Adrian Trinchi

Investigation of the oxygen gas sensing performance of Ga2O3 thin films with different dopants

Abstract The oxygen gas sensing performance of Ga2O3 semiconducting thin films doped with Ce, Sb, W and Zn have been investigated. These thin films have been prepared by the sol–gel process and were deposited on sapphire transducers with inter-digital electrodes and a platinum heater integrated. The sensors were exposed to various concentrations of oxygen gas in an ambient of nitrogen and the gas sensing performance has been examined. The responses of sensors doped with Ce, Sb, W and Zn were stable and reproducible at their respective operating temperatures. It was observed that Ga2O3 films doped with Ce, Zn and W are promising for oxygen gas sensing applications.

A novel Love-mode device based on a ZnO/ST-cut quartz crystal structure for sensing applications

A novel Love-mode surface acoustic wave (SAW) sensor with ZnO guiding layer and 90° rotated ST-cut quartz crystal substrate will be presented. Analysis of this device with different thicknesses of ZnO films was undertaken. It will be shown that this novel structure offers distinct advantages over previously fabricated Love-mode structures. These advantages include significantly high sensitivity, small temperature coefficient of frequency and high electromechanical coupling coefficient.

Investigation of sol-gel prepared CeO2-TiO2 thin films for oxygen gas sensing

Abstract The oxygen gas sensing performance of semiconducting CeO 2 –TiO 2 thin films have been investigated. These thin films have been prepared by the sol–gel process utilizing a non-alkoxide as the main precursors. For gas sensing measurements, the films were deposited by the spin coating technique onto alumina substrates with interdigital transducers located on the top and a micro-heater on the bottom. For the microstructural characterization, the thin films were deposited onto single crystal silicon substrates. X-ray photoelectron spectroscopy (XPS), Auger electron spectrometry (AES) and scanning electron microscopy (SEM) were employed to analyze the films. These films were exposed to various concentrations of O 2 gas and their electrical responses were measured.

A Pt/Ga/sub 2/O/sub 3/-ZnO/SiC Schottky diode-based hydrocarbon gas sensor

In this paper, a novel metal-reactive insulator-silicon carbide device with a catalytic layer for hydrocarbon gas-sensing is presented. This structure, employed as a Schottky diode, utilizes sol-gel prepared Ga/sub 2/O/sub 3/-ZnO layer as the reactive insulator. The sensor has been exposed to propene gas, which lowers the barrier height of the diode. The responses were stable and repeatable at operating temperatures between 300 and 600/spl deg/C. The response to propene in different ambients was examined. The effect of diode bias has been investigated by analyzing the sensors response to various propene concentrations when held at constant currents of 2 and 8 mA.

Investigation of sol-gel prepared Ga-Zn oxide thin films for oxygen gas sensing

Gallium oxide-zinc oxide (Ga 2 O 3 -ZnO) thin films have been prepared by the sol-gel process and their oxygen gas sensing performance has been investigated. These semiconducting films were deposited on alumina substrates with interdigital electrodes and single crystal silicon substrates for the electrical and microstructural characterization. X-ray photoelectron spectroscopy (XPS) showed that the actual concentrations of Ga and Zn thin films differ from the nominal values in the prepared solutions. Additionally, the concentration of ZnO decreases when the annealing temperature increases. Scanning electron microscopy (SEM) revealed that films with Ga/Zn atomic ratio 90:10 possess cracks and are inhomogeneous when compared to those with that of 50:50. The sensors with Zn 50 at.% had a much larger response at lower operating temperature (<430 C) compared to the Ga-dominated sensors, which operate above 450°C. Furthermore, these sensors showed greatest performance at temperatures in the range of 380-420 C. It was found that by increasing the amount of ZnO in the thin film sensors, the operating temperature decreased as well as the base resistance.

Photoluminescence enhancement of carbon dots by gold nanoparticles conjugated via PAMAM dendrimers

Carbon dots (CDs) have many fascinating fluorescent properties, however, their low quantum yield limits their applications. In this study, the photoluminescence (PL) of CDs in the vicinity of gold nanoparticles (Au NPs) is enhanced significantly due to the surface plasmon resonance (SPR) of the Au NPs. This is achieved by conjugating Au NPs and CDs to dendrimers (PAMAM) through an amidation reaction, resulting in the formation of the Au-PAMAM-CD conjugates. The maximum 62-fold enhancement was obtained with an optimized molar ratio between Au NPs, PAMAM, and CDs. In this process, PAMAM, which serves as a spacer, can keep Au NPs and CDs at an appropriate distance for PL enhancement. The adjustment of the amount of Au NPs or CDs linked to PAMAM can induce the optimum PL enhancement. This strategy can be easily applied to different metal-space-fluorophore systems to enhance the fluorescence of fluorophores.

