such as ease of synthesis and processing, has given these polymers a wide range of applications in the microelectronics industry, in biological field and also as humidity, chemical and mechanical sensors. The principal interest in the use of polymers lies in the scope for low cost manufacturing. Organic polymers offer several advantages over analogous inorganic semiconductors, the most important of which are the processability and the large surface film technology together with the possibility of tuning the polymer properties through a chemical design of the constituent units. In contrast, problems of environmental stability and the inability to process these into useful devices constitute the main drawbacks of organic materials. To set a material suitable for applications in various technological fields one has to improve the processability, mechanical strength and environmental stability of the polyheterocycles: one method adopted to do this is synthesizing the composites of conducting polymers within a matrix of insulating polymers. In this paper, the science of conducting polymers will be discussed. A review from literature on selected applications of organic devices based on conducting polythiophene and its composites will be discussed with a view to targeting the areas of future research in this topic.

Nanoscale optoelectronic switches and logic devices

The photoelectrochemical photocurrent switching (PEPS) effect, in the beginning regarded as a scientific curiosity, has become a field of extensive study for numerous research groups all over the world. This unique effect can be utilized for nanoscale switching and information processing, furthermore, is can serve as an interface between molecular information processing and macroscopic electronics. This review summarizes recent efforts in understanding photocurrent switching effects and their application for the construction of nanoscale switches and logic devices. Furthermore, some future prospects concerning the development of electronic/optoelectronic devices based on photoactive semiconducting hybrid materials are presented.

Characterization and photocatalytic activity of poly(3-hexylthiophene)-modified TiO2 for degradation of methyl orange under visible light

Poly(3-hexylthiophene) (P3HT) was synthesized via chemical oxidative polymerization with anhydrous FeCl(3) as oxidant, 3-hexylthiophene as monomer, chloroform as solvent. TiO(2) nanoparticles modified by a small amount of P3HT (TiO(2)/P3HT) were prepared by blending TiO(2) nanoparticles and P3HT in chloroform solution. The resulting photocatalysts were characterized by the methods of TEM, XRD, FT-IR, XPS and UV-vis diffuse reflectance spectroscope. The photocatalytic activity of TiO(2)/P3HT was investigated by degrading methyl orange under visible light. The degradation rate of methyl orange was 88.5 and 13.5% when it was degradated by TiO(2)/P3HT and neat TiO(2)(P-25) for 10h, respectively. In addition, TiO(2)/P3HT nanocomposites showed excellent photocatalytic stability after 10 cycles under visible light irradiation. A possible mechanism for the photocatalytic oxidative degradation was also discussed.

Facile optimal synthesis of inherently electroconductive polythiophene nanoparticles

The straight dope: Polythiophene (PTh) nanoparticles with a narrow size distribution were successfully synthesized by a chemical oxidative polymerization (see image). The highest conductivity of virgin PTh is 3.1x10(-4) S cm(-1) and can be dramatically enhanced to 50 S cm(-1) by doping in iodine vapor.Polythiophene (PTh) nanoparticles were successfully synthesized by a simple chemical oxidative polymerization in the presence of a very small amount of cetyltrimethylammonium bromide (CTAB). The polymerization yield, particle size, bulk electrical conductivity, and solubility of the PTh nanoparticles have been optimized by adjusting the CTAB/FeCl(3) oxidant/thiophene monomer ratio, thiophene concentration, polymerization temperature, and reaction time. The structure of the PTh nanoparticles was systematically characterized by IR and UV/Vis spectroscopy, wide-angle X-ray diffraction, laser particle-size analysis, field-emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that the number-average diameter (D(n)) and size polydispersity index (PDI) of the particles decrease significantly from 4.19 microm and 1.21 to 203 nm and 1.056, respectively, with a slightly increasing CTAB concentration. SEM and TEM reveal that the PTh particle size is reduced to 67 and 36 nm, respectively. The conductivity increases on raising the FeCl(3)/thiophene ratio or on lowering the CTAB concentration and polymerization temperature. A moderate monomer concentration and polymerization time are very beneficial for achieving highly conducting PTh. The highest conductivity of virgin PTh is 3.1x10(-4) S cm(-1) and can be further elevated to 50 S cm(-1) by doping in iodine vapor. Under optimized polymerization conditions, the significant variation of the conductivity of the PTh particles in virgin and doped states was well confirmed by the intensity and wavelength of the UV/Vis spectral band owing to the large pi conjugation. The PTh particles demonstrate uncommon characteristics including easy synthesis, low cost of production, large pi-conjugated structure, high conductivity, solution processability, and extensive potential for further application.

Nanostructured polyaniline/titanium dioxide composite anode for microbial fuel cells

A unique nanostructured polyaniline (PANI)/mesoporous TiO(2) composite was synthesized and explored as an anode in Escherichia coli microbial fuel cells (MFCs). The results of X-ray diffraction, morphology, and nitrogen adsorption-desorption studies demonstrate a networked nanostructure with uniform nanopore distribution and high specific surface area of the composite. The composite MFC anode was fabricated and its catalytic behavior investigated. Optimization of the anode shows that the composite with 30 wt % PANI gives the best bio- and electrocatalytic performance. A possible mechanism to explain the excellent performance is proposed. In comparison to previously reported work with E. coli MFCs, the composite anode delivers 2-fold higher power density (1495 mW/m(2)). Thus, it has great potential to be used as the anode for a high-power MFC and may also provide a new universal approach for improving different types of MFCs.

Optoelectronic Switches Based on Wide Band Gap Semiconductors

Switching of photocurrent direction in semiconducting systems upon changes of the electrode potential or incident light wavelength was realized by a series of photoelectrodes covered with titania modified with pentacyanoferrate complexes, [Fe(CN)(5)L](n)(-) (L = NH(3), thiodiethanol, thiodipropanol). These materials were characterized by optical spectroscopy and electrochemistry. The structure of the surface complexes was modeled using simple quantum-chemical models. The electrodes described in this paper enable control of the photocurrent direction by two stimuli: Changing the wavelength or the photoelectrode potential easily switches the direction of photocurrent. The materials are different from those of similar characteristics studied by other authors: They are not composites comprising of two types of semiconductors but rather engineered uniform materials. The photocurrent switching phenomenon is an intrinsic feature resulting from a specific electronic structure of the surface-modified semiconductor.