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Suspended particulate matter (PMx) is one of the most important environmental pollutants. Miniaturized sensors capable of measuring and analyzing PMx are crucial in environmental research fields. The quartz crystal microbalance (QCM) is one of the most well-known sensors that could be used to monitor PMx. In general, in environmental pollution science, PMx is divided into two main categories correlated to particle diameter (e.g., PM < 2.5 µm and PM < 10 µm). QCM-based systems are capable of measuring this range of particles, but there is an important issue that limits the application. In fact, if particles with different diameters are collected on QCM electrodes, the response will be a result of the total mass of particles; there are no simple methods to discriminate the mass of the two categories without the use of a filter or manipulation during sampling. The QCM response depends on particle dimensions, fundamental resonant frequency, the amplitude of oscillation, and system dissipation properties. In this paper, we study the effects of oscillation amplitude variations and fundamental frequency (10, 5, and 2.5 MHz) values on the response, when particle matter with different sizes (2 µm and 10 µm) is deposited on the electrodes. The results showed that the 10 MHz QCM was not capable of detecting the 10 µm particles, and its response was not influenced by oscillation amplitude. On the other hand, the 2.5 MHz QCM detected the diameters of both particles, but only if a low amplitude value was used.

Introduction: The Solar System dust is the smallest Solar System building block, and therefore its study allows understanding the early stages of the Solar System formation. The comprehension of the Solar System formation and evolution processes is also constrained by the inventory and spatial distribution of volatiles in our System. In particular, the delivery process of volatiles of astrobiological interest (water and organics) to the Earth is a key issue to understand the life formation in our planet. Asteroids and comets may have been the source of these volatiles to the terrestrial planets’ atmospheres and to the Earth’s oceans. The boundary between asteroids and comets is not well defined, and many main-belt asteroids are probably volatile-rich and would become cometary if they were moved to the inner Solar System. Piezoelectric Crystal Microbalances (PCMs) are widely used sensors to monitor dust and particles deposition processes in space and to characterize material outgassing in vacuum. This kind of sensors converts mass changes into fundamental resonance frequency variations, according to Sauerbrey equation [1]. In this work we present VISTA (Volatile in-Situ Thermogravimeter Analyser), one of the two scientific payloads on board MILANI Cubesat, as part of the ESA Hera Program. The MILANI Cubesat development is led by Tyvak International, prime contractor of a consortium composed by entities and institutions from Italy, Czech Republic and Finland. The main MILANI objective is executing a scientific mission aiming at studying the binary asteroid system Didymos-Dimorphos, characterizing the asteroid with a dust sensor, i.e. VISTA, and a spectrometer, i.e. ASPECT. VISTA is developed by an Italian Consortium composed by three Research Institutes: INAF-IAPS (National Institute of Astrophysics - Institute for Space Astrophysics and Planetology), CNR-IIA (National Council of Research – Institute of Atmospheric Pollution) and Politecnico di Milano. HERA Mission goals: Hera is a planetary defence mission under development at the European Space Agency (ESA), launching in October 2024. Hera is the European contribution to the international Asteroid Impact Deflection Assessment (AIDA) cooperation, the first planetary defence mission, in collaboration with NASA, who is responsible for DART (Double Asteroid Redirection Test) kinetic impactor spacecraft. Hera will travel to a binary asteroid system, the Didymos-Dimorphos pair of near-Earth asteroids, and will study and characterize the asteroid system after the DART impact in September 2022. In the framework of Hera mission, VISTA will accomplish the following scientific goals: 1) detect the presence of dust particles smaller than 10 µm (residual dust particles from the impact and suspended dust in the binary system or coming from dust levitation process); 2) characterization of volatiles (e.g. water) and light organics (e.g. low carbon chain compounds) by using Thermo-Gravimetric Analysis (TGA) cycles (the desorption rates ad specific temperatures are used to characterize e volatiles and organics desorbed from the sensor surface); 3) molecular contamination monitoring in support to other Cubesat instruments and ASPECT spectrometer, coming from outgassing processes on-board the spacecraft, that usually happen in the first days or weeks in orbit. VISTA Heritage: The Consortium has a considerable heritage in the design, manufacturing and testing of PCM-based instrumentation both for laboratory and space applications coming from different ITT-Emits ESA Projects: 1) CAM (Contamination Assessment Microbalance), developed for “Evaluation of an in-situ Molecular Contamination Sensor for space use” (2014-2016) (Figure 1); 2) CAMLAB (Contamination Assessment Microbalance for LABoratory) developed for “Development of a European Quart Crystal Microbalance” (2017-2019) (Figure 2). Figure 1. PCM Engineering Model developed during CAM-ESA Project for space applications. Figure 2. PCM breadboard developed during CAMLAB-ESA Project for laboratory applications. Working principle: PCMs exploit the piezoelectric properties of quartz crystals, as mass deposition on the sensing area of the instrument induces variations of the crystal resonance frequency. The core of VISTA is composed of: 1) two quartz crystals mounted in a sandwich-like configuration (one sensing crystal and the other reference crystal); 2) a Thermal Control System (TCS), composed by two integrated heaters and a Thermoelectric Cooler (TEC); 3) a Proximity Electronics (PE). The instrument is also capable of performing Thermo-Gravimetric Analysis, a technique used to monitor thermal processes involving volatile compounds, e.g absorption/desorption and deposition/sublimation, by means of the built-in heaters. The TEC is used to cool down the sensor and enhance the condensation of particles on the microbalance. VISTA is capable of monitoring particles lower than 5-10 µm and sub-µm particles. VISTA technical characteristics are shown in Table 1. Table 1. VISTA technical characteristics. The sublimated compounds can be characterized by calculating the enthalpy of sublimation ΔHsub, which can be retrieved with two methods: 1) by considering the deposition rates and using Van’t Hoff relation [3]; 2) by using Langmuir relation [4]. Conclusions and future works: In this work, the VISTA instrument working principle and heritage were presented. Qualification activities are currently ongoing on the VISTA Engineering Qualification Model (EQM), shown in Figure 3, in order to qualify the sensor within the expected mechanical and thermal environment and evaluate the instrument performances in a representative environment, prior integration on the MILANI Cubesat. The next phase of the research activities will be the manufacturing, integration and testing of VISTA Flight Model (FM), that will launch in 2024. Figure 3. VISTA EQM developed for MILANI cubesat/HERA Space Mission. References: [1] G. Sauerbrey 1959, Z. Phys., 155, 206-222; [2] Palomba E. (2016), OLEB, 46 (2-3); [3] S.W. Benson et al. 1968; [4] I. Langmuir, 1913.

