Papers by matteo falasconi
Sensors and Actuators B-chemical, 2004
Influence of phase composition, structural peculiarities and grain size of Fe 2 O 3 -SnO 2 nanoco... more Influence of phase composition, structural peculiarities and grain size of Fe 2 O 3 -SnO 2 nanocomposites prepared by sol-gel technology on gas-sensitive properties of the corresponding gas sensors has been studied in the paper. The characteristics of thin film sensors were obtained with regards to NO 2 and C 2 H 5 OH. Behaviour of thick film sensors was estimated in humid C 2 H 5 OH ambient. High sensitivity of Fe 2 O 3 -SnO 2 samples containing highly dispersive Fe 2 O 3 phase has been revealed. The composites consisting of poorly crystallised ␣-Fe 2 O 3 along with Sn(IV)-␣-Fe 2 O 3 solid solution demonstrate maximum sensitivity to ethanol. Structural and functional distinctions of the Fe 2 O 3 -SnO 2 composites obtained by using different Fe-precursors (Fe 3+ and Fe 2+ inorganic salts) have been revealed. Mechanisms of the processes, which determine gas-sensitive behaviour of the composites, are considered. 11 12 13 14 15 16 17 of the complex oxide systems and their gas-sensitive prop-67 erties regarding NO 2 and C 2 H 5 OH has been made. 68 2. Experimental 69 Simple oxides/hydroxides of iron and tin were prepared 70 by hydrolysis of the corresponding inorganic precursors 71 by using base agent (aqueous solution of NH 3 ). The pre-72 cipitate then was washed thoroughly and transformed 73 into colloidal solution (sol). The Fe 2 O 3 -SnO 2 composites 74 (Fe:Sn = 1:9, 1:1, 9:1) were formed by mixing iron and 75 tin oxides/hydroxides in the required proportions followed 76 by annealing of the dried species at different temperatures 77 (300, 500, 600, 800 • C) [5]. Fe 2+ precursors (FeCl 2 , FeSO 4 ) 78 were used along with more common Fe 3+ inorganic salts 79 (FeCl 3 , Fe(NO 3 ) 3 , Fe 2 (SO 4 ) 3 . Using Fe 3+ precursors leads 80 to the formation of ␣-Fe 2 O 3 species; meanwhile, hydroly-81 sis of Fe 2+ salts under certain conditions allows to obtain 82 metastable ␥-modification of iron oxide [10]. Thus, two 83 types of the composites were prepared: ␣-Fe 2 O 3 -SnO 2 (by 84 mixing ␣-Fe 2 O 3 and SnO 2 sols) and ␥-Fe 2 O 3 -SnO 2 (by 85 mixing ␥-Fe 2 O 3 and SnO 2 sols). 86 Structural investigations were carried out by XRD, EPR, 87 TEM and Mössbauer spectroscopy. 88 The sensing layers were heated at 550 • C in air dur-89 ing 20 h. High-temperature treatment provides measur-90 able range of the layer resistance. Measurements of the 91 temperature-dependent conductivity of the oxide layers 92 were carried out in the region of temperature 100-500 • C at 93 RH 30%. Gas-sensitive properties of thin film species were 94 mostly studied regarding 1 ppm NO 2 (RH 40%). Thick 95 film sensors were measured in humid ethanol vapours (RH 96 98%) within the range 0. 025-1. 0‰ (0. 1‰ corresponds 97 to 45 mg/m 3 of ethanol), thus modelling alcohol content 98 in human's expirated air. A flow of gas was obtained by 99 commercial ethanol generator GS-1 (Analitpribor, Kiev).
Artificial olfaction systems, which mimic human olfaction by using arrays of gas chemical sensors... more Artificial olfaction systems, which mimic human olfaction by using arrays of gas chemical sensors combined with pattern recognition methods, represent a potentially low-cost tool in many areas of industry such as perfumery, food and drink production, clinical diagnosis, health and safety, environmental monitoring and process control. However, successful applications of these systems are still largely limited to specialized laboratories. Sensor drift, i.e., the lack of a sensor's stability over time, still limits real industrial setups. This paper presents and discusses an evolutionary based adaptive drift-correction method designed to work with state-of-the-art classification systems. The proposed approach exploits a cutting-edge evolutionary strategy to iteratively tweak the coefficients of a linear transformation which can transparently correct raw sensors' measures thus mitigating the negative effects of the drift. The method learns the optimal correction strategy without the use of models or other hypotheses on the behavior of the physical chemical sensors.
