Gadolinium oxide (Gd2O3) nanoparticles with very small size, and narrow size distribution were synthesized by infiltration of Gd(NO₃)₃.6H₂O as an oxide precursor into the pores of SBA-15 mesoporous silica using a wet-impregnation technique. High resolution transmission electron microscopy and X-ray diffraction show that during the hydrothermal treatment of the precursor at 550 °C, gadolinium oxide nanoparticles inside the silica pores are formed. Subsequent dissolution of the silica template by NaOH resulted in well dispersed nanoparticles with an average diameter of 3.6 ± 0.9 nm.

Starting with an ammonical solution of zinc acetate, dense single crystal ZnO nanorod arrays were grown directly on high surface area porous 3D nickel foam substrates using a low temperature hydrothermal route. Heterogeneous nucleation of the nanorods with diameters around 100 nm can be conveniently and reproducibly Controlled by adjusting the amount of ammonia added to the growth solution. X-ray diffraction and HRTEM analysis confirmed the single phase wurtzite structure and c-axis orientation of the as grown ZnO nanorod arrays. Cathodoluminescence measurements indicate that the as-grown nanorod arrays were rich in atomic defects and gave strong orange emissions in the visible region. The nanorod arrays on unique 3D substrate are expected to improve the sensitivity and efficiency of ZnO based electrochemical sensors and heterogeneous catalysts.

Two types of SiC based field effect transistor sensors, with Pt or Ir gate, were tested to detect methanol in the concentration range of 0–1600 ppm for both process control and leak detection applications. The methanol response was investigated both with and without oxygen, since the process control might be considered as oxygen free application, while the sensor is operated in air during leak detection. Pt sensors offered very fast response with appreciably high response magnitude at 200 °C, while Ir sensors showed both higher response and response time up to 300 °C, but this decreased considerably at 350 °C. Cross sensitivity effect in presence of oxygen, hydrogen, propene and water vapor was also investigated. The presence of oxygen improved the response of both sensors, which is favorable for the leak detection application. Hydrogen had a large influence on the methanol response of both sensors, propene had a negligible influence, while water vapor changed direction of the methanol response for the Pt sensor. The detection mechanism and different sensing behavior of Pt and Ir gate sensors were discussed in the light of model reaction mechanisms derived from hybrid density-functional theory quantum-chemical calculations.

Chelated gadolinium ions, e. g., GdDTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd2O3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r(1) and r(2) values almost as high as those for free Gd3+ ions in water. The Gd2O3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI.

A simple method is presented to grow thick honeycomb β-Ni(OH)2 films on 3D nickel foam substrates at80 °C using nickel sulfate and ammonia as the starting materials. The porous honeycomb network structureof the films with pore openings about 0.5–1 μm wide is built from seamlessly connected polycrystallinenanowalls, approximately 10–20 nm thick. The amount of ammonia added to the growth solution and thegrowth time were found to be critical parameters in determining the morphology and pore structure ofthe films. Air annealing of the as-prepared films resulted in polycrystalline NiO films with morphologiessimilar to those of their hydroxide precursors.

Pt and Ir SiC based Field Effect Transistor sensors were tested to detect low concentration of methanol (<200 ppm) for both process control and leak detection applications. Pt sensors gave good and very fast response at 200°C, while Ir sensors gave larger but much slower response. The presence of oxygen improved the response of the sensor which was favorable for the leak detection application. The influence of hydrogen and propene to the sensor response was also studied. Beside the experimental work, the detection mechanism and different sensing behavior of Pt and Ir were studied by quantum chemical calculations.

A silicon carbide based field effect transistor (SiC-FET) structure was used for methanol sensing. Due to the chemical stability and wide band gap of SiC, these sensors are suitable for applications over a wide temperature range. Two different catalytic metals, Pt and Ir, were tested as gate contacts for detection of methanol. The sensing properties of both Ir gate and Pt gate SiC-FET sensors were investigated in the concentration range 0.3–5% of methanol in air and in the temperature range 150–350 °C. It was observed that compared to the Ir gate sensor, the Pt gate sensor showed higher sensitivity, faster response and recovery to methanol vapour at comparatively lower temperature, with an optimum around 200 °C. Quantum-chemical calculations were used to investigate the MeOH adsorption and to rationalize the observed non-Langmuir behavior of the response functions. The methanol sensing mechanism of the SiC-FET is discussed.

