Electrosynthesis of self-standing single crystalline Te nanostructures in an ionic liquid
Abstract
Tellurium and its alloys are used in many applications such as photoconductors, piezoelectric devices, thermoelectric generators and coolers [1]. For this thermoelectric application, the transport properties (thermal conductivity, electrical resistivity, Seebeck coefficient) of tellurium and its compounds can be improved by nanostructuring [2]. At the nanoscale, one-dimensional core-shell structures could present interesting properties like a low thermal conductivity and a high Seebeck coefficient. Electrochemical deposition is a low cost technique widely used in literature for the synthesis of nanowires. But nanostructuring is generally made by template assisted electrodeposition which presents many drawbacks for synthesis of core-shell structures.
The aim of this work is to obtain, without template, one-dimensional self-standing tellurium nanostructures on which a shell could easily be deposited. For this purpose, Room-Temperature Ionic Liquids (RTILs) appear as promising solvents. Indeed, it has been highlighted that they can act as stabilizing agents for nanoparticles and nanostructured films synthesis [3]. In a previous work, we showed that free standing single cristalline Te nanowires can be obtained at moderate temperature (60-120°C) in a mixture of piperidinium-based ionic liquids [4]. Here we present a systematic study of the influence of synthesis parameters on the deposits morphology, investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The obtained results show that it’s possible to control the shape (nanowires, nanotubes) and the size (diameter, length) of the deposited nanostructures by varying the deposits growth rate. This can be made by moduling the applied potential and the electroactive species concentration.