We present the novel electronic olfactory system EOS835 manufactured by Sacmi Imola s.c.a.r.l. ba... more We present the novel electronic olfactory system EOS835 manufactured by Sacmi Imola s.c.a.r.l. based on the University of Brescia electronic nose prototype Pico2. The EOS835 is a reliable system equipped with very sensitive and stable thin-film metal oxide gas sensors. A new feature extraction algorithm (phase space integral) has been applied to improve the system classification performance. The electronic nose
Sensors and Actuators B-chemical, 2008
In this work we propose a low-cost electronic nose based on a resistance to period converter read... more In this work we propose a low-cost electronic nose based on a resistance to period converter readout system, suitable to handle a wide range of resistance values (from kΩ up to tens of GΩ) with high accuracy (
Sensors and Actuators B-chemical, 2005
We observe the change of aromatic compounds in the headspace of white truffles (Alba’s Truffle) a... more We observe the change of aromatic compounds in the headspace of white truffles (Alba’s Truffle) after storage at +4°C over a period of a few days. Measurements have been performed using SPME-GC-MS technique and the Pico2-electronic nose (EN) developed at Sensor Lab. in Brescia. The EN shows a very high sensitivity towards the truffle’s relevant molecules such as 2,4-dithiapentane and
Fungal growth can occur on green coffee beans along all the distribution chain, eventually bringi... more Fungal growth can occur on green coffee beans along all the distribution chain, eventually bringing on health hazards to consumers, because of the production of toxic metabolites (mycotoxins) [1]. Besides, the sensorial contamination due to volatiles by-products of fungal metabolism could cause defects on coffee also after roasting. Therefore, it is necessary to devise strategies to detect and quantify fungal infection and toxin production at early stages of the food chain. One of the most promising techniques is the analysis of volatile compounds in the headspace gas surrounding the samples. The aim of this work was to verify the ability of the Electronic Nose (EN EOS835) to early detect the microbial contamination of Arabica green coffee. This EN is equipped with Metal Oxide Semiconductor sensor array. Gas chromatography coupled to mass spectrometry (GC-MS) analysis of the static headspace of non-contaminated Arabica green coffee samples was carried out to confirm the EN ability to provide satisfactory indications about the presence of contamination.
Food Control, 2010
The application of an electronic nose equipped with a Metal Oxide Semiconductor sensor array for ... more The application of an electronic nose equipped with a Metal Oxide Semiconductor sensor array for the detection of Alicyclobacillus acidoterrestris and A. acidocaldarius artificially inoculated in peach, orange and apple fruit juices is described in this study. Overall the system was able to detect the presence of Alicyclobacillus spp. in all the tested fruit juices at 24 h from inoculation. The electronic nose could detect bacterial concentration as low as <10 2 colony forming unit/ml and it was also able to classify bacterial contamination independently of the Alicyclobacillus species. The gas chromatography-mass spectrometry characterization of the volatile profile of orange juices confirmed the existence of quantitatively different patterns between contaminated and uncontaminated samples.
Sensors and Actuators B-chemical, 2007
In the gas sensor field, principal component analysis (PCA) is still the mostly used technique fo... more In the gas sensor field, principal component analysis (PCA) is still the mostly used technique for exploratory data analysis, although the human judgment of PCA plots often determines the classification results. In this paper, we propose a new approach based on cluster analysis (CA) in combination with cluster validity (CLV) that can be used to objectively infer and assess the
Sensors and Actuators B-chemical, 2008
We tested the detection properties of four MOX sensors toward different ozone mixtures to identif... more We tested the detection properties of four MOX sensors toward different ozone mixtures to identify sets of sensing layers and interfering compounds concentrations most suitable for a reliable detection of ozone. The measurement campaign lasted 1 year divided in four sessions. We collected a substantial amount of measurements (more than 500) with diverse interfering gases: ammonia, ethanol, ethylene, carbon monoxide and humidity. Due to the dimension of the data set it could not be analyzed using the conventional methods generally applied for characterizing gas sensors: evaluating the sensor performance by visual inspection of the sensors responses is unfeasible. For this reason we systematically applied the exploratory data analysis methodology. We used some simple but effective statistical techniques to insight the data. This approach allows us to draw sound conclusions about the causes of variation in the data, e.g. time (sensors' long-term stability) or interfering effects of different chemical compounds. All the analysis techniques employed in this work are implemented in a software package developed at our laboratory.