The performance of a magnetic resonance imaging contrast agent (CA) depends on several factors, including the relaxation times of the unpaired electrons in the CA. The electron spin relaxation time may be a key factor for the performance of new CAs, such as nanosized Gd2O3 particles. The aim of this work is, therefore, to study changes in the magnetic susceptibility and the electron spin relaxation time of paramagnetic Gd2O3 nanoparticles diluted with increasing amounts of diamagnetic Y2O3. Nanoparticles of (GdxY1-x)2O3 (0 e x e 1) were prepared by the combustion method and thoroughly characterized (by X-ray di.raction, transmission electron microscopy, thermogravimetry coupled with mass spectroscopy, photoelectron spectroscopy, Fourier transform infrared spectroscopy, and magnetic susceptibility measurements). Changes in the electron spin relaxation time were estimated by observations of the signal line width in electron paramagnetic resonance spectroscopy, and it was found that the line width was dependent on the concentration of yttrium, indicating that diamagnetic Y2O3 may increase the electron spin relaxation time of Gd2O3 nanoparticles.

This study reports ZnO nanoparticles and thin film surface modification using a two-step functionalization strategy. A small silane molecule was used to build up a stabilizing layer and for conjugation of biotin (vitamin B7), as a specific tag. Biotin was chosen because it is a well-studied bioactive molecule with high affinity for avidin. ZnO nanoparticles were synthesized by electrochemical deposition under oxidizing condition, and ZnO films were prepared by plasma-enhanced metal organic chemical vapor deposition. Both ZnO nanoparticles and ZnO thin films were surface modified by forming a (3-mercaptopropyl)trimethoxysilane (MPTS) layer followed by attachment of a biotin derivate. lodoacetyl-PEG2-biotin molecule was coupled to the thiol unit in MPTS through a substitution reaction. Powder X-ray diffraction, transmission electron microscopy, X-ray photoemission electron microscopy, atomic force microscopy. X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy were used to investigate the as-synthesized and functionalized ZnO materials. The measurements showed highly crystalline materials in both cases with a ZnO nanoparticle diameter of about 5 nm and a grain size of about 45 nm for the as-grown ZnO thin films. The surface modification process resulted in coupling of silanes and biotin to both the ZnO nanoparticles and ZnO thin films. The two-step functionalization strategy has a high potential for specific targeting in bioimaging probes and for recognition studies in biosensing applications.

A systematic study is performed of the influence of surfactant and temperature on the aspect ratio and monodispersity of Au nanorods, synthesized by a seed-mediated growth technique in water using cetyltrimethylammonium bromide (CTAB) as surfactant. The changes in aspect ratio with temperature show an "anomalous" behaviour, where the aspect ratio first decreases with increasing temperature, reaching a minimum at about 55^oC, and after that increases again reaching a maximum at about 80^oC. A physical explanation of the observed behaviour is proposed. It has also been studied how the CTAB concentration in the cleansing water used in the post-synthesis treatment of the samples affected the stability of the gold suspension. It was found that without the presence of a surfactant such as CTAB in the washing medium, only very few centrifugations can be carried out without considerable loss of product. Characterization of prepared samples was performed with UV-Vis and TEM.

