STEADY‐STATE NEAR‐INFRARED DETECTION OF SINGLET MOLECULAR OXYGEN: A STERN‐VOLMER QUENCHING EXPERIMENT WITH SODIUM AZIDE

Abstract— A sensitive near‐infrared detection system incorporating improvements to existing methodologies has been used to characterize the sodium azide quenching of the steady‐state luminescence of singlet molecular oxygen at 1270 nm. Stern‐Volmer plots which were linear up to 80% quenching of the 1O2 generated by rose bengal and eosin Y yielded a rate constant of 5.8 ± 0.1 times 108M−1 s−1 for the quenching of 1O2 in water, while the rate constants obtained in deuterium oxide with the same sensitizers were 6.28 times 108M−1 s−1 and 6.91 times 108M−1 s−1 respectively. A flow system minimized the effects of photobleaching of the rose bengal. With a mercury arc light source, the instrument can be used in photosensitization experiments to detect low levels of 1O2 production in aqueous media.

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