Food Research International, 2010
In this paper the skill of an electronic nose to early diagnose the natural contamination by Alic... more In this paper the skill of an electronic nose to early diagnose the natural contamination by Alicyclobacillus spp. in commercial flavoured drinks is presented. The instrument was able to identify contaminated products at very low bacterial loads (tens of copies/ml), with an excellent classification rate (almost 100%). The identification of Alicyclobacillus spp. by means of the electronic nose was not based on the analysis of the secondary metabolites, as it is done by classical analytical techniques, thus allowing a surprising capability in recognising the contaminated products at early stage of growth. This study strongly suggests the use of the Electronic Noses as screening tools in industrial quality control laboratories but at the same time it underlines some limits still present in the technology.
One of the most promising architectures of third generation solar cells is integration of single ... more One of the most promising architectures of third generation solar cells is integration of single crystalline nanowires as electron transporters in anodes of electrochemical cells. The nanowire-based cells aim at significantly increase cell efficiency thanks to the higher mobility of electrons along the single crystalline lattice of the nanowires with respect to traditional polycrystalline networks, greatly reducing electron-hole recombination controllable
Sensors and Actuators B-chemical, 2005
... Although many different methods for the detection of fungal spoilage are known, for a critica... more ... Although many different methods for the detection of fungal spoilage are known, for a critical ... The experiments were carried out by means of two headspace sampling techniques: a static headspace ... At first, the raw data were examined and a qualitative evaluation of the sensor ...
Sensors and Actuators B-chemical, 2010
In this study a metal oxide sensor array is exposed to a time-dependent amount of gas inside the ... more In this study a metal oxide sensor array is exposed to a time-dependent amount of gas inside the sensor chamber of negligible "dead" volume. Special parameters of the response kinetics are used for multiparametric featuring of volatile organic compounds (VOCs). The composition of the atmosphere in the chamber varies due to the time-dependent release of the VOCs from a solid phase micro-extraction (SPME) fiber into the flow of synthetic air. Four types of volatile compounds, namely acetone, acetic acid, acetaldehyde and butyric acid, that are known being frequently emitted from infected wounds, are tested in this study. The explorative data analysis (EDA) of the features is performed for the sensor outputs obtained at different carrying gas flow rates and the VOC amounts. Influence of specific aspects of the SPME based sampling on the sensor outputs is estimated. It is demonstrated by the PCA results that the target compounds cannot be distinguished below 3-4 ppm if only the sensor outputs based on the signal magnitudes are used for the featuring of VOCs (static-compatible features). The dynamic features add significant information and allow a better discrimination of the volatile compounds. The classification of the target volatile compounds can additionally be improved by precise control of the VOCs expansion in the chamber in the dynamic exposure approach.
Food Control, 2009
Microbial contamination can easily affect processed tomato, thus determining both organoleptic ad... more Microbial contamination can easily affect processed tomato, thus determining both organoleptic adulterations and potential health risks for customers. Innovative techniques for a rapid and reliable diagnose of spoilage, such as electronic nose technology, are highly requested in order to guarantee food safety and to improve production. In this work canned peeled tomatoes were artificially spoiled with different kinds of microbial flora and then were analyzed by means of an electronic nose based on thin film metal oxide gas sensors. Preliminary analyses by dynamic-headspace gas chromatographic-mass spectrometry showed significant differences in the semi-quantitative volatile compounds profile of spoiled tomato samples just after few hours from contamination, thus suggesting to employ the electronic nose for an early diagnose of microbial presence. The electronic nose was indeed able to reveal contamination, even at early stages depending on the type of contaminant (e.g. for Saccharomyces cerevisiae and Escherichia coli), and to recognize spoiled tomato samples with good classification performances.
Based on an array of combined metal oxide and conductive polymer gas sensors electronic an odor r... more Based on an array of combined metal oxide and conductive polymer gas sensors electronic an odor recognition system is being developed for detection of bacteria types at the early stages of wound infection. It is proved by GC-MS studies that living bacteria that are typical infectious agents in clinical practice can be distinguished from each other by means of a limited set of key volatile products. Using a set of these reference volatile compounds criteria for selection and calibration of gas sensors were defined. Aiming to increase reliability of bacteria identification SPME preconcentration was used for sampling of the headspace air and response to variable concentrations of volatiles emitted from the SPME fiber is processed for evaluation of the output parameters of the sensor module. Discrimination between classes of volatile products is obtained by a PCA analysis of the dynamic parameters of sensor responses to the headspace air of clinical samples collected by swabbing.