Recently, much attention has been given to the development of biofunctionalized nanoparticles with magnetic properties for novel biomedical imaging. Guided, smart, targeting nanoparticulate magnetic resonance imaging (MRI) contrast agents inducing high MRI signal will be valuable tools for future tissue specific imaging and investigation of molecular and cellular events. In this study, we report a new design of functionalized ultrasmall rare earth based nanoparticles to be used as a positive contrast agent in MRI. The relaxivity is compared to commercially available Gd based chelates. The synthesis, PEGylation, and dialysis of small (3−5 nm) gadolinium oxide (DEG-Gd₂O₃) nanoparticles are presented. The chemical and physical properties of the nanomaterial were investigated with Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. The proton relaxation times as a function of dialysis time and functionalization were measured at 1.5 T. A capping procedure introducing stabilizing properties was designed and verified, and the dialysis effects were evaluated. A higher proton relaxivity was obtained for as-synthesized diethylene glycol (DEG)-Gd₂O₃ nanoparticles compared to commercial Gd-DTPA. A slight decrease of the relaxivity for as-synthesized DEG-Gd₂O₃ nanoparticles as a function of dialysis time was observed. The results for functionalized nanoparticles showed a considerable relaxivity increase for particles dialyzed extensively with r₁ and r₂ values approximately 4 times the corresponding values for Gd-DTPA. The microscopy study showed that PEGylated nanoparticles do not activate neutrophils in contrast to uncapped Gd₂O₃. Finally, the nanoparticles are equipped with Rhodamine to show that our PEGylated nanoparticles are available for further coupling chemistry, and thus prepared for targeting purposes. The long term goal is to design a powerful, directed contrast agent for MRI examinations with specific targeting possibilities and with properties inducing local contrast, that is, an extremely high MR signal at the cellular and molecular level.

Silver nanowires with a diameter of 30 nm and typical lengths of 5–10 μm have been synthesized in an aqueous medium. To initiate the reaction, citrate ions were used, and during the reaction the aromatic organicmolecules polymerize forming “straight” chain surfactants which support the formation of nanowires. Characterization by TEM and HRETM revealed the nanowires to be highly crystalline with a growth along the [110] direction.

Zinc oxide is a wide band gap (similar to 3.4ev) semiconductor material, making it a promising material for high temperature applications, such as exhaust and flue environments where NO and NO2 monitoring is increasingly required due to stricter emission controls[1]. In these environments water vapour and background levels of oxygen are present and, as such, the effect of humidity on the sensing characteristics of these materials requires further study. The reaction mechanisms in the presence of water vapour are poorly understood and there is a need for deeper understanding of the principles and mechanisms of gas response of these materials. An investigation of the influence of changing water vapour (H2O) and oxygen (O-2) backgrounds on the response of nanoparticulate Ga-doped ZnO resistive sensors is presented.

Wide bandgap materials like SiC, ZnO, AlN form a strong platform as transducers for biosensors realized as e.g. ISFET (ion selective field effect transistor) devices or resonators. We have taken two main steps towards a multifunctional biosensor transducer. First we have successfully functionalized ZnO and SiC surfaces with e.g. APTES. For example ZnO is interesting since it may be functionalized with biomolecules without any oxidation of the surface and several sensing principles are possible. Second, ISFET devises with a porous metal gate as a semi-reference electrode are being developed. Nitric oxide, NO, is a gas which participates in the metabolism. Resistivity changes in Ga doped ZnO was demonstrated as promising for NO sensing also in humid atmosphere, in order to simulate breath.

Thin films of the perovskite and garnet structured gadolinium ferrites GdFeO3 and Gd3Fe5O12 have been synthesized by a sol-gel method, based on stoichiometric mixtures of acetyl acetone chelated Gd3+ and Fe3+ dissolved in 2-methoxy ethanol. After spin coating onto Si wafers, and heating in air at 700 degrees C for 20 h, neatly grown essentially single phase films were obtained. From X-ray photoelectron spectroscopy an iron deficiency is observed in the uppermost layer of both films, implying that the crystallites preferably end in planes rich in Gd and O but not in Fe. The films were also characterized by X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, and magnetic measurements.

