| Description |
Monitoring and remediation of environmental contaminants (biological and chemical) form the crux of global water resource management. There is an extant need to develop point-of-use, low-power, low-cost tools that can address this problem effectively with min imal environmental impact. Nanotechnology and microfluidics have made enormous ad vances during the past decade in the area of biosensing and environmental remediation. The "marriage" of these two technologies can effectively address some of the above-mentioned needs [1]. In this dissertation, nanomaterials were used in conjunction with microfluidic techniques to detect and degrade biological and chemical pollutants. In the first project, a point-of-use sensor was developed for detection of trichloroethylene (TCE) from water. A self-organizing nanotubular titanium dioxide (TNA) synthesized by electrochemical anodization and functionalized with photocatalytically deposited platinum (Pt/TNA) was applied to the detection. The morphology and crystallinity of the Pt/TNA sensor was characterized using field emission scanning electron microscope, energy dis persive x-ray spectroscopy, and X-ray diffraction. The sensor could detect TCE in the concentrations ranging from 10 to 1000 ppm. The room-temperature operation capability of the sensor makes it less power intensive and can potentially be incorporated into a field-based sensor. In the second part, TNA synthesized on a foil was incorporated into a flow-based microfluidic format and applied to degradation of a model pollutant, methylene blue. The system was demonstrated to have enhanced photocatalytic performance at higher flow rates (50-200 ^L/min) over the same microfluidic format with TiO2 nanoparticulate (commercial P25) catalyst. The microfluidic format with TNA catalyst was able to achieve 82% fractional conversion of 18 mM methylene blue in comparison to 55% in the case of the TiO2 nanoparticulate layer at a flow rate of 200 L/min. The microfluidic device was fabricated using non-cleanroom-based methods, making it suitable for economical large-scale manufacture. A computational model of the microfluidic format was developed in COMSOL Multiphysics® finite element software to evaluate the effect of diffusion coefficient and rate constant on the photocatalytic performance. To further enhance the photocatalytic performance of the microfluidic device, TNA synthesized on a mesh was used as the catalyst. The new system was shown to have enhanced photocatalytic performance in comparison to TNA on a foil. The device was then employed in the inactivation of E. coli O157:H7 at different flow rates and light intensities (100, 50, 20, 10 mW/cm2). In the second project, a protocol for ultra-sensitive indirect electrochemical detection of E. coli O157:H7 was reported. The protocol uses antibody functionalized primary (magnetic) beads for capture and polyguanine (polyG) oligonucleotide functionalized sec ondary (polystyrene) beads as an electrochemical tag. The method was able to detect concentrations of E. coli O157:H7 down to 3 CFU/100 mL (S/N=3). We also demonstrate the use of the protocol for detection of E. coli O157:H7 seeded in wastewater effluent samples. |
