1,721,054 research outputs found
2D materials for room-temperature chemoresistive gas sensing
No full textTwo-dimensional materials have naturally attracted the interest of the re- searchers due to their unusual and captivating properties such as high- carrier mobility, tunable band gap, high mechanical strength and thermal conductivity, allowing the extensive application in the field of nanoelectron- ics, supercapacitors, sensors, H2 storage, drug delivery, fuel cells, transis- tors and polymer nanocomposites. The increasing demand for highly sen- sitive, selective, cost-effective, low power consuming, stable and portable sensors has stimulated extensive research on new chemoresistive sensing materials in order to overcome typical drawback of the commonly used metal-oxide semiconductors-based devices. The emergence of new candi- dates including graphene, graphene oxide, reduced graphene oxide, transi- tion metal dichalcogenides, phosphorene, etc., has shown great potentialities in gas sensing field applications due to their high surface-to-volume ratio, low noise, tunable band gap and sensitivity of electronic properties to the changes in the surroundings. This thesis work aims to exploit these promis- ing features for reversible and controlled interaction of adsorbed chemi- cal species on novel two-dimensional materials. Starting from graphene, graphene oxide and exfoliated black phosphorous their properties were tai- lored through decoration with different organic and inorganic functional groups and their performance were compared to the pristine materials, en- visaging possible applications in order to contribute to the innovation in chemoresistive gas sensing research. Particular attention has been paid to material synthesis, characterization and gas sensor performance metrics at room temperature such as sensitivity, specificity, detection limit, response time and reversibility. The presented work concludes with the current chal- lenges and future perspectives for two-dimensional materials in gas sensing applications.I materiali bidimensionali hanno recentemente attirato l’attenzione della comunità scientifica grazie alle loro inusuali proprietà intrinseche come, ad esempio, l’alta mobilità dei carrier, il band-gap modulabile, l’alta resistenza meccanica e l’elevata conducibilità termica. L’insieme di queste caratter- istiche li rende fortemente appetibili per svariate applicazioni nel campo della nanoelettronica, della sensoristica ed in generale nella trasduzione di segnali di diversa natura. In questo senso, la continua richiesta di disposi- tivi altamente sensibili, selettivi, economici, efficienti, stabili e compatti ha stimolato la ricerca di nuovi materiali nel campo dei sensori chemoresistivi allo scopo di limitare ed arginare gli svantaggi dei materiali attualmente maggiormente utilizzati come i semiconduttori basati su ossidi metallici. Nuovi candidati come il grafene, l’ossido di grafene, l’ossido di grafene ri- dotto, i dicalcogenuri dei metalli di transizione ed il fosforene offrono grandi possibilità grazie all’ampia superficie attiva, al ridotto rumore elettrico e all’elevata sensibilità alle variazioni ambientali che li circondano. Il lavoro di tesi qui presentato mira a sfruttare le promettenti caratteristiche dei materiali bidimensionali al fine di ottenere l’adsorbimento controllato e re- versibile di diverse specie chimiche in fase gassosa sulla superficie di nuovi materiali. Partendo da grafene, ossido di grafene e fosforo nero esfoliato sono stati prodotti tre nuovi materiali grazie a funzionalizzazioni con composti organici ed inorganici. Successivamente, sono stati testati come materiali sensibili rispetta diversi gas e le loro performance sono state comparate con i corrispettivi composti di partenza allo scopo di verificare l’ottenimento di incrementi prestazionali. Particolare attenzione è stata posta alla sintesi, alla caratterizzazione e alla valutazione delle performace di sensing come sensibilità, specificità, limite di rilevabilità, tempi di risposta e reversibilità della reazione superficiale. Il lavoro si conclude con le sfide e le prospettive future nell’utilizzo di materiali bidimensionali nel campo della sensoristica gassosa
Multiparameter chipless RFID sensor tag for humidity and NO2 determination
No full textThis paper reports a chipless RFID sensor tag to be used for the simultaneous determination of both humidity and NO2 concentration in the environment. The tag is based on the use of functionalized ELC resonators with two different sensitive materials. The detection strategy allows for a wireless determination of both environmental parameters because the resonators work at different frequencies and react differently to the selected environmental parameters
Insights into the Sensing Mechanism of a Metal-Oxide Solid Solution via Operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy
Full text linkRecently, the influence of Nb addition in the oxide solid solution of Sn and Ti was investigated with regard to the morphological, structural and electrical properties for the production of chemoresistive gas sensors. (Sn,Ti,Nb)xO2-based sensors showed promising features for ethanol monitoring in commercial or industrial settings characterized by frequent variation in relative humidity. Indeed, the three-metal solid solution highlighted a higher response level vs. ethanol than the most widely used SnO2 and a remarkably low effect of relative humidity on the film resistance. Nevertheless, lack of knowledge still persists on the mechanisms of gas reaction occurring at the surface of these nanostructures. In this work, operando Diffuse Reflectance Infrared Fourier Transform spectroscopy was used on SnO2- and on (Sn,Ti,Nb)xO2-based sensors to combine the investigations on the transduction function, i.e., the read-out of the device activity, with the investigations on the receptor function, i.e., compositional characterization of the active sensing element in real time and under operating conditions. The sensors performance was explained by probing the interaction of H2O and ethanol molecules with the material surface sites. This information is fundamental for fine-tuning of material characteristics for any specific gas sensing applications
First-Principles Study of Electronic Conductivity, Structural and Electronic Properties of Oxygen-Vacancy-Defected SnO2
