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Bottom- and top-contact organic thin film transistors (OTFTs) were fabricated, using poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT-C16) as p-type channel semiconductors. Four different types of OTFTs were fabricated and investigated as gas sensors against three volatile organic compounds, with different associated dipole moments. The OTFT-based sensor responses were evaluated with static and transient current measurements. A comparison between the different architectures and the relative organic semiconductor was made.

This article reviews recently published work concerning improved understanding of, and advancements in, organic and polymer semiconductor vapor-phase chemical sensing. Thin-film transistor sensors ranging in size from hundreds of microns down to a few nanometers are discussed, with comparisons made of sensing responses recorded at these different channel-length scales. The vapor-sensing behavior of nanoscale organic transistors is different from that of large-scale devices, because electrical transport in a nanoscale organic thin-film transistor depends on its morphological structure and interface properties (for example injection barrier) which could be modulated by delivery of analyte. Materials used in nanoscale devices, for example nanoparticles, nanotubes, and nanowires, are also briefly summarized in an attempt to introduce other relevant nano-transducers.

The electrosynthesis of copper and silver core-shell nanoparticles (NPs) by the sacrificial anode technique, employing tetraoctylammonium (TOA) salts as base electrolyte for the first time, is described. These surfactants were selected because they combine high NP stabilizing power with useful disinfecting properties. The resulting colloids were mixed with a solution of an inert dispersing polymer and used to prepare nanostructured composite thin films. The morphologies and chemical compositions of the nanomaterials were characterized by Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The TEM reveals that the average core diameter of the metal NPs ranges between 1.7 and 6.3 nm, as a function of the nature of the metal and of the electrosynthesis conditions, and does not change significantly upon inclusion in the polymer matrix. An appreciable concentration of the metal is detected on the nanoparticle surface by XPS. High-resolution XP spectra indicate that both copper and silver are present at zero oxidation state in all of the materials (colloids and composite films). This demonstrates the high efficiency of the surfactant at controlling the morphology and the chemical composition of the nanodispersed metal in both the as-synthesized colloid and in the polymeric dispersion. The nanocoatings are shown to exert a marked inhibitory effect on the growth of eukaryote and prokaryote target microrganisms, and experimental evidence of a synergic disinfecting effect due to the surfactant and the nanodispersed metal is provided. On the basis of these stability and bioactivity results, it is clear that Cu-NPs and Ag-NPs are suitable for application in disinfecting or antifouling paint and coating formulations.

The polymerization of ortho-phenylenediamine (o-PD) on Highly Oriented Pyrolytic Graphite (HOPG) at different pH (1,3,5,7) was investigated by electroanalytical and spectroscopic methods. Cyclic voltammetry was used both to polymerize o-PD and to study the electroactivity of the resulting poly(ortho-phenylenediamine) (PPD) film. A redox couple associated to the PPD electroactivity, deeply influenced by the pH adopted during polymerization, was recorded. A correlation between this feature and the electrochemistry shown by the oligomers of o-PD, generated in solution during the polymer synthesis, was also found. A comparison between the absorption spectra, in the visible region, of the soluble oligomers and of the PPD films was also performed, suggesting that changes in both the polymer and the oligomer structure occur and are highly related to the polymerization pH. In particular, a higher degree of conjugation is exhibited by the PPD films electrosynthesised at lower pH and this likely explains the higher conductivity as well as the higher electroactivity shown by the material obtained in these conditions.

A new type of nanomaterial has been developed as antibacterial additive for food packaging applications. This nanocomposite is composed of copper nanoparticles embedded in polylactic acid, combining the antibacterial properties of copper nanoparticles with the biodegradability of the polymer matrix. Metal nanoparticles have been synthesised by means of laser ablation, a rising and easy route to prepare nanostructures without any capping agent in a liquid environment. As prepared, nanoparticle suspensions have been easily mixed to a polymer solution. The resulting hybrid solutions have been deposited by drop casting, thus obtaining self-standing antibacterial packages. All samples have been characterized by UV-Vis spectroscopy, X-ray photoelectron spectroscopy and electro-thermal atomic absorption spectroscopy. Ion release data have been matched with bioactivity tests performed by Japanese Industrial Standard (JIS) method (JIS Z 2801:2000) against Pseudomonas spp., a very common Gram-negative microbial group able to proliferate in processed food. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The morphological (TEM) and chemical (XPS, ARXPS) characterizations of fluoropolymer films modified with palladium particles (CFx(Pd)) are reported in this article. The films, which have different levels of metal content, have been deposited by ion beam co-sputtering a Teflon target and a palladium one. Composite films with a thickness of a few nanometers have also been deposited and analyzed. For all degrees of thickness, the analyses show the fluoropolymer nature of the hosting material, the nanoscopic character of metal domains, and their uniform distribution in the polymer matrix. The likely application of this ion sputter-deposited material in the sensor field has also been preliminary tested. [ABSTRACT FROM AUTHOR]

Poly(phenyleneethynylene) (PPE) conjugated polymers bearing glucose units are used as enantioselective active layers in vapor-sensing devices. As a novel approach, a conjugated polymer bearing chiral pendant groups is used to detect different enantiomers, natural and synthetic menthol molecules in the present case. The surface analytical characterization of the organic layer reveals a compact and smooth morphology. By means of a quartz crystal microbalance revealing system, the polymer bearing glucose chiral sites is demonstrated to interact more favorably with the natural menthol. Promising perspectives are seen for the use of such polymers in chiral, chemically sensitive resistors or even transistors. [Copyright &y& Elsevier]