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The cation pump activity of the ocular lens was damaged by exposure to light in the presence of riboflavin phosphate. The intensit of ight was similar to that used for reading purposes. The observed light-induced damage was due to superoxide or its derivatives, the superoxide being produced photochemically. Such damage was attenuated by vitamin C in amounts comparable to that in the aqueous humor. Thus, a new role for the high ascorbate level present in the anterior chamber fluid and the lens has been suggested. Ascorbate in other tissues also might have this novel physiological function of protecting against damage due to superoxide and its derivatives produced during normal cellular oxidation. The concentration of ascorbic acid (vitamin C) in the aqueous humor of man, monkey, and many other animals is one of the highest among the various body fluids (1). The prevalence of this high level of ascorbate has been attributed to the ability of the ciliary epithelium to transport this compound actively from the plasma to the posterior chamber through the blood aqueous barrier (2). For reasons undefined at the present time, the concentration of ascorbate is also high in tissues surrounding the aqueous humor-namely, the cornea and the lens. The concentration in the latter tissue in many instances is second only to that in adrenals (1). Although the importance of ascorbic acid in hydroxylation reactions is known in many tissues, the relevance of a high ascorbate level in the aqueous humor and the lens is not precisely known, although it has been suggested that photochemical oxidation of ascorbic acid in the anterior chamber serves to provide hydrogen peroxide to the lens. The peroxide, in turn, may regulate the tissue hexose monophosphate shunt through the following series of interlinked reactions

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CeO2 nanoparticles (NPs) with average particle size of ∼17 nm were grown on graphene sheets by simply mixing cerium chloride as the Ce precursor with graphene oxide (GO) in distilled water and the simultaneous reduction of GO to reduced graphene oxide (rGO), followed by a one-step hydrothermal treatment at 150 °C. A unique blue to green tuneable luminescence was observed as a function of the excitation wavelength. With this method, significant applications of rGO-CeO2 nanocomposites in many optical devices could be realized. The photocatalytic activity of the as-synthesized CeO2 and rGO-CeO2 nanocomposite was investigated by monitoring the degradation of methylene blue (MB) dye under direct sunlight irradiation. The rGO-CeO2 nanocomposite exhibited excellent photocatalytic activity compared to CeO2 NPs by degrading 90% of the MB dye in 10 min irradiation under sunlight. This property of rGO-CeO2 nanocomposites was ascribed to the significant suppression of the recombination rate of photo-generated electron-hole pairs due to charge transfer between rGO sheets and CeO2 NPs and the smaller optical band-gap in the rGO-CeO2 nanocomposite.