Surface Understanding at Atomic Scale Guides the Rational Design of CeO2 Nanoisozymes for Biosensing
Yung-Kang Peng
Department of Chemistry, City University of Hong Kong, Kowloon Tong, Hong Kong SAR.
E-mail : ykpeng@cityu.edu.hk
Abstract
Recently, ceria (CeO2) nanoparticle has been shown a potential artificial enzyme in mimicking natural enzymes such as phosphatase (Fig. 1a) and peroxidase (Fig. 1b). However, the origin behind its enzyme-mimetic property is still unclear nowadays. Different interpretation even disagreement regarding the role of surface Ce4+/Ce3+ ratio can be often found in literature. From our point of view, this is due to reactant molecules interact only with Ce cations on topmost surface while XPS collects target information few nanometers from surface. Herein, CeO2 shapes (Fig. 1c) with terminal (111), (110), (100) facet were tested in these two reactions. Octahedron (111) shows the highest activity in phosphatase mimicking (Fig. 1d) among three shapes while it is nearly inactive in mimicking peroxidase (Fig. 1e). In stark contrast, cube is inert in the former reaction but very active in the latter one. No apparent difference in their XPS spectra as expected (Fig. 1f). Instead, using TMPO-31P NMR for surface investigation (Fig. 1g), we have successfully correlated the observed activity in these two reactions with surface Ce electron density in the order of cube (100) > rod (110) > octahedron (111). The excellent peroxidase-like activity of cube was further combined with glucose oxidase/redox dye for glucose/glutathione detection.
Figure 1.
(a) Phosphatase- & (b) peroxidase-mimicking reactions over (c) CeO2 shapes. (d) and (e) are corresponding results of (a) and (b). (f) XPS (g) trimethylphosphine oxide (TMPO)-31P NMR spectra of CeO2 shapes.
Short Bio
Dr. Will Yung-Kang Peng obtained his bachelor’s degree in Chemistry in 2009 from National Chung Cheng University (Taiwan) and graduated as a Master of Science in 2011 from National Taiwan University. After a year of military service (R.O.C.) and research assistant, he started PhD study in 2013 at Wolfson Catalysis Centre of Inorganic Chemistry Laboratory at University of Oxford (UK) under the supervision of Prof. Dr. S. C. Edman Tsang, for which he received a Clarendon scholarship from University of Oxford (top 3% Oxford admitted graduates of 2013 year). He obtained his PhD degree in 2017 and stayed in the same group for postdoc. During his stay in Oxford, he has developed a new route to study catalysts’ surface which has led to publications in some respectable journals such as Nature Catalysis, Nature Communication, JACS, Chemical Science, Materials Today etc. He joined the City University of Hong Kong as an Assistant Professor in May 2018. His current research interest is working on the understanding of material surface for the rational design of hetero(photo) catalysts for catalytic nanomedicine and biosensing.