Set 092015

The role of polarization-induced reorientation of DNA strands on organic field-effect transistor-based biosensors sensitivity at high ionic strength

Stefano Lai, Massimo Barbaro, Annalisa Bonfiglio

Appl. Phys. Lett. 107, 103301 (2015)

The detection of the intrinsic charge of biochemical molecules is a promising strategy for the fabrication of field-effect transistor (FET)-based sensors for direct, non-destructive detection of several biochemical reactions. Nevertheless, the high ionic concentration of standard environments for biochemical species represents a significant limitation to this sensing strategy. Here, an investigation on the physical mechanisms behind the ability of an organic FET-based sensor to detect DNA hybridization at high ionic strengths is proposed. The capability of the device to correctly detect single-stranded DNA oligonucleotides and their hybridization with a complementary target sequence has been analyzed in detail. In particular, the electrical response in solutions with different ionic strengths was investigated and put in relation with the nano-scale properties of DNA strands employed as receptors. Fluorescence analysis shows that it is possible to electrically modify their orientation and consequently improve the device sensitivity in conditions close to those occurring during hybridization.

 Scritto da in 9 settembre 2015  Avvisi  Commenti disabilitati su NEW PUBLICATION:”The role of polarization-induced reorientation of DNA strands on organic field-effect transistor-based biosensors sensitivity at high ionic strength”
Set 022015

Self-encapsulation of organic thin film transistors by means of ion implantation

P. Cosseddu, B. Fraboni, A. Scidà, Y.Q. Wang, M. Nastasi, A. Bonfiglio

Synthetic Metals, Volume 209, November 2015, Pages 178-182


Long-term stability of devices based on organic materials is still impeding the diffusion of these structures in real applications. In this paper we have investigated the effects of low energy, combined, ion implantation (N and Ne) in the evolution of the electrical performances of pentacene-based Organic Thin Film Transistors (OTFTs) over time by means of current–voltage and photocurrent spectroscopy analyses. We have demonstrated that the selected combination of ions allows reducing the degradation of charge carriers mobility, and also stabilization of the devices threshold voltage over a long time (over 2000 h).

 Scritto da in 2 settembre 2015  Avvisi  Commenti disabilitati su NEW PUBLICATION: “Self-encapsulation of organic thin film transistors by means of ion implantation”
Mag 262015

Maria Girleanu , Giulia Casula , Christian Blanck , Marc Schmutz , Christophe Contal , Navaphun Kayunkid , Piero Cosseddu , Annalisa Bonfiglio , Ovidiu Ersen , and Martin Brinkmann

J. Phys. Chem. C, 2015, 119 (23), pp 13115–13123
DOI: 10.1021/acs.jpcc.5b03646
Publication Date (Web): May 22, 2015
Nucleation and growth of silver nanoparticles were studied on the surface of an n-type organic semi-conductor (N′-bis(n-octyl)-dicyanoperylene-3,4:9,10- bis(dicarboxyimide) (N1400)) as a function of the deposition rate τ and the substrate temperature Ts. Electron tomography was used to probe the bulk diffusion of Ag in the N1400 layers. No Ag nanoparticles are formed in the bulk of N1400 even for high substrate temperatures Ts = 125 °C, indicating that Ag diffusion in the organic semiconductor is marginal. The NPs distribution on the surface of N1400 is essentially determined by the surface roughness of the N1400 films. A transition in the nucleation mode of Ag NPs on N1400 is evidenced as a function of Ts: for Ts ≤ 50°C, Ag NPs form random patterns whereas for Ts ≥ 75 °C linear arrays of aligned NPs are observed. Such arrays result from step edge decoration of the N1400 terraces. The surface density of Ag NPs is thermally activated but the activation energy depends on the structure of the N1400 films: the smaller the crystal size of the N1400 grains, the larger the activation energy.
 Scritto da in 26 maggio 2015  Avvisi  Commenti disabilitati su NEW PUBLICATION: “Controlling the Growth of Silver Nanoparticles on Thin Films of an n-type Molecular Semiconductor”
Mar 062015

An organic transistor-based system for reference-less electrophysiological monitoring of excitable cells

Andrea Spanu, Stefano Lai, Piero Cosseddu, M. Tedesco, Sergio Martinoia & Annalisa Bonfiglio

Scientific Reports 5, Article number: 8807, doi:10.1038/srep08807

In the last four decades, substantial advances have been done in the understanding of the electrical behavior of excitable cells. From the introduction in the early 70’s of the Ion Sensitive Field Effect Transistor (ISFET), a lot of effort has been put in the development of more and more performing transistor-based devices to reliably interface electrogenic cells such as, for example, cardiac myocytes and neurons. However, depending on the type of application, the electronic devices used to this aim face several problems like the intrinsic rigidity of the materials (associated with foreign body rejection reactions), lack of transparency and the presence of a reference electrode. Here, an innovative system based on a novel kind of organic thin film transistor (OTFT), called organic charge modulated FET (OCMFET), is proposed as a flexible, transparent, reference-less transducer of the electrical activity of electrogenic cells. The exploitation of organic electronics in interfacing the living matters will open up new perspectives in the electrophysiological field allowing us to head toward a modern era of flexible, reference-less, and low cost probes with high-spatial and high-temporal resolution for a new generation of in-vitro and in-vivo monitoring platforms.

 Scritto da in 6 marzo 2015  Avvisi  Commenti disabilitati su NEW PUBLICATION: “An organic transistor-based system for reference-less electrophysiological monitoring of excitable cells”
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