Effect Of Water Stable Crystalline Nanoparticle NC₆₀ On The Production Of Reactive Oxygen Species

With its increasing production and utilization, C₆₀ would be inevitably released into the environment, and the crystalline aggregates of nanoscale C₆₀ colloid suspensions(usually referred to as n C₆₀) ranging from a few tens to several hundred nanometers could be formed unintentionally upon release of C₆₀ into natural water. Recently, the fate of n C₆₀ as well as its transportation behavior and ecological effects have caused great concerns. According to the previous research, reactive oxygen species（ROS） are considered as key factors and have close relationship with n C₆₀’s adverse effect. However, the question of that whether n C₆₀ produces or quenches ROS is still no answer. In views of the insufficient results about the interaction effect of n C₆₀ and ROS, we conducted experiments to study the formation mechanism of n C₆₀ in water, and the relation of n C₆₀’s characteristics and its ROS production ability; We established the ROS-related reaction to investigate the effect of n C₆₀; Lastly we did research on the removal and acute toxicity of n C₆₀, and discussed the relation of ROS production and n C₆₀’s residual toxicity. The findings of this research are listed as follows:1. The formation of n C₆₀ in water is followed three-step principle, and water constituents have great effect on the formation process and characteristics of n C₆₀.Asymmetric Flow Field Flow Fractionation（AF4） is used to investigate the changes on size distribution in the n C₆₀ formation process, we found that during this process, C₆₀ is firstly interact with H2 O, and large aggregates are formed, and then are dispersed into several small size particles, that called n C₆₀ nanoparticles. The increasing of H+ and ionic strength make it difficult to form n C₆₀, while NOM, surfactants and solid suspension could promote the n C₆₀ formation process.2. The size distribution and dispersion status are key factors to affect the production of ROS by n C₆₀.The compact structure of n C₆₀ could not release ROS unless n C₆₀ are dispersed by TX100, O2·- and 1O2 are detected in n C₆₀/TX100 solution. With the increasing ofTX100 concentration, the number of small particles in n C₆₀ solution is increased, and the yield of ROS is also increased, these results prove that the dispersion status has a close relation with n C₆₀’s ROS production ability.3. n C₆₀ could interact with ROS by different manners, such as catalytical, quenching, inhibited effect.n C₆₀ could catalyze H₂O₂ to transform into the pair of HO2·/O2·- in the dark,because n C₆₀ is a good electron mediator to enhance the electron transfer process, leading to the yield of HO2·/O2·- increase;n C₆₀ could react with·OH,but the reaction is diffusion limited; n C₆₀ disrupts the O2·- generation process, because n C₆₀ seizes elections and gets the priority to adsorb the electrons, leading to the generation of O2·-decrease.4. ROS generation is closely related with n C₆₀’s residual toxicity.n C₆₀ could be removed by coagulation-sedimentation-filtration process, but surfactant, NOM and SS greatly decrease the removal rate of n C₆₀, leading to that the n C₆₀ residues are detected in filtrates. Microtox test results showed that TX100 could evoke phototoxicity of n C₆₀ due to ROS generation under UV irradiation.The findings suggested that ROS is closely related with the fate of n C₆₀, the detection and identification of ROS should be paid great attention when assessing n C₆₀’s ecological effect. Results of this research provide new ideas to research the mechanism of n C₆₀’s toxicity.