| 1. |
- Ahrens, Lutz
(författare)
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Real-time detection of per-fluoroalkyl substance (PFAS) self-assembled monolayers in nanoporous interferometers
- 2022
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Ingår i: Sensors & Actuators: B. Chemical. - : Elsevier BV. - 0925-4005. ; 355
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Tidskriftsartikel (refereegranskat)abstract
- Identification and quantification of per- and polyfluoroalkyl substances (PFASs) remain challenging due to their chemical diversity, and their inert optical and chemical nature. Here, we present an optical system integrating perfluorosilane-functionalized nanoporous anodic alumina (NAA) interferometers with reflectometric interference spectroscopy (RIfS) for real-time, label-free detection of self-assembled monolayers (SAMs) of perfluorooctanoic acid (PFOA) as a model PFAS. Measured changes in the effective optical thickness (Delta OTeff) of NAA interferometers made it possible to study the fluorous interaction-induced self-assembly of PFOA molecules with perfluorosilane functional molecules of varying length, in real time and in situ. Analysis of key sensing parameters-sensitivity, low limit of detection and linearity-allowed us to determine the most optimal molecular length of perfluorosilanes to maximize immobilization of PFOA onto functional surfaces. Freundlich and Langmuir isotherm models were adapted to experimentally acquired values of Delta OTeff to elucidate the mechanism of PFOA-perfluorosilane interactions. Interpretation of these models suggests that PFOA binds to perfluorosilanes functional groups immobilized onto the inner surface of NAA interferometers through a fluorous interaction-induced Freundlich mechanism. The potential real-life applicability of this system was demonstrated by detecting the formation of PFOA-based SAMs in aqueous matrices of varying complexity (i.e. ultrapure, deionized, tap, and river water). This study provides new insights into how functional surface chemistries can be engineered to maximize sensitivity and selectivity to PFAS, harnessing fluorous interactions-with implications for future deployable systems to detect and remove these emerging toxicants.
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| 2. |
- Bouchikhi, Benachir, et al.
(författare)
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Formaldehyde detection with chemical gas sensors based on WO3 nanowires decorated with metal nanoparticles under dark conditions and UV light irradiation
- 2020
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 320
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Tidskriftsartikel (refereegranskat)abstract
- We report results of formaldehyde gas (CH2O) detection under dark conditions and UV light irradiation with pristine tungsten trioxide nanowires (WO3 NWs) and metal nanoparticles decorated WO3 NWs gas sensing layers. The resistive layers were deposited by one step aerosol assisted chemical vapor deposition (AACVD) on commercial alumina substrates with 10-pair interdigitated platinum electrodes. The elaborated gas sensors, based on pristine WO3 and on WO3 decorated with Au, Pt, Au/Pt, Ni and Fe nanoparticles, were investigated towards three concentrations of formaldehyde gas (5, 10 and 15 ppm) under dark conditions and under UV light irradiation at the wavelength of 394 nm. Two main effects were observed: firstly, under UV light irradiation the response time for CH2O desorption was significantly reduced with the exception of the nanomaterial with Fe NPs dopant; secondly, the gas induced baseline shift was reduced under UV light irradiation conditions. These results can be explained by the additional energy induced by the UV light, accelerating the adsorption-desorption processes. The results obtained confirmed that both the decoration of WO3 NWs with selected metal nano particles as well as sensors operation under UV light irradiation are a practical and affordable way to enhance gas sensing towards formaldehyde detection, although both strategies applied together did not introduce an amplified synergetic effect.
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| 3. |
- Bunnfors, Kalle, et al.
(författare)
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Nanoparticle activated neutrophils-on-a-chip : A label-free capacitive sensor to monitor cells at work
- 2020
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 313
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Tidskriftsartikel (refereegranskat)abstract
- Neutrophil granulocytes are the most abundant white blood cells in mammals and vital components of the immune system. They are involved in the early phase of inflammation and in generation of reactive oxygen species. These rapid cell-signaling communicative processes are performed in the time frame of minutes. In this work, the activity and the response of neutrophil granulocytes are monitored when triggered by cerium-oxide based nanoparticles, using capacitive sensors based on Lab-on-a-chip technology. The chip is designed to monitor activation processes of cells during nanoparticle exposure, which is for the first time recorded on-line as alteration of the capacitance. The complementary metal oxide semiconductor engineering chip design is combined with low temperature co-fired ceramic, LTCC, packaging technology. The method is label free and gently measures cells on top of an insulating surface in a weak electromagnetic field, as compared to commonly used four-point probes and impedance spectroscopy electric measurements where electrodes are in direct contact with the cells. In summary, this label free method is used to measure oxidative stress of neutrophil granulocytes in real time, minute by minute and visualize the difference in moderate and high cellular workload during exposure of external triggers. It clearly shows the capability of this method to detect cell response during exposure of external triggers. In this way, an informationally dense non-invasive method is obtained, to monitor cells at work.
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| 4. |
- Burgues, Javier, et al.
