| 1. |
- Asres, Georgies Alene, et al.
(author)
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Ultrasensitive H2S gas sensors based on p-type WS2 hybrid materials
- 2018
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In: Nano Reseach. - : Springer. - 1998-0124 .- 1998-0000. ; 11:8, s. 4215-4224
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Journal article (peer-reviewed)abstract
- Owing to their higher intrinsic electrical conductivity and chemical stability with respect to their oxide counterparts, nanostructured metal sulfides are expected to revive materials for resistive chemical sensor applications. Herein, we explore the gas sensing behavior of WS2 nanowire-nanoflake hybrid materials and demonstrate their excellent sensitivity (0.043 ppm-1) as well as high selectivity towards H2S relative to CO, NH3, H2, and NO (with corresponding sensitivities of 0.002, 0.0074, 0.0002, and 0.0046 ppm-1, respectively). Gas response measurements, complemented with the results of X-ray photoelectron spectroscopy analysis and first-principles calculations based on density functional theory, suggest that the intrinsic electronic properties of pristine WS2 alone are not sufficient to explain the observed high sensitivity towards H2S. A major role in this behavior is also played by O doping in the S sites of the WS2 lattice. The results of the present study open up new avenues for the use of transition metal disulfide nanomaterials as effective alternatives to metal oxides in future applications for industrial process control, security, and health and environmental safety.
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| 2. |
- Imani, Roghayeh, et al.
(author)
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A Fully Additive Fabrication Approach for sub-10-Micrometer Microvia Suitable for 3-D System-in-Package Integration
- 2023
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In: Proceedings - IEEE 73rd Electronic Components and Technology Conference, ECTC 2023. - : Institute of Electrical and Electronics Engineers Inc.. - 9798350334999 - 9798350334982 ; , s. 1926-1931
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Conference paper (peer-reviewed)abstract
- The semiconductor industry demands high input/output (I/O) density, requiring sub-l0-micrometer microvia. Here we propose a novel, fully additive, economical approach for creating and copper plating of microvias. The experimental process consisted of three stages. In Stage I, a polyurethane layer was spin-coated onto a FR-4 PCB base, followed by target copper layer deposition using the sequential build-up-covalent bonded metallization (SBU -CBM) method. In Stage II, first another layer of polyurethane was spin-coated on the top of the target copper layer, and then a microvia was created on the polyurethane layer using a picosecond pulsed ultraviolet (UV) laser. Finally, in Stage III, the SBU-CBM method was used to selectively copper plating of the microvia. Optical microscopy and cross-section scanning electron microscopy (SEM) images confirmed the successful formation and copper plating of sub-l0 micrometer microvia.
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| 3. |
- Kordás, Krisztián, et al.
(author)
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Nanoparticle Dispersions
- 2013
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In: Springer Handbook of Nanomaterials. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642205941 - 9783642205958 ; , s. 729-776
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Book chapter (peer-reviewed)abstract
- This chapter aims to provide an insight into the physics and chemistry of nanoparticle–liquid systems. The first part of the chapter discusses parameters and effects that influence dispersion stability (Sect. 20.1), including particle size and shape as well as the interactions at the interface between the solid and liquid phases. Section 20.2 summarizes the practical aspects of making a dispersion, collecting and listing hundreds of examples from contemporary literature. Because of the broad spectrum of materials in question, the survey is limited to dispersions of inorganic nanoparticles including metals, their oxides/sulfides, some (compound) semiconductors, as well as nanostructured carbon particles such as fullerenes, nanotubes, and graphene/graphite (Sect. 20.3). Dispersions of polymers of either synthetic or biological origin lie beyond the scope of this work. Since a very large fraction of applications are related to various surface coatings using dispersions as the source of nanoparticles, Sect. 20.4 is devoted to drying phenomena and particle self-ordering.
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| 4. |
- Kukkola, Jarmo, et al.
(author)
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Electrical transport through single-wall carbon nanotube-anodic aluminum oxide-aluminum heterostructures
- 2010
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In: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 21:3, s. 35707-
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Journal article (peer-reviewed)abstract
- Aluminum foils were anodized in sulfuric acid solution to form thick porous anodic aluminum oxide (AAO) films of thickness approximately 6 microm. Electrodes of carboxyl-functionalized single-wall carbon nanotube (SWCNT) thin films were inkjet printed on the anodic oxide layer and the electrical characteristics of the as-obtained SWCNT-AAO-Al structures were studied. Nonlinear current-voltage transport and strong temperature dependence of conduction through the structure was measured. The microstructure and chemical composition of the anodic oxide layer was analyzed using transmission and scanning electron microscopy as well as x-ray photoelectron spectroscopy. Schottky emission at the SWCNT-AAO and AAO-Al interfaces allowed by impurity states in the anodic aluminum oxide film together with ionic surface conduction on the pore walls of AAO gives a reasonable explanation for the measured electrical conduction. Calcined AAO is proposed as a dielectric material for SWCNT-field effect transistors.
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| 5. |
- Kukkola, Jarmo, et al.
