The Role of Halogens in the Synthesis of Semiconductor Nanocrystals

Abstract

Abstract:The presence of halogen compounds in the synthesis of semiconductor nanocrystals (NCs) produced by hot injection drastically influence their capping ligand sphere and/or chemical reactivity, allowing for the growth of hybrid systems, including composites combining NCs decorating carbon sp 2 surfaces. As a result, the presence of halide anions on the surface of some NCs has proven to have a positive impact on the optical and electrical properties. In this work the effects that halogen co-solvents (including alkylchlorides, bromides, and iodides) induce in the synthesis of rod-like Wurtzite CdSe NCs generated by hot-injection will be reviewed. The proposed mechanism of the reaction as well as a detailed characterization of the capping ligand sphere by Nuclear Magnetic Resonance (NMR) and X-Ray photoelectron Spectroscopy (XPS) will be discussed. Correlated cyclic voltammetry (CV) and XPS studies have been performed to address the effect of the halide anions on the NCs surface. Finally an example of the effect of the addition of chlorine-containing co-solvents on the synthesis of PbS rock-salt NCs will be shown.

The Many “Facets” of Halide Ions in the Chemistry of Colloidal Inorganic Nanocrystals

“…The above considerations merit a comprehensive treatment on this subject which so far has been lacking in the literature. Recent review articles, such as that by Juarez and Lohse, have attempted at giving an outlook on the influence of halide ions on the synthesis of semiconductor and metal NCs, respectively. , However, we aim to go beyond the conventional wisdom to paint a unifying picture that can be put to good use by a practicing nanochemist in designing more focused NC synthesis and functionalization strategies. The seemingly unconnected reports in the literature give rise to chemical trends having underlying principles common to all classes of nanomaterials, and we aim to demonstrate the same to the reader by furnishing an updated account of research in this area and by finally providing a thorough outlook.…”

Insights into the formation mechanism of two-dimensional lead halide nanostructures

“…28,29 Additionally, co-ligands namely halogen alkanes can be used to synthesize CdSe pyramids or PbS nanosheets. 13,30 3 Lead iodide is a direct band gap semiconductor with a gap between 2.3 and 2.4 eV 31 and a crystal structure which consist of layers of hexagonally close packed iodine and lead atoms oriented perpendicular to the c-axis. 32,33,34 Using specific synthesis parameters it is possible to prepare crystals of PbI2 with specific orientations of the layers.…”

Anion-Directed Synthesis of Core–Shell and Janus Hybrid Nanostructures

“…Chloride ions are known to be surface-active species with a significant propensity to adsorb onto metallic surfaces. ,− As a result, chloride ions in the solution, present as counterions from the CZTS metal precursors, would be expected to adsorb on the surface of silver nanoparticles. This surface chemistry, formed in the presence of chloride counterions, facilitates the nucleation of Cu 2 S onto the seed and the growth of CZTS onto silver nanoparticles to form core–shell Ag@CZTS.…”