(författare)
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Gas Distribution Mapping and Source Localization Using a 3D Grid of Metal Oxide Semiconductor Sensors
- 2020
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 304
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Tidskriftsartikel (refereegranskat)abstract
- The difficulty to obtain ground truth (i.e. empirical evidence) about how a gas disperses in an environment is one of the major hurdles in the field of mobile robotic olfaction (MRO), impairing our ability to develop efficient gas source localization strategies and to validate gas distribution maps produced by autonomous mobile robots. Previous ground truth measurements of gas dispersion have been mostly based on expensive tracer optical methods or 2D chemical sensor grids deployed only at ground level. With the ever-increasing trend towards gas-sensitive aerial robots, 3D measurements of gas dispersion become necessary to characterize the environment these platforms can explore. This paper presents ten different experiments performed with a 3D grid of 27 metal oxide semiconductor (MOX) sensors to visualize the temporal evolution of gas distribution produced by an evaporating ethanol source placed at different locations in an office room, including variations in height, release rate and air flow. We also studied which features of the MOX sensor signals are optimal for predicting the source location, considering different lengths of the measurement window. We found strongly time-varying and counter-intuitive gas distribution patterns that disprove some assumptions commonly held in the MRO field, such as that heavy gases disperse along ground level. Correspondingly, ground-level gas distributions were rarely useful for localizing the gas source and elevated measurements were much more informative. We make the dataset and the code publicly available to enable the community to develop, validate, and compare new approaches related to gas sensing in complex environments.
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| 5. |
- Chung, Nguyen Xuan, et al.
(författare)
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Optimized electrochemical breakdown etching using temporal voltage variation for formation of nanopores in a silicon membrane
- 2021
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 331
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Tidskriftsartikel (refereegranskat)abstract
- Dielectric breakdown etching is a well-known method of making nanopores on thin (similar to 50 nm) dielectric membranes. However, voltage driven translocation of biomolecules through such nanopores becomes extremely fast. For improved detection, for instance by the current blockage, a high-aspect-ratio nanopore could be beneficial for slowing down the translocation. High-aspect-ratio nanopore on silicon fabrication requires a well-controlled process and is dependent on specific crystal orientation, dopant type and resistivity of substrate. Therefore, an optimized method of processing high-aspect-ratio nanopores is necessary considering the advantage of a silicon membrane being able to be integrated with standard CMOS processing. Here, we present an optimized fabrication method for mass-producing a single and an array of nanopores on a thick (2 mu m) silicon device layer based on a silicon-on-insulator (SOI) wafer. A method of temporal voltage variation is exploited to optimize the etching parameters for the nanopore formation during electrochemical breakdown etching, diameters of nanopores around 12 nm have been achieved. Besides, the correlation between the parameters of etching and nanopore diameter is deduced. The processed high-aspect-ratio nanopore enables applications in single-molecule sensing such as DNA, exosomes, viruses, and protein markers. The developed process is inexpensive, fast and can be batch fabricated.
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| 6. |
- Colozza, Noemi, et al.
(författare)
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Multiparametric analysis by paper-assisted potentiometric sensors for diagnostic and monitoring of reinforced concrete structures
- 2021
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 345
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Tidskriftsartikel (refereegranskat)abstract
- Reinforced concrete has been employed worldwide as a leading building material for public and private structures as well as in modern sculptural art. Although the unrivalled mechanical strength and modelling versatility of this material, several interrelated processes are responsible for its progressive degradation (e.g., carbonation, penetration of aging-promoting agents), decreasing its long-last durability and representing a risk for the public security or the cultural heritage. With the aim to tackle this issue, the present work reports a novel configuration of a screen-printed sensor, obtained by the combination of flexible and robust polyester support and wax-printed filter paper device for the direct application on the concrete surface. Our sensor consists of a polyester-printed three-electrochemical cell that allows dual measurements on reinforced concrete, namely (i) the evaluation of corrosion probability of the metallic reinforcements (which outperforms the half-cell potential standard method) and (ii) the employment of a pH-sensitive iridium oxide film for the measurement of the pH of concrete. The paper was used as a porous material capable of ensuring the electrochemical connection between the Ag/AgCl printed electrode and the concrete solid matrix, acting also as a protective envelope for the electrode. After the laboratory tests, which revealed the noteworthy performances of the sensors in distinguishing among different levels of corrosion as well as measuring the pH of concrete, the developed sensor was applied for on-site measurement at the Giacomo Manzu Museum (Ardea, Italy), demonstrating its suitability for the real application to cultural heritage conservation. Overall, this easy-to-handle and non-invasive diagnostic device provides an innovative analytical approach for the on-site and prompt multiparametric monitoring of the physico-chemical phenomena that endanger the long-lasting preservation of reinforced concrete structures.
