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We studied the anisotropic charge transport properties of solution-grown organic single crystals based on a dipolar molecule 4HCB (4-hydroxy-cyanobenzene) by electrical transport measurements, current-voltage and space charge limited current (SCLC), and by X-ray diffraction analyses.Optical excitation differently affects the flow of charge carriers along the two main planar crystal axis, altering the charge transport anisotropy induced by the molecular π-orbitals stacking. We attribute this behaviour to the presence of an intrinsic molecular dipole and to its different orientation within the crystal lattice. The anisotropy of transport along the three crystallographic directions has been assessed by electrical characterization and correlated to the crystal molecular packing as determined by X-ray analyses.

Direct inkjet printing of a complete and working amperometric biosensor for the detection of hydrogen peroxide, based on horseradish peroxidase (HRP), has been demonstrated. The device has been realized with a commercial printer. A thin layer of PEDOT:PSS, which was in turn covered with HRP, was inkjet printed on top of an ITO-coated glass slide. The active components of the device retained their properties after the thermal inkjet printing. The whole device has been encapsulated by means of a selectively permeable cellulose acetate membrane. The successful electron transfer between the PEDOT:PSS covered electrode and the enzyme has been demonstrated, and the biosensor evidenced very good sensitivity, in line with the best devices realized with other techniques, and a remarkable operational stability. This result paves the way for an extensive application of “biopolytronics”, i.e. the utilization of conductive/semiconductive polymers and biologically active molecules to design bioelectronic devices using a common PC, and exploiting normal commercial printers to print them out.

Steady state photoconductivity and x-ray diffraction combined with optical and electronic spectroscopies were applied to study spin coated poly(3-hexylthiophene) (P3HT) films mechanically rubbed using a teflon bar. As expected, photoconductivity evidenced a strong increase in the photo-response along the rubbing direction. But, while rubbing during annealing at a temperature of 70 °C resulted in a sizeable photocurrent anisotropy along the direction parallel or perpendicular to the rubbing, the samples rubbed at room temperature (RT) showed an isotropic and comparatively stronger enhancement of absorption and photoconductivity spectral features. According to these observations, rubbing at RT resulted in a significant increase in local order and macroscopic alignment of the film, while a higher degree of global order but with a relaxed local structure was obtained after rubbing at 70 °C.

The electrochemical treatment of Indium Tin Oxide (ITO) supported on glass slides was explored as a conveninet route to create nanostructured electrodes, in an attempt to increase the performances of enzyme-based amperometric sensors. The effect of this treatment on the morphological, physical, and optical properties of the ITO (SEM, AFM, WLI, X-ray analysis, UV-Vis transmittance) was investigated, as well as on its electrical characteristics (sheet resistance). Working bioelectrodes were fabricated on the nanostructured ITO layers, and the relations between the characteristics of the devices and the treatments effects on the ITO were analyzed and discussed. A positive effect of the elctrochemically obtained nanostructures on the affinity of the organic layer for the electrons injected from the ITO surface was found.

We report on the overall improvement of a single layer organic light-emitting diode device based on poly{[3-hethylthiophene]-co-3-[2-( p -cyano-phenoxy)ethyl]thiophene} or namely PTOPhCN. This polymer was recently developed by adding a cyano group as a side-chain substituent of the thiophenic backbone onto the main polymer chain and showed promising results for light-emitting diode devices. Using an improved device layout, bright red electroluminescence was obtained at 4 V and showed a luminance of about 400 cd/m 2 at 8 V with current densities in the order of 6000 A/m 2 .

