F. Di Francesco | Università di Pisa (original) (raw)

Papers by F. Di Francesco

Atmospheric Environment, 2001

Although in most cases annoying atmospheric emissions do not menace public health, they are less ... more Although in most cases annoying atmospheric emissions do not menace public health, they are less and less tolerated because of the e!ects on quality of life. Several approaches have been proposed to face this problem but none of them o!ers a completely satisfying solution. The development of electronic noses, which promise to mimic human sense of smell by means of a sensor array and a pattern recognition model, o!ers new interesting perspectives. In this paper, an electronic nose based on conducting polymer sensors and a fuzzy logic-based pattern recognition system is tested with waste water samples, obtaining 87% recognition rate on the test set. Current limits of this new technology are discussed and a strategy for their overcoming is proposed.

Sensors and Actuators B-Chemical, 2003

This work reports electrical resistance measurements and on line UV-Vis-NIR spectra for sensors, ... more This work reports electrical resistance measurements and on line UV-Vis-NIR spectra for sensors, fabricated from poly(3,3 0 -dipentoxy-2,2 0 -bithiophene) (I) or poly[3,3 0 -2-(2-ethoxy)ethoxy-2,2 0 -bithiophene] (II) doped with FeCl 3 , Fe(ClO 4 ) 3 , or CuCl 2 , and tested against vapours of o-xylene, n-butanol, benzene, methanol, n-heptane, and 3-pentanone over a 50-66,444 ppm (v/v) concentration range in argon. Each sensor was exposed repeatedly and randomly to the test vapours in a wide concentration range over a maximum of 41 times and 25 days. Neat argon sweeping was performed between test vapour injections to recover base line conditions and test sensor reversibility. The percentage changes of electrical resistance, relative to the value measured before exposure, and of the sensor absorbance at 880-1400 nm, both varied linearly according to the concentration used. The sensitivities a were calculated from the linear regression analysis of 80 sets of DR, C values for a total of about 400 measurements, in order to assess the influence of several parameters, i.e. the chemical nature of the sensor, the fabrication, the exposure time to the test vapour, and the ageing in air. The data analysis demonstrated that sensitivity depends on the chemical nature of both the sensor and the test vapour and on the length of exposure. Data collected with a 90 s exposure gave the narrower range of standard deviation values, amounting to 14% of the calculated a value in the worst case, whereas a values over the range of sensor and test vapour combinations varied from 3:4 Â 10 À5 for I doped FeCl 3 versus MeOH to 231 Â 10 À5 for I doped with Fe(ClO 4 ) 3 versus o-xylene. A significant base line drift was observed at the longest working time, but it was not proven to affect the sensitivity of the sensor. The concomitant changes of the sensors and of the electronic spectra offer intriguing scope to further investigate the nature of the sensor-test vapour interaction. # (M.C. Gallazzi). 0925-4005/02/$ -see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 5 -4 0 0 5 ( 0 2 ) 0 0 3 2 3 -4

2007 IEEE International Symposium on Industrial Electronics, 2007

In vivo fMRI study of the human olfactory system is difficult not only because the devoted areas ... more In vivo fMRI study of the human olfactory system is difficult not only because the devoted areas in human cortex are much less extended than those of the other sensory systems, but also for the presence of a high magnetic susceptibility around the olfactory stations. This work presents the results obtained in the attempt of developing a robust and reproducible

Molecular and Biochemical Parasitology, 2005

A measurement chamber for the dynamic exposure of a sensor array to gaseous or liquid samples is ... more A measurement chamber for the dynamic exposure of a sensor array to gaseous or liquid samples is presented. The device has been designed to optimise sensor response signals in terms of stability, reproducibility, response time and amplitude. This chamber has a radially symmetric flow splitter, which allows homogeneous flow conditions with low velocity gradients, and avoids significant recirculating zones and

Electronic nose (e-nose) architectures usually consist of several modules that process various ta... more Electronic nose (e-nose) architectures usually consist of several modules that process various tasks such as control, data acquisition, data filtering, feature selection and pattern analysis. Heterogeneous techniques derived from chemometrics, neural networks, and fuzzy rules used to implement such tasks may lead to issues concerning module interconnection and cooperation. Moreover, a new learning phase is mandatory once new measurements have been added to the dataset, thus causing changes in the previously derived model. Consequently, if a loss in the previous learning occurs (catastrophic interference), real-time applications of e-noses are limited. To overcome these problems this paper presents an architecture for dynamic and efficient management of multi-transducer data processing techniques and for saving an associative short-term memory of the previously learned model. The architecture implements an artificial model of a hippocampus-based working memory, enabling the system to be ready for real-time applications. Starting from the base models available in the architecture core, dedicated models for neurons, maps and connections were tailored to an artificial olfactory system devoted to analysing olive oil. In order to verify the ability of the processing architecture in associative and short-term memory, a paired-associate learning test was applied. The avoidance of catastrophic interference was observed.

