308 research outputs found

    Nanotechnology Applications for Chemical and Biological Sensors

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    Recent discoveries indicate that when the materials are brought down to sizes in the range 1–100 nm, theseexhibit unique electrical, optical, magnetic, chemical, and mechanical properties. Methods have now beenestablished to obtain the monodisperse nanocrystals of various metallic and semiconducting materials, single-walled and multi-walled nanotubes of carbon and other metallic and non-metallic materials together withorganic nanomaterials such as supra-molecular nanostructures, dendrimers, hybrid composites with tailoredfunctionalities. The high surface-to-volume ratio with an added element of porosity makes these highly potentialcandidates for chemical and biological sensor applications with higher degree of sensitivity and selectivity ascompared to their bulk counterparts. The paper reviews the recent developments and applications of chemicaland biological sensors based on nanomaterials of various structural forms.Defence Science Journal, 2008, 58(5), pp.636-649, DOI:http://dx.doi.org/10.14429/dsj.58.168

    Nano-derived sensors for high-temperature sensing of H2, SO2 and H2S

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    The emission of sulfur compounds from coal-fired power plants remains a significant concern for air quality. This environmental challenge must be overcome by controlling the emission of sulfur dioxide (SO2) and hydrogen sulfide (H2S) throughout the entire coal combustion process. One of the processes which could specifically benefit from robust, low cost, and high temperature compatible gas sensors is the coal gasification process which converts coal and/or biomass into syngas. Hydrogen (H2), carbon monoxide (CO) and sulfur compounds make up 33%, 43% and 2% of syngas, respectively. Therefore, development of a high temperature (\u3e500°C) chemical sensor for in-situ monitoring H2, H2S and SO2 levels during coal gasification is strongly desired. The selective detection of SO2/H2S in the presence of H2, is a formidable task for a sensor designer. In order to ensure effective operation of these chemical sensors, they must inexpensively function within the gasifier\u27s harsh temperature and chemical environment. Currently available sensing approaches, which are based on gas chromatography, electrochemistry, and IR-spectroscopy, do not satisfy the required cost and performance targets.;There is also a substantial necessity for microsensors that can be applied inexpensively, have quick response time and low power consumption for sustained operation at high temperature. In order to develop a high temperature compatible microsensor, this work will discourse issues related to sensor stability, selectivity, and miniaturization. It has been shown that the integration of nanomaterials as the sensing material within resistive-type chemical sensor platforms increase sensitivity. Unfortunately, nanomaterials are not stable at high temperatures due to sintering and coarsening processes that are driven by their high surface to volume ratio. Therefore, new hydrogen and sulfur selective nanomaterial systems with potentially highly selective and stable properties in the proposed harsh environment were investigated. Different tungstates and molybdates (WO3, MoO3, MgMoO4, NiMoO4, NiWO4, Sr2MgWO6 (SMW), Sr2MgMoO6 (SMM), SrMoO4, and SrWO4) were investigated at the micro- and nano-scale, due to their well-known properties as the reversible absorbents of sulfur compounds. Different morphologies of aforementioned compounds as well as microstructural alterations were also the subject of the investigation. The fabrication of the microsensors consisted of the deposition of the selective nanomaterial systems over metal based interconnects on an inert substrate. This work utilized the chemi-resistive (resistive-type) microsensor architecture where the chemically and structurally stable, high temperature compatible electrodes were sputtered onto a ceramic substrate. The nanomaterial sensing systems were deposited over the electrodes using a lost mold method patterned by conventional optical lithography.;Development of metal based high temperature compatible electrodes was crucial to the development of the high temperature sensor due to the instability of typically used noble metal (platinum) based electrode material over ceramic substrates. Therefore, the thermal stability limitations of platinum films with various adhesion layers (titanium (Ti), tantalum (Ta), zirconium (Zr), and hafnium (Hf)) were characterized at 800 and 1200°C. Platinum (Pt)-zirconium (Zr)-hafnium (Hf) were investigated. The high-temperature stable composite thin film architecture was developed by sequential sputter deposition of Hf, Zr and Pt. In addition to this multilayer architecture, further investigation was carried out by using an alternative DC sputtering deposition process, which led to the fabrication of a functionally-gradient platinum and zirconium composite microstructure with very promising high temperature properties. The final process investigated reduced labor, time and material consumption compared to methods for forming multilayer architectures previously discussed in literature.;In addition to electrical resistivity characterization of the different thin film electrode architectures, the chemical composition, and nano- and micro-structure of the developed nanomaterial films, as well as sensing mechanism, were characterized by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray and ultraviolet photoelectron spectroscopies (XPS and UPS), atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), Raman spectroscopy, temperature programmed reduction (TPR) and transmission electron microscopy (TEM). The macro-configurations of the sensors were tested and analyzed for sensitivity and cross-sensitivity, response time and recovery time, as well as long term stability. The microsensor configuration with optimized nanomaterial system was tested and compared to a millimeter-size sensor platform in terms of sensitivity and accuracy. Electrochemical relaxation (ECR) technique was also utilized to quantify the surface diffusion kinetics of SO2 over the chosen sensor material surface. The outcomes of this research will contribute to the economical application of sensor arrays for simultaneous sensing of H2, H2S, and SO2

