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Advancing the Study of Chemical, Structural and Surface Transformations in Colloidal Nanocrystals

Final Report Summary - TRANS-NANO (Advancing the Study of Chemical, Structural and Surface Transformations in Colloidal Nanocrystals)

Colloidal inorganic nanocrystals (NCs) are among the most investigated nanomaterials in nanoscience due to their extreme versatility. Research on NCs went through much advancement lately, especially on synthesis, assembly and on the study of their transformations. However, the integration of NCs with fabrication tools that employ conditions such as irradiation, etching and annealing is at a very early stage since we do not have a systematic knowledge of what transformations are triggered in the NCs under those conditions. Also, an issue related to the incorporation of NCs in materials/devices is whether, over time, the NCs will remain as they are, or they will transform into other structures. Plus, these transformations in NCs are poorly studied as they require fast recording techniques. The broad aim of this proposal is to investigate chemical and structural transformations in nanomaterials. There are multiple reasons for doing this. First, when materials are shrunk to nanometer size, they behave differently from when they are in the macroscale size, so there is a fundamental interest in it. Second, as more and more applications are claimed for nanomaterials, one needs to ascertain how materials and devices that incorporate nanoscale components will behave over time, as these components might age or transform much faster than expected or even evolve towards unforeseen behavior. Third, if we fully understand how materials behave at the nanoscale, we can then use this knowledge to develop new nanoscale fabrication tools. In this ERC project, we have made substantial progress in all these issues. First, we have developed new standardized nanoscale materials that we have used as testing grounds for a wide series of external stimuli that we have applied to them (heating, exposure to ionizing radiation or oxidative/reducing environment, etching agents, acids/bases and metal cations/anions, mechanical stresses). We have carefully studied how these materials have evolved under these stimuli, also depending on the initial structural and compositional characteristics of these “testers”. From these experiments we have then learned new ways to approach applications ranging from light emitting devices, photodetectors, gas sensors, electrodes for batteries, flexible conducing components, systems for sequestering toxic heavy metals from contaminated liquids, and single nanowire devices. The extensive knowledge acquired in this project has also enabled us to establish a series of guidelines on how certain nanoscale materials need to be analyzed under the electron microscope.