Introduction: Quartz Crystals Microbalances (QCMs) are widely used sensors for monitoring and characterizing dust and particles deposition processes in different planetary environments and measuring material contamination coming from outgassing sources in space, in support to other instruments (e.g. spectrometers). Furthermore, they are capable of detecting and measuring the presence of volatile com-pounds of astrobiological interest such as water and organics. These measurements can be particularly relevant when performed on primitive asteroids or comets, or on targets of potential astrobiological interests, e.g. Mars [1]. These sensors convert mass changes into fundamental resonance frequency variations, according to Sauerbrey equation [2]. The VISTA (Volatile In Situ Thermogravimetry Analyser) instrument is a QCM-based device able to perform measurements of abundance of volatiles and dust particles in planetary and asteroidal environments. The instrument can characterize the planetary regolith from 5-10 µm to sub-µm particles and monitor the contamination processes on board satellites (cubesat, etc.) caused by molecular outgassing. VISTA is one of the two scientific payloads of MILANI CubeSat, developed by Tyvak International that leads a consortium composed by entities and institutions from Italy, Czech Republic and Finland, in the framework of the Hera program of the European Space Agency (ESA). Hera, due to launch in 2024, is the ESA part of the Asteroid Impact & Deflection Assessment (AIDA) international collaboration with NASA, who is responsible for the Double Asteroid Redirection Test (DART) kinetic impactor spacecraft. The main objective of MILANI is the study of the binary asteroid system Didymos-Dimorphos, characterizing the asteroid with a dust sensor (VISTA) and a spectrometer (ASPECT). In this work, the calibration operations and the performance tests, to assess VISTA capability of characterizing volatile compounds and simulant contaminations in vacuum chamber at low temperatures. The sensor has been developed by an Italian Consortium composed by three Research Institutes: INAF-IAPS (National Institute of Astrophysics - Institute for Space Astro-physics and Planetology), CNR-IIA (National Council of Research – Institute of Atmospheric Pollution) and Politecnico di Milano and led by INAF-IAPS. Figure 1. VISTA EQM developed for ESA Hera space mission. Working Principle: The instrument core is a QCM whose frequency variations directly depends on the deposited sample mass on the crystal surface during sublimation, condensation and absorption/desorption processes. The instrument consists of: 1) two quartz crystals mounted in a sandwich-like configuration; 2) a Thermal Control System (TCS), composed by two integrated heaters and a Thermoelectric Cooler (TEC); 3) a Proximity Electronics (PE). VISTA is also capable of performing Thermo-Gravimetric Analysis, which is a technique used to monitor thermal processes involving volatile compounds, e.g. deposition/sublimation and absorption/desorption. It can also monitor particles lower than 5-10 µm and sub-µm particles [1]. Calibration: The QCM frequency can change not only due to the mass deposition/release, but also due to the variation of environmental parameters, such as temperature and pressure. In order to disentangle frequency variations due to mass deposition and environmental parameters, the sensor is calibrated by measuring the frequency as a function of temperature. According to literature [3], the frequency-temperature curve follows a third-degree polynomial (Figure 2). Figure 2. QCM frequency as a function of temperature in vacuum. Performance tests: VISTA capability to detect contaminant depositions and to monitor the accumulation and desorption processes is verified by placing an effusion cell containing an organic compound, used as a contamination source, placed in the Field Of View (FOV) of the sensing crystal and heated up to 100°C. The experimental setup is shown in Figure 3. Figure 3. VISTA EQM experimental setup for contamination simulation. The QCM is connected with four screws with a copper U shape and in contact with a cold sink set to -10°C to help the molecules condensation on the crystal surface. The frequency is monitored during the tests and the deposited flux can be retrieved (Figure 4) at each temperature set point. Figure 4. Deposition test from +50°C to +100°C. Two methods can be used to retrieve the enthalpy of sublimation ΔHsub by using the deposition rates, i.e. the Van’t Hoff relation [4] or Langmuir relation [5]. Thus, by measuring two different deposition rates, k1 and k2, at two different close temperatures T1 and T2, it is possible to obtain the compound ΔHsub by means of Van’t Hoff relation or throughout the temperature range by using Langmuir relation. TGA cycles are then performed by heating the crystals by means of the built-in heaters. After the heating cycles, the frequency returns to its initial value, thus indicating that all the deposited mass desorbed during the test (Figure 5). Figure 5. TGA cycles from +15°C to +50°C and from +40°C to +70°C. The desorption rates from crystals surface can be used as well to calculate the ΔHsub and compare it with the ΔHsub results obtained during the depositions/contamination processes. References: [1] E. Palomba et al (2016), OLEB, 46(2-3; [2] G. Sauerbrey (1959), Z. Phys., 155, 206-222; [3] D. Salt (1987); [4] S.W. Benson et al., 1968; [5] I. Langmuir, 1913.

