Browsing by Subject "photobleaching"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Application of Luminescent Materials to Optical Sensing(2014-09-05) Ritter, Sarah CDevelopment of sensors for detection of various chemical and biological species is an important and ever-growing field. In particular, optical-based sensors enable a remote, rapid method for continuous or on-demand monitoring. Monitoring humidity is important across many applications, such as humidity control within moisture-sensitive environments and in medical, semiconductor, and food science fields. Following a study of photobleaching, defect-related emission of zinc oxide nanoparticles was monitored as a function of relative humidity. An important next step is its application to monitoring toxic gases, as air pollution has been identified as a major health concern. Of importance for the biomedical field is monitoring key blood analytes for human health. Monitoring blood pH is critical for specific patient groups, such as those suffering from diabetic ketoacidosis and congenital lactic acidosis. A pH-sensitive fluorophore was loaded within red blood cells for use as a continuous blood analyte monitor. Future work will focus on glucose, as current estimates show that one out of every three children born in 2000 will develop diabetes in his or her lifetime ? thus, the global impact of this disease is immense. Results from ZnO studies indicate that photobleaching is related to the surface area to volume ratio. ZnO nanoparticles display a linear response to humidity with a sensitivity of 0.008417 RH^-1 and 0.01898 RH^-1 for nitrogen and air environments, respectively. Owing to reversibility and high sensitivity, ZnO nanoparticles have great potential as optical-based environmental sensors. Results from dye-loaded ghost studies indicate that fluorescence intensity of intracellular dyes report on extracellular pH. Resealed ghosts loaded with a fluorescein isothiocyanate-glycylglycine conjugate reversibly track pH with a resolution down to 0.014 pH unit. For use in vivo, the development of an NIR pH-sensitive dye was paramount. Unfortunately, all NIR dyes tested exhibited poor pH sensitivity while displaying sensitivity to external factors (e.g., temperature, concentration, proteins). However, circulation kinetics of resealed ghosts were easily monitored once injected in vivo with an optical fiber-based system. Although the cells were rapidly removed from circulation, the loaded ghosts resulted in higher signal than would be expected for free dye alone. Once optimized, the resealed ghosts could serve as a long-term, continuous, circulating biosensor for the management of diseases.Item Evaluation of the Bioherbicide Phoma macrostoma for Use in Southern Turfgrass Systems(2014-01-13) Smith, Jonathon M.Phoma macrostoma Montagne is a fungus being developed as a natural herbicide for selective broadleaf weed control. The solid fermentation of P. macrostoma on grain produces a product that is applied as a dry granule. Herbicidal activity is characterized by foliar bleaching and necrosis of susceptible broadleaf weeds. Previous research with this product was limited to cool-season climates, and information is limited regarding appropriate application rates or efficacy at higher temperatures and weeds associated with warm-season turf. Spectrum of weed control is still being explored, most recently in Texas. Multiple years of field and greenhouse research were conducted in College Station, TX, to evaluate the efficacy of P. macrostoma for broadleaf weed control. Field studies showed that P. macrostoma was effective at controlling slender aster (Aster subulatus var. ligulatus Shinners), with higher application rates providing 89 to 94% control. Field studies also showed that P. macrostoma was able to maintain efficacy at high temperatures, with maximum temperatures of 41?C. Greenhouse studies indicated a variable weed control spectrum, with P. macrostoma providing excellent control of dandelion (Taraxacum officinale Weber ex F.H. Wigg.), but little to no activity on other weeds including common mallow (Malva neglecta Wallr.) and common purslane (Portulaca oleracea L.). Growth chamber studies indicate that environmental factors such as temperature and moisture affect the efficacy by P. macrostoma, and culturalpractices such as nitrogen fertilization coupled with P. macrostoma application may enhance herbicidal activity. Over the course of this research, no injury was observed on any species of warm-season turfgrass, making P. macrostoma a promising biorational option for natural weed control in lawns.