Research

Nanomaterials play a key role in modern technology and society, because of their unique physical and chemical characteristics. The synthesis of nanomaterials is maturing but surprisingly little is known about the exact roles that different experimental parameters have in tuning their final properties. It is hereby of crucial importance to understand the connection between these properties and the (three-dimensional) structure or composition of nanomaterials.

We focus on the design and use of nanomaterials in fields as diverse as plasmonics, electrosensing, nanomagnetism and in applications such as art conservation, environment and sustainable energy. In all of these studies, the consortium integrates (3D) quantitative transmission electron microscopy and X-ray spectroscopy with density functional calculations of the structural stability and optoelectronic properties as well as with accelerated molecular dynamics for chemical reactivity. The major challenge is to link the different time and length scales of the complementary techniques in order to arrive at a complete understanding of the structure-functionality correlation. Through such knowledge, the design of nanostructures with desired functionalities and the incorporation of such structures in actual applications, such as e.g. highly selective sensing and air purification are become feasible. In addition, the techno-economic and environmental performance is assessed to support the further development of those applications.

Since the ultimate aim of this interdisciplinary consortium is to contribute to the societal impact of nanotechnology, the NanoLab is striving go beyond the study of simplified test materials and will focus on nanostructures for real-life, cost-effective and environmentally-friendly applications.

The research statement of the NanoLab consortium is to rationally design and use nanomaterials in fields as diverse as plasmonics, electrosensing, nanomagnetism and in applications such as art conservation, environment and sustainable energy. We therefore propose a synergistic and multidisciplinary approach that is based on the combination of the following complementary tools:

• Chemical and structural characterization of nanomaterials (EMAT, AXES). The EMAT group has the required transmission electron microscopy (TEM) instrumentation and the extensive expertise for a state-of-the-art, in-depth characterization of nanomaterials. A large set of electron microscopy techniques will be employed to quantitatively measure the structure and composition of nanomaterials with atomic resolution. Nowadays, such investigations are even possible in 3D. In addition, also the properties and the behavior of nanomaterials in realistic conditions can be studied through techniques such as plasmon mapping and by exploiting in-situ holders. X-ray based techniques are used by AXES in the field of cultural heritage, more precisely in the application of nano-beams to access high-spatial resolution information on fragments sampled from historical or model artworks. This will be a fertile ground for intense collaborations with EMAT, since electron microscopy measurements can yield complementary higher resolution information, albeit at an even more local scale. 
• Theory and modelling of nanomaterials (CMT, PLASMANT, EMAT). Statistical quantification of TEM data-sets will be done by EMAT, with the goal to translate TEM images to numbers for the unknown structure parameters. This is essential to link the experimental outcome to theoretical modelling. The consortium indeed offers vast expertise on multiscale modelling of nanomaterials. This covers ab-initio, tight binding and finite element/differences approaches for the investigation of structural and opto-electronic properties and classical molecular dynamics (MD) simulations for modelling the growth of nanoparticles or cluster formation. The expertise of PLASMANT on the modelling of growth and clustering processes at experimentally relevant (long) time scales will be of great importance. For the magnetic state of nanoparticles micromagnetic simulations will be performed by the CMT group with the use of the MuMax3 micromagnetics code developed in collaboration with University of Ghent. In all cases, a quick feedback loop between experiment and theory will provide the fundamental understanding of the structure-properties connections.
•  Economic modelling (ENM, DuEL, AXES). One of the unique aspects of our consortium is that the techniques described above will be complemented with techno-economic and environmental modelling of emerging technologies with input and feedback from AXES and DuEL regarding the proposed applications, described in more detail in the section below. The impacts on technology, economy, environment and society will be considered during the development of a new technology following the different stages, indicated by Technology Readiness Levels (TRLs). The expertise of ENM on integrated assessment, using a broad range of methods (e.g. multi criteria decision making), considering different TRL levels, is an essential aspect of the NanoLab enabling us to guide technology and material development towards a sustainable society.
  

