Prof. Giuseppe Portale

Reassessing existing kinetochore maps by imaging key kinetochore proteins at different stages of the cell cycle using STimulated Emission Depletion microscopy.

Supervisor: Dr. Rifka Vlijm

Research group: Molecular Biophysics

The kinetochore is a key network of many proteins with an important role in cell division which ensures the correct segregation of chromosomes by facilitating a connection between the centromere and microtubules. Studies using different types of assays have shown CENPA is essential for the recruitment of kinetochore proteins and Hec1 is one of the primary binding sites of microtubules. Imaging, localization and structural conclusions about these proteins have been drawn using confocal microscopy, which is limited by the well known diffraction limit. The project consists of using STED microscopy to image kinetochore proteins CENPA and Hec1 during metaphase and draw conclusions that help us better understand the structures these proteins form during cell division.

Synthesis and characterization of C8S3 double walled nanotube structures

Supervisor: Prof. Maxim S. Pchenitchnikov

Research group: Optical Condensed Matter Physics

Developing technology capable of efficient solar energy absorption and long-range lossless transport of it has recently been a point of research interest in nanoscience. A lot of inspiration has been drawn from nature, especially in the case of photosynthesis. In order to replicate the functionality of such complex systems (e.g. green sulfur bacteria [1]), research attention has been drawn towards self-assembled molecular aggregates (J-aggregates) which represent molecular clusters that are capable of dipole moment alignment upon light excitation. This in turn creates a highly delocalized exciton state spanning across hundreds of tightly packed molecules. Key properties of interest represent higher absorption coefficients upon aggregation in solvents, low loss transmission of energy from one site onto another, etc. 

In the following project, the self-assembled C8S3-3 dye molecules DWNT structure is investigated upon laser irradiation. Furthermore, we are modifying the tubular structure by incorporating C8S3-5 molecules into the J-aggregates with concentrations given by a 25:1 ratio of C8S3-3 molecules to C8S5-3. Due to the overlap of the dopant molecule’s absorption spectrum with the exciton photoluminescence (PL) spectrum, the excitonic energy is funnelled towards the dopant through Forster-like energy transfer. The goal is to experimentally check the stability and control the exciton diffusion length in the C8S3-5 doped nanotubes, which will be correlated to the laser dosage. The irradiation effects will be studied through ultrafast time-resolved spectroscopy, which is used for detailed characterization of energy transport and transfer dynamics.

References:

[1] Chen, Jing-Hua, et al. “Architecture of the photosynthetic complex from a green sulfur bacterium.” Science 370.6519 (2020): eabb6350.

[2] Kriete, Björn. Exciton dynamics in self-assembled molecular nanotubes. Diss. University of Groningen, 2020.

Emergence of self-synthesizing coacervates from dynamic combinatorial libraries

Supervisor: Prof. Sijbren Otto

Research group: Otto lab

Compartmentalization is one of the main characteristics allowing living systems to protect themselves from the outside world. Among different compartment materials, coacervates have shown great potential as models to study the origin of life. However, the mechanism by which these compartments can emerge from their building blocks is still unexplored. Recently, a building block was found that can form coacervates through dynamic combinatorial chemistry. The main focus of this project will be on the study of making self-synthesizing coacervates. In this project, we aim to figure out how environmental changes, such as temperature and mechanical agitation, can affect the coacervation ability of the building blocks. In order to investigate the role of these changes, a building block will be studied and techniques, such as LC-MS and UPLC, will be used to investigate the library formed by the building block. In addition, the emergence of coacervates will be studied using UV-Vis spectroscopy, and fluorescence/confocal microscopy.

Transforming a 2D semiconductor into a semimetal by laser-induced crystal phase change

Supervisor: Dr. Marcos H. D. Guimarães

Research Group: Opto-spintronics of Nanostructures

In this work, I explore the controlled modification of the crystal structure of the two-dimensional (2D) semiconductor 2H-MoTe2 to its metallic tetragonal (1T’) phase by means of local laser irradiation. This effect can be used to create a one-dimensional lateral contact between the 2D semiconductor and the 2D metal, with excellent contact properties. The phase change is confirmed by Raman scattering, which probe the change in lattice vibrations due to the phase transformation. Finally, I will show how we can use these 2D metal semiconductor-metal lateral heterostructures for functional devices using the state-of-the-art nanofabrication techniques. Through electronic transport and photocurrent measurements, I will demonstrate the excellent contact properties of these structures and their potential for future electronic devices.