Passive air samplers (PASs), which provide time-averaged concentrations of gaseous mercury over the timescale of weeks to months, are promising for filling a gap in the monitoring of atmospheric mercury worldwide. Their usefulness will depend on their ease of use and robustness under field conditions, their availability and affordability, and most notably, their ability to provide results of acceptable precision and accuracy. Here we describe a comparative evaluation of three PASs with respect to their ability to precisely and accurately record atmospheric background mercury concentrations at sites in both southern Italy and southern Ontario, Canada. The study includes the CNR-PAS with gold nanoparticles as a sorbent, developed by the Italian National Research Council, the IVL-PAS using an activated carbon-coated disk, developed by the Swedish Environmental Research Institute, and the MerPAS® using a sulfur-impregnated activated carbon sorbent, developed at the University of Toronto and commercialized by Tekran. Detection limits are deduced from the variability in the amount of mercury quantified in more than 20 field blank samples for each PAS. Analytical and sampling precision is quantified through 22 triplicate deployments for each PAS, ranging in duration from 2 to 12 weeks. Accuracy and bias are assessed through comparison with gaseous elemental mercury concentrations recorded by Tekran 2537 automated mercury analyzers operating alongside the PASs at both locations. The performance of the PASs was significantly better in Italy, with all of them providing concentrations that are not significantly different from the average concentrations of the Tekran 2537 instruments. In Canada, where weather conditions were much harsher and more variable during the February through April deployment period, there are differences amongst the PASs. At both sites, the MerPAS® is currently the most sensitive, precise, and accurate among the three PASs. A key reason for this is the larger size and the radial configuration of the MerPAS®, which results in lower blank levels relative to the sequestered amounts of mercury when compared to the other two PASs, which rely on axial diffusion geometries. Since blank correction becomes relatively smaller with longer deployments, performance tends to be closer amongst the PASs during deployments of 8 and 12 weeks.

The aim of this work is a technical review about Quartz Crystal Microbalance (QCM) sensors used in space missions, i.e. Space Shuttle flights, i.e. NASA Space Transportation System (NASA STS) and satellite missions, that aimed at monitoring the contamination generated by outgassing processes of materials onboard satellites and sensitive payloads. The contamination processes are critical for scientific instrumentation (e.g. optics, telescopes, detectors) because scientific measurements and performances can be jeopardized or worsened by uncontrolled contamination. This issue has been addressed by the space agencies, e.g. NASA, ESA and JAXA that have implemented many different studies to monitor the material outgassing and degradation in space environment. During the past years, the QCM sensors have become the baseline solution for measuring material outgassing and characterizing the on-orbit contamination environment. This work summarizes the main QCM applications in Space and their findings, providing an overview of the sensors’ performances in terms of stability, power, data rate, measurement accuracy and resolution. Different QCM technologies will be compared highlighting the advantages of their use for the next space missions and instrumentations that require an accurate monitoring of contamination environment. In particular, due to more severe contamination requirements for next payloads and instrumentations, QCM sensors would be useful to estimate the cleanliness degree by evaluating the induced contamination and degradation on sensitive instrumentations.

This work describes the design of a holder for a quartz crystal microbalance for space application. The main objectives of the conceived system are to hold the quartz crystal providing adequate support in the expected mechanical and thermal environments, and to assure the functionalities of the instrument, i.e. measuring the oscillation frequency and the crystal temperature or heating the crystal during regeneration phases. A kinematic mounting has been designed to be manufactured by stereolithography because this technology allows achieving high spatial resolution and complex shapes that are needed to implement an easy assembling and mounting of the holding system. Moreover, the 3D printing technology would provide a cost-effective solution even for small series production.