Ultrasmall gadolinium oxide nanoparticles doped with terbium ions were synthesized by the polyol route and characterized as a potentially bifunctional material with both fluorescent and magnetic contrast agent properties. The structural, optical, and magnetic properties of the organic-acid-capped and PEGylated Gd2O3:Tb3+ nanocrystals were studied by HR-TEM, XPS, EDX, IR, PL, and SQUID. The luminescent/fluorescent property of the particles is attributable to the Tb3+ ion located on the crystal lattice of the Gd2O3 host. The paramagnetic behavior of the particles is discussed. Pilot studies investigating the capability of the nanoparticles for fluorescent labeling of living cells and as a MRI contrast agent were also performed. Cells of two cell lines (THP-1 cells and fibroblasts) were incubated with the particles, and intracellular particle distribution was visualized by confocal microscopy. The MRI relaxivity of the PEGylated nanoparticles in water at low Gd concentration was assessed showing a higher T-1 relaxation rate compared to conventional Gd-DTPA chelates and comparable to that of undoped Gd2O3 nanoparticles.

Electrochemical synthesis and physical characterization of ZnO nanoparticles functionalized with four different organic acids, three aromatic (benzoic, nicotinic, and trans-cinnamic acid) and one nonaromatic (formic acid), are reported. The functionalized nanoparticles have been characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV−vis, and photoluminescence spectroscopy. The adsorption of the organic acids at ZnO nanoparticles was further analyzed and interpreted using quantum-chemical density-functional theory computations. Successful functionalization of the nanoparticles was confirmed experimentally by the measured splitting of the carboxylic group stretching vibrations as well as by the N(1s) and C(1s) peaks from XPS. From a comparison between computed and experimental IR spectra, a bridging mode adsorption geometry was inferred. PL spectra exhibited a remarkably stronger near band edge emission for nanoparticles functionalized with formic acid as compared to the larger aromatic acids. From the quantum-chemical computations, this was interpreted to be due to the absence of aromatic adsorbate or surface states in the band gap of ZnO, caused by the formation of a complete monolayer of HCOOH. In the UV−vis spectra, strong charge-transfer transitions were observed.

Zinc oxide is an interesting material for bio and chemical sensors. it is a semiconducting metal oxide with potential as an integrated multisensing sensor platform, which simultaneously detects Parameters like change in field effect, mass and Surface resistivity. in this investigation we have used resistive sensor measurements regarding the oxygen gas sensitivity in order to characterize sensing layers based on electrochemically produced ZnO nanoparticles and PE-MOCVD grown ZnO films. Proper annealing procedures were developed in order to get stable sensing properties and the oxygen sensitivity towards operation temperature was investigated. The ZnO nanoparticles showed a considerably increased response to oxygen as compared to the films. Preliminary investigations were also performed regarding the selectivity to other gases present in car exhausts or flue gases.

Gold nanoparticles (Au-NPs) are electrochemically synthesized in the presence of tetra-alkylammonium stabilizers and used as active element in Field Effect capacitive gas sensors. Before use, the sensing area is treated by a relatively mild annealing procedure aimed to partially remove the organic stabilizer without loosing the nano-structured character of the particles. Both pristine and annealed materials have been subjected to a spectroscopic and morphological characterization (by means of UV-Vis, XPS, TEM, SEM techniques). Preliminary results on the application of AuNPs as gate material for NO, sensing are reported. The sensor is able to detect NO, with appreciable selectivity and low response towards the other tested gases (C3H6, CO, H-2, NH3).

Synthesis of very small (about 4 nm) perovskite structured gadolinium orthoferrite nanoparticles (GdFeO₃) was performed by the polyol method. The material shows promising relaxivity properties and potential as a contrast agent in magnetic resonance imaging. The perovskite nanoparticles were characterized by x-ray diffraction, transmission electron microscopy, energy dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, magnetic resonance, and magnetization measurements. Upon heating in air at 800 °C for 3 h the size of the crystals increased to about 40 nm. The crystalline structure of the heat treated compound is in good agreement with perovskite GdFeO₃ as the primary product. Contributions from various secondary phases were also identified, including one hitherto unknown phase with the suggested composition 'Gd₃FeO₆' and isostructural with Gd₃GaO₆. The novel 'Gd₃FeO₆' phase appears to be kinetically stabilized in the nano state.

