Surface chemistry altering electronic behaviour of liquid metal-derived tin oxide nanosheets.

Possessing excellent electronic properties and high chemical stability, semiconducting n-type two-dimensional (2D) tin dioxide (SnO) nanosheets have been featured in sensing and electrocatalysis applications recently. Derived from non-layered crystal structures, 2D SnO has abundant unsaturated dangling bonds existing at the surface, providing interfacial activity. How the surface chemistry alters the electronic properties of 2D SnO nanomaterials remains unexplored. In this study, we synthesised ultra-thin 2D SnO nanosheets using a liquid metal (LM) touch printing technique and investigated experimentally and theoretically how the interactions of organic solvents composed of alkyl and hydroxyl groups with the surface of LM-derived 2D SnO modulate the electronic properties. It was found that alkane solvents can physically absorb onto the SnO surface with no impact on the material conductivity. Alcohol-based solvents on the other hand interact with the SnO surface chemical absorptions primarily, in which oxygen atoms of hydroxyl groups in the alcohols form bonds with the surface atoms of SnO. The binding stability is determined by the length and configuration of the hydrocarbon chain in alcohols. As representative long-chain alcohols, 1-octanol and 1-pentanol attach onto the SnO surface strongly, lowering the binding energy of Sn and reducing the electron transfer ability of SnO nanosheets. Consequently, the electronic properties, conductivity and electronic mobility of SnO nanosheet-based electronic devices are decreased significantly.