The development and implementation of light-based technologies is widely under-realized despite their important role in solving many of the grand challenges facing our society, including water resources, environmental remediation, and energy conservation. We have observed a clear need for understanding and guidance about characterization and reporting on illumination systems used in laboratory studies of these processes. Subtle aspects of illumination sources and their characterization methods can introduce significant uncertainty in the data gathered from light-based experiments. By clearly understanding the sources of these uncertainties, the advancement of photo-activated processes for engineered environmental systems can be realized.  In this research, we broadly explored the variables present in common laboratory illumination systems, using both chemical and optical methods. Valerophenone and ferrioxalate actinometry were paired with optical radiometry in four different common light systems used in photochemistry experiments. Various aspects of the light systems were studied, including bulb type and manufacturer as well as age, to illustrate the critical utility of tracking both power output and spectral distribution of the incident light applied to photochemical reactions. The degradation kinetics of methyl orange and carbamazepine under illumination with TiO<sub>2</sub> were used as a case study for interpreting the photon flux values found from the chemical and optical methods.  Light sources specified to have narrow emission ranges were found to have broad emissions at a variety of other wavelengths. In addition, the spectral distribution of a given bulb over time is shown to shift in unpredictable ways, including decreased flux at key wavelengths, but also shifting peak maxima. Finally, we present a method to normalize photocatalysis kinetic data by the incident light flux so that research progress can be leveraged across the community. These outcomes provide the tools needed for consistent optical characterization in photochemical research and will aid the transition of light-activated research towards improved reproducibility and enhanced technology transfer to applications.

Leveraging chemical actinometry and optical radiometry to reduce uncertainty in photochemical research

256th National Meeting (2018)

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