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We implemented and developed a number of different mechanical patterning methods, including soft hot embossing, rapid prototyping, sub-μm fluidics, high-temperature and room-temperature nanoimprinting lithography, to fabricate planar periodic structures based on organic materials. Patterns were faithfully transferred to many different organic compounds, including polymers, low-molar-mass compounds, and blends, up to 100-nm scale resolution. Lithography does not reduce the emission yields of light-emitting organic compounds, thus opening the way to the one-step realization of organic-based confined optoelectronic devices. We carefully investigated the possible changes in the optical properties (absorbance, luminescence, and quantum yield) of light-emitting species, thus ruling out any possible degradation of the active materials after patterning. In particular, the observed increase in the external luminescence yield is ascribed to the reduced self-absorption within the dielectric slab of the organic film, as a consequence of the pattern-induced enhanced forward scattering. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This work represents an innovative study that, for the first time, explores the possibility to use waste flours to produce thermoplastic polymeric bio-films. To the best of our knowledge, this is the first time that waste flours, derived from bakeries, pizzerias or pasta factories, have been proposed for the production of bio-polymers, as a replacement of neat starch. To this aim, durum waste flour derived from a pasta factory, soft waste flour derived from pizzerias and neat maize starch used as control material were firstly analyzed from dimensional, morphological and chemical points of view. Afterwards, waste flour films were produced by the addition of a nature-based plasticizer, glycerol. Mechanical characterization of the plasticized thermoplastic films, produced by compression molding, evidenced low performances, even in the case of the neat maize starch. In order to improve the mechanical properties, the possibility to include polylactic acid and cardanol-based plasticizer was also investigated. Mass transport properties of all the produced bio-films were investigated by measuring their water vapor permeability and hygroscopic absorption. The durability properties of the bio-films were assessed by accelerated ageing tests, while the bio-degradability of the waste-based films was evaluated by measuring the solubility and the degradation in water. The physicochemical analyses of the novel bio-films evidenced good mechanical properties, specifically, the waste-based films showed a lower hygroscopic absorption and water solubility than those of the blends containing neat starch.

The possibility to use carbon nanotubes (CNTs) enriched with a certain amount of metal nanoparticles for photo-inducing the combustion of liquid fuel sprays, gaseous and solid fuels was investigated in different research works. CNTs photo-ignition phenomenon has been used to trigger the combustion of different fuel typologies, demonstrating better features compared with those obtained by employing a traditional spark-plug. These improvements are due to the presence of distributed ignition nuclei inside the combustion chamber, so obtaining better values of the peak pressure, ignition delay and combustion duration. In this work, the CNTs photo-ignition phenomenon has been analyzed in order to find the minimum energy values needed to trigger the ignition, by varying the light pulse parameters and the nanoparticles concentration, Multi Wall CNTs (MWCNTs) – ferrocene, by weight. Afterwards, the results of combustion processes, triggered by using the nanoparticles, are shown comparing them with those obtained by means the spark plug and with results already published related to other fuel typologies. Hence, an overview of the possible applications of this photo-ignition phenomenon, beside that of the automotive field, is presented, also considering the disadvantages of the Xe-lamp based triggering system. Therefore, after a critical discussion on the light source typology until now used (Xenon lamp), by reporting the possible contraindications deriving from the use of this light source in most of the applicative fields, a solution is here proposed. It involves the substitution of the Xe lamp with LED sources, showing also the related experimental setup. This solution is also strengthened by the our experimental observations of CNTs photo-ignition by using high-power white LEDs as light source, never reported up to now in the literature, and by better characteristics of adaptability, robustness, easy driving and benefits provided by the LEDs rather than the Xenon lamp.

