Methodology for determining singlet oxygen quantum yield in dimethyl sulfoxide.

Area of Science:

• Photochemistry
• Chemical Kinetics
• Spectroscopy

Background:

• Singlet oxygen (¹O₂) is a crucial reactive oxygen species with broad applications.
• The singlet oxygen quantum yield (ФΔ) quantifies ¹O₂ generation efficiency by dyes.
• Existing ФΔ measurement methods utilize ¹O₂ photoluminescence or reactivity.

Purpose of the Study:

• To investigate the applicability of a previously proposed method for determining ФΔ based on the reaction between Dimethyl Sulfoxide (DMSO) and ¹O₂.
• To identify and characterize the reaction termination point in the DMSO-¹O₂ reaction.
• To establish robust methodologies for accurate ФΔ determination in DMSO.

Main Methods:

• Monitoring the absorption spectrum change of DMSO upon ¹O₂ generation.
• Investigating the effect of excitation power density on the DMSO-¹O₂ reaction.
• Analyzing the relative degradation rate of a chemical probe in the presence of ¹O₂ and DMSO.

Main Results:

• The DMSO-¹O₂ reaction exhibits a termination point, indicated by spectral absorption reaching a plateau.
• The time to reach saturation is inversely proportional to excitation power density, necessitating measurements before this point.
• The chemical probe method shows an inflection point; measurements should be taken after this point for accurate ФΔ determination in DMSO.

Conclusions:

• Accurate ФΔ determination in DMSO necessitates selecting appropriate time windows specific to the measurement method.
• The study provides a robust methodology for reliable ФΔ measurements in DMSO.
• Understanding reaction termination is key for optimizing ¹O₂ generation efficiency studies.