One-dimensional nanostructures of trigonal tellurium with various morphologies can be synthesized using a solution-phase approach

Abstract

This article describes a solution-phase, self-seeding approach to the large-scale synthesis of one-dimensional (1D) nanostructures of trigonal tellurium (t-Te) with diameters ranging from 50 to hundreds of nanometers, and lengths up to tens of micrometers. These highly anisotropic nanostructures were formed through the reduction of orthotelluric acid (or tellurium dioxide) by hydrazine at various refluxing temperatures. Nuclei formed in the reduction process had a strong tendency to grow along the c-axis due to the inherently anisotropic structure of t-Te. Depending on the solvent and refluxing temperature, the growth of t-Te nanostructures was found to follow two distinct paths. When the reaction was refluxed in water and at temperatures below 100 °C, the initial reduction products were a mixture of nanocrystallites of t-Te and spherical colloids of amorphous tellurium (a-Te). When this mixture was aged at room temperature, the a-Te colloids slowly dissolved into the solution and grew into nanowires on the nanocrystallites of t-Te. When the reaction was carried out in pure ethylene glycol (or mixtures with water) and refluxed at temperatures above 100 °C, the 1D nanostructures of t-Te were directly formed in the reduction process. The exact morphology of these anisotropic nanostructures was mainly controlled by the refluxing temperature (Tr); typical examples include spines (Tr < 100 °C), filaments (Tr = 100–160 °C), needles (Tr = 160–180 °C), and tubular structures (Tr > 180 °C). These uniform, relatively monodispersed 1D nanostructures could form stable dispersions in ethylene glycol or water, and be used as the building blocks or templates to generate more complex nanostructured materials.