This work is aimed at the development of innovative, easy and cheap methods for the stabilization, inertization and valorisation of the organic fraction of municipal solid waste (OFMSW). For the first time, two original processes for transforming the organic waste into an inert, odorless and sanitized material were here proposed. The first one, called dual step, starts with grinding of the OFMSW, by means of an industrial shredder. After being finely ground, the organic waste was exposed to a sterilization process by means of UV/ozone radiations or thermal treatment (stabilization phase) in order to obtain a complete removal of the OFMSW&rsquo, s bacterial activity. By means of several microbiological analyses, the best sterilization method was chosen. The incorporation in a thermosetting matrix was, then, carried out through mixing the sterilized and finely ground organic waste into a water soluble urea formaldehyde (UF) based resin, with a formaldehyde content less than 1% wt, followed by a thermal treatment for UF-resin crosslinking (inertization phase). An alternative cheaper and easier process, called one step, was also proposed and investigated, by combining the sterilization with the curing thermal process (at higher temperature) of the thermosetting matrix. The preliminary experimental results reported in this paper suggest that both the proposed methods could be considered suitable for the production of high valorized innovative OFMSW-derived panels or bricks that could find application in several fields, such as building or construction materials. Finally, a brief description of the prototype machinery, properly designed for implementing OFMSW stabilization and valorization processes, is reported.

The aim of this manuscript is to provide an overview about the possible applications of carbon nanotubes (CNTs) on two of the most crucial fields of the modern civilization, namely the electronic and propulsion ones. Specifically, implementation examples of some common electronic devices as MOSFETs, diodes and sensors, based on the unusual and exotic properties of CNTs are briefly shown. Moreover, by exploiting the photo-ignition property of CNTs (by means of an intense luminous pulse), this carbon-based material can be used to trigger the combustion of different kind of fuels in propulsion applications. In this context, the experimental results of the photo-ignition process of dry mixtures of CNTs enriched with metallic catalyzer, employing LED-based radiation source, are reported as well as the results related to the combustion tests of different fuels, mixed with air, in a combustion chamber.

This article describes the photo-induced ignition process of multi-walled carbon nano-tubes (MWCNTs)/ferrocene mixtures by pulsed Xe lamps using programmable driving boards with adjustable parameters, such as variable flash rate and pulse’s energy/intensity. Varying the energy of incident light pulse, minimum ignition energy values were found as a function ofmixture weight ratio, observing that a higherMWCNT amount with respect to metal nano-particles leads to lower ignition energy. The photo-induced ignition of CNTsmixed with nano-particles was then used iin a properly realized experimental setup for triggering the combustion of CNT-enriched fuel mixtures. Different types of gaseous fuels mixed with air (CH4, liquid propane, and H2) were tested. The combustion process triggered by MWCNTs/ferrocene photo-ignition shows better performances, for all used gaseous fuels and for all tested air/fuel ratios, compared with those obtained by using a traditional spark plug. In particular, CNT-based photo-induced combustion evolves more rapidly with shorter ignition delays, higher peak pressure values, and a higher fuel burning rate as observed by reported experimental tests.

Aim of this work is to describe the electronic driving system and the entire experimental setup realized in order to photo-ignite a gaseous fuel/air mixture enriched with Multi-wall carbon nanotubes (MWCNTs) with added metal impurities, makers of photo-ignition process. The realized electronic boards present different features such as variable flash brightness, pulse duration and high flash rate, allowing to fully characterize the combustion process under investigation. Varying the Xenon light source's parameters, the needed light energy/power to ignite MWCNT/Fe mixtures with different weight ratio was found. Experimental results show that lower energy thresholds are required with increasing MWCNTs amount respect to ferrocene. Then, the photo-induced ignition of CNTs mixed with nanoparticles was used in a properly realized experimental setup for triggering the combustion of different CNT-enriched air/fuel mixtures (CH 4 , Liquid Propane and H 2 ). The combustion tests triggered by MWCNTs/ferrocene photo-ignition show better performances (shorter ignition delays, higher peak pressure values and a higher fuel burning rate), for all used gaseous fuels and all tested air / fuel ratios, compared with those obtained by using a traditional spark plug.

