A room temperature polyaniline nanofiber hydrogen gas sensor

Abstract—Electro-conductive polyaniline (PANI) nanofiber based Surface Acoustic Wave (SAW) gas sensors have been investigated with hydrogen (H2) gas. A template-free, rapidly mixed method was employed to synthesize polyaniline nanofibers using chemical oxidative polymerization of aniline. The nanofibers were deposited onto a layered ZnO/64º YX LiNbO3 SAW transducer for gas sensing applications. The novel sensor was exposed to various concentrations of H2 gas at room temperature. The sensor response, defined as the relative variation in operating frequency of oscillation due to the introduction of the gas, was 3.04 kHz towards a 1 % H2 concentration. A relatively fast response time of 8 sec and a recovery time of 60 sec with good repeatability were observed at room temperature. Due to room temperature operation, the novel gas sensor is promising for environmental and industrial applications. I

Superhard Phases of Simple Substances and Binary Compounds of the B-C-N-O System: from Diamond to the Latest Results (a Review)

The basic known and hypothetic one- and two-element phases of the B-C-N-O system (both superhard phases having diamond and boron structures and precursors to synthesize them) are described. The attention has been given to the structure, basic mechanical properties, and methods to identify and characterize the materials. For some phases that have been recently described in the literature the synthesis conditions at high pressures and temperatures are indicated.Comment: Review on superhard B-C-N-O phase

THE AQUEOUS AND NON-AQUEOUS ELECTROCHEMISTRY OF POLYACETYLENE : APPLICATION IN HIGH POWER DENSITY RECHARGEABLE BATTERIES

Le polyacétylène peut être dopé par des moyens chimiques ou électrochimiques en solution aqueuse jusqu'au régime métallique. Les caractéristiques de certaines batteries rechargeables sélectionnées, qui employent des électrodes de (CH)x, dans des électrolytes non-aqueux, sont décrites.Polyacetylene can be doped either chemically or electrochemically in aqueous solution to the metallic regime. The characteristics of selected rechargeable batteries employing (CH)x, electrodes in non-aqueous electrolytes are described

Compact, flexible conducting polymer/graphene nanocomposites for supercapacitors of high volumetric energy density

Graphene is extensively utilized in energy storage devices because of its high surface area and electronic conductivity as well as ease of electrode fabrication. But graphene sheets often stack themselves in polymeric matrices leading to poor capacitive performance. This problem was addressed herein by developing and inserting respectively two types of nano-sized conducting polymers into graphene interlayer spacing. The resulting hydrogel composite electrodes demonstrated efficient electron transfer for fast and reversible Faradaic reactions at the interface. Theoretical modelling by the density functional theory suggested that the reduction involve 2Hþ transfer steps from polyaniline to graphene oxide: the first step would be an epoxy-ring opening process after activation of the CeO bond, and the second step would be CeO rupture leading to a de-epoxidation process. This binder-free electrode demonstrated high cycling performance and ultrahigh volumetric capacitance of 612 F cm3 , being 10 times higher than the activated carbon used in the current industry. The study represents a step forward towards the fabrication of flexible, high-energy density supercapacitors.Mahmoud Moussa, Maher F. El-Kady, Safwat Abdel-Azeim, Richard B. Kaner, Peter Majewski, Jun M

Pt/MoO3 nano-flower/SiC Schottky diode based hydrogen gas sensor

In this paper, we report the development of a\ud novel Pt/MoO3 nano-flower/SiC Schottky diode based device\ud for hydrogen gas sensing applications. The MoO3\ud nanostructured thin films were deposited on SiC substrates\ud via thermal evaporation. Morphological characterization of\ud the nanostructured MoO3 by scanning electron microscopy\ud revealed randomly orientated thin nanoplatelets in a densely\ud packed formation of nano-flowers with dimensions ranging\ud from 250 nm to 1 μm. Current-voltage characteristics of the\ud sensor were measured at temperatures from 25°C to 250°C.\ud The sensor showed greater sensitivity in a reverse bias\ud condition than in forward bias. Dynamic response of the\ud sensor was investigated towards different concentrations of\ud hydrogen gas in a synthetic air mixture at 250°C and a large\ud voltage shift of 5.7 V was recorded upon exposure to\ud 1% hydrogen

Self-assembly and cross-linking of conducting polymers into 3D hydrogel electrodes for supercapacitor applications

Conducting polymer hydrogels (CPH) have attracted interest for use in electronics, biomedical devices, tissue engineering, drug delivery, and energy storage thanks to their electroactivity along with an outstanding capacity to absorb large amounts of water. They are often made by polymerizing a conducting monomer in the presence of a nonconducting polymer scaffold, which can be detrimental to the electrical conductivity of the resulting polymer hydrogel. In this study, we demonstrate an innovative approach for the synthesis of conducting polymer hydrogels (CPH) without using either additives or cross-linkers, leading to conjugated polymers with enhanced electronic conductivity and large surface areas. The feasibility and versatility of our approach are demonstrated by producing a wide range of CPHs including polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene), whose biocompatibility and electronic conductivity offer great potential for use as bioactive scaffolds for tissue regeneration and stimulation. The excellent mechanical properties of CPHs can be attributed to the intermolecular forces generated between conducting polymer chains and/or their environment that maintain the hydrogel structure, acting as self-cross-linkers. Given the outstanding charge storage properties, polyaniline hydrogel was utilized as an active material in redox supercapacitors, which delivered a high gravimetric capacitance of 492 F g–1 at a current density of 1 A g–1. We have also demonstrated that polyaniline (PANi) can be used as a cross-linking agent for the preparation of a 3D graphene hydrogel with high volumetric and areal capacitances, enabling supercapacitors with excellent electrochemical performance and long-term cycling stability.Mahmoud Moussa, Maher F. El-Kady, Deepak Dubal, Tran Thanh Tung, Md Julker Nine; Nahla Mohamed, Richard B. Kaner, Dusan Losi

Transistor por efeito de campo e fotocondutor de poli(o-metoxianilina).

RESUMO: Esse artigo apresenta resultados sobre fabricação e caracterização de um transistor por efeito de campo (FET) tendo a poli(o-metoxianilina) - POMA - como material ativo. Uma adaptação de processos de microeletrônica tradicional foi feita para a confecção desse dispositivo. O FET desenvolvido apresentou modulação por voltagem de porta Vg, mas operou mesmo em Vg=0. A corrente de dreno I D aumentou significativamente sob iluminação na região da radiação visível e infravermelho próximo, mostrando o caráter fotocondutor da POMA dopada e, portanto, do dispositivo. Um modelo teórico baseado nos mecanismos de condução eletrônica da POMA, e de efeitos de interface metal-polímero foi elaborado, ajustando-se muito bem aos resultados experimentais.<br>ABSTRACT: A field effect transistor - FET made from poly(o-methoxyaniline) (POMA), which is a conductive polymer, was developed. Several modifications were carried out to adapt the procedures generally used in traditional device developments. The characteristic of the FET produced was sensible to the gate modulation, but it operates even for V G = 0. The drain current I D enhanced under visible and near infrared radiation, showing the photoconductor character of POMA and, consequently, of the device. A theoretical model, based on the electronic properties of POMA and on the metal-polymer interface, was developed which is in good agreement with the experimental results