Electrochemical sensors for nutrients, volatile organic compounds and viral pathogens
Date
2022-08
Authors
Ibrahim, Hussam
Major Professor
Advisor
Dong, Liang
Lu, Meng
Castellano, Michael
Pandey, Santosh
Anand, Robbyn
Committee Member
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Abstract
Electrochemical sensors often provide high sensitivity in detecting low-concentration target analytes. Despite the remarkable progress in the field of wearable sensors, developing low-cost electrochemical wearables for monitoring plant growth, nutrition, and health status is still in the infancy stage. Similarly, electrochemical wearables for monitoring respiratory diseases using exhaled breath as an analyte are emerging and require more research to meet development and application challenges. This dissertation reports two novel wearable plant sensors and one wearable biomedical sensor and demonstrates how artificial enzymes, artificial antibodies, nanocatalysts, and low-cost manufacturing methods can be synergized to improve sensitivity, specificity, selectivity, and long-term monitoring capability while exploring and extending new applications of wearable technology.
First, I developed a wearable nitrate sensor capable of quantifying nitrate levels in the plant. Cobalt macrocycle in vitamin B12 (VB12) is used as an artificial enzyme of the sensor. VB12 and graphene oxide (GO) are introduced into a photosensitive host epoxy resin that can be photopatterned and then laser-pyrolyzed to form a carbon-based bio-functional nanocomposite. The resulting nanocomposite contains an artificial enzyme network with a microscale patterning resolution that can be used as a sensing material for detecting various biochemical species through redox reactions occurring at signature potentials. A MEMS needle-shaped C-GO-VB12 nitrate sensor is demonstrated for the in-situ quasi-continuous measurement of stalk nitrate of maize plants over a long time. The sensor exhibits a shelf life of several months with almost no performance degradation.
Second, I developed a wearable volatile organic compound sensor for plants. The sensor monitors methanol emission directly from the plant's leaf under field conditions with high portability and easy installation and use. The sensor uses a composite of conducting polymer microcrystallites of poly(2-amino-1,3,4-thiadiazole) and platinum nanoparticles, poly(ATD)-PtNPs. Poly(ATD) provides a highly electrocatalytic activity with redox behavior, while PtNPs are used to modify the conducting polymer as a catalyst during the electrochemical oxidation of methanol. The advantages of poly(ATD) and PtNPs are synergized for high sensitivity and selectivity of the sensor for detecting methanol with a sub-ppm limit of detection. Further, infusing a polymer electrolyte into the porous electrode enables an all-solid-state amperometric sensor. The sensor is integrated with a miniature gas collection chamber and capped with a hydrophobic gas diffusion membrane to minimize the influence of environmental humidity on the sensor performance. The sensor demonstrates to detect methanol emissions from the leaf of maize plants.
Finally, I developed an in-mask, cost-effective sensor for collecting, recognizing, and detecting a respiratory virus (influenza H1N1 virus) in exhaled breath. The virus sensor is formed with nanocavities complementary to H1N1 virus particles on the surface of an electrodeposited conducting polymer on laser-induced graphene. A layer of hydrophilic hydrogel is infused with an aqueous electrolyte solution and coated on the surface of an electrochemical sensing element to solve the issue of respiration-induced water loss from the sensor surface. Virus particles from the exhaled breath are diffused to the sensor surface through the porous interior structure of hydrogel. The hydrogel layer can absorb water vapor from the exhaled breath, thus improving electrolyte retention and assuring a constantly moist environment for the sensor. The sensor is tested with flowing virus-containing moist air into the face mask. The sensor exhibits a fast response time superior to other rapid tests and conventional polymerase chain reaction-based methods.
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dissertation