This work aims to investigate and characterize the photo-ignition phenomenon of MWCNT/ferrocene mixtures by using a continuous wave (CW) xenon (Xe) light source, in order to find the power ignition threshold by employing a different type of light source as was used in previous research (i.e., pulsed Xe lamp). The experimental photo-ignition tests were carried out by varying the weight ratio of the used mixtures, luminous power, and wavelength range of the incident Xe light by using selective optical filters. For a better explanation of the photo-induced ignition process, the absorption spectra of MWCNT/ferrocene mixtures and ferrocene only were obtained. The experimental results show that the luminous power (related to the entire spectrum of the Xe lamp) needed to trigger the ignition of MWCNT/ferrocene mixtures decreases with increasing metal nanoparticles content according to previously published results when using a different type of light source (i.e., pulsed vs CW Xe light source). Furthermore, less light power is required to trigger photo-ignition when moving towards the ultraviolet (UV) region. This is in agreement with the measured absorption spectra, which present higher absorption values in the UV–vis region for both MWCNT/ferrocene mixtures and ferrocene only diluted in toluene. Finally, a chemo-physical interpretation of the ignition phenomenon is proposed whereby ferrocene photo-excitation, due to photon absorption, produces ferrocene itself in its excited form and is thus capable of promoting electron transfer to MWCNTs. In this way, the resulting radical species, FeCp2+∙ and MWCNT−, easily react with oxygen giving rise to the ignition of MWCNT/ferrocene samples.

This paper describes the design and testing of programmable driving boards for turning on Xenon flash lamps, with the aim to photo-ignite a gaseous fuel/air mixture enriched with Multi-walled carbon nanotubes with added metal impurities, makers of photo-ignition process. The key factor of realized electronic boards is the availability to adjust the triggering parameters of pulsed Xe lamps, allowing to fully characterize the combustion process under investigation. By using the designed PC-configurable boards in the realized experimental setups, the effects of Xenon light source's parameters such as pulse luminous intensity, flash-rate and time duration have been investigated in order to find the needed light energy/power to ignite MWCNT/Fe mixtures with different weight ratio (from 1:4 to 4:1). Experimental results show that lower energy thresholds are required with increasing MWCNTs amount respect to ferrocene.

In this work, a field effect transistor based on a deoxyguanosine derivative (a DNA base) is demonstrated. Our experiments on transport through the source and drain electrodes interconnected by self-assembled guanine ribbons (Gottarelli et al. Helv. Chim. Acta 1998, 81, 2078; Gottarelli et al. Chem. Eur. J. 2000, 6, 3242; Giorgi et al. Chem Eur. J. 2002, 8, 2143) suggest that these devices behave like p-channel MOSFETs, The devices exhibit a maximum voltage gain of 0.76. This prototype transistor represents a starting point toward the development of biomolecular electronic devices.

Wurtzitic GaN epilayers having both Ga and N-polarity were grown by reactive molecular beam epitaxy (MBE) using a plasma-activated nitrogen source on c-plane sapphire. The polarities were verified by convergent beam electron diffraction (CBED). High-resolution X-ray diffraction, atomic force microscopy (AFM) imaging and transmission electron microscopy (TEM) were employed to characterize the structural defects present in the films. The different topographic features of Ga and N-polarity samples and their appearance after wet etching were correlated to the measured X-ray rocking curve peak widths for both symmetric [0002] and asymmetric [1014] diffraction. For Ga-polarity samples, the [0002] diffraction is narrower than the [1014] diffraction, while for N-polarity ones the [0002] peaks are broader than [1014]. The half width of [1014] peaks for both polarity types were in the range of 5-7 arcmin indicative of, among possibly other defects, a high density of pure edge threading dislocations lying parallel to the c-axis. The 1-2 arcmin [0002] linewidths of Ga-polarity samples suggest a low density of screw dislocations, which corresponds with the TEM observations where the screw dislocation density is less than 10 7 cm -2 . In N-polarity samples, however, the [0002] diffraction peak was typically wider than 5 arcmin, suggesting either a higher density of edge dislocations and inversion domains in N-polarity samples, or the columnar structural features in AFM images, where the effective coherence length for X-ray diffraction is drastically reduced.

