Ligands play a crucial role in the synthesis of colloidal nanocrystals. Nevertheless, only a handful molecules are currently used, oleic acid being the most typical example. Here, we show that mono-alkyl phosphinic acids are another interesting ligand class, forming metal complexes with a reactivity that is intermediate between the traditional carboxylates and phosphonates.We first present the synthesis of n-hexyl, 2-ethylhexyl, n-tetradecyl, n-octadecyl, and oleyl phosphinic acid. These compounds are suitable ligands for high-temperature nanocrystal synthesis (240-300°C) since, in contrast to phosphonic acids, they do not form anhydride oligomers. Consequently, CdSe quantum dots synthesized with octadecylphosphinic acid are conveniently purified, and their UV-Vis spectrum is free from background scattering. The CdSe nanocrystals have a low polydispersity and a photoluminescence quantum yield up to 18%. Furthermore, we could synthesize CdSe and CdS nanorods using phosphinic acid ligands, with high shape purity. We conclude that the reactivity towards TOP-S and TOP-Se precursors decreases in the series: cadmium carboxylate > cadmium phosphinate > cadmium phosphonate.By introducing a third and intermediate class of surfactants, we enhance the versatility of surfactant-assisted syntheses.

Gold nanoparticles (Au NPs) and gold-based nanomaterials combine unique properties relevant for medicine, imaging, optics, sensing, catalysis, and energy conversion. While the Turkevich–Frens and Brust–Schiffrin methods remain the state-of-the-art colloidal syntheses of Au NPs, there is a need for more sustainable and tractable synthetic strategies leading to new model systems. In particular, stabilizers are almost systematically used in colloidal syntheses, but they can be detrimental for fundamental and applied studies. Here, a surfactant-free synthesis of size-controlled colloidal Au NPs stable for months is achieved by the simple reduction of HAuCl4 at room temperature in alkaline solutions of low-viscosity mono-alcohols such as ethanol or methanol and water, without the need for any other additives. Palladium (Pd) and bimetallic Au x Pd y NPs, nanocomposites and multimetallic samples, are also obtained and are readily active (electro)catalysts. The multiple benefits over the state-of-the-art syntheses that this simple synthesis bears for fundamental and applied research are highlighted.

Understanding the mechanisms for nanoparticle nucleation and growth is crucial for the development of tailormade nanomaterials. Here, we use X-ray total scattering and Pair Distribution Function analysis to follow the...

Manganese dioxide MnO2 compounds are widely used in electrochemical applications e.g. as electrode materials or photocatalysts. One of the most used polymorphs is γ-MnO2 which is a disordered intergrowth of...

In one word, how would you describe your research?We will use two words -Nanostructure analysis. The research done in our research group at University of Copenhagen focuses on understanding synthesis/structure and structure/ property relations in nanostructured, inorganic materials. For this work, we use a range of X-ray and neutron methods, especially X-ray total scattering with Pair Distribution Function (PDF) analysis. In contrast to other crystallographic methods, PDF analysis allows to extract structural information from materials with no long-range order, which makes it possible to develop detailed models for the atomic arrangements in nanomaterials. We use X-ray total scattering methods for e.g., in situ studies of material formation, which allows us to map reaction pathways and link reaction mechanism to polymorph formation. We collaborate with the Billinge group at Columbia University, who are leading in development of the PDF method.