Michele Penza

Bio: Michele Penza is an academic researcher from ENEA. The author has contributed to research in topics: Carbon nanotube & Optical fiber. The author has an hindex of 40, co-authored 139 publications receiving 4604 citations. Previous affiliations of Michele Penza include University of Bari.

Nox gas sensing characteristics of wo3 thin films activated by noble metals (pd, pt, au) layers

Abstract: WO3-based gas sensor devices have been fabricated by reactive rf sputtering on glass substrates. Palladium (Pd), platinum (Pt), gold (Au) noble metals (100–600 A) were evaporated as activator layers onto WO3 thin films and Al layers (1500 A) were sputtered on top of them as upper electrodes for sensor output. The described sensing element was found to possess excellent sensitivity towards NO and NO2 gases, at low temperatures (100–300°C). The optimum operating temperature was 150 and 200°C for Pt, Pd and Au, respectively. The resistance of the thin-film gas sensor increases reversibly in the presence of low concentrations of NO (0–440 ppm) and NO2 (0–10 ppm) gases in air. The activator layers have an promotional effect on the speed of response to NOx at low temperatures and on selectivity enhanced with respect to other reducing gases (CO, CH4, H2, SO2, H2S, NH3). The temperature dependence of response and recovery times has been examined. The influence of the thickness of the noble metals on NOx gases sensitivity has been investigated. The NO and NO2 gases calibration curves have been recorded for the optimum performances of each fabricated sensor-device.

Carbon nanotubes as SAW chemical sensors materials

Abstract: We have designed, fabricated and characterized surface acoustic waves (SAWs) sensors coated by either single-wall carbon nanotubes (SWCNTs) or multi-wall carbon nanotubes (MWCNTs) for chemical detection of volatile organic compounds (VOCs), at room temperature. The carbon nanotubes (CNTs) were deposited by a spray-painting method onto ST,X-quartz substrates, coated by SiO2 films, used to implement the SAW sensors configured as 433.92 MHz two-port resonator-based oscillators. Upon individual exposure to tested VOCs such as ethanol, ethylacetate and toluene in nitrogen, the resonance frequency of the SAW oscillating sensor exhibits high downshift of a few hundreds (a few tens) of kHz for SWCNTs (MWCNTs) films dispersed into solvent of ethanol. High sensitivity of carbon nanotubes-coated SAW sensors has been achieved, at room temperature. The selectivity to VOCs under test can be controlled by the type of organic solvent used to disperse the carbon nanotubes as sensing materials onto SAW sensors. Preliminarily, some sensing mechanisms between chemical species to be detected and the carbon nanotubes will be discussed.

Tungsten trioxide (WO3) sputtered thin films for a NOx gas sensor

Abstract: WO3 thin films have been deposited by reactive rf sputtering onto low-cost glass substrates as gas sensitive coatings. The properties of the grown films have been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) in order to characterize their structure, composition, surface chemistry. The d.c. electrical response to different gases of the WO3 thin films has been measured in the temperature range from 100 to 400°C showing an increase of electrical resistance with a good sensitivity towards NOx gas at 250°C. WO3 thin films oppositely detect also NH3, H2, H2S, SO2 gases by decreasing the electrical resistance and are practically insensitive to interfering gases like CO, CH4 in the same temperature range. The sensing characteristics of the NOx gas detector based on tungsten trioxide (WO3) thin films are reported.

Odour detection methods: olfactometry and chemical sensors

Abstract: The complexity of the odours issue arises from the sensory nature of smell. From the evolutionary point of view olfaction is one of the oldest senses, allowing for seeking food, recognizing danger or communication: human olfaction is a protective sense as it allows the detection of potential illnesses or infections by taking into account the odour pleasantness/unpleasantness. Odours are mixtures of light and small molecules that, coming in contact with various human sensory systems, also at very low concentrations in the inhaled air, are able to stimulate an anatomical response: the experienced perception is the odour. Odour assessment is a key point in some industrial production processes (i.e., food, beverages, etc.) and it is acquiring steady importance in unusual technological fields (i.e., indoor air quality); this issue mainly concerns the environmental impact of various industrial activities (i.e., tanneries, refineries, slaughterhouses, distilleries, civil and industrial wastewater treatment plants, landfills and composting plants) as sources of olfactory nuisances, the top air pollution complaint. Although the human olfactory system is still regarded as the most important and effective “analytical instrument” for odour evaluation, the demand for more objective analytical methods, along with the discovery of materials with chemo-electronic properties, has boosted the development of sensor-based machine olfaction potentially imitating the biological system. This review examines the state of the art of both human and instrumental sensing currently used for the detection of odours. The olfactometric techniques employing a panel of trained experts are discussed and the strong and weak points of odour assessment through human detection are highlighted. The main features and the working principles of modern electronic noses (E-Noses) are then described, focusing on their better performances for environmental analysis. Odour emission monitoring carried out through both the techniques is finally reviewed in order to show the complementary responses of human and instrumental sensing.

Pattern Recognition and Machine Learning

Abstract: Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

American Society for Testing and Materials

Abstract: The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

Environmental applications of carbon-based nanomaterials.

Abstract: The unique and tunable properties of carbon-based nanomaterials enable new technologies for identifying and addressing environmental challenges. This review critically assesses the contributions of carbon-based nanomaterials to a broad range of environmental applications: sorbents, high-flux membranes, depth filters, antimicrobial agents, environmental sensors, renewable energy technologies, and pollution prevention strategies. In linking technological advance back to the physical, chemical, and electronic properties of carbonaceous nanomaterials, this article also outlines future opportunities for nanomaterial application in environmental systems.

Metal oxides for solid-state gas sensors: What determines our choice?

Abstract: The analysis of various parameters of metal oxides and the search of criteria, which could be used during material selection for solid-state gas sensor applications, were the main objectives of this review. For these purposes the correlation between electro-physical (band gap, electroconductivity, type of conductivity, oxygen diffusion), thermodynamic, surface, electronic, structural properties, catalytic activity and gas-sensing characteristics of metal oxides designed for solid-state sensors was established. It has been discussed the role of metal oxide manufacturability, chemical activity, and parameter's stability in sensing material choice as well.