The characterization and modelling techniques listed above already have been successfully applied in the investigation of model-like nanomaterials under well controlled conditions. Here, our aim is to go further and exploit the collaboration between fundamental and applied science to enable a description of realistic nanomaterials in working conditions. We envisage that such investigations will certainly boost the functionalities of nanomaterials and their applications:

• Plasmonic nanoparticles and photocatalysis used for sensors, air purification or water splitting (DuEL, AXES, EMAT, PLASMANT, CMT, ENM). The application field of plasmonic nanomaterials stretches from (bio)sensing, over medical applications, to surface enhanced Raman spectroscopy (SERS), catalysis and many more. Moreover, a thorough understanding of the plasmonic behavior will lead to a significant improvement of the photocatalytic performance in sunlight and therefore lies at the heart of advanced air purification technology. Our aim is to understand the connection between the size, shape and elemental composition of the plasmonic particle, the final properties and device performance. So far, TEM measurements to determine these parameters were only performed prior to or post usage. Being able to investigate structural and compositional changes during the reaction will deliver essential insight on the stability and lifetime of the plasmonic nanostructures.
•  Nanoparticles and their assemblies used for sensing and drug-delivery (EMAT, CMT, PLASMANT, ENM). Clustering of nanoparticles is a phenomenon that can be exploited for some purposes but should be avoided in other applications. For example, in drug-delivery applications magnetic nanoparticles need to be in a superparamagnetic state in order to avoid clustering. The shape and size, the shell structure or the nature of ligands present at the surface of the nanoparticles will strongly influence magnetic properties and inter-particle interactions. In addition, core-shell nanoparticles show the potential for combining properties, such as for example magnetism and plasmonics. Our aim is to understand the connection between the 3D structure and the properties of clusters. Insights will be reached by combining quantitative 3D characterization of the structure of the assemblies, measurements of their plasmonic resonances and magnetic states (EMAT), and modelling of the magnetic and optical properties as well as the driving forces behind the self-assembly process (CMT, PLASMANT).
•  Electrochemical (bio/photo)-sensors enhanced by nanoparticles (AXES, DuEL, EMAT, ENM). Nanoparticles have been shown to enhance the sensitivity and selectivity of electrochemical sensors and biosensors providing a route to miniaturized devices. Furthermore, they can be combined with bio-recognition elements and employed as photo-electrochemical sensors. Our aim is to unravel the mechanism for plasmonic enhancement of photosensitizers' activity and based on these insights to develop new photoreactive materials. 
• 2D materials used for plasmonics, (electrochemical) sensors, photo-catalysts or water filtration (CMT, PLASMANT, EMAT, AXES, DuEL). Due to their large surface-volume ratio, the wide range of possible opto-electronic properties and ease of functionalization, 2D materials are candidate materials in applications of interest to the consortium. CMT is an expert in the modelling of opto-electronic properties of 2D materials, whereas EMAT is able to measure their structure with atomic resolution. By taking advantage of involvement of CMT and EMAT groups in the Graphene Flagship, our goal is to explore the use of functionalized 2D materials in the applications of interest to DuEL and AXES, such as photocatalysis, water filtration and electrochemical sensors.
•  Heterogeneous mixtures of oxide nanoparticles for art conservation (AXES, EMAT, CMT). Environmental factors, such as light (affects mostly inorganic matter), humidity and temperature (affects mostly organic matter) are triggering agents for the degradation of oil paintings. To optimize the long-term conservation and restoration of paintings it is of high relevance to accurately establish the impact of these factors and study their degradation pathways. Our aim is to combine the AXES expertise on X-ray spectroscopy with the TEM expertise existing at EMAT in order to offer a comprehensive picture of the degradation process. Moreover, chemical and structural information will be supplemented with ab-initio investigations performed at CMT on the changes of the optical properties as well as the energy landscape of the involved reactions.