Talanta, 2009
The aromatic profile of microbiologically contaminated canned tomatoes was analyzed by the dynami... more The aromatic profile of microbiologically contaminated canned tomatoes was analyzed by the dynamic headspace extraction technique coupled with gas chromatography-mass spectrometry. Canned tomatoes contaminated with Escherichia coli, Saccharomyces cerevisiae and Aspergillus carbonarius were analyzed after 2 and 7 days. About 100 volatiles were detected, among which alcohols, aldehydes and ketones were the most abundant compounds. Gas chromatographic peak areas were used for statistical purposes. First, principal component analysis was carried out in order to visualize data trends and clusters. Then, linear discriminant analysis was performed in order to detect the set of volatile compounds ables to differentiate groups of analyzed samples. Five volatile compounds, i.e. ethanol, -myrcene, o-methyl styrene, 6-methyl-5-hepten-2-ol and 1-octanol, were found to be able to better discriminate between uncontaminated and contaminated samples. Prediction ability of the calculated model was estimated to be 100% by the "leaveone-out" cross-validation. An electronic nose device was then used to analyze the same contaminated and not contaminated canned tomato samples. Preliminary results were compared with those obtained by dynamic headspace gas chromatography-mass spectrometry, showing a good agreement.
In the present work we investigate the potential use of the Electronic Nose EOS835 (SACMI scarl, ... more In the present work we investigate the potential use of the Electronic Nose EOS835 (SACMI scarl, Italy) to early detect Alicyclobacillus spp in two flavoured soft drinks. These bacteria have been acknowledged by producer companies as a major quality control target microorganisms because of their ability to survive commercial pasteurization processes and produce taint compounds in final product. Electronic Nose was able to distinguish between uncontaminated and contaminated products before the taint metabolites were identifiable by an untrained panel. Classification tests showed an excellent rate of correct classification for both drinks (from 86% uo to 100%). High performance liquid chromatography analyses showed no presence of the main metabolite at a level of 200 ppb, thus confirming the skill of the Electronic Nose technology in performing an actual early diagnosis of contamination.
In this report the responses of metal oxide sensors to varying amount of gas in air are used for ... more In this report the responses of metal oxide sensors to varying amount of gas in air are used for multiparameter featuring of volatile compounds. The composition of the atmosphere is varied by time dependent release of gas from a SPME fiber into flow of synthetic air. Sensor outputs are described by sets of parameters related to the characteristics of gas injection and the sensor response kinetics. The sets of sensor parameters are processed by explorative data analysis (EDA) software comprising customizable feature, correlation and principal component analysis (PCA). This method is applied for distinguishing between four volatile compounds acetone, acetic acid, acetaldehyde and butyric acid, and is aimed at recognition of compounds emitted from infected wounds that is the subject of the WOUNDMONITOR project. The amounts of the target compounds can be evaluated by the EDA analysis if the magnitudes of signals are processed. Analysis of pure dynamic parameters results in separation between the types of the volatile compounds.
Sensors and Actuators B-chemical, 2005
We present an analysis of roasted coffee ripening performed by the novel Electronic Olfactory Sys... more We present an analysis of roasted coffee ripening performed by the novel Electronic Olfactory System EOS835, manufactured by the Italian company Sacmi Imola s.c.a.r.l., which is based on thin film semiconductor metal oxide gas sensors. We focused our analysis on: (1) exploratory data analysis for systematically investigating the outcomes of different sampling conditions and therefore selecting advantageous settings; (2) feature
IEEE Sensors Journal, 2007
ABSTRACT In this paper, a new electronic system for gas detection is presented. Particular attent... more ABSTRACT In this paper, a new electronic system for gas detection is presented. Particular attention is focused on electronic noses that employ several resistive sensors. New resistive sensors may have high value due to new substances (TiO2) or to low-cost fabrication process and, supposing to use these sensors together with traditional ones (SnO2), a novel instrument to manage high-value resistive sensors varying over a wide range, from kilohms to gigohms is required. The proposed hardware approach is a modular architecture which takes advantage from an improved resistance-to-period converter, where sensors are DC powered. Experimental results show a relative standard deviation below 0.01% and a relative displacement to the reference line less than 1% over six decades if commercial resistors are considered. A prototype has been realized to manage up to eight sensors, detect and estimate substance concentrations, and communicate results to the Internet.
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Papers by matteo falasconi