Sub-20 nm-Fe3O4 square and circular nanoplates: synthesis and facet-dependent magnetic and electrochemical properties.

We present an effective method to synthesize 15 nm magnetite nanocrystals with the morphology of square and circular nanoplates, which expose (001) facet and (111) facet, respectively. The magnetic property and electrochemical behavior towards As(III) exhibit strong facet-dependent characteristics. Theoretical calculations confirm the facet-dependent characteristics and provide the corresponding explanations.

Investigation of the facet-dependent performance of α-Fe2O3 nanocrystals for heavy metal determination by stripping voltammetry.

We find for the first time that the electrochemical performances of the α-Fe2O3 nanostructures depend on their exposed facets. Density functional theory calculations are carried out to better and scientifically understand the effect of different exposed facets at the atomic-scale level.

Facet-dependent electrochemical properties of Co3O4 nanocrystals toward heavy metal ions.

We revealed an interesting facet-dependent electrochemical behavior toward heavy metal ions (HMIs) based on their adsorption behaviors. The (111) facet of Co3O4 nanoplates has better electrochemical sensing performance than that of the (001) facet of Co3O4 nanocubes. Adsorption measurements and density-functional theory (DFT) calculations reveals that adsorption of HMIs is responsible for the difference of electrochemical properties. Our combined experimental and theoretical studies provide a solid hint to explain the mechanism of electrochemical detection of HMIs using nanoscale metal oxides. Furthermore, this study not only suggests a promising new strategy for designing high performance electrochemical sensing interface through the selective synthesis of nanoscale materials exposed with different well-defined facets, but also provides a deep understanding for a more sensitive and selective electroanalysis at nanomaterials modified electrodes.

Homochiral xanthine quintet networks self-assembled on Au(111) surfaces.

Xanthine molecule is an intermediate in nucleic acid degradation from the deamination of guanine and is also a compound present in the ancient solar system that is found in high concentrations in extraterrestrial meteorites. The self-assembly of xanthine molecules on inorganic surfaces is therefore of interest for the study of biochemical processes, and it may also be relevant to the fundamental understanding of prebiotic biosynthesis. Using a combination of high-resolution scanning tunneling microscopy (STM) and density functional theory (DFT) calculations, two new homochiral xanthine structures have been found on Au(111) under ultrahigh vacuum conditions. Xanthine molecules are found to be self-assembled into two extended homochiral networks tiled by two types of di-pentamer units and stabilized by intermolecular double hydrogen bonding. Our findings indicate that the deamination of guanine into xanthine leads to a very different base pairing potential and the chemical properties of the base which may be of relevance to the function of the cell and potential development of human diseases. Moreover, the adsorption of xanthine molecules on inorganic surfaces leading to homochiral assemblies may be of interest for the fundamental understanding of the emerged chirality at early stages of life.