No full textThe use of computer simulations has become almost essential for prediction and interpretation of device's performance. In gas sensing field, the simulation of specific conditions, which determine the physical-chemical properties of widely used metal oxide semiconductors, can be used to investigate the performance of gas sensors based on these kinds of materials. The aim of this work was to evaluate the physical-chemical properties of tin dioxide employed for environmental and health gas sensing application and to investigate the influence of oxygen vacancies on its properties by means of density functional theory. Two samples, having different concentration of oxygen vacancies, were deeply studied in terms of their structural, electronic and electrical properties. It was proved the influence of oxygen vacancies on lattice parameter. By increasing oxygen vacancies concentration, the increased number of impurity states took these closer to the conduction band minimum, which can lead to an easier adsorption process of oxygen species and their availability to be exchanges with the molecules of the target gases. In this way a reduction of the operating temperature can be observed, thus reducing the power consumption of devices, while keeping the catalytic performance of the material
Investigation on the Development, Stabilization and Impact of Thermally Induced Oxygen Vacancies on the Chemoresistive Sensing Properties of MOX
No full textGas sensors based on metal oxide (MOX) semiconductors doped with oxygen vacancies (VO) have many advantages over stoichiometric MOX, such as higher surface reactivity and lower operating temperature. However, preparing reduced MOX is challenging, and the impact of different VO types and concentration on sensing performance is still unclear. In this work, we developed a tailored reducing thermal treatment for creating controlled VO in MOX. The effect of the length and temperature of the treatment was investigated using several characterization methods. Finally, measurements were performed to evaluate the impact of VO type and concentration on reduced MOX sensing performance
Neural-network-driven Electronic Nose Enhancing Artificial Olfaction in Non-invasive Diagnostics
No full textThis paper presents an e-nose specifically designed for non-invasive diagnostics and human volatilome analysis. The sensing technology is based on a 10-sensors array of both commercial Metal Oxide (MOX) gas sensors and custom-fabricated counterparts. Thanks to a versatile pneumatic system, it is capable of analyzing response signals from various sample types, including exhaled breath and the headspace of human biological samples. A neural-network-based model is adopted to enhance the classification capability. The device's effectiveness is demonstrated through experimental tests with both chemical standards and mixtures resembling human biosamples, achieving a 97.1% classification accuracy with 7 prepared test samples. The experimental results, along with the capability to discriminate correctly the test samples in presence of water, confirm the system's efficacy in the context of non-invasive diagnostics and human volatilome analysis
Chitin Nanocrystal Films for Flexible Biodegradable Electronics
No full textFlexible devices are increasingly required in fields such as soft robotics, healthcare, and precision agriculture, where their ability to stretch and conform to non-planar surfaces is essential. All these applications traditionally employ polymeric and plastic substrates, such as polyimides, which nevertheless contribute to electronics waste. Recently, there is a growing interest towards biocompatible, biobased, and even biodegradable substrates. An extremely interesting biobased material coming from the animal kingdom is chitin, which – despite being considered a waste product of the fishing industry – is the most used carbohydrate to create resistant yet flexible structures. This paper reports the development of a solution processing water-based method for the realization of chitin, using a TEMPO mediated oxidation with minimal oxidants. In this study, we focus on characterizing the substrate and investigating its mechanical and thermal degradation properties. The objective is to assess the impact of various oxidant concentrations, to find the most effective one for creating flexible, strong, and temperature-resistant substrates
Improving Hydrogen Selectivity in Semiconductor Metal Oxide Gas Sensors with Cellulose Nanocrystal Membranes
Full text linkAs hydrogen (H2) gains traction as a clean energy carrier, the need for reliable and selective gas sensors becomes increasingly urgent, particularly for detecting H2 leaks amidst complex gas environments. While semiconducting metal oxide (SMOX)-based sensors are attractive due to their low cost and high sensitivity, their poor selectivity remains a major limitation. In this work, we address this challenge by integrating a gas-selective membrane into the sensor packaging, without altering the sensing material itself. The membrane is produced in situ by drop-casting a suspension of cellulose nanocrystals (CNCs) within the sensor housing. The CNCs self-assemble into a thin, gas-permeable barrier upon solvent evaporation. This simple addition significantly reduces cross-sensitivity to common interfering gases, suppressing the response to 30 ppm of ethanol (EtOH), acetone, ammonia (NH3), nitrogen dioxide (NO2), and carbon monoxide (CO) by factors of approximately 160, 1500, 370, 90, and 20, respectively, while reducing the H2 signal by only a factor of 6. The result is a substantial improvement in H2 selectivity using a low-cost, scalable approach that preserves the original sensor architecture. This method offers a practical path to enhanced performance in SMOX-based gas sensors for safety and energy applications
Chipless RFID Sensors: A Discussion on the Potentialities and Recent Advancements
No full textIn this work we are proposing a discussion on the potential of an innovative class of microwave sensors, known as chipless RFID sensors. We are also investigating, thanks to a final comparative view, the most important studies related to our research in the field. We focus on sensing environmental quantities such as humidity and nitrogen dioxide (NO2) with the Nafion 117 and tin dioxide materials
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