This study reports the preparation of conductive multi-walled carbon nanotubes (MWCNTs)-polystyre... more This study reports the preparation of conductive multi-walled carbon nanotubes (MWCNTs)-polystyrene (PS) nanocomposites using latex technology. The MWCNTs were first well dispersed in methanol solution and then added to a suspension of the monodispersed 230 nm PS latex synthesized by emulsion polymerization with sodium dodecylsulfate anionic surfactant. Both FESEM and HRTEM images indicate that the resulting PS latices are closed to spherical dots with a particle size about 230 ± 4 nm. The HRTEM micrograph of MWCNT-PS nanocomposites shows the MWCNT is well separated and uniformly distributed between the monodispersed PS latices. The T g of MWCNT-PS nanocomposites is gradually increased with increasing the content of MWCNT, indicating possible interaction between MWCNT and PS latices to limit the motivation of PS. The conductivities of 1.5 wt.% and 6.5 wt.% MWCNT-PS nanocomposites are more than four and ten orders in magnitude higher than that of PS without MWCNT, respectively.

Sensors and Microsystems, 2001

309 OPTIMIZATION OF SENSOR PRODUCTION BY MEANS OF EXPER1MENTAL DESIGN Tarita Biver, Giovanni Piog... more 309 OPTIMIZATION OF SENSOR PRODUCTION BY MEANS OF EXPER1MENTAL DESIGN Tarita Biver, Giovanni Pioggia, Alessio Moriconi. Centra 1nterdipartimentale di Ricerca" E. Piaggio"-Universita di Pisa Via Diotisalvi 2, 56126 Pisa (1taly) Phone:+ 39 050 553639, ...

Journal of Breath Research, 2008

The design, realization and testing of a CO 2 -triggered breath sampler, capable of a separate co... more The design, realization and testing of a CO 2 -triggered breath sampler, capable of a separate collection of dead space and end-tidal air on multiple breaths, is presented. This sampling procedure has advantages in terms of the sample volume, insights regarding the origin of compounds, increased reproducibility and higher concentrations of compounds. The high quality of design and the speed of the components ensure a breath-by-breath estimate of dead volume, as well as the comfort and safety of the subject under test. The system represents a valid tool to contribute to the development of a standardized sampling protocol needed to compare results obtained by the various groups in this field.

Microchemical Journal - MICROCHEM J, 2005

Over the last few years, breath analysis for the routine monitoring either of metabolic disorders... more Over the last few years, breath analysis for the routine monitoring either of metabolic disorders caused by specific diseases or occupational exposure to toxic substances has become more and more attractive due to its noninvasiveness.Several approaches have been proposed for sample collection, treatment, and analysis. This paper gives a critical overview of the analytical devices and procedures used for breath analysis. Results on the identification of chemicals in human breath for a selection of diseases are discussed.

Sensors and Actuators B: Chemical, 2002

A¯uid dynamic study of a sensor chamber used in a hit-commercial electronic nose is presented. In... more A¯uid dynamic study of a sensor chamber used in a hit-commercial electronic nose is presented. In order to optimise the sensor signals in terms of stability, repeatability as well as amplitude and response time, the in¯uence of many factors of the sampling device has to be kept under control. Concerning the characteristics of¯ow, the existence of a time-window where each sensor is exposed to a constant odour concentration has to be assured. This condition can be achieved by the proper dimensioning of the chamber volume and by other modi®cations to the inlet and outlet. The numerical analysis was performed by a CFD code which solves the Navier±Stokes equations for a dilatable¯uid in 3D enclosures, discretised with ®nite volume elements. Two con®gurations were simulated: a basic case, referring to the conditions existing in the commercial device, and an optimised case. In each case, a static solution was calculated for the¯ow ®eld and then the dynamic evolution of odour concentration was simulated by solving the transient transport equation of a tracer injected as a square pulse¯ow. Far from optimum conditions were found for the basic case; the improvement achieved through simple modi®cations in the geometry of the chamber for the optimised case was discussed. # 2002 Published by Elsevier Science B.V.

Biosensors and Bioelectronics, 2007

An impedentiometric electronic tongue based on the combination of a composite sensor array and ch... more An impedentiometric electronic tongue based on the combination of a composite sensor array and chemometric techniques aimed at the discrimination of soluble compounds able to elicit different gustative perceptions is presented. A composite array consisting of chemo-sensitive layers based on carbon nanotubes or carbon black dispersed in polymeric matrices and doped polythiophenes was used. The electrical impedance of the sensor array was measured at a frequency of 150 Hz by means of an impedance meter. The experimental set-up was designed in order to allow the automatic selection of a test solution and dipping of the sensor array following a dedicated measurement protocol. Measurements were carried out on 15 different solutions eliciting 5 different tastes (sodium chloride, citric acid, glucose, glutamic acid and sodium dehydrocholate for salty, sour, sweet, umami and bitter, respectively) at 3 concentration levels comprising the human perceptive range. In order to avoid over-fitting, more than 100 repetitions for each sample were carried in a 4-month period. Principal component analysis (PCA) was used to detect and remove outliers. Classification was performed by linear discriminant analysis (LDA). A fairly good degree of discrimination was obtained.