M.Sc Thesis

M.Sc StudentBayn Alona
SubjectThe Study of Field Effect Transistors Based on Polycycle
Aromatic Hydrocarbons for the Detection and
Classification of Volatile Organic
DepartmentDepartment of Nanoscience and Nanotechnology
Supervisor PROF. Hossam Haick
Full Thesis textFull thesis text - English Version


Volatile organic compounds (VOCs) tend to evaporate easily at room temperature. Many VOCs are associated with emissions from industrial processes (e.g., heating oil, aldehydes, alcohols), transportation (e.g., gasoline, diesel), and use of organic solvents (e.g., benzene, butadiene, hexane) that are in part toxic or carcinogenic. Furthermore, several VOCs associated with metabolic and/or pathophysiologic processes have been used for diagnosing a wide variety of diseases.  Although highly selective sensors do exist for a limited number of substances, such gas sensors are very sensitive to cross-interfering substances and provide an overall result in response to a general class or group of chemically related contaminants. Additionally, such gas sensors are highly affected by the humidity in the environment examined.

The present thesis focuses on the development and study of Field effect transistors (FETs) that are based on polycyclic aromatic hydrocarbons (PAHs) for detecting various VOCs with minimal (or negligible) sensitivity to humidity. Towards this end, we have developed silane-modified PAH-FETs, where the silane modification diminishes the sensitivity of the device to humidity-initiated hysteresis. With this feature, we demonstrate the ability of PAH-FET sensor arrays in conjunction with statistical pattern recognition methods to: (i) discriminate between aromatic and non-aromatic VOCs; (ii) distinguish between polar and non-polar non-aromatic compounds; and to (iii) identify specific VOCs within the sub-groups (i.e. aromatic compounds, polar non-aromatic compounds, non-polar non-aromatic compounds).

Patterns based on different independent electronic features from an array of PAH-FETs may bring us one step closer to creating a unique fingerprint for individual VOCs in real-world applications. Moreover, an examination of the mechanism of VOC/PAH interaction is conducted in order to try and further understand the electrical response received from the sensors in the exposure experiments. The QCM and FTIR devices are used to shed light on the sorption process of the VOC in the sensing layer as well as to analyze the interaction between the analytes and the active sites of the PAH molecules. The exploration of the interactions is the key for future manufacture of superior sensors and further improvement of the sensing abilities of the array.

Ultimately, the results presented here could lead to the development of cost-effective, lightweight, low-power, noninvasive tools for the widespread detection of VOCs in real-world applications, including, but not confined to, environmental, security, food industry, health-related, and breath analysis disease diagnostics.