Availability of reliable and quick methods to investigate defects and polarity in GaN films is of great interest. We have used photo-electrochemical (PEC) and hot wet etching to determine the defect density. We found the density of whiskers formed by the PEC process to be similar to the density of hexagonal pits formed by wet etching and to the dislocation density obtained by transmission electron microscopy (TEM). Hot wet etching was used also to investigate the polarity of MBE-grown GaN films together with convergent beam electron diffraction (CBED) and atomic force microscopy (AFM). We have found that hot H 3 PO 4 etches N-polarity GaN films very quickly resulting in the complete removal or a drastic change of surface morphology. On the contrary, the acid attacks only the defect sites in Ga-polar films leaving the defect-free GaN intact and the morphology unchanged. The polarity assignments, confirmed by CBED experiments, were related to the as-grown surface morphology and to the growth conditions.

Electrical, structural, and optical properties of a free-standing 200 μm thick n-type GaN template grown by hydride vapor phase epitaxy have been investigated. Hall mobilities of 1100 and 6800 cm 2 /V s have been obtained at room temperature and 50 K, respectively. Quantitative analysis of acceptor concentration, donor concentration and donor activation energy has been conducted through simultaneous fitting of the temperature dependent Hall mobility and carrier concentration data which led to a donor concentration of 2.10×10 16 cm −3 and an acceptor concentration of 4.9×10 15 cm −3 . The resultant donor activation energy is 18 meV. The analysis indicates that the dominant scattering mechanism at low temperatures is by ionized impurities. The extended defect concentrations on Ga- and N-faces were about 5×10 5 cm −2 for the former and about 1×10 7 cm −2 for the latter, as revealed by a chemical etch. The full width at half maximum of the symmetric (0 0 0 2) X-ray diffraction peak was 69″ and 160″ for the Ga- and N-faces, respectively. That for the asymmetric (10–14) peak was 103″ and 140″ for Ga- and N-faces, respectively. The donor bound exciton linewidth as measured on the Ga- and N-face (after a chemical etch to remove the damage) is about 1 meV each at 10 K. Instead of the commonly observed yellow band, this sample displayed a green band, which is centered at about 2.45 eV.

We have fabricated amorphous hydrogenated carbon films by rf plasma enhanced chemical vapor deposition with very low ion bombardment energy. We demonstrate that the optical gap of the films can be tuned in a wide range, from 3.46 up to 4.95 eV, i.e., close to the diamond gap ~5.5 eV!, by proper control of the negative dc self-bias voltage. This behavior suggests that a dramatic reduction in the content and clustering of the sp2 sites occurs by lowering the ion bombardment energy.

We have studied the recombination mechanism of InGaAs/GaAs V-shaped quantum wire lasers under electrical injection and in high magnetic field, from well below to above lasing threshold. The emission originates from free-carrier recombination independent of temperature and injection density. No excitonic contribution is found, indicating that excitons are weakly bound in these wires due to the internal piezoelectric field causing a strong Stark effect. A quantitative analysis of the piezoelectric field is performed by measuring the screening induced blue-shift of the electroluminescence at different densities and comparing it with the piezoelectric potential calculated from the quantum wire cross-sections observed by transmission electron microscopy. (C) 1999 Elsevier Science Ltd. All rights reserved.

A key challenge of the current research in nanoelectronics is the realization of biomolecular devices. The biomolecules have specific functionalies that can be exploited for the implementation of electronic and optoelectronic devices. Different nanotechnological strategies have been pursued to implement the biomolecular devices, following a bottom-up or a topdown approach depending on the used biomolecule and on its functionality. In this paper we present our results on the implementation of nano-biomolecular devices based on modified DNA nucleosides and metalloproteins. The first kind of devices is based on a DNA base, the guanosine, which is engineered in two different modified forms: the lipophilic deoxyguanosine derivative 1, and the lipophilic 8-oxodeoxiguanosine. These biomolecules show strong electron-donor properties and internal dipole. Moreover these modified nucleosides exhibit self-assembly and self-recognition properties, resulting in the formation of two-dimensional ordered supramolecular structures in the solid state. The aggregates show a clear semiconductor behaviour with blue band-gap and coherent band transport. These are used, in combination with nanopatterned metallic contacts separated by narrow gaps between 200 nm and 30 nm, to fabricate novel biomolecular electronic devices with excellent photodiode behaviour and metal/semiconductor/metal characteristics at room temperature. A three terminal device, like field effect transistor based on a deoxyguanosine derivative (a DNA base), is demonstrated. A totally different approach is followed for the implementation of devices based on proteins. The use of electron-transfer proteins, such as the blue copper protein azurin (Az), is particularly attractive because of its natural redox properties and their self assembly capabilities. Our results about the fabrication, characterization and modelling of devices based on this redox protein are presented.. The charge transfer process in protein devices depends on their redox centers (the metal atom) and their orientation in the solid state, achieved through different immobilization methods. A biomolecular electron rectifier is demonstrated by interconnecting two gold nanoelectrodes with an azurin monolayer immobilized on SiO2. The device exhibits a clear rectifying behavior with discrete current. steps in the positive wing of the current-voltage curve, which are ascribed to resonant tunnelling through the redox active center. The basic properties of Azurin-based three terminal devices are also reported. A prototype of biomolecular transistor in the solid state and operating in air, based on such class of proteins is presented.