An environmental pollutant of great concern is NOx (nitrogen monoxide and nitrogen dioxide). Here we report the utilisation of electrochemically synthesised gold and palladium nanoparticles as catalytically active gate material on gas sensitive field effect sensor devices. The synthesised nanoparticles have been characterised by TEM and XPS, and the morphology of the thermally treated nanostructured sensing layers has been investigated using SEM and XPS. Measurements on the gas response of the palladium as well as the gold nanoparticle sensors towards a number of analytes found in automotive gas exhausts were performed and their response patterns were compared. The initial gas response measurements show interesting sensing properties for both the gold and the palladium nanoparticle sensors towards NOx detection.

There is a demand for more efficient and tissue-specific MRI contrast agents and recent developments involve the design of substances useful as molecular markers and magnetic tracers. In this study, nanoparticles of gadolinium oxide (Gd₂O₃) have been investigated for cell labeling and capacity to generate a positive contrast. THP-1, a monocytic cell line that is phagocytic, was used and results were compared with relaxivity of particles in cell culture medium (RPMI 1640). The results showed that Gd₂O₃-labeled cells have shorter T₁ and T₂ relaxation times compared with untreated cells. A prominent difference in signal intensity was observed, indicating that Gd₂O₃ nanoparticles can be used as a positive contrast agent for cell labeling. The r₁ for cell samples was 4.1 and 3.6 s^-1 mm^-1 for cell culture medium. The r₂ was 17.4 and 12.9 s^-1 mm^-1, respectively. For r₁, there was no significant difference in relaxivity between particles in cells compared to particles in cell culture medium, (p_r1 = 0.36), but r₂ was significantly different for the two different series (p_r2 = 0.02). Viability results indicate that THP-1 cells endure treatment with Gd₂O₃ nanoparticles for an extended period of time and it is therefore concluded that results in this study are based on viable cells.

A series of gas sensing layers based on indium oxide doped with gold were prepared by using the aerosol technology fordeposition as the active contact layer in a metal oxide semiconductor capacitive device. The interaction between the measuredspecies and the insulator surface was quantified as the voltage changes at a constant capacitance of the device. The sensor propertieswere investigated in the presence of H₂, CO, NH₃, NO, NO₂ and C₃H₆ at temperatures between 100–400 ^oC. Significant differencesin the morphology of the layer and its sensitivity were noted for different preparation methods and different gas environments.

     Gold nanoparticles (Au-NPs) have been synthesised using a sacrificial anode electrolysis in the presence of tetra-alkyl-ammonium halides, employed as cationic stabilizers. Catalytic NPs have been then deposited on top of Field Effect (FE) gas sensing devices and subjected to mild annealing procedures. Transmission Electron Microscopy (TEM) shows that the NP average core diameter is around 5 nm. X-Ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) have been applied to the surface characterization of the annealed NP films used as active sensing layers. Morphological and spectroscopic results demonstrate that the annealed inorganic nano-clusters are finely dispersed and maintain a metallic oxidation state. Au-NPs can be proficiently employed as gate material in Si-Field Effect Gas Sensors. Preliminary results show interesting selectivity and sensitivity sensing features towards NO_x detection.