Per evitare l'esposizione dei lavoratori a potenziali gas/vapori tossici con effetti di intossicazione acuta o talvolta letali, sta diventando necessario per le aziende utilizzare tecnologia indossabile associata alla cosiddetta Intelligenza Artificiale per prevenire gli infortuni dei lavoratori, creando così lavoratori più protetti. Queste tecnologie sono basate sull'uso congiunto di sistemi di raccolta e analisi di dati ottenuti da sensori incorporati nei caschi, in braccialetti o in giubbotti, per allertare i dipendenti e i loro manager in tempo reale. Le soluzioni sono le più differenti, ma il più delle volte comprendono una serie di sensori indossabili che monitorano informazioni quali respirazione, esposizione a gas tossici, frequenza cardiaca, postura e movimento. I dispositivi così fatti sono destinati ad essere utilizzato all'interno delle fabbriche, ma possono essere utilizzati anche da lavoratori in aree esterne. Si può provare a fare una classificazione dei principali ambiti di applicazione di queste tecnologie, anche se sicuramente non esaustiva: oTracciamento della posizione del lavoratore oMonitoraggio dei segni vitali e i rischi ambientali oMitigazione dei rischi fornendo informazioni a distanza oMiglioramento della formazione del personale La presente proposta progettuale affronta i primi due punti che sono propedeutici ai successivi. Il tracciamento della posizione è uno dei punti fondamentali per conoscere dove il lavoratore si trova utilizzando sensori GPS posti nel caschetto o indossati negli abiti di lavoro, con diverse utilità. L'altro ambito di applicazione è il monitoraggio dei segni vitali e dei rischi ambientali. Oggi esistono potenzialmente diversi dispositivi indossabili che monitorano i segni vitali dei lavoratori: occhiali intelligenti che rilevano la sonnolenza e abbigliamento intelligente che va monitora la variabilità della frequenza cardiaca e il volume respiratorio. Alcuni studi sul monitoraggio della fatica dei lavoratori con i sensori indossabili dimostrano che gli incidenti aumentano quando le condizioni psicofisiche non sono perfette. Ma i sensori indossabili possono anche monitorare l'esposizione dei lavoratori a condizioni gravose come, per esempio, il monitoraggio dell'esposizione dei dipendenti allo stress da calore o da agente chimico. Monitorare questi parametri può fornire al lavoratore informazioni utili per programmare le sue pause o il ricambio di aria nel suo luogo di lavoro. Nella prima fase della proposta progettuale IIA, in collaborazione con gli altri partners, si è occupata della selezione degli scenari applicativi di interesse per la definizione di un set di sostanze target. A causa delle condizioni di isolamento generato dalla pandemia di COVID 19, si è optato di effettuare test e validazioni in laboratori di chimica che sono di facile accesso ai partners del progetto (come per es. i laboratori di IIA, ed. 14, dedicati alla sensoristica e allo sviluppo di materiali, forniti di cappe chimiche, quattro laboratori ed un corridoio) dove, l'accesso ad una serie di solventi e prodotti chimici, può permettere di simulare anche scenari di tipo industriale (es. solventi organici a differenti concentrazioni dalle lavorazioni con resine e vernici, ecc.) o in generale lavorativi (es. acido acetico dagli archivi fotografici, ammoniaca dalla produzione di prodotti per l'agricoltura, ecc.). Per le concentrazioni di interesse verranno considerate e testate sia quelle incluse nelle normative (livelli consentiti di esposizione in tempi differenti) sia quelle più elevate ed in grado di generare repentinamente un segnale di allarme. Per lo sviluppo dei sensori, dalla esperienza del precedente BRIC (BRIC16 ID12), IIA ha ottimizzato la tecnica di deposizione per elettrofilatura, sia standardizzando il processo, sia selezionando i materiali più promettenti per le attività della proposta. Nel primo caso, la standardizzazione è stata possibile grazie all'implementazione della strumentazione presso IIA con un sistema commerciale in grado di impostare e monitorare ciascuna fase all'interno del processo di deposizione (Fluidnatek LE-50, Bioinicia). Nel secondo caso sono stati sviluppati e testati una serie di sensori compositi di nuova generazione e comparati ai sensori sviluppati per il recedente BRIC. Infatti i sensori conduttivi sviluppati per il precedente studio, seppur estremamente promettenti, richiedevano un controllo della temperatura di lavoro, che se da un lato ha permesso di modulare la sensibilità e selettività dei sensori ai vari gas (Frontiers in Chemistry 2018, Nanomaterials 2019), dall'altro su un sistema indossabile richiederebbe un incremento nei consumi energetici e quindi un maggiore ingombro. Come materiale di base si è utilizzato il polivinilpirrolidone, (PVP), che è un polimero idrosolubile di formula (C6H9NO)n, costituito da monomeri di 1-vinil-2-pirrolidone. È solubile anche in alcool e altri solventi polari. Commercialmente è usato come agente di rivestimento, ma è utilizzato anche negli inchiostri, prodotti per capelli, vernici, pesticidi e dentifrici. Viene utilizzato come additivo alimentare in qualità di stabilizzante. Si utilizza quale agente legante nella preparazione dei granulati per compresse, infatti ha buone proprietà leganti (evita la rottura delle compresse mantenendo legata la massa da comprimere) e allo stesso tempo ha il vantaggio di non prolungare il tempo di disgregazione. Per quanto riguarda la sua tossicità, si reputa sia una sostanza molto sicura e lo testimonia il fatto che viene utilizzata da più di mezzo secolo nei prodotti più svariati. Addirittura, si è utilizzato per diluire il plasma umano destinato alle trasfusioni durante la Seconda guerra mondiale. L'esposizione ad UV per alcuni minuti, generando la formazione di radicali, genera una serie di nuovi legami tra le catene all'interno della singola fibra, rendendolo, in funzione del tempo di esposizione, insolubile o differentemente solubile nei vari solventi, assumendo così nuove proprietà chimico-fisiche e maggiore stabilità. Poiché è un materiale poco costoso ed estremamente semplice da elettrofilare, è stato qui studiato come struttura di base nanofibrosa. In questo capitolo sono riportate tutte le attività svolte per la progettazione e la fabbricazione dell'interfaccia analogica digitale per l'acquisizione dei segnali provenienti dai sensori conduttometrici sviluppati. Il secondo capitolo è articolato in tre sezioni: nella prima è riportato lo sviluppo dell'interfaccia sensori, la seconda tratta le attività inerenti lo sviluppo del sistema di misura per laboratorio dove "l'interfaccia sensori" sarà integrata e testata, nella terza ed ultima sono riportati alcuni dettagli sul software sviluppato per il sistema di misura da laboratorio.

Nanomaterials such as gold nanoparticles employed as solid-state sensors have attracted attention in recent years due to their ability to detect poisonous elements in the indoor/outdoor environment. Herein, chemoresistive sensors based on gold nanoparticles (AuNPs) functionalized with mixed thiol ligands were tested as sensing materials. Specifically, the electrical response of gold nanoparticles-based sensors was tested against Hg0vap, H2S, SO2, NH3, and relative humidity (RH) at room temperature. Gold nanoparticles samples were synthesized by the wet reduction method and then deposited as thin films on suitable interdigitated transducers. Electrical conductivity measurements allowed evaluating a semiconducting behavior of the colloids. A selective and reproducible sensing behavior toward Hg0vap was observed in the range 0.1-1.0 ng/mL, allowing simple and reliable resistive devices to be obtained. An irreversible interaction mechanism, based on formation of an Au-Hg direct bond, was observed in the case of isolated AuNPs samples. Interconnected AuNPs exhibited a reversible behavior as assessed by Micro Raman, XRD, XPS, AFM, SEM, and UV-vis and FTIR spectroscopies together with DLS measurements. Broadening of the plasmonic band and an increase in the mean particle size upon contact with Hg0vap was observed. Morphological characterization revealed the formation of aggregates after interaction between Hg0vap and AuNPs. XRD and Micro Raman measurements collected on the nonexposed and Hg-exposed nanoparticles suggest their structural rearrangement at the surface and formation of an Au-Hg alloy with Hg mechanically trapped within the bulk material. The simple and cost-effective fabrication of these sensors has prospect in the future as nanodevices for real-time outdoor air quality monitoring.

Adsorption and detection of environmental total gaseous mercury (TGM) was studied by using gold nanoparticles (AuNPs) on purpose functionalized with dithiol ligands, i.e. Biphenyl-4,4′-dithiol (BI) or p-Terphenyl-4,4′′-dithiol (TR), suitable for nanoparticles based network formation. AuNPs-BI and AuNPs-TR with size 6–8 nm were deposited onto quartz fibres and used as adsorbent materials for the detection of TGM, both indoor for adsorption studies, at defined concentrations (∼4.5 ng m−3 Hg), and outdoor, at the vapour mercury concentration of the environmental countryside (∼1.5 ng m−3 Hg). The role of relative humidity (RH) in the absorption process has been observed. A high Hg adsorption capability, also when exposed to sub ppb concentration, has been observed. A cold vapour atomic fluorescence spectroscopy (CVAFS) detector was used to determine gaseous mercury concentrations lower than 2 ng m−3, with a robust and reproducible procedure. Moreover, the use of quartz fibres substrate covered with AuNPs-BI or AuNPs-TR, and used for more than thirty times during the experiments, makes them competitive in the use in large-scale measurement campaigns.

