ABSTRACT
The modification of Au nanoparticles can improve the antioxidant activity of CeO2, however, nano Au/CeO2has also met some problems such as low atomic utilization, the limit of reaction conditions, and high cost. Au single atom catalysts can well solve the above-mentioned problems, but there are some contradictory results about the activity of single atom Au1/CeO2and nano Au/CeO2. Here, we synthesized rod-like Au single atom Au/CeO2(0.4% Au1/CeO2) and nano Au/CeO2(1% Au/CeO2, 2% Au/CeO2and 4% Au/CeO2), and their antioxidant activity from strong to weak is 0.4% Au1/CeO2, 1% Au/CeO2, 2% Au/CeO2and 4% Au/CeO2, respectively. The higher antioxidant activity of 0.4% Au1/CeO2is mainly due to the high Au atomic utilization ratio and the stronger charge transfer between Au single atoms and CeO2, resulting in the higher content of Ce3+. Due to the coexistence of Au single atoms and Au NPs in 2% Au/CeO2, the antioxidant activity 2% Au/CeO2is higher than that of 4% Au/CeO2. And the enhancement effect of Au single atoms was not affected by the concentration of ·OH and material concentration. These results can promote the understanding of the antioxidant activity of 0.4% Au1/CeO2and promote its application.
ABSTRACT
Gold nanoparticle (AuNP) modification shows great advantages in improving the antioxidant activity of nanoCeO2. However, the improved effect of AuNP modification becomes smaller and even results in the decrease of antioxidant ability due to severe aggregation with increasing nanomaterial concentration. Additionally, the effects of photo-properties of AuNPs on the antioxidant activity of nanoCeO2 have not been studied. In response to these problems, core-shell-shaped Au@CeO2 was synthesized which took Au nanorods (AuNRs) as carriers and had a layer of CeO2 NP coating. The antioxidant activity of Au@CeO2 was evaluated by the UV-vis method in the methyl violet-Fenton system. Results showed that AuNRs could improve the antioxidant activity of nanoCeO2 due to the increase in the amount of Ce3+ on the surface of nanoCeO2, and the enhancing effect remained across the whole experimental concentration range due to the good dispersibility of AuNRs. Additionally, a further increase in the antioxidant ability of Au@CeO2 was found with 5 min visible light irradiation, and continuous irradiation during a 25 min time reaction, which resulted in more obvious enhanced antioxidant ability. This phenomenon was attributed to the localized surface plasmon resonance of AuNRs triggered by photons which induced charge transfer from AuNRs to nanoCeO2, thus making the cyclic transformation between Ce3+ and Ce4+ easier.
ABSTRACT
Many nanomaterials have been reported to have enzyme-like activities and are considered as nanozymes. As a multifunctional nanozyme, nanoceria has received much attention due to the dual oxidation states of Ce3+/Ce4+ which facilitate redox reactions at the particle surface. Despite the advantages of nanozymes, their limited activity and lack of enzyme specificity are still problems to be resolved. DNA is used to modulate the oxidase activity of nanoceria because it has recently become an important molecule in bionanotechnology. However, the current research on the effect of DNA on the oxidase mimetic activity of nanoceria is contradictory. It has been discovered that nanoceria used in recent works are different, including in particle size, doping and concentration, and these differences may affect the interaction between DNA and nanoceria, and then affect the oxidase mimetic activity of nanoceria. Hence, it is important to clarify the factors that affect the interaction between DNA with nanoceria. In this work, the interactions between DNA and nanoceria with three different morphologies (nanoparticles, nanocubes, and nanorods) have been investigated. Experimental results show that DNA has different influences on the oxidase mimetic activity of nanoceria with different morphologies. The oxidase mimetic activity of CeO2 nanoparticles and nanocubes increased, but that of CeO2 nanorods decreased, after DNA modification. The mechanism of these experimental results has been explored, and it has been found that it is the interaction between cerium and the phosphate backbone of DNA that changes with the different morphologies, resulting in the varying effect of DNA on the oxidase mimetic activity of nanoceria. These results may provide a better understanding of the effect of DNA on the oxidase mimetic activity of nanoceria and promote the applications of nanoceria.
