Singlet oxygen quantum yields (Φd) in water using beetroot extract and an array of LEDs

Journal of the Brazilian Chemical Society

Juliano A. Bonacin²  Fábio M. Engelmann²  Divinomar Severino¹  Henrique E. Toma¹  Mauricio S. Baptista¹ 

[1] ,Universidade de São Paulo Instituto de Química São Paulo SP ,Brazil

关键词: beetroot;    betacyanin;    quantum yield;    singlet oxygen;    phenothiazines;    photodynamic therapy;   

DOI  :  10.1590/S0103-50532009000100006

来源: SciELO

【 摘 要 】

It is proposed a simple and inexpensive strategy to determine singlet oxygen (¹O2) quantum yields (ΦΔ) of photosensitizers (PS) in water using beetroot extract containing betacyanin (Bc) and a set of light emitting diodes (LEDs) for excitation. Bc, a cationic natural dye, was obtained by flash chromatography purification from the red beet extract (Beta vulgaris) and employed as a convenient probe for ¹O2 detection. Solutions of Bc and PS were illuminated with an array of LEDs adapted in the cuvette compartment of a commercial spectrophotometer, and the decrease in Bc absorbance was followed as a function of time. Bc photobleaching decreased in de-aerated solution and increased in D2O, indicating the involvement of ¹O2. The observed photobleaching rate constant (k obs) was proportional to the LED intensity, concentration and ΦΔ of the PS. By keeping the light source constant we could estimate the overlap integral (R) between the LED emission and PS absorbance for different PS concentrations. The slope of R versus k obs is the value of the photobleaching rate constant (k), which was shown to be proportional to ΦΔ. Values of ΦΔ obtained by this method were compared with those obtained by measuring NIR (near infrared) emission for a series phenothiazine dyes.

【 授权许可】

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