This work deals with temperature characterization of Cr-Au and Ti-Au deposited resistors on quartz crystal microbalances designed for Space. The advantage of the proposed configuration is that direct heating of the electrode’s area can be obtained as well as a measurement of the quartz crystal temperature. In this view, characterization of the deposited materials is of primary importance to provide accurate temperature measurement and retrieve reliable results for thermogravimetric analyses. The behavior of the deposited material has been verified down to cryogenic temperatures. The characterization in cryogenic condition evidenced that the linearity error is limited to 4 °C at the liquid nitrogen temperature but the regression standard deviation can be reduced to one order of magnitude if a third-order polynomial is used to fit the experimental data.

Most QCM-based devices devoted to PM measurement use substrates of various kinds to collect and retain particles. The novelty of this work is the possibility to use an integrated microheater actuator to change the substrate collecting features during the particulate adsorption. In fact, this paper presents preliminary results about the exploitation of a HQCM (Heated Quartz Crystal Microbalance) in particulate matter (PM) measurements. HQCM is a 10 MHz quartz crystal microbalance with a microheater and a resistive temperature detector (RTD) implemented on its surface. The effects of the sensor surface temperature (T 1 = 20 °C and T 2 = 80 °C) on the PM detection have been studied by a suitable particulate measurement system, where the HQCM coated by grease, worked both as impaction plate and mass sensor. HQCM was tested providing to it a sequence of impulses of microsphere of Cerium (IV) oxide dispersed in synthetic air (715 μg/m 3 of PM 2.5 and 43 μg/m 3 of PM 1 , lasting 1 min) and recording the consequent resonant frequency shift. The results have shown that the HQCM was able to detect PM both at T = 20 °C and at 80° C. Grease coated HQCM exhibited a good frequency stability at T = 80 °C (± 5 Hz) with a negligible grease mass loss during several heating cycles. Furthermore, the results have shown that the surface temperature changes the collection capacity. In particular at higher temperature (80 °C) the frequency change was 2.5 times greater than that at lower temperature (20 °C).

This paper describes a methodology to perform chemical analyses in landfill areas by integrating multisource geomatic data. We used a top-down approach to identify Environmental Point of Interest (EPI) based on very high-resolution satellite data (Pleiades and WorldView 2) and on in situ thermal and photogrammetric surveys. Change detection techniques and geostatistical analysis supported the chemical survey, undertaken using an accumulation chamber and an RIIA, an unmanned ground vehicle developed by CNR IIA, equipped with a multiparameter sensor platform for environmental monitoring. Such an approach improves site characterization, identifying the key environmental points of interest where it is necessary to perform detailed chemical analyses.

Landfills play an important role in urban society. Consequently, an accurate management and planning of such anthropic activities are essential to improve decision making eco-strategies. The application of remote sensing techniques may improve the monitoring of different environmental matrices and the assessment of both gas emission in the atmosphere and leachate migration. This work describes a multi-source approach based on remote sensing and field data. To achieve this goal a downscaling and multi-temporal approach was adopted by using aerial photos, multispectral and hyperspectral imagery and overnight thermal and photogrammetric surveys. The integration of such different geomatic processing techniques allows to detect Environmental Point of Interest (EPI) inside and around the landfill.

In this work we report the results concerning the integration of a thin layer of an organic polymer (pentacene) on a quartz crystal microbalance (QCM) used for pollutant detection at room temperature. Volatile organic compounds (VOC) are one of the major air pollutants. They are directly involved in the photochemistry of the ozone layer and can affect human health. Exposure to VOC may happen in indoor or outdoor environments, both for short or longer period of time in domestic or working conditions. Among VOCs, mono aromatic compounds such as benzene, toluene or xylenes (often referred as BTX) have carcinogenic, narcotic and neurotoxic properties. Thin films of pentacene were obtained by thermal physical vapor deposition both on transducers and silicon substrates. Structural and morphological characterizations by FTIR and AFM analysis confirm analogy between layered material before and after BTX exposition. QCM was chosen as a transducer due to the kind of interactions involved between material and the target gases. The device was exposed to BTX both in dry and wet conditions. The measurements results where compared also with those collected during the exposure toward humidity and ethanol. A clear discrimination between the different analytes was found.

An environmentally friendly conductive sensor to measure gases and volatile organic compounds (VOCs) in moistened environments, has been designed and fabricated. To achieve this goal, a biodegradable electrospun nanofibrous scaffold based on a polymer blend containing polyaniline and poly-3-hydroxybutirrate (PANi/PHB) has been employed. Several fabrics composed of distinct proportions of the two polymers have been tested. Morphology, electrical parameters and sensing features of the biodegradable nanofibrous layers have been investigated. The nanofibrous layers obtained through electrospinning technology carried out directly on chemoresistors resulted in highly porous membranes and the potentials of such blended scaffolds have been analyzed, focusing the attention on the influence of humidity on the features of the resulting sensors, also in terms of reproducibility and stability of their responses. Sensor responses to ammonia and further two chemical compounds differently interacting with PANi (i.e. triethylamine and acetic acid) have been measured in dry air and at different percentages of relative humidity, in order to assess in possible applications the influence of PHB in the interactions of PANi with the analytes tested. Due to the properties of the electrospun nanofibres used in these chemoresistors, water vapours seemed to hugely improve the chemical interactions with the selected analytes. This effect suggests a potential use of the proposed chemosensors in monitoring also strongly moist environments.