(author)
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Gas sensors based on anodic tungsten oxide
- 2011
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In: Sensors and actuators. B, Chemical. - : Elsevier B V. - 0925-4005 .- 1873-3077. ; 153:2, s. 293-300
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Journal article (peer-reviewed)abstract
- Nanostructured porous tungsten oxide materials were synthesized by the means of electrochemical etching (anodization) of tungsten foils in aqueous NaF electrolyte. Formation of the sub-micrometer size mesoporous particles has been achieved by infiltrating the pores with water. The obtained colloidal anodic tungsten oxide dispersions have been used to fabricate resistive WO3 gas sensors by drop casting the sub-micrometer size mesoporous particles between Pt electrodes on Si/SiO2 substrate followed by calcination at 400 °C in air for 2 h. The synthesized WO3 films show slightly nonlinear current–voltage characteristics with strong thermally activated carrier transport behavior measured at temperatures between −20 °C and 280 °C. Gas response measurements carried out in CO, H2, NO and O2 analytes (concentration from 1 to 640 ppm) in air as well as in Ar buffers (O2 only in Ar) exhibited a rapid change of sensor conductance for each gas and showed pronounced response towards H2 and NO in Ar and air, respectively. The response of the sensors was dependent on temperature and yielded highest values between 170 °C and 220 °C.
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| 6. |
- Kukkola, Jarmo, et al.
(author)
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Inkjet-printed gas sensors : metal decorated WO3 nanoparticles and their gas sensing properties
- 2012
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In: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 22:34, s. 17878-17886
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Journal article (peer-reviewed)abstract
- Inkjet deposition is an attractive technology to localize nanomaterials in an area-selective manner on virtually any kind of surfaces. Great advantages of the method are effective usage of materials, low processing temperatures and few required manufacturing steps, thus enabling rapid prototyping and bulk production with reasonably low cost. A number of different electrical devices such as light emitting diodes, transistors and solar cells have already been demonstrated, reflecting the versatility of inkjet printing. In this paper, we collect the contemporary results on inkjet deposited gas sensors and show examples of such gas sensing devices based on surface modified WO3 nanoparticles for efficient discrimination of various gaseous analytes from sub-ppm up to nearly 0.1% concentration levels in air.
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| 7. |
- Kukkola, Jarmo, et al.
(author)
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Room temperature hydrogen sensors based on metal decorated WO3 nanowires
- 2013
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In: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 186, s. 90-95
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Journal article (peer-reviewed)abstract
- The emerging hydrogen economy has created a demand for the development of improved hydrogen sensors operating at room temperature. In this work, we present hydrogen detectors based on metal decorated WO3 nanowires that were able to detect 1000 ppm of H-2, even at room temperature (30 degrees C), with relatively short recovery time and high sensitivity. The nanowires were synthesized by a hydrothermal process and decorated with PdO and PtOx nanoparticles by decomposition of Pd(acac)(2) and Pt(acac)(2) precursors. The gas responses were tested for H-2, NO, H2S and CO analyte gases in an air buffer at 150,200 and 250 degrees C (H-2 also at 30,70 and 130 degrees C).
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| 8. |
- Lloyd Spetz, Anita, et al.
(author)
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Chemical sensor systems for emission control from combustions
- 2013
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In: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 187:SI, s. 184-190
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Journal article (peer-reviewed)abstract
- Environmental and health concern has increased the importance to monitor and control emissions like toxic gases and particulate matter from combustion processes. The silicon carbide-field effect transistor (SiC-FET) technology offers versatile and powerful sensors for gas detection also in combination with combustion of particles. Emission control has been demonstrated e. g. for small and medium sized power plants and diesel exhausts. The potential danger of nanoparticles makes such detectors interesting not only for detection of concentration and size of particles but also detection of the content of particles. Due to the possibility of operating the sensor devices in different independent modes (e. g. temperature- and bias-modulated) the SiC-FET technology also lends itself for the future development of sensor adaptation, self-diagnosis and auto calibration, which is expected to improve the performance of such a combined gas/particle sensor system. Here we report progress on the sensor technology itself, the application of a sensor system as an alarm for ammonia emission and preliminary results of particle detection in diesel exhausts and particles from a power plant and a steel plant.
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| 9. |
- Lloyd Spetz, Anita, et al.
(author)
-
Chemical sensor systems for environmental and emission control
- 2013
-
In: Proc. SPIE Defence, Security + Sensors. - : SPIE.
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Conference paper (peer-reviewed)abstract
- Focusing on environment and health aspects, the importance of monitoring and controlling dangerous gases and particulate matter increases. For this purpose we present a new version of silicon carbide based gas sensors with improved properties and suitable for high temperature and harsh environments such as power plants or car exhausts. Development of sulfur dioxide sensors for a power plant application is described as well as sensors for detection of ammonia in connection with the SCR process where urea is converted to ammonia, which reduces nitric oxide components in the exhausts. We also describe progress on nanoparticle detection, especially related to detection of the content of adsorbed particles through heating and detection of emitted molecules by a sensor array. Some results are also presented from impedance spectroscopy for detection of the concentration of nanoparticles but with the potential to reveal more details about the particles such as shape and kind of particles. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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| 10. |
- Lloyd Spetz, Anita, et al.
(author)
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Improved chemical sensors track and control emissions
- 2013
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In: SPIE Newsroom. - : SPIE - International Society for Optical Engineering. - 1818-2259.
-
Other publication (pop. science, debate, etc.)abstract
- Sensitive, low-cost silicon carbide-based gas sensors can detect toxic emissions and hazardous nanoparticulate matter in previously untenable environments.
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