We have approached the synthesis of colloidal InAs nanocrystals (NCs) using amino-As and ligands that are different from the commonly employed oleylamine (OA). We found that carboxylic and phosphonic acids led only to oxides, whereas tri-noctylphosphine, dioctylamine, or trioctylamine (TOA), when employed as the sole ligands, yielded InAs NCs with irregular sizes and a broad size distribution. Instead, various combinations of TOA and OA delivered InAs NCs with good control over the size distribution, and the TOA:OA volume ratio of 4:1 generated InAs tetrapods with arm length of 5−6 nm. Contrary to tetrapods of II− VI materials, which have a zinc-blende core and wurtzite arms, these NCs are entirely zinc-blende, with arms growing along the ⟨111⟩ directions. They feature a narrow excitonic peak at ∼950 nm in absorption and a weak photoluminescence emission at 1050 nm. Our calculations indicated that the bandgap of the InAs tetrapods is mainly governed by the size of their core and not by their arm lengths when these are longer than ∼3 nm. Nuclear magnetic resonance analyses revealed that InAs tetrapods are mostly passivated by OA with only a minor fraction of TOA. Molecular dynamics simulations showed that OA strongly binds to the (111) facets whereas TOA weakly binds to the edges and corners of the NCs and their combined use (at high TOA:OA volume ratios) promotes growth along the ⟨111⟩ directions, eventually forming tetrapods. Our work highlights the use of mixtures of ligands as a means of improving control over InAs NCs size and size distribution.

Resum iv Acronyms ixI express my special thanks to my supervisor, Dr. Juan I. Climente (Nacho), whose ability and knowledge were pure gold for my learning process. Most of the things I know, not only during this dissertation but also along my chemistry degree, are because of him. Personally, his dedication and deftness to teach me during all these past years and especially his guidance during this doctoral program were priceless. Undoubtedly, I can be sure that Nacho can be considered for me, let's say, as my academic father.I also thank my tutor, Prof. Dr. Josep Planelles. It goes without saying that he is like the tribal shaman or the oracle of the QQ Group. His years of experience and his physical intuition make him, without a doubt, the cornerstone of this wonderful group. His advice was unvaluable.Of course, I would like to thank David (in a few months Dr. David Macias). He was a great colleague and is naturally a greater person. From him, I take his calm in stressful situations.In addition, I strongly thank my parents for helping me financially support this doctorate. Unfortunately, in Spain, governments apparently do not have much interest in science. This fact affects a large number of outstanding potential researchers who, due to different factors, are unable to pay for resources, dissemination of their results, or even worse, for doctorate enrolment.Finally, I would like to thank my partner Mical from the bottom of my heart for being fully supportive of me when all of these ups and downs that involve a doctorate programme arose. Thanks to her I could get away from that workaholic instinct, which should be shut off in some cases to preserve good mental health.