We present here a novel experimental setup able to measure the enthalpy of sublimation of a given compound by means of Piezoelectric Crystal Microbalances (PCM). This experiment was performed in the TG-Lab facility in IAPS-INAF, dedicated to the development of TGA sensors for space measurements, such as detection of organic and non-organic volatile species and refractory materials in planetary environments. In order to study physical-chemical processes concerning the Volatile Organic Compounds (VOC) present in atmospheric environments, the setup has been tested on Dicarboxylic acids. Acids with low molecular weight are among the components of organic fraction of particulate matter in the atmosphere, coming from different sources (biogenic and anthropogenic). Considering their relative abundance, it is useful to consider Dicarboxylic acid as "markers" to define the biogenic or anthropogenic origin of the aerosol, thus obtaining some information of the emission sources. In this work, a temperature controlled effusion cell was used to sublimate VOC, creating a molecular flux that was collimated onto a cold PCM. The VOC re-condensed onto the PCM quartz crystal allowing the determination of the deposition rate. From the measurements of deposition rates, it was possible to infer the enthalpy of sublimation of Adipic acid, i.e. Δ Hsub: 141.6 ± 0.8 kJ mol−1, Succinic acid, i.e. 113.3 ± 1.3 kJ mol−1, Oxalic acid, i.e. 62.5 ± 3.1 kJ mol−1 and Azelaic acid, i.e. 124.2 ± 1.2 kJ mol−1 (weight average values). The results obtained are in very good agreement with literature within 10 % for the Adipic, Succinic and Oxalic acid.

Benzene, toluene and xylene (BTX) are an important part of the volatile organic compounds (VOCs) to be detected and monitored in the air, due to their toxicity towards human health. One of the most reliable technique used in BTX detection is gas chromatography (GC), which presents a high sensitivity. On the other hand, it has important drawbacks, such as high costs, the need for qualified personnel and frequent maintenance. To overcome these drawbacks, this work reports the development of a low cost and portable BTX gas detection system based on a mini chromatographic cartridge, a photo ionization detector (PID), a simple control unit (based on Arduino architecture) and a mini pump. In order to separate the BTX components, we propose the use of a cartridge 80 mm in length, composed of several commercial chromatographic column sections. To test the system performances, we have injected different amounts (from about 0.3 to 5.3 µg) of benzene, toluene and xylene and two of the most frequent possible interferents (ethanol, acetone). Experimental results have shown different retention time values (i.e., 25 ± 0.5 s, 51 ± 1.2 s and 117 ± 4 s, respectively) for benzene, toluene and xylene.

Structural and functional properties of polymer composites based on carbon nanomaterials are so attractive that they have become a big challenge in chemical sensors investigation. In the present study, a thin nanofibrous layer, comprising two insulating polymers (polystyrene (PS) and polyhydroxibutyrate (PHB)), a known percentage of nanofillers of mesoporous graphitized carbon (MGC) and a free-base tetraphenylporphyrin, was deposited onto an Interdigitated Electrode (IDE) by electrospinning technology. The potentials of the working temperature to drive both the sensitivity and the selectivity of the chemical sensor were studied and described. The effects of the porphyrin combination with the composite graphene&ndash, polymer system appeared evident when nanofibrous layers, with and without porphyrin, were compared for their morphology and electrical and sensing parameters. Porphyrin fibers appeared smoother and thinner and were more resistive at lower temperature, but became much more conductive when temperature increased to 60&ndash, 70 &deg, C. Both adsorption and diffusion of chemicals seemed ruled by porphyrin according its combination inside the composite fiber, since the response rates dramatically increased (toluene and acetic acid). Finally, the opposite effect of the working temperature on the sensitivity of the porphyrin-doped fibers (i.e., increasing) and the porphyrin-free fibers (i.e., decreasing) seemed further confirmation of the key role of such a macromolecule in the VOC (volatile organic compound) adsorption.

In the present work, the study and the performances of an adsorbent material for gaseous mercury employed in different diffusive bodies geometries is presented. The material is based on gold nanoparticles (AuNPs) deposited on quartz fibres filters, suitable for bonding the gaseous mercury through an amalgamation process. Following thermal desorption and analysis, the behavior of different diffusive samplers prototypes was compared. Both indoor and outdoor exposures were carried out in order to evaluate the advantages and shortcomings of the geometries in study at different sites. From the outdoor long-term exposures, a constant uptake rate (Ur), with a low influence coming from the environmental conditions, was observed for the axial geometry, reporting a high coefficient of determination (R2 0.97). Indoor exposures showed a higher reproducibility, along with a higher coefficient of determination (R2 0.99). The presented results allowed us to observe different behaviors coming from two kinds of diffusive samplers designs, showing different adsorption rates and data dispersion. This allowed us to focalize our attention on the most suitable design from these two tested prototypes, for this kind of adsorbent material.

Passive sampling systems (PASs) are a low cost strategy to quantify Hg levels in air over both different environmental locations and time periods of few hours to weeks/months. For this reason, novel nanostructured materials have been designed and developed. They consist of an adsorbent layer made of titania nanoparticles (TiO2NPs, &le, 25 nm diameter) finely decorated with gold nanoparticles. The TiO2NPs functionalization occurred for the photocatalytic properties of titania-anatase when UV-irradiated in an aqueous solution containing HAuCl4. The resulting nanostructured suspension was deposited by drop-casting on a thin quartz slices, dried and then incorporated into a common axial sampler to be investigated as a potential PAS device. The morphological characteristics of the sample were studied by High-Resolution Transmission Electron Microscopy, Atomic Force Microscopy, and Optical Microscopy. UV-Vis spectra showed a blue shift of the membrane when exposed to Hg0 vapors. The adsorbed mercury was thermally desorbed for a few minutes, and then quantified by a mercury vapor analyzer. Such a sampling system reported an efficiency of adsorption that was equal to &asymp, 95%. Temperature and relative humidity only mildly affected the membrane performances. These structures seem to be promising candidates for mercury samplers, due to both the strong affinity of gold with Hg, and the wide adsorbing surface.