A Review of Surface Functionalized Amine Terminated Dendrimers for Application in Biological and Molecular Sensing

Dendrimers are three dimensional nanosized synthetic molecules that have internal cavities and numerous surface groups. In recent times they have received increased attention in sensing applications. For dendrimers to be used as sensors, they most commonly require functionalization at their surface. This is because the surface is generally the first point of contact between the dendrimer and the outside world, hence surface functionalization serves to selectively home in on the target analyte. Further, sensor signals may be transmitted through surface functionalities e.g. fluorochromic molecules. It is therefore important to document surface functionalization approaches. Dendrimers with amine surface groups have the advantage of being able to be conjugated to other molecules via an amide linkage, which is one of the most fundamental and widespread chemical bonds in nature. In this paper we demonstrate the properties of dendrimers that make them so applicable to sensing. We review several methods for functionalizing dendrimers via an amide linkage, as well as present a review of surface functionalized polyamidoamine, polyamine, and polypeptide dendrimers that have been employed for biological, chemical and molecular sensing.

A room temperature polyaniline nanofiber hydrogen gas sensor

Electro-conductive polyaniline (PANI) nanofiber based surface acoustic wave (SAW) gas sensors have been investigated with hydrogen (H 2) gas. A template-free, rapidly mixed method was employed to synthesize polyaniline nanofibers using chemical oxidative polymerization of aniline. The nanofibers were deposited onto a layered ZnO/64deg YX LiNbO3 SAW transducer for gas sensing applications. The novel sensor was exposed to various concentrations of H2 gas at room temperature. The sensor response, defined as the relative variation in operating frequency of oscillation due to the introduction of the gas, was 3.04 kHz towards a 1% H2 concentration. A relatively fast response time of 8 sec and a recovery time of 60 sec with good repeatability were observed at room temperature. Due to room temperature operation, the novel gas sensor is promising for environmental and industrial applications

Microstructure of a Paint Primer - a Data-Constrained Modeling Analysis

Metallic aerospace components are commonly painted with a primer to improve their corrosion resistance. The primer contains a polymer matrix with embedded corrosion inhibitor and filler particles. Its performance is determined by the microscopic distributions of the particles. Various techniques have been used to quantify such distributions, including X-ray micro-computed tomography (CT). However, its success is sometimes limited by factors such as different particles having similar X-ray CT absorption properties and their size being smaller than the resolution of micro-CT. In this paper, we have performed two X-ray CT measurements on a paint primer sample consisting of SrCrO4 corrosion inhibitor particles and UV-absorbing TiO2 filler particles. Fe and Ti targets were used as X-ray sources with different spectral distributions. The measured CT data sets were used as constraints for a data-constrained microstructure modeling (DCM) prediction of the sample’s microscopic structures. DCM model predictions were compared with experimental elemental surface maps and showed reasonable degree of agreement, suggesting X-ray micro-CT combined with DCM modeling would be a powerful technique for detailing the dynamics of chromate-inhibited primers and other multiphase systems where the components are sensitive to incident X-ray energy.

Data-Constrained Microstructure Characterization with Multispectrum X-Ray Micro-CT

Conventional X-ray microcomputed tomography (micro-CT) is not usually sufficient to determine microscopic compositional distributions as it is limited to measuring the X-ray attenuation of the sample, which for a given dataset can be similar for materials of different composition. In contrast, the present work enables three-dimensional compositional analysis with a data-constrained microstructure (DCM) modeling methodology, which uses two or more CT datasets acquired with different X-ray spectra and incorporates them as model constraints. For providing input data for DCM, we have also developed a method of micro-CT data collection that enables two datasets with different X-ray spectra to be acquired in parallel. Such data are used together with the DCM methodology to predict the distributions of corrosion inhibitor and filler in a polymer matrix. The DCM-predicted compositional microstructures have a reasonable agreement with energy dispersive X-ray images taken on the sample surface.