Solution-Based Straight and Branched CdTe Nanowires

Abstract

The synthesis, characterization, and optical properties of high quality straight and branched CdTe nanowires (NWs) are described. A solution-based (solution-liquid-solid) approach is used to synthesize the NWs by employing a low melting bimetallic nanoparticle catalyst to induce one-dimensional (1D) growth. This leverages advances in the development of high quality colloidal quantum dots (QDs) with emerging techniques for manufacturing 1D nanomaterials. Resulting straight and branched CdTe NWs have diameters below twice the corresponding bulk exciton Bohr radius and, as a consequence, exhibit confinement effects in their linear absorption. Size distributions range from 15% to 20%, with NW lengths commonly exceeding 10 µm. Intrawire diameter variations are on the order of 5%. High-resolution transmission electron microscopy (TEM) images reveal that the wires are crystalline and grow exclusively along the <111> and <0001> directions of the corresponding zincblende and wurtzite phases. Branched NW morphologies include tripod, v-shape, y-shape, "merge-y", and "higher-order" structures. Preliminary optical studies of both straight and branched NWs are reported, including estimates of the absorption cross section and electrochemical band offsets. Such NWs open up avenues for further investigating the effects of size and shape on the optical/electrical properties of 1D nanomaterials and also have potential uses as active elements in photovoltaics and/or polarization sensitive photodetectors.

Ultrathin Nanowires—A Materials Chemistry Perspective

“…[49] In this case, the nanowires were not stuck to a surface, as in the case of VLS methods, but were instead dispersed in the fluid phase. By using Bi/Au alloy colloidal nanocrystals, Kuno's group demonstrated the synthesis of veryhigh-quality ultrathin CdSe [50] and CdTe [51] nanowires in solution at relatively low temperatures.…”

Facile Synthesis of Straight and Branched CdTe Nanowires Using CdO as Precursor

“…2 In a typical preparation, TOPO (6 g, 0.028 mol), TOP (5 ml, 0.026 mol), TBP-Te (25 mol Te), and DOPA (0.071 g, 0.32 mmol) are added to a three-necked flask in a glovebox. The flask is then taken out and connected to a Schlenk line immediately.…”

“…1 CdTe is an important semiconductor material with the near-infrared band gap and large bulk absorption coefficient. CdTe NWs have attracted great research interests [2][3][4][5][6][7][8][9][10][11] since its inception. 12 With the discovery of solution-liquid-solid (SLS) 13 process for NWs growth, a number of high quality solution-based semiconductor NWs were synthesized using low melting catalyst nanoparticles at low temperatures (T<400 C).…”

“…However, it is very difficult to prepare CdTe NWs via the SLS approach due to the incompatibility of Te precursors (e.g., TOP-Te, TBP-Te and TeCl 4 with Bi catalyst as an injecting mixture. In 2006, Kuno and co-workers 2 firstly synthesized straight and branched CdTe NWs using dimethylcadmium (Cd(CH 3 2 as Cd precursor via SLS growth. However, Cd(CH 3 2 is extremely toxic, pyrophoric, expensive, unstable at room temperature, and explosive at elevated temperatures, 14 which limits the development of CdTe NWs.…”

“…[3][4][5] Herein we demonstrate a facile approach to both straight and branched CdTe NWs of high quality via a safe and economical procedure, in which CdO was used as Cd precursor and the amount of TOPO/TOP solvent mixture employed in each synthesis was largely reduced in comparison with the reported synthetic strategies. 2 The clear yellow stock solution of TBP-Te (0.04 M) was made by dissolving Te shot (0.32 g 2.5 mmol) in TBP (60 ml 20 mmol).…”