This research activity investigates the temperature-frequency relationship of quartz crystal microbalance for thermogravimetric analyses in space. The microbalance configuration is innovative because of built-in heater and temperature sensor made by metallic films deposited on the crystal. This configuration allows direct temperature measurement over the sensing area, an essential feature for a thermogravimetric sensor that must operate in a wide temperature range, in transient conditions and/or with unknown external heat flux. In fact, beside the deposited mass, the oscillating frequency of the crystal strongly depends on the temperature of the electrode area. In this work, the effect of the temperature on the microbalance frequency has been addressed for the case of uniform distribution, in the temperature range from −20°C to 100°C but the methodology hereafter presented, can be applied to vider temperature ranges where a specific microbilance might be required to operate.

This paper presents the VISTA (Volatile In Situ Thermogravimetry Analyser) instrument, conceived to perform planetary in-situ measurements. VISTA can detect and quantify the presence of volatile compounds of astrobiological interest, such as water and organics, in planetary samples. These measurements can be particularly relevant when performed on primitive asteroids or comets, or on targets of potential astrobiological interest such as Mars or Jupiter's satellite Europa. VISTA is based on a micro-thermogravimetry technique, widely used in different environments to study absorption and sublimation processes. The instrument core is a piezoelectric crystal microbalance, whose frequency variations are affected by variations of the mass of the deposited sample, due to chemical processes such as sublimation, condensation or absorption/desorption. The low mass (i.e. 40 g), the low volume (less than 10 cm3) and the low power (less than 1 W) required makes this kind of instrument very suitable for space missions. This paper discusses the planetary applications of VISTA, and shows the calibration operations performed on the breadboard, as well as the performance tests which demonstrate the capability of the breadboard to characterize volatile compounds of planetary interests. © 2015, Springer Science+Business Media Dordrecht.

VISTA (Volatile In Situ Thermogravimetry Analyser) is a µ-Thermogravimeter sensor developed by Consortium of Italian Institutes. ThermoGravimetric Analysis (TGA) is a widely used technique to monitor thermal processes involving volatile compounds, e.g. deposition/sublimation and absorption/ desorption. The instrument core is composed by a Piezoelectric Crystal Microbalance (PCM), equipped with built-in heater and built-in temperature sensor, and provided of its own Proximity Electronics (PE). The PCM oscillation frequency linearly depends on the mass deposited on its sensible area (according to Sauerbrey equation) while the PCM temperature can be increased by means of integrated heaters. Thus, mass and volatile composition can be inferred by the frequency change and by desorption temperature, respectively. The instrument is divided in two sensor heads: VISTA1, able to monitor outgassing processes in space, and VISTA2, able to reach higher temperatures, studying the dehydration and organics decomposition in minerals in different environmental conditions. An Engineering Model of VISTA1 and a laboratory breadboard of VISTA2 have been developed. Pure organic compounds and contaminant have been characterized by using deposition processes and TGA cycles obtaining some physical-chemical parameters, i.e. enthalpy of sublimation/evaporation, $\Delta \pmb{H}_{sub, evap}$ , deposition rates, $\pmb{k}$ and vapor pressures, $P_{vap}$ . The instrument concept, the scientific objectives and the laboratory measurements are explained in this work.

In this paper we show the developing and the applications of a remotely controlled terrestrial vehicle (or Unmanned Ground Vehicles--UGV) provided with an integrated sensory system for environmental monitoring. The developed system is aimed to monitor some of the key air pollutants and harmful compounds, usable in contaminated sites at high risk to human health. The system is a 4WD radio-controlled vehicle, with small dimensions and low weight, complemented by a sensory system based on hybrid sensors technology (e.g. optic, electrochemical, gravimetric, etc...). These features allow this system to be easily used when inspection missions are required, before or after any environmental disaster. It is able to measure, in few minutes, the atmospheric particulate matter (PM1, PM2.5, PM10), CO2 and CO, H2S, SO2, NO2 in the range between 15 and 5000 ppb. Moreover, it is equipped with a telemetry system for the remote-controlled navigation, including a high-resolution camera, a GPS antenna, an anemometer and proximity sensors. The core of the device is a microprocessor board able to assist the navigation, acquiring values from sensors, transfer/record data and control tens input/outputs up to a distance of 1 km. In this work we report some information regarding the integration, the calibration and the data related to the monitoring of a waste landfill in the closing phase, during the construction of the extractor for generated biogas.

Quartz crystal microbalances have been used as measuring and monitoring devices for particle deposition on sensitive surfaces such as optical mirrors, thermal radiators, solar arrays, and other equipment used in space exploration. Moreover, microbalances have been applied in space to perform thermo-gravimetric analyses in order to infer about the type of volatile and condensable material. When the object of contamination monitoring is an intrinsically cold surface, e.g. a radiator, an effective cooling is required to achieve the same (or slightly lower) condensing temperature. The cooling problem of the microbalance sensing area has found promising solution from the use of thermoelectric coolers, the only compact and lightweight devices that can be housed in a typical microbalance envelope. Nevertheless, performance of the thermoelectric element at low temperature is a known issue so that restricts most applications above −40°C therefore there is a lack of data about performances below that temperature and characterization in expected environment is generally required. Thus, in this work cooling performance of commercial thermoelectric elements has been assessed at low temperature along with its survival to thermal cycling in off condition, in order to assess its applicability for the space borne microbalance under development.

