Porous CeO2 nanozyme with visible-light-enhanced catalase-mimicking activities by ligand-to-metal charge transfer

Nanozymes are promising synthetic alternatives to natural enzymes owing to their unique physical and chemical properties, but improving their thermocatalytic activity often involves complex procedures. This study introduces a light-induced approach to enhance the catalytic activity of facilely prepared porous cerium oxide ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>P</mml:mi> <mml:mo>-</mml:mo> <mml:msub><mml:mtext>CeO</mml:mtext> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:math> ) nanozymes. Under visible light irradiation, the catalytic efficiency <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>(</mml:mo> <mml:mrow><mml:msub><mml:mi>k</mml:mi> <mml:mrow><mml:mi>c</mml:mi> <mml:mi>a</mml:mi> <mml:mi>t</mml:mi></mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msub><mml:mi>K</mml:mi> <mml:mi>m</mml:mi></mml:msub> </mml:mrow> <mml:mo>)</mml:mo></mml:mrow> </mml:math> of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>P</mml:mi> <mml:mo>-</mml:mo> <mml:msub><mml:mtext>CeO</mml:mtext> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:math> more than doubles compared to its thermocatalytic efficiency. Spectroscopic analyses reveal that this enhancement stems from a ligand-to-metal charge transfer (LMCT) band, arising from peroxide species adsorbed on the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>P</mml:mi> <mml:mo>-</mml:mo> <mml:msub><mml:mtext>CeO</mml:mtext> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:math> surface. As a practical demonstration, P-CeO2 exhibits visible-light enhanced scavenging of reactive oxygen species (ROS) <i>in vitro</i>. Overall, this study provides new mechanistic insights of using LMCT-induced visible light catalysis for the improvement of catalytic activity of light-responsive nanozymes.