Molecule-based single crystals are promising materials for FETs applications, but usually special crystal growth conditions on the device surface are needed to obtain good samples. We prepared several single crystals starting from a commercial molecule, para-hydroxy-cyanophenol (HOPhCN), by a wet growing technique, and we investigated the correlations between the molecular packing and the anisotropy of the charge transport on the surface of organic crystals through measurements conducted between properly oriented contacts placed on the crystal. An anisotropic gate effect depending from the crystallographic orientation was found in single crystals of para-hydroxy-cyanophenol, grown from organic solution. Although with very low currents, this effect is well visible, and could be potentially exploited for fabricating bi-functional OFETs. In addition, also a response to white light illumination of the electrcical characteristics of the crystals was found, suggesting the that inside the crystals light-induced detrapping occurs. More work is presently being carried on in order to further investigate these phenomena, with particular reference to the gate anisotropic behaviour. Moreover, other organic molecules are being investigated in this sense

Organic thin film devices based on conjugated small molecules and polymers are receiving quite a large attention due to their potential in optoelectronic, photovoltaic and sensor applications, given the interesting possibility to fabricate cheaply and quickly devices able to be applied in many fields of electronics [1]. In spite of the rapid progress that has taken place on the applied side, our basic understanding of the electronic properties of organic materials is still limited the rather low chemical and structural purity of the thin films used in device fabrication that has so far prevented a systematic study of the intrinsic electronic properties of organic semiconductors. In organic thin films, the presence of grain boundaries and interfacial disorder limits the charge carrier mobility and results in the broadening of the device on/off transition. Grain boundaries can be eliminated in organic semiconductors by growing single crystals of small conjugated organic molecules. We have investigated the electronic transport properties of single crystals based on a thiophene derivative recently synthesized [2], by Space Charge Limited Current (SCLC) analyses and photocurrent (PC) spectroscopy. The structural properties of the crystals have been investigated by X-ray diffraction and Atomic force microscopy. SCLC analyses allowed to obtain information on the charge carrier mobility and on the presence of electrically active deep levels associated to structural defects that affect the carrier transport. PC spectra provided information on the distribution of the electronic excited states and on the major energy gap transition energies We identified a strong anisotropic behaviour of the crystals that we discuss by correlating the electrical and structural results.

The utilization of semiconducting and conducting polymers for the fabrication of computer-assisted printable-on-demand electrodes (the so-called “biopolytronics” concept) is a very interesting field of investigation for the realization of third generation bioelectronic devices such as biosensors, biofuel cells,…. In this line, we studied in the last years fully inkjet printed glucose oxidase (GOD)-based electrode, realized over ITO substrates [L. Setti, A. Fraleoni-Morgera, B. Ballarin, A. Filippini, D. Frascaro, C. Piana, Biosens. Bioel., 2005, 20, 2019; L. Setti, C. Piana, S. Bonazzi, B. Ballarin, D. Frascaro, A. Fraleoni-Morgera, S. Giuliani, Anal. Lett., 2004, 37, 1559]. For enhancing the performances of these devices a deeper understanding of the phenomena of electronic transfer between inorganic electrodes such as ITO, and organic materials able to conduct electrical currents, such as for example PEDOT:PSS, is needed. In this view, we realized surface modifications of ITO at a nano-scale, and we investigated the effect of such a treatment over the performances of inkjet printed GOD-based electrodes. In particular, investigations over the ITO surface morphology (AFM, white light interferometer, SEM, etc) and electrical characteristics (sheet resistance) have been carried on, and related to the performances of devices fabricated and tested. Together with an overview of the technologies used for the realization of biological and electronic inks, as well as for printing enzyme-based electrodes, are reported.

La linea progettuale, qui illustrata, è inserita nelle attività di uno dei laboratori a rete regionali chiamato LITCAR (Laboratorio Integrato Tecnologie e Controllo Ambientale nel ciclo di vita dei Rifiuti) finanziato tramite il PRRIITT della regione Emilia-Romagna. Il progetto si è occupato dello sviluppo e della realizzazione di inchiostri per stampa ink-jet a basso impatto ambientale che favoriscono il recupero della carta da macero ed il trattamento biologico delle acque reflue di disinchiostrazione. Tali inchiostri sono stati sviluppati attraverso le attività del laboratorio in collaborazione con ENEA di Bologna e vengono attualmente commercializzati con il nome di Ink-no-Ink dalla azienda Lesepidado srl (Bologna). Ink-no-Ink è stato classificato tra i primi 64 progetti innovativi segnalati da IlSole24ore nel volume Italian Applications del 2006. Lesepidado ha ricevuto nel 2007 il premio nazionale IMPRESA-AMBIENTE per la realizzazione di Ink-No-Ink

