Designing a System for Measuring and Optimizing the Photothermal Conversion Efficiencies of Two Dimensional Nanomaterials for Cancer Therapy

Abstract

Cancer is a devastating disease with no definitive cure currently. Current treatments are invasive and can cause inreprepable damage to the human body. Alternative cancer treatment methods involving nanomaterials have been sought primarily for their ability to treat cancer non-invasively. This is accomplished in a variety of ways and combinations of treatments such as photothermal therapy, photodynamic therapy and drug delivery. In this thesis, the photothermal properties of tungsten and molybdenum compounds are studied for prospective use in photothermal therapy cancer treatments. A femtosecond laser is used to alter the morphology, stoichiometry and chemistry of the tungsten disulfide (WS2) and molybdenum disulfide (MoS2) starting materials. This resulted in a novel synthesis method for creating two dimensional (2D) tungsten semi-carbide (W2C) through carburizing WS2 and synthesizing plasmonic substoichiometric molybdenum oxide (MoO3-x) through the partial oxidation of MoS2. These novel nanomaterials were then characterized using grazing incidence x-ray diffraction (GIXRD), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Raman spectroscopy to confirm the corresponding carburization and partial oxidation. Optical and photothermal studies were conducted to determine the feasibility of these materials as a photothermal agent used in photothermal therapy. Absorption spectroscopy was used to study the materials’ interaction with light, specifically in the near infrared (NIR) wavelengths. A custom measurement system was designed and engineered to measure the photothermal conversion efficiency (PTCE) of both the 2D W2C and the plasmonic MoO3-x. The PTCE was measured to be 27% and 33% for the 2D W2C and the plasmonic MoO3-x, respectively. This suggests both materials are strong candidates as a photothermal agent for use in photothermal therapy.