Applications of Carbon Nanotube based Chemiresistors for Breath Analysis and Hydrogen Storage Sensing

Carbon nanotubes are excellent transducers that can translate changes in their local chemical environmental into electrical signals to sense chemical species. Their applications as transducers can be attributed to their high surface area to volume ratio, dimensionality in the nanoscale, and conductivity that is dependent on their local chemical potential. The nanotubes are functionalized with other nanomaterials such as metal oxides, noble metal nanoparticles, and metal organic frameworks to improve sensitivity and selectivity. These nanomaterials have known favorable interactions with analytes serve as selective receptors. The nanotube transducers also need a corresponding measurement device to measure the changes in their optical or electrical properties to be considered a fully functioning sensor. In this work, functionalized carbon nanotube gas sensors integrated into breathalyzers are used to detect Delta-9-tetrahydrocannabinol (THC) and acetone in the breath. THC is the main psychoactive compound in cannabis that is responsible psychoactive effects such as drowsiness, alteration of perception, and anxiety. THC is known to be present in the exhaled breath up to several hours after smoking. Acetone is a metabolic byproduct of fat metabolism and is an important analyte to monitor to prevent a potentially deadly condition called ketoacidosis or titrate food intake to treat type 2 diabetes or drug resistant epilepsy. A major issue with carbon nanotube sensors is their cross sensitivity to volatile compounds in the breath including water vapor. To resolve this issue for sensing THC, atypical sensor measurements and data analysis techniques were used such as removing bias across the sensor to allow volatile compound to desorb and then focus on the recovery portion of the sensor traces. This strategy enabled selective detection of THC over other breath components. To detect acetone, a dehumidifier based on microfluidic channels that removed water vapor from breath samples was developed. The last portion of this work focuses on using palladium nanoparticle functionalized carbon nanotubes to study hydrogen gas absorption and desorption in a MOF called HKUST-1. This MOF is known to increase the hydrogen absorption capacity of palladium and improve the absorption and desorption dynamics