Towards pathway analysis of oxygen photosensitization by polycyclic aromatic hydrocarbons in microheterogeneous media
Date
2018
Authors
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Publisher
University of Delaware
Abstract
Advancing analysis on the mechanisms behind reactive oxygen species (ROS) production through photosensitization has applications within areas of synthesis, toxicology, and photodynamic therapy. Current direct analysis methods require costly instrumentation, which have led to the development of cheaper analysis methods with spectroscopic techniques such as luminescent, colorimetric and spectral probes. However, these spectroscopic techniques face difficulty in measuring ROS in natural and complex environments due to spectral overlap and the production of multiple components from side reactions. The focus herein is to introduce methodology and assemble automated instrumentation that can be used as a foundation to investigate the mechanisms of photosensitization of oxygen by polycyclic aromatic hydrocarbons (PAHs) in natural and complex environments by reaction progress monitoring. The preliminary studies described here were conducted in octanol, which is reportedly a microheterogeneous solvent. In the future, the methodology introduced can be combined with colorimetric or spectral probe techniques and numerical techniques, such as self-modeling curve resolution and reaction progress kinetic analysis, to monitor and separate individual spectral components to determine mechanistic and kinetic information. Actinometer measurements indicated the instrumental setup irradiates samples at approximately 10 times that of surface solar irradiance on a midsummer day at 400 nm, without irradiation in the area of direct sensitization of molecular oxygen. PAH photodegradation measurements in octanol show a relationship between the rate of degradation to the activation energy barrier of the formation of the endoperoxide transition state in the formation of ROS and the irradiation power.