    The Thirteenth Annual Conference YUCOMAT 2011: Programme and the Book of Abstracts

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    The First Conference on materials science and engineering, including physics, physical chemistry, condensed matter chemistry, and technology in general, was held in September 1995, in Herceg Novi. An initiative to establish Yugoslav Materials Research Society was born at the conference and, similar to other MR societies in the world, the programme was made and objectives determined. The Yugoslav Materials Research Society (Yu-MRS), a nongovernment and non-profit scientific association, was founded in 1997 to promote multidisciplinary goal-oriented research in materials science and engineering. The main task and objective of the Society has been to encourage creativity in materials research and engineering to reach a harmonic coordination between achievements in this field in our country and analogous activities in the world with an aim to include our country into global international projects. Until 2003, Conferences were held every second year and then they grew into Annual Conferences that were traditionally held in Herceg Novi in September of every year. In 2007 Yu-MRS formed two new MRS: MRS-Serbia (official successor of Yu-MRS) and MRS-Montenegro (in founding). In 2008, MRS – Serbia became a member of FEMS (Federation of European Materials Societies)

    The Fifteenth Annual Conference YUCOMAT 2013: Programme and the Book of Abstracts

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    The First Conference on materials science and engineering, including physics, physical chemistry, condensed matter chemistry, and technology in general, was held in September 1995, in Herceg Novi. An initiative to establish Yugoslav Materials Research Society was born at the conference and, similar to other MR societies in the world, the programme was made and objectives determined. The Yugoslav Materials Research Society (Yu-MRS), a nongovernment and non-profit scientific association, was founded in 1997 to promote multidisciplinary goal-oriented research in materials science and engineering. The main task and objective of the Society has been to encourage creativity in materials research and engineering to reach a harmonic coordination between achievements in this field in our country and analogous activities in the world with an aim to include our country into global international projects. Until 2003, Conferences were held every second year and then they grew into Annual Conferences that were traditionally held in Herceg Novi in September of every year. In 2007 Yu-MRS formed two new MRS: MRS-Serbia (official successor of Yu-MRS) and MRS-Montenegro (in founding). In 2008, MRS – Serbia became a member of FEMS (Federation of European Materials Societies)

    Modification of polyethylene terephthalate track etched membranes by planar magnetron sputtered Ti/TiO2 thin films

