Structural Characterization of Oleylamine- and Dodecanethiol-Capped Ge_1–xSn_x Alloy Nanocrystals

Abstract

Microwave-assisted heating methods have been used to synthesize oleylamine-capped Ge1–x Sn x nanocrystals. By varying the reaction temperature while keeping the Ge and Sn precursor concentrations constant, Ge1–x Sn x nanocrystals with Sn compositions of 13.9 ± 2.1% over the 3.8–9.3 nm size range have been achieved. The oleylamine-capping ligand is replaced with dodecanethiol without affecting the Sn composition of the nanocrystals. The Sn composition is obtained from employing Vegard’s law on the lattice parameters obtained from the Rietveld refinement of powder X-ray diffraction patterns. Scanning transmission electron microscopy provides particle size and morphology. Extended X-ray absorption fine structure at the Sn and Ge edges of the dodecanethiol-capped nanocrystals confirms the solid solution, which is further supported by Raman spectroscopy. 1H NMR and FTIR are used to characterize the surface ligand capping before and after ligand exchange. Tauc plot analysis of UV–vis–NIR spectra to determine the indirect optical band gap for oleylamine- and dodecanethiol-capped Ge1–x Sn x nanocrystals is reported. This work demonstrates the effects of synthesis temperature on the particle size, composition, and structure of Ge1–x Sn x nanocrystals.

Phase‐Controlled Pd‐Sn Nanostructures via Co‐Digestive Ripening: Catalytic Performance for Base‐Free Oxidation of Benzyl Alcohol

“…Trioctylphosphine is a high‐boiling point surfactant with a long alkyl chain that imparts good steric hindrance leading to the good dispersion of nanoparticles. It is anticipated that OLA gets displaced by TOP partially or completely [64] . This was evidenced by 31 P NMR spectroscopy for one of the OLA‐TOP capped Pd−Sn samples.…”

“…It is anticipated that OLA gets displaced by TOP partially or completely. [64] This was evidenced by 31 P NMR spectroscopy for one of the OLA-TOP capped PdÀ Sn samples. A singlet in the 31 P{ 1 H} NMR spectrum at À 32.2 ppm for the neat TOP was found to be shifted downfield to À 19.5 ppm for the Pd 3 Sn-OLA-TOP sample (Figure S10).…”

Strong Metal–Support Interaction over PtPdCu/Al2O3 toward Hydrogenation of Nitrobenzene

“…Typically the synthetic colloidal nanoparticles are capped with surfactants as a stabilizer, thus, these nanoparticles may not be directly used as catalysts since the presence of ligands in the end product is detrimental for adsorption and activation of reactants and also weakens metal–support interactions. , It is therefore necessary to remove surface capping agents to expose active sites and modulate metal–support interactions between nanoparticles and a substrate through post-treatment. Various methods have been applied to remove surfactants, including hot solution washing, acid washing, UV-ozone irradiation, annealing in gas, , and ligand exchange, , but all these methods have shown certain limitations or negative influences on microstructure and catalytic performance of the supported catalysts . Ligand exchange, which displaces long-chain organics by small molecules with much lower boiling point and mass, has also been used as one of the mildest methods for cleaning capping agents with little influences to the synthesized nanoparticles .…”

Green Synthesis of Ge1−xSnx Alloy Nanoparticles for Optoelectronic Applications

“…Recently, various Ge-Sn materials, including alloy nanocrystals [6], quantum dots [7], nanowires [8], and core/shell particles [9] have been reported. Different strategies such as pulsed laser melting [10], epitaxial growth [11], microwave synthesis [12] and solution-based methods [13] have been investigated to produce direct gap group IV semiconductors. Of all the strategies, colloidal synthesis of high-quality Ge 1−x Sn x without phase segregation of Sn is a desirable route that would enable inexpensive fabrication, processing, and device assembly [14].…”