A new type of transistor is presented. It is realised by using a metalloprotein; namely, azurin. Thanks to their natural functional characteristics, which involve inter- and intramolecular electron transfer, metalloproteins are good candidates for biomolecular nanoelectronics. The implementation of a prototype of protein transistor operating in air and in the solid state based on self-organised films of azurins is reported. Experimental current–voltage characteristics are shown. The new device presents an ambipolar behaviour as the gate bias voltage is changed. Exploiting this peculiar characteristic, a fully integrated logic gate which can be a good starting point for a new class of nanoelectronics devices has been realised.

Different nanotechnological strategies have been selected to implement biomolecular devices following a bottom-up or top-down approach depending on the biomolecule and on its functionality. Biomolecules have particular functionality and self-assembling capabilities that can be exploited for the implementation of both bioelectronic devices and multipurpose engineered biosurfaces. Surface preparation with supramolecular methods and microcontact printing have been developed and optimised to realise suitable functionalised surfaces. These surfaces can be used to link metalloproteins and enzymes for the implementation of nanobioelectronic devices and planar biosensors or to bind cells in order to promote their growth along predefined tracks and grooves. Some possible applications of these biosurfaces are shown and discussed. Results are presented for the realisation of a biomolecular nanodevice working in air based on the metalloprotein azurin immobilised in the solid state, the formation and characterisation of functional glutamate Dehydrogenase monolayers for nanobiosensing applications, the results of soft lithography processes on azurin for biosensor implementation, and the development of physiological self-assembled patterns of laminin-1 for cell culture applications and hybrid devices.

In this work, we investigate the formation of redox protein Azurin (Az) monolayers on functionalized oxygen exposing surfaces. These metallo-proteins mediate electron transfer in the denitrifying chain of Pseudomonas bacteria and exhibit self-assembly properties, therefore they are good candidates for bio-electronic applications. Azurin monolayers are self-assembled onto silane functionalized surfaces and characterized by atomic force microscopy (AFM). We show also that a biomolecular field effect transistor (FET) in the solid state can be implemented by interconnecting an Azurin monolayer immobilized on SiO 2 with two gold nanoelectrodes. Transport experiments, carried out at room temperature and ambient pressure, show FET behavior with conduction modulated by the gate potential.

Molecules are attractive to develop nano-electronic devices. In this paper a new type of transistor is realized by using self-organized films of the Guanosine molecule, a modified DNA base. With its 40 nm channel length the transistor is a good starting point for a new class of nano-electronics devices. Experimental current-voltage characteristics are shown. A circuital model is also proposed.

In this work, a field effect transistor based on deoxyguanosine derivatives (a DNA basis) is demonstrated by means of systematic transport experiments. Our nanodevices were fabricated starting from a deoxyguanosine derivative (dG(C-10)(2)) layer interconnecting planar nano-electrodes, with separation in the 20-40nm range. The three terminal devices exhibit a maximum voltage gain of 0.76. Though the quick aging and the reproducibility of the devices have to be improved, the realization of a transistor-like device represents a starting point towards the development of planar solid-state bio-molecular electronic devices.

