Effect of UV radiation on the structure of graphene oxide in water and its impact on cytotoxicity and As(III) adsorption

TL;DR

This study investigates how UV radiation alters graphene oxide's structure and stability in water, affecting its arsenic adsorption capacity and cytotoxicity, with implications for environmental safety and contaminant transport.

Contribution

It demonstrates UV-induced structural changes in graphene oxide and their effects on arsenic adsorption and cytotoxicity, providing new insights into environmental behavior of GO.

Findings

UV radiation reduces GO functional groups and zeta potential.

Arsenic adsorption decreases initially but recovers after prolonged UV exposure.

GO remains highly cytotoxic despite structural degradation.

Abstract

Graphene oxide (GO) is widely used in different applications, however once release into the environment it can change its structure and affect the transport of important contaminants such as arsenic. In this work we show that UV radiation, even in the range of 28-74 uW/cm2 of irradiance up to 120 h of exposure, can induce important changes in the structure of graphene oxide, by eliminating -OH and C=O functional groups. This reduction affected the stability of graphene oxide in water by decreasing its zeta potential from 41 to 37 mV with the increase of the exposure time. Our results showed that after 24 h of UV exposure, As(III) adsorption capacity decreased from 5 mg/g to 4.7 mg/g, however after 48 h of irradiation the adsorption increased with time, reaching 5.1 mg/g at 120 h under 74 uW/cm2 of irradiation. Computer modelling showed that even a degraded GO structure can have an interaction energy of 53 kcal/mol with H3AsO3. Furthermore, we observed that despite clear changes in surface composition and particle size, the reduction of graphene oxide maintained a high degree of cytotoxicity since cell viability decreased to 60% with a 50 ug/ml dose; except for the sample irradiated at 74 uW/cm2 for five days, which showed 20% with the same concentration.