Eye Melanin Free Radical Kinetics and Mechanism in Relation to the Roginsky—Zeldovich (or Elovich) Equation and the Adsorption of Oxygen by Semiconductors

Abstract

Eye melanin free radical decay was previously shown to conform to an equation derived from a postulate that the rate‐limiting step was electron conduction across the liquid—solid interface at the surface of the melanin particle. It is shown here that this equation closely approximates the Roginsky—Zeldovich (or Elovich) equation for oxygen adsorption on inorganic semiconductor solids, which provides two convenient graphical criteria for this type of kinetics. Because the behavior of charge carriers is essentially similar in liquids and solids, it is believed that this derivation of the Roginsky—Zeldovich (or Elovich) equation is also applicable to phenomena at solid—solid interfaces in inorganic semiconductors. The similarity between the kinetics of melanin free radicals and semiconductor oxygen adsorption, together with previous experimental data indicating a dependence of melanin radical concentration on oxygen concentration, suggests that the eye melanin free radical process may involve oxygen adsorption with electron transfer across the surface of the melanin particle.