Laurie Dudik

Solar-Light Photoamperometric and Photocatalytic Properties of Quasi-transparent TiO2 Nanoporous Thin Films

Transparent photocatalytic surfaces are of ever increasing importance for many applications on self-cleaning windows and tiles in everyday applications. Here, we report the formation and photocatalytic testing of a quasi-transparent thin and nanoporous titania films deposited on glass plates. Sputtered Ti thin films were anodized in fluoride-ion-containing neutral electrolytes to form optically semitransparent nanoporous films, which transformed to be completely transparent after thermal annealing. The nanoporous films were studied at different stages, such as before and after anodization, as well as after thermal annealing using scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis and Raman spectroscopy. It was observed that anodization at 20 V of high-temperature deposited titanium films resulted in regular nanopore films with pore diameters of 30 nm. Structural investigations on the transparent nanopore arrays reveal the presence of anatase phase TiO(2) even after annealing at 500 °C, which was confirmed by XRD and Raman spectroscopy measurements. The solar-light induced photocatalytic decomposition of stearic acid and photoconductivity characteristics of these nanoporous thin films are also presented.

A calorimetric combustible gas detector employing platinum film heaters

Abstract Calorimetric sensors employing exposed metallic film heaters have been evaluated on gas mixtures containing hydrogen or carbon dioxide. The sensor output exhibits high sensitivity to the tested gases. A combustible gas detector based on the described method appears suitable for integration into a multicomponent gas analyzer.

Sample/reagent adsorption on alumina versus Pyrex substrates of microfabricated electrochemical sensors

Platinum redox sensors have been microfabricated for potentiometric detection in diffusional microtitration of microliter-size fluid samples. Two different materials, alumina ceramic and Pyrex glass, have been studied for their suitability as sensor substrates. Adsorptions of reagent and/or sample on an alumina ceramic substrate and a Pyrex glass substrate are compared. Using iodimetric redox titration, significant adsorption of both reagent and sample occurs on alumina ceramic substrates. This causes contamination and cross-contamination of samples, leading to highly irreproducible results. Reproducibility with a 1.6% coefficient of variation has been achieved using a platinum redox sensor deposited on a Pyrex substrate for the analysis of 20 μL sample microdroplets. Due to the large surface area relative to the small sample volume, surface processes can have a significant effect on the analysis of microsamples. Therefore, precautions must be taken to minimize problems arising from air interference and sensor/sample, sensor/reagent and reagent/sample interfaces.

Dissolved Wear Metal Monitoring in Lubricating Fluids

Lubricating fluids play a critical role in the operation of many machines in commerce, industry, and the military. Failure of a lubricant often results in accelerated metal wear and the release of wear debris in the lubricant. Early detection of abnormal metal wear is important for fault detection and failure prevention. An electrochemical cell can be operated in a lubricating fluid in such a way that the operating characteristics of the cell can provide an indication of the chemistry of the fluid. For example, certain ions in the fluid, such as wear metal ions, will react to particular potential values applied to electrodes in the electrochemical cell. By applying a changing potential across the electrodes in an electrochemical cell and observing the resulting current it is possible to detect and identify the ionic species present in the lubricating fluid. The objective is to provide real-time monitoring of lubricating fluids using an in situ sensor to detect and diagnose conditions leading to machinery failure. A series of experiments have been conducted to confirm the ability of an electrochemical cell to detect wear metal ions in lubricating fluids extracted from machinery. Additional tests have been conducted to test the hypothesis that the presence and amount of wear metal ions corresponds to the type and amount of wear particles in the fluid. Initial laboratory tests have established a positive correlation with wear particles detected in used lubricating oil with ion presence determined using ion chromatography. The results reported indicate that a small, real-time multielement sensor with an electrochemical cell will be able to detect wear metal ions and provide an early indication of unusual material wear. This capability may provide an early warning of atypical wear patterns and provide a cue to an operator or service engineer indicating the type of fault occurring and the specific component experiencing wear or early failure.Copyright

Manufacturing of low-cost enzymatic biosensors using thick film processing

Single-use disposable biosensors are of importance in many applications related to health care, patient management, environmental monitoring, food and water quality analysis, personal safety and national security. Enzymatic biosensors using electrochemical detection techniques can be considered a platform technology. This study focuses on the development of high performance enzymatic biosensors based on this platform technology and their manufacturing methods. The applications of thick-film screen printing and ink-jet printing techniques to manufacture the single-use, disposable biosensors are feasible and technically attractive. Experimental results will be presented to demonstrate the effectiveness of the printing technologies in the manufacturing of these biosensors with high performance characteristics.