The use of sensors and sensing devices in breath analysis is a very recent achievement in medicine. In this study, a portable pre-industrial device capable of monitoring NO in lung exhaled in respect to the ATS/ERS guidelines was designed and manufactured. The proposed equipment, called NOESIS, involved the use of a conductive polymer doped with nanofibres of an electrospun metal oxide, and was characterised by high sensing features, low power consumption, cost-effectiveness and cheapness. The properties of the sensor and the strategies utilised to achieve such results in that device are here reported and discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Some attempts to improve sensing features of a previously investigated chemosensor for NO breath monitoring, based on a nanofibrous layer of titania coated by a very thin layer of PEDOT:PSS were reported here. The time necessary for sensor response, linked to a few seconds of duration of breath lung, was overcome by designing and implementing two measuring procedures allowing the gas to flow throughout the sensor for more time (at least 90 s): a fixed volume breath storage chamber collecting a portion of the exhaled air and a recirculation path where the sampling gas recirculated through the sensor until reaching a satisfactory response. Thus a serpentine coil shaped chamber with a total volume of about 100 cm3 was designed with the aid of finite element method (FEM) simulations and the whole measuring set-up (i.e. pump, Nafion® tubing, oxidizing cartridge and sensor chamber) was comprised in a loop layout. The adoption of these strategies resulted in a LOD of about 6 ppb assuming of working with an actual handheld diagnostic device. Specifically, when the sensor was exposed to NO concentrations between 5 ppb and 300 ppb (limited to 90 s of measurement), sensor responses resulted to be linear and clearly distinct from the noise, with an accuracy

Nitrogen dioxide concentrations have been measured with a chemoresistor that change its conductance when exposed to NO 2 . The device uses a nanostructured inorganic scaffold (TiO 2 nanofibers) to support a conductive polymer (PEDOT:PSS) used as a sensitive membrane. The electrospinning technique was adopted to deposit the scaffold, since it allows to obtaining materials with a considerable surface to volume ratio. The role of the relative humidity on the gas sensor response has been studied both in terms of relative response and rate of response variation, for RH ranging from 0% to 30%. The presence of humidity in the surrounding atmosphere changes the kinetics of absorption/desorption processes. The measurement of the response rate as a function of the concentration of NO 2 , for various values of relative humidity, shows a non-monotonic trend that becomes stable for humidity values larger than 17% RH. In best humidity condition the sensor response was about 1% for 250 ppb of NO 2 .

From recent literature [1], electrospinning results to be one of the best tools, among the various nanotechnologies, for designing and developing smart sensing systems, both for the uniqueness of the resulting nanostructures and for production rate and cost. The use of electrospun fibers in photonics is a promising research field aimed at developing novel microscale optical sensors, that are generally appreciated for their high sensitivity, fast response time and low power consumption. Recently, very effective electrospun fluorescent fibers have been realized by using transparent or optically inert polymers properly doped with inorganic quantum dots [2]. The advantages of QDs over the traditional fluorescent molecules include high intensity of emission, good photostability, and long fluorescence lifetime. In the present study, titania nanofibrous layers decorated with fluorescent core/shell nanoparticles (QDs) have been designed ad investigated as potential optical sensors for detecting toxic gases in air (e.g. NH3). Initially, fluorescent (CdSe)ZnS core-shell quantum dots were synthesized, according to literature, [3] and then used to decor titania nanofibres according two strategies: the first one by drop-casting, the second one by chemical functionalization in situ. Their different arrangements over the fibres were characterized by AFM (Atomic Force Microscopy) and HR-TEM (High-Resolution Transmission Electron Microscopy), and their optical performances were investigated by spectrophotometry and spectrofluorometry as well as fluorescence microscopy. A very low cost and compact sensing device was designed and implemented (by a 3D-printer) to irradiate fibres (low power LED: 390 nm; 5 mW) and capture images (Raspicam digital camera). The luminance (PL) changes of the samples, before and after gas exposure, were measured through a developed software (by using Python). Effects of relative humidity and temperature were investigated too.

The toxicity of mercury, its ubiquitous presence and the complexity of its cycle in the environment push for urgent actions at both local and global level to develop detection and monitoring systems characterized by fast responses, low cost, low maintenance and ease of use. As a result of the combination of gold affinity for mercury with the nanoscale size of the frameworks, gold nanostructures look the most promising nanomaterials for creating novel sensors with sensing features comparable to those of commercial complex and expensive analytical systems currently available. Composite nanofibrous electrospun layers of titania decorated with gold nanoparticles (AuNPs) were fabricated to obtain nanostructured materials capable of adsorbing elemental mercury. Linker-free gold nanoparticles were grown on the electrospun titania nanofibers through the photocatalytic reduction of tetrachloroauric acid carried out by UV-irradiated nanofibers of titania in the presence of an organic capping reagent. Chemoresistors employing such decorated nanomaterials were then created in order to detect mercury vapors in the atmosphere. Various decorations of titania nanofibers with gold nanoparticles deposited onto distinct substrates were morphologically investigated at nanoscale. The electrical properties of the resulting chemoresistors were assessed. The capacity of chemoresistors employing various amounts of AuNPs for detecting low concentrations of mercury vapors (tens of ppt) in both static and dynamic (i.e. under a carrier gas flow – synthetic air) conditions was tested. The potential of the resulting sensors in environmental monitoring of elemental mercury vapors is discussed.

Thermogravimetry (TG) or Thermogravimetric Analysis (TGA) is a widely used technique to obtain information about thermal stability and composition and to monitor different thermal processes of materials. The TGA analysis is frequently used to monitor the deposition/sublimation and absorption/desorption processes of volatiles compounds in different environments: outgassing rates from degassing in space [1], dehydration and organics decomposition in minerals [2] and the fate of various materials in atmospheric environments [3]. In particular, it is possible to obtain a characterization of organic compounds by using Quartz Crystal Microbalance (QCM)-based sensors, equipped with an integrated heater in order to study the deposition and desorption processes. In this work, an organic compound (used as contaminant source) was characterized by using the breadboard of a QCM-based sensor, i.e. CAM (Contamination Assessment Microbalance), which shows several improvements compared to the previous Quartz Crystal Microbalance sensors used by European Space Agency (ESA) and National Aeronautics and Space Administration (NASA) [1,4]. CAM instrument aims to monitor contaminants and outgassing materials which are released by spacecrafts during in-orbit space missions characterizing the contaminant source by means of Thermogravimetric technique. The organic compound desorption rates and the enthalpy of sublimation (ΔHsub) were retrieved by using the Langmuir relation while the sensor regeneration was obtained by means of thermal cycles by using the integrated heaters on crystal surface. The CAM breadboard validation, the experimental procedure and results are presented, and compared previous works.