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    This study investigates the surface modification of polyethylene terephthalate track-etched membranes by planar magnetron sputtering of titanium and titanium dioxide thin films to improve its hydrophilicity and photocatalytic activity. After cold plasma treatment to enhanced adhesion, Ti thin films were deposited by planar magnetron sputtering and TiO2 thin films by reactive magnetron sputtering in an Ar-O2 gas atmosphere. The morphology of the deposited thin films was characterised using atomic force microscopy and scanning electron microscopy. The pores retained a mostly circular shape. However, the modified track membrane's surface pore diameter reduced from 0.2 µm to 0.15 µm for Ti coated samples and 0.08 µm for Ti-TiO2 coated samples. Structural studies using X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and Raman spectroscopy of Ti and TiO2 thin films revealed the intricate composition of the sputtered thin films which was a result of the complexity of sputtering on top of the porous polymer support. Additional investigations in surface wettability and bandgap showed a significant change in the track membrane surface's hydrophilicity and photocatalytic properties after depositing TiO2-Ti, adding to the self-cleaning properties of the coated TM

    Plasmonic Doped Semiconductor Nanocrystals: Properties, Fabrication, Applications and Perspectives

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    Degenerately doped semiconductor nanocrystals (NCs) are of recent interest to the NC community due to their tunable localized surface plasmon resonances (LSPRs) in the near infrared (NIR). The high level of doping in such materials with carrier densities in the range of 1021 cm^-3 leads to degeneracy of the doping levels and intense plasmonic absorption in the NIR. The lower carrier density in degenerately doped semiconductor NCs compared to noble metals enables LSPR tuning over a wide spectral range, since even a minor change of the carrier density strongly affects the spectral position of the LSPR. We focus on copper chalcogenide NCs and impurity doped metal oxide NCs as the most investigated alternatives to noble metals. We shed light on the structural changes upon LSPR tuning in vacancy doped copper chalcogenide NCs and deliver a picture for the fundamentally different mechanism of LSPR modification of impurity doped metal oxide NCs. We review on the peculiar optical properties of plasmonic degenerately doped NCs by highlighting the variety of different optical measurements and optical modeling approaches. These findings are merged in an exhaustive section on new and exciting applications based on the special characteristics that plasmonic semiconductor NCs bring along.Comment: 97 pages, 33 figure

    Determination of hydrogen-containing gases in air with SnO2-based sensors

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    Methods of monodisperse SnO2 crystallites and SnO2-TiO2 composites synthesis were developed. Obtained materials were studied using SEM, TEM, FTIR, XRD methods. Sensors based on these materials were made, and their capability of detecting hydrogen in dry and humid air was investigated. Several different approaches to improvement of sensing devises characteristics were proposed in present study: doping of one metal oxide (SnO2) with another (TiO2) in different ways (mixing or co-precipitating); use of one-dimensional nanowire as a sensing element to detect H2S; application of reactor which converts ammonia to a compound convenient for its detection; analysis of n-dimensional experimental data array with principal components method for acetone selective detection with a single sensor. For every approach, promising results indicating potential for their application are obtained

    The Sixteenth Annual Conference YUCOMAT 2014: Programme and the Book of Abstracts

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    The First Conference on materials science and engineering, including physics, physical chemistry, condensed matter chemistry, and technology in general, was held in September 1995, in Herceg Novi. An initiative to establish Yugoslav Materials Research Society was born at the conference and, similar to other MR societies in the world, the programme was made and objectives determined. The Yugoslav Materials Research Society (Yu-MRS), a nongovernment and non-profit scientific association, was founded in 1997 to promote multidisciplinary goal-oriented research in materials science and engineering. The main task and objective of the Society has been to encourage creativity in materials research and engineering to reach a harmonic coordination between achievements in this field in our country and analogous activities in the world with an aim to include our country into global international projects. Until 2003, Conferences were held every second year and then they grew into Annual Conferences that were traditionally held in Herceg Novi in September of every year. In 2007 Yu-MRS formed two new MRS: MRS-Serbia (official successor of Yu-MRS) and MRS-Montenegro (in founding). In 2008, MRS – Serbia became a member of FEMS (Federation of European Materials Societies)
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