Insights into the Sensing Mechanism of a Metal-Oxide Solid Solution via Operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy

Recently, 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

Fabrication of a Highly NO2-Sensitive Gas Sensor Based on a Defective ZnO Nanofilm and Using Electron Beam Lithography

Hazardous substances produced by anthropic activities threaten human health and the green environment. Gas sensors, especially those based on metal oxides, are widely used to monitor toxic gases with low cost and efficient performance. In this study, electron beam lithography with two-step exposure was used to minimize the geometries of the gas sensor hotplate to a submicron size in order to reduce the power consumption, reaching 100 °C with 0.09 W. The sensing capabilities of the ZnO nanofilm against NO2 were optimized by introducing an enrichment of oxygen vacancies through N2 calcination at 650 °C. The presence of oxygen vacancies was proven using EDX and XPS. It was found that oxygen vacancies did not significantly change the crystallographic structure of ZnO, but they significantly improved the electrical conductivity and sensing behaviors of ZnO film toward 5 ppm of dry air

Sub-ppm NO2 Detection through Chipless RFID Sensor Functionalized with Reduced SnO2

NO2 is an important environmental pollutant and is harmful to human health even at very low concentrations. In this paper, we propose a novel chipless RFID sensor able to work at room temperature and to detect sub-ppm concentration of NO2 in the environment. The sensor is made of a metallic resonator covered with NO2-sensitive tin oxide and works by monitoring both the frequency and the intensity of the output signal. The experimental measurements show a fast response (a few minutes) but a very slow recovery. The sensor could therefore be used for non-continuous threshold monitoring. However, we also demonstrated that the recovery can be strongly accelerated upon exposure to a UV source. This opens the way to the reuse of the sensor, which can be easily regenerated after prolonged exposure and recycled several times

Room Temperature Chemoresistive Gas Sensor Based on Organic-Functionalized Graphene Oxide

In the wide palette of chemoresistive sensing materials, hybrid nanocomposites have quickly gained [...

Roadmap on printable electronic materials for next-generation sensors

The dissemination of sensors is key to realizing a sustainable, ‘intelligent’ world, where everyday objects and environments are equipped with sensing capabilities to advance the sustainability and quality of our lives—e.g., via smart homes, smart cities, smart healthcare, smart logistics, Industry 4.0, and precision agriculture. The realization of the full potential of these applications critically depends on the availability of easy-to-make, low-cost sensor technologies. Sensors based on printable electronic materials offer the ideal platform: they can be fabricated through simple methods (e.g., printing and coating) and are compatible with high-throughput roll-to-roll processing. Moreover, printable electronic materials often allow the fabrication of sensors on flexible/stretchable/biodegradable substrates, thereby enabling the deployment of sensors in unconventional settings. Fulfilling the promise of printable electronic materials for sensing will require materials and device innovations to enhance their ability to transduce external stimuli—light, ionizing radiation, pressure, strain, force, temperature, gas, vapours, humidity, and other chemical and biological analytes. This Roadmap brings together the viewpoints of experts in various printable sensing materials—and devices thereof—to provide insights into the status and outlook of the field. Alongside recent materials and device innovations, the roadmap discusses the key outstanding challenges pertaining to each printable sensing technology. Finally, the Roadmap points to promising directions to overcome these challenges and thus enable ubiquitous sensing for a sustainable, ‘intelligent’ world

2D materials for room-temperature chemoresistive gas sensing

Two-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

Sensori di gas, la precisione può essere anche low cost

Utilizzo di tecnologia a basso costo e di facile implementazione al servizio dei sistemi di supporto decisionale per l’agricoltura. Questo uno degli obiettivi del progetto “Positive – Protocolli operativi scalabili per l’agricoltura di precisione”, finanziato dal Bando Por-Fesr 2014-2020. Positive nasce dalla convinzione che la gestione ottimizzata e integrata della produzione agricola sia imprescindibile dall’esperienza sul campo, ma al contempo sia occasione di sviluppo tecnologico. Lo scopo è rendere disponibili su scala regionale indici di interesse agronomico ricavabili dalle immagini satellitari, affiancati dalle informazioni prodotte da una rete di sensori a terra e predisporre un’infrastruttura informatica che renda concretamente fruibile su tutto il territorio regionale irrigazione e fertirrigazione di precisione

Sensori di gas, la precisione può essere anche low cost

Utilizzo di tecnologia a basso costo e di facile implementazione al servizio dei sistemi di supporto decisionale per l’agricoltura. Questo uno degli obiettivi del progetto “Positive – Protocolli operativi scalabili per l’agricoltura di precisione”, finanziato dal Bando Por-Fesr 2014-2020. Positive nasce dalla convinzione che la gestione ottimizzata e integrata della produzione agricola sia imprescindibile dall’esperienza sul campo, ma al contempo sia occasione di sviluppo tecnologico. Lo scopo è rendere disponibili su scala regionale indici di interesse agronomico ricavabili dalle immagini satellitari, affiancati dalle informazioni prodotte da una rete di sensori a terra e predisporre un’infrastruttura informatica che renda concretamente fruibile su tutto il territorio regionale irrigazione e fertirrigazione di precisione

Nanomaterial-Based Electric and Electronic Gas Sensors, Handbook of II-VI Semiconductor-Based Sensors and Radiation Detectors: Sensors, Biosensors and Radiation Detectors: Vol. 3,

Great attention has been dedicated to the development and use of solid-state gas sensors based on nanostructured semiconductors in recent decades. Metal oxide semiconductors (MOSs) are definitely the most investigated materials, but they have shown several shortcomings, including the lack of selectivity and stability over time, which have limited their use in many applications. This has led researchers to design and synthesise advanced nanostructured materials based on other types of semiconductors, able to overcome the limitations of MOSs towards the development of devices with optimised sensing performance. Among several alternatives, nanostructured II–VI transition metal chalcogenides (TMCs) are promising candidates for gas sensor development, due to their very interesting physicochemical features. These include: (i) wide and tunable bandgap; (ii) size-tunable radiation absorption and emission; (iii) catalytic and photocatalytic properties and (iv) the possibility to tune the nanostructure morphology and crystal structure by using simple and inexpensive methods. Although scarcely investigated in the gas sensing field so far, preliminary studies published over the last 10 years have shown peculiar sensing properties of TMCs, which could open up a future integration of these materials into commercial gas monitoring devices. This chapter presents a critical analysis of the state of the art related to the synthesis and use of II–VI TMC nanomaterials (NMs) for the development of electrical and electronic gas sensors

Applications of Chipless RFID Humidity Sensors to Smart Packaging Solutions

: Packaging solutions have recently evolved to become smart and intelligent thanks to technologies such as RFID tracking and communication systems, but the integration of sensing functionality in these systems is still under active development. In this paper, chipless RFID humidity sensors suitable for smart packaging are proposed together with a novel strategy to tune their performances and their operating range. The sensors are flexible, fast, low-cost and easy to fabricate and can be read wirelessly. The sensitivity and the humidity range where they can be used are adjustable by changing one of the sensor's structural parameters. Moreover, these sensors are proposed as double parameter sensors, using both the frequency shift and the intensity variation of the resonance peak for the measure of the relative humidity. The results show that the sensitivity can vary remarkably among the sensors proposed, together with the operative range. The sensor suitability in two specific smart packaging applications is discussed. In the first case, a threshold sensor in the low-humidity range for package integrity verification is analyzed, and in the second case, a more complex measurement of humidity in non-hermetic packages is investigated. The discussion shows that the sensor configuration can easily be adapted to the different application needs