The size distribution and magnetic properties of ultra-small gadolinium oxide crystals (US-Gd₂O₃) were studied, and the impact of polyethylene glycol capping on the relaxivity constants (r₁, r₂) and signal intensity with this contrast agent was investigated. Size distribution and magnetic properties of US-Gd₂O₃ nanocrystals were measured with a TEM and PPMS magnetometer. For relaxation studies, diethylene glycol (DEG)-capped US-Gd₂O₃ nanocrystals were reacted with PEG-silane (MW 5000). Suspensions were adequately dialyzed in water to eliminate traces of Gd³⁺ and surfactants. The particle hydrodynamic radius was measured with dynamic light scattering (DLS) and the proton relaxation times were measured with a 1.5 T MRI scanner. Parallel studies were performed with DEG–Gd₂O₃ and PEG-silane–SPGO (Gd₂O₃,< 40 nm diameter). The small and narrow size distribution of US-Gd₂O₃ was confirmed with TEM (~3 nm) and DLS. PEG-silane–US-Gd₂O₃ relaxation parameters were twice as high as for Gd–DTPA and the r₂/r₁ ratio was 1.4. PEG-silane–SPGO gave low r₁ relaxivities and high r₂/r₁ ratios, less compatible with positive contrast agent requirements. Higher r₁ were obtained with PEG-silane in comparison to DEG–Gd₂O₃. Treatment of DEG–US-Gd₂O₃ with PEG-silane provides enhanced relaxivity while preventing aggregation of the oxide cores. This study confirms that PEG-covered Gd₂O₃ nanoparticles can be used for positively contrasted MR applications requiring stability, biocompatible coatings and nanocrystal functionalization.

Objective: Nanosized materials of gadolinium oxide can provide high-contrast enhancement in magnetic resonance imaging (MRI). The objective of the present study was to investigate proton relaxation enhancement by ultrasmall (5 to 10 nm) Gd₂O₃ nanocrystals.

Materials and methods: Gd₂O₃ nanocrystals were synthesized by a colloidal method and capped with diethylene glycol (DEG). The oxidation state of Gd₂O₃ was confirmed by X-ray photoelectron spectroscopy. Proton relaxation times were measured with a 1.5-T MRI scanner. The measurements were performed in aqueous solutions and cell culture medium (RPMI).

Results: Results showed a considerable relaxivity increase for the Gd₂O₃–DEG particles compared to Gd-DTPA. Both T ₁ and T ₂ relaxivities in the presence of Gd₂O₃–DEG particles were approximately twice the corresponding values for Gd–DTPA in aqueous solution and even larger in RPMI. Higher signal intensity at low concentrations was predicted for the nanoparticle solutions, using experimental data to simulate a T₁-weighted spin echo sequence.

Conclusion: The study indicates the possibility of obtaining at least doubled relaxivity compared to Gd–DTPA using Gd₂O₃–DEG nanocrystals as contrast agent. The high T ₁ relaxation rate at low concentrations of Gd₂O₃ nanoparticles is very promising for future studies of contrast agents based on gadolinium-containing nanocrystals.

  Nanocrystalline TiO₂ powders of the rutile polymorph, synthesized by a sol–gel method, were treated with water solutions containing, respectively, formic, acetic, and citric acid and glycine in order to study the adsorption properties of these organic species. The samples were characterized by FTIR, Raman, powder XRD, and TEM. It was found that HCOOH, CH₃COOH and HOC(COOH)(CH₂COOH)₂—but not NH₂CH₂COOH—adsorbed onto TiO₂. The adsorption of HCOOH, CH₃COOH and NH₂CH₂COOH onto the (110) surface of rutile was also studied by quantum-chemical periodic density functional theory (DFT) calculations. The organic molecules were from the computations found to adsorb strongly to the surfaces in a bridge-coordinating mode, where the two oxygens of the deprotonated carboxylic acid bind to two surface titanium ions. Surface relaxation is found to influence adsorption geometries and energies significantly. The results from DFT calculations and ab initio molecular-dynamics simulations of formic acid adsorption onto TiO₂ are compared and match well with the experimental IR measurements, supporting the bridge-binding geometry of carboxylic-acid adsorption on the TiO₂ nanoparticles.

In this project, we have explored RuO₂ and Ru nanoparticles (∼ ∼10 and ∼ ∼5 nm, respectively, estimated from XRD data) to be used as gate material in field effect sensor devices. The particles were synthesized by wet chemical procedure. The capacitance versus voltage characteristics of the studied capacitance shifts to a lower voltage while exposed to reducing gases. The main objectives are to improve the selectivity of the FET sensors by tailoring the dimension and surface chemistry of the nanoparticles and to improve the high temperature stability. The sensors were characterized using capacitance versus voltage measurements, at different frequencies, 500 Hz to 1 MHz, and temperatures at 100–400°C. The sensor response patterns have been found to depend on operating temperature. X-ray photoelectron spectroscopy (XPS) analyses were performed to investigate the oxidation state due to gas exposure. Quantum-chemical computations suggest that heterolytic dissociative adsorption is favored and preliminary computations regarding water formation from adsorbed hydrogen and oxygen was also performed.