For many years, the electronic transducers have been dominated by inorganic materials. However, mechanical flexibility is often necessary as this would allow the integrated circuits to be twisted, bent and rolled without any effect on the electrical characteristics of the device. On the basis conducting polymers have attracted much interest for the development of biosensors due to their propertiesto be excellent materials for immobilization of biomolecules, favouring the rapid transfer of the charges produced by the biochemical reactions to the electronic circuitry used for the signal elaboration. In 2000 Sirringhaus et al. (Science 290, 2123) have demonstrated a direct inkjet printing of complete transistor circuits, based on solution-processed polymer conductors, insulators and self-organizing semiconductors and recently we have developed a set of techniques for the realization of computer-assisted design and fabrication of third generation biosensors based on synthetic macromolecules, as charge-transfer mediators and protective layers, and biological molecules, as sensing elements (Setti et al., 2005), which was named biopolytronics. With ink jet technology, virtually any complex bioelectronic pattern can be directly printed to a flexible or rigid surface in the size of a pixel using electronic and biological inks, giving very high-resolution patterns. Here we present an overview on biopolytronics reporting possible approaches for formulating biologically and electronically active water-based inks for thermal inkjet technology, containing respectively different enzymatic activities (redox enzymes such as glucose oxidase and peroxidase) and conjugated polymers (conducting polymers such as PEDOT/PSS and regioregular poly(3-hexylthiophene), r-P3HT), opening the way for a wide range of possibilities in the realization of bioelectronic devices using inkjet technology.

L’impatto ambientale di un prodotto o di un processo è generalmente valutato utilizzando un approccio “from bottom to up” applicando un maggior controllo del danno ambientale del prodotto stesso durante il suo ciclo di vita. Tuttavia, la sostenibilità di un prodotto dovrebbe essere preventiva mettendo a punto un processo in grado di evitare il danno, applicando quindi cambiamenti sostanziali sia sul prodotto stesso che sul processo. L’eco-design è uno strumento fondamentale per lo sviluppo di tale approccio, in cui viene presa in considerazione ogni parte della realizzazione e dell’applicazione del prodotto, al fine di ottenerne uno nuovo, in accordo con il concetto di sostenibilità. In questo contesto si è inserito il seguente studio che ha portato allo sviluppo di un nuovo inchiostro per tecnologia inkjet ad uso ufficio a basso impatto ambientale tramite uno studio di eco-design di prodotto. Il ciclo di vita del prodotto ha tenuto conto delle tre principali linee di produzione che caratterizzano la carta stampata da ufficio: la produzione dell’inchiostro, la produzione delle cartucce e la produzione della carta compresivi dei loro eventuali recuperi e riusi. Da specifici studi di LCA (Life Cycle Assessment) di confronto si sono potuti individuare i punti critici sui quali realizzare un eco-design di prodotto che sono oggetto di questa comunicazione relativa ad una delle linee di ricerca del laboratorio a rete LITCAR nato nell’ambito del Programma Regionale per la Ricerca Industriale, l’Innovazione ed il Trasferimento Tecnologico, PRRIITT, (legge n. 7/2002) sulla base delle indicazioni contenute nel VI Programma Quadro per l’Ambiente. Lo studio qui descritto si inserisce in particolare nell’Obiettivo Realizzativo 4 “Inchiostri ecologici per tecnologia Ink-jet e piattaforme per il riciclo della carta da macero” della Linea Progettuale 1 “Prevenzione, tramite innovazione dei processi, per la riduzione di quantità e pericolosità dei rifiuti”.