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| 7. |
- Cuartero, Maria, PhD, 1984-
(författare)
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Electrochemical sensors for in-situ measurement of ions in seawater
- 2021
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 334
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Tidskriftsartikel (refereegranskat)abstract
- In the current water monitoring panorama, certain benefits are expected to arise when the modus operandum of analysis shifts from sampling-based to purely in-situ approaches. Since the appearance of the first submersible conductivity-temperature-depth (CTD) probe in the 80 s, clear efforts to move towards decentralized strategies have been reported in the literature, with some having even been brought to the stage of fruitful commercialization. Among the portfolio of available analytical techniques, only a handful of approaches offer clear potential for implementation in submersible devices, in terms of adequate analytical features, autonomy, feasibility of miniaturization, and ease of portability. Electrochemical sensors have demonstrated excellent characteristics for this purpose, particularly in the detection of ions. The present review analyses electrochemical sensors that have shown an aptitude for in-situ measurements of ions, including trace metals, nutrients, and carbon species in seawater. The previous 5 years have been selected as the main period for review, although in some instances comment is made upon earlier contributions to the field or commercialized devices, where these are deemed to exemplify crucial technological advancements. There is a notable lack of electrochemical sensors being deployed in in-situ applications, and this scarcity is even more stark when seawater is considered: only a very few cases have been demonstrated under such challenging conditions. With the aim of providing inspiration towards genuine advances in the field of in-situ seawater analysis, this work also highlights some laboratory scale research as well as studies concerning other environmental waters than seawater.
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| 8. |
- Ding, R., et al.
(författare)
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Gold-modified paper as microfluidic substrates with reduced biofouling in potentiometric ion sensing
- 2021
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 344
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Tidskriftsartikel (refereegranskat)abstract
- Microfluidic sampling media based on paper and its modifications with either gold nanoparticles or sputtered gold were evaluated for potentiometric determination of Na+, K+, and Cl– ions in clinically relevant samples. The measurements were conducted in comparison to other commonly considered microfluidic substrates, i.e. sponge, polyester textile, and polyamide textile. Ion determination was done by using solid-contact ion-selective electrodes based on plasticized PVC membranes for Na+, K+, and Cl– ions and utilizing PEDOT(PSS) or PEDOT(Cl) as the ion-to-electron transducer. The solid-contact ion-selective electrodes and a solid-state reference electrode were placed directly on the substrate into which the sample solution was wicked. Transport of bovine serum albumin (BSA) through the paper substrate was studied by ellipsometry. Modification of the paper substrates by gold nanoparticles (AuNPs) was found to slow down the transport of BSA through the paper, when compared with unmodified paper substrates and when compared with all the other alternative sampling matrices studied. The retention of BSA obtained with AuNP-modified paper substrates significantly improved the accuracy of the potentiometric ion determinations in sweat, saliva, artificial tears, and artificial serum. The potentiometric results were validated by inductively coupled plasma optical emission spectrometry (ICP-OES) and ion chromatography (IC). The study indicates that modification of paper by AuNPs is a feasible approach to reduce biofouling of sensors that are used in the paper-based analysis of clinically relevant samples. © 2021 Elsevier B.V.
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| 9. |
- Domenech, Guillem, et al.
(författare)
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Highly sensitive SnO2 nanowire network gas sensors
- 2023
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Ingår i: Sensors and actuators. B, Chemical. - : ELSEVIER SCIENCE SA. - 0925-4005 .- 1873-3077. ; 383
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present a methodology for the localized growth of nanowires on prespecified areas of micro -hotplates that allows to independently adjust the devices resistance and its response to the gas. This is achieved through the fabrication stripes containing the nanowires, with or without the presence of a gap in the stripe, giving rise that the nanowires bridge the current. The methodology is demonstrated growing SnO2 nanowire-based chemoresistors and the fabricated sensors have been characterized against CO and NO2. The results show the capability of tailoring nanowire stripe sizes from 1 to 100 mu m, including empty areas of the same sizes along the sensing material, and a response increase by a factor of up to 500. We attribute the response enhancement to the absence of nucleation seeds in the gap area, where only arching nanowires can allow the current to flow between electrodes. In this way, the current flow along the bridge of nanowires is restricted principally to the surface conduction, which is controlled by the interaction of the nanowires with gases.
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| 10. |
- Domènech-Gil, Guillem, Mr. Doctor, et al.
(författare)
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Benefits of virtual sensors for air quality monitoring in humid conditions
- 2021
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier Science SA. - 0925-4005 .- 1873-3077. ; 344
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Tidskriftsartikel (refereegranskat)abstract
- The gas sensing mechanisms, response, and behaviour of a real and a virtual solid-state chemical gas sensor operating either in static or in dynamic mode have been compared. The analysis was done by exposing simultaneously both sensors to different concentrations of various volatile organic compounds diluted in dry, as well as humid, synthetic air. The results revealed similar responses and behaviours for both types of measurement modes when the sensors were exposed towards single gas compounds, but a sensitivity enhancement in measurements comprising mixtures of gases when the sensors were operated in dynamic mode. The method used is able to overcome surface saturation problems and is beneficial for applications where mixtures of gases diluted in relative humidity are present.
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