Nanomaterials are usually used to electrochemically detect trace heavy metal ions with high sensitivity. At present, numerous studies have reported that the noble nano metal and the conductive carbon nanomaterials are used as the electrochemical modifier to detect heavy metal ions. Researchers usually attribute the enhanced electrochemical signal to the high specific surface area of nanomaterials. However, the essence of the enhanced electrochemical response using nanomaterials, especially the design of electrochemical interface with high sensitivity from atomic scale is still scarcely reported.
In the past three years, the research group led by Prof. Jinhuai Liu and Prof. Xingjiu Huang in Institute of Intelligent Machines (IIM), Chinese Academy of Sciences, has utilized non-noble nano metal- nanoscale metal oxides to achieve electrochemical determination of heavy metal ions in water with ultra-high sensitivity. Moreover, the correlation between the selective electrochemical behavior of nanomaterials and their adsorption performance was proposed.（Anal. Chem., 2013, 85, 2673; Anal. Chem., 2013, 85, 3984; Small, 2013, 9, 2233; Electrochem. Commun., 2013, 34, 270; Electrochem. Commun. 2013, 30, 59; Analyst, 2013, 138, 1812; Analyst, 2012, 137, 2183; Chem. Commun., 2011, 47, 11062）.
Based on their previous studies, researchers from IIM cooperated with Prof. Qunxiang Li from University of Science and Technology of China (USTC) in combining electroanalysis and theoretical calculations effectively. And the idea of designing electrochemical interface towards heavy metal ions from the aspect of crystal facet of nanoscale metal oxides at atomic scale was proposed. Researchers found that the sensitivity of the (111) facet of Co3O4 nanocrystals toward heavy metal ions was higher than that of the (001) facet.
The results of adsorption experiments showed that the (111) facet of Co3O4 nanocrystals exhibit higher adsorption capacity toward heavy metal ions than the (001) facet. The theoretical calculation results demonstrated that compared with the (001) facet, the (111) facet of Co3O4 nanocrystals showed higher adsorption energy, more adsorption sites and lower diffusion barrier of ions on its surface. The reviewers said “The results are interesting and quite nicely supported by DFT calculations”. The research not only proposed the new idea of designing electrochemical interface with high sensitivity from the aspect of crystal facet at atomic scale but also revealed the essence of the enhanced electrochemical response by nanomaterials. The related result has been accepted for publication in Scientific Reports (Sci. Rep. 3, 2886; DOI: 10.1038/srep02886 (2013)).