We show that the electron-transfer protein azurin can be used to fabricate biomolecular rectifiers exploiting its native redox properties, chemisorption capability and electrostatic features. The devices consist of a protein layer interconnecting nanoscale electrodes fabricated by electron beam lithography. They exhibit a rectification ratio as large as 500 at 10 V, and operate at room temperature and in air. (C) 2003 American Institute of Physics.

The leakage–current in planar nanojunctions, usually employed to realize molecular field-effect devices, is investigated. Resonances are observed on p-doped substrates when the voltage drop between drain and gate electrodes is around 1.1 V. These resonances are related to resonant tunneling via impurity atoms and are otherwise not observed on n-type substrates.

We report on the high-resolution patterning of III–V semiconductors through polymeric masks by a soft lithographic technique based on micromolding in capillaries. The basic study of the capillarity process and the optimization of the technological steps allowed us to transfer patterns on both GaAs and InP with resolution of 800 nm over areas up to 1 cm2 and of a few microns over areas up to 4 cm2.

A free-standing GaN template grown by hydride vapor phase epitaxy has been characterized by transmission electron microscopy ~TEM!. The TEM investigation was augmented by x-ray diffraction, defect delineation etching process followed by imaging with atomic force microscopy and variable temperature photoluminescence. The density of dislocations near the N face was determined to be, in order, 3613107, 4613107, and about 13107 cm22 by cross-sectional TEM, plan-view TEM, and a defect revealing etch, respectively. The same methods on the Ga face revealed the defect concentration to be, in order, less than 13107 cm22 by plan-view TEM, less than 53106 cm22 by cross-sectional TEM, and 53105 cm22 by defect revealing hot H3PO4 acid, respectively. The full width at half maximum of the symmetric ~0002! x-ray diffraction peak was 69 and 160 arc sec for the Ga and N faces, respectively. That for the asymmetric (101I4) peak was 103 and 140 arc sec for Ga and N faces, respectively. The donor bound exciton linewidth was about 1meV each at 10 K, and a green band centered at about 2.44 eV was observed.

We report a flexible method for the patterning of organic semiconductors in the submicrometer range, which we have successfully applied to thin films of poly(p-phenylene vinylene) (PPV) prepared on a variety of substrates, such as quartz, indium–tin oxide coated glass, or inorganic dielectric mirrors. The method is based on holographic lithography performed by a corner cube interferometer of our own design and construction, followed by Ar-ion etching.

Defects in GaN layers grown by hydride vapor-phase epitaxy have been investigated by photoelectrochemical (PEC) etching, and by wet etching in hot H3PO4 acid and molten potassium hydroxide (KOH). Threading vertical wires (i.e., whiskers) and hexagonal-shaped etch pits are formed on the etched sample surfaces by PEC and wet etching, respectively. Using atomic-force microscopy, we find the density of “whisker-like” features to be 2×109 cm−2, the same value found for the etch-pit density on samples etched with both H3PO4 and molten KOH. This value is comparable to the dislocation density obtained in similar samples with tunneling electron microscopy, and is also consistent with the results of Youtsey and co-workers [Appl. Phys. Lett. 73, 797 (1998); 74, 3537 (1999)].

A free-standing 300-μm-thick GaN template grown by hydride vapor phase epitaxy has been characterized for its structural and optical properties using x-ray diffraction, defect delineation etch followed by imaging with atomic force microscopy, and variable temperature photoluminescence. The Ga face and the N face of the c-plane GaN exhibited a wide variation in terms of the defect density. The defect concentrations on Ga and N faces were about 5×105 cm−2 for the former and about 1×107 cm−2 for the latter. The full width at half maximum of the symmetric (0002) x-ray diffraction peak was 69 and 160 arc sec for the Ga and N faces, respectively. That for the asymmetric (10–14) peak was 103 and 140 arc sec for Ga and N faces, respectively. The donor bound exciton linewidth as measured on the Ga and N faces (after a chemical etching to remove the damage) is about 1 meV each at 10 K. Instead of the commonly observed yellow band, this sample displayed a green band, which is centered at about 2.44 eV.