( Introduction ...)Singlet Oxygen measurement

Introduction
The chemistry, spectroscopy, and reactivity of singlet oxygen, ¹O₂, is of considerable interest in environmental applications, novel organic syntheses and mechanisms of photo-oxygenation.¹ Recently, research has been directed towards understanding the biological effects of ¹O₂, such as the photodynamic destruction of cells in the presence of a dye, oxygen, and light.

An understanding of the mechanisms that produce ¹O₂ is required for the synthesis of new anti-cancer agents used in photodynamic therapy. The spectroscopic properties of the dye and ¹O₂ may be characterized using fluorescence spectroscopy. The emission of ¹O₂ is in the near-IR, around 1280 nm. The SPEX FLUOROLOGsystem easily detects this signal, with the appropriate emission gratings and a suitable detector. Most multi-alkali photomultiplier tubes, such as the R928P, respond to wavelengths up to 800 nm. InGaAs detectors extend this range to nearly 1700 nm.

The SPEX DSS-IGA020L InGaAs detector is an excellent choice for ¹O₂ measurements. It operates at liquid-nitrogen temperature to minimize thermal noise. Usable from 8001700 nm, the InGaAs detector provides a smooth overlap with the standard R928P photomultiplier tube.

Experiment and Results
As an example of ¹O₂ detection, generated using a transition-metal complex, a solution of tris2-2-bipyridine ruthenium(II) chloride, [Ru(bpy)₃]Cl₂, in D₂O, was used as a generator of ¹O₂.² The optical density of the solution was 0.3 A above the D₂O baseline at 450 nm. To enhance the yield of ¹O₂, the solution was saturated with O₂
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