Synthesis of metal-oxide nanoparticles and utilization of these particles as gate materials for field-effect sensor devices is reported. Improved selectivity to specific gases is expected by modulating the size of the oxide nanoparticles or impregnating them with catalytic metals. Another objective is to improve the long-term thermal stability of the sensors, since the metal loaded nanoparticles may prevent thermally induced restructuring of the gate layer, which is often a problematic issue for the catalytic metal layers. Because of its reasonably high electrical conductivity, which is especially important for the capacitive gas sensors, ruthenium dioxide has been identified to be one of the potential candidates as gate material for the field-effect sensor devices. Interestingly, this material has been found to change its resistivity in different gaseous ambients. When used as a gate material, sensitivity to reducing gases has been observed for the RuO₂/SiO₂/4H-SiC capacitors. Changes in the resistivity of the films due to various gas exposures have also been recorded. Morphological studies of nanoparticles (SiO₂ and Al₂O₃), loaded or impregnated with catalytic metals (e.g. Pt), have been performed.

Catalytically active nanoparticles used as gate material on SiC-FET gas sensors. The goal is to improve the selsectivity and senstitivty.The sensors are sensitive towards oxidising and reducing gases (H2, NH3, C3H6).

Thin films of the perovskite structured Na_0.5K_0.5NbO₃ (NKN) have been synthesized with three different sol–gel methods, viz. the alkoxide method, a modified Pechini method and a somewhat novel oxalate method, based on 2-methoxy ethanol as solvent with oxalic acid and ethylene glycol as chelating ligand and stabilizer. Only one method (the modified Pechini method) gave pure NKN phase while the other two methods gave extra peaks in the X-ray diffraction patterns, indicating that other, unidentified, phases were present. SEM images revealed grain sizes ranging from 100 to 300 nm.

The surface interactions between Y₂O₃ nanocrystals and the organic molecules formic acid, diethylene glycol (DEG), and tetramethoxy silane (TMOS), have been studied experimentally and by quantum chemical calculations with the intent to elucidate the chemisorption characteristics such as adsorbate vibrational spectra and adsorption structures. Nanocrystal synthesis was performed by a colloidal method based on polyols and by a rapid combustion method. The products were experimentally characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS).

In the quantum chemical calculations, the B3LYP hybrid density functional ab initio method was used to study the chemisorption of formic acid, DEG and TMOS at the surface of Y₁₂O₁₈ clusters. From a comparison of calculated and experimental vibrational spectra, the binding mode for formic acid on Y₂O₃ was inferred to be of bridge or bidentate type. The XPS and FT-IR experiments showed that DEG is chemisorbed on the particle surface. The experimental IR spectra of DEG chemisorbed on Y₂O₃ were consistent with an adsorption mode where the hydroxyl groups are deprotonated according to the quantum-chemical computations. The adsorption energy is of the order of 370 kJ mol⁻¹ for formic acid, 550 kJ mol⁻¹ for DEG, and 60 kJ mol⁻¹ for TMOS, according to the quantum chemical calculations.

Nanocrystals of Gd₂O₃ have been prepared by various methods, using, e.g., trioctylphosphine oxide (TOPO), diethylene glycol (DEG) or glycine. The crystalline particles were of sizes 5 to 15 nm. Different carboxylic acids, e.g., oleic acid or citric acid, were adsorbed onto the surface of the particles made with DEG. IR measurements show that the molecules coordinate to the Gd₂O₃ surface via the carboxylate group in a bidentate or bridging manner. The organic-acid/particle complexes were characterised by XRPD, TEM, FTIR, Raman, and XPS.