 Self-assembly and crystallisation of spiropyran-based molecules in solution

Supervisor: Prof. Giuseppe Portale

Research group: Polymer Physics Group

Molecular switches are molecules that can change between two or more stable states, each with slightly different properties. Spiropyrans are a type of molecular switches which have been studied for close to a century and that can change between the closed spiropyran form and the open merocyanine form where a C-O bond is broken. They change their properties as a response to external stimuli and have therefore found growing interest in fields such as photodetection or advanced drug delivery.

Rather than just studying their molecular properties, the purpose of this line of research is to study how they self-aggregate in water in order to form supramolecular structures. This is done by turning the initial hydrophobic spiropyrans into a more amphiphilic molecule through the binding of ethylene glycol groups. This process is commonly known as PEGylation, coming from attaching hydrophilic polyethylene glycol chains to nanostructures or macromolecules in order to make them more soluble in water.

Using various techniques, such as UV/Vis spectroscopy, GISAXS and DLS, I will be characterising the supramolecular self-assembly of various different spiropyrans with varying ethylene glycol (EG) groups attached. The self-assembly occurs when the initial acetonitrile solution is added to water, in which the spiropyrans are much less soluble. Both the aggregates’ shape and size and the kinetics behind the self-assembly are of interest, in order to establish how the varying EG size changes these. It is also of interest to identify if these aggregates can change shape in response to stimuli, such as light irradiation.

Characterization of single molecules (sCBT) and effects of 2D materials on the properties of single molecules

Supervisor: Prof. Richard Hildner

Research group: Optical Spectroscopy of Functional Nanosystems (OSFN)

Single-molecule spectroscopy developed into a powerful tool during the past decades. Organic molecules at very low concentrations (nM to pM) are used to study local interactions in a variety of systems, e.g. protein folding and association in life sciences or establishing structure-property relationships in novel materials for organic solar cells, transistors or thermoelectric generators. At the same time 2-dimensional materials, such as graphene or transition metal dichalcogenides (TMD) attracted substantial attention in recent years due to their outstanding properties and their potential for applications e.g. in sensors and electronics.

In this project we want to unite those fields and perform spectroscopy of single organic molecules deposited on 2D materials with the aim to study the interaction of a localised (Frenkel) exciton on the molecule with the delocalised Mott-Wannier excitons of the 2D material.

Role of twin boundaries in controlling the local properties of La0.67Sr0.33MnO3 thin film grown on LaAlO3 (001) substrate

Supervisor: Prof. Tamalika Banerjee

Research group: Spintronics of Functional Materials

Manganites are strongly correlated oxide materials, well known for their competing ground states with nearly equal energies. This forms an important playground in which the dominant energy interactions, can be controlled by an external stimulus such as temperature, strain, doping, and electric field. We show how the morphology of LSMO thin films, grown by Pulsed Laser Deposition, can be controlled by growing them on textured substrates, such as LaAlO3 (LAO). We find that a 10 nm thick LSMO film grown on an LAO substrate shows stripe-patterned twin domains with an overall out-of-plane magnetic anisotropy. The combinations of twins and strains locally alter the physical properties of the grown film. Using magnetic and electrical probing, we investigate the local change of functional properties, which is important in the context of designing brain-inspired computing schemes.

Photocurrent spectroscopy of van der Waals antiferromagnetic CrPS4 Devices

Supervisor: Dr. Marcos H. D. Guimarães

Research Group: Opto-spintronics of Nanostructures

Magnetic devices have been prominent for data storage for several decades due to their long retention times and low power consumption. However, the transport of magnetic information in these devices is complex and their speed still needs to catch up to their more recent electronic counterparts. The recently discovered two-dimensional (2D) magnets open the door for studying magnetism in low dimensions and combining semiconducting and magnetic properties.

In this project, I explore the interplay between light, magnetism, and electric currents in a new 2D van der Waals antiferromagnet, namely-CrPS4. To investigate the effect of crystal symmetries on the photocurrent, I fabricated CrPS4 field-effect transistors with a circular geometry of electrodes, where the photocurrent can be measured at different crystal directions. I will also show how the photocurrents respond to different temperatures, and light polarizations and wavelengths. Finally, I will show how the photocurrent mechanisms in nanometer-thick flakes can be elucidated using scanning photocurrent spectroscopy.

Electrochemical Reduction of 5-hydroxymethyl furfural (HMF) with Nickel Boride (NixB) Nanocrystals

Supervisor: Dr. Loredana Protesescu

Research group: Nanomaterials Chemistry Group & Electrocatalysis Group 

Electrocatalysis is an interface-dominated process in which the activity of a catalyst strongly depends on the adsorption/desorption behaviours of the reactants/intermediates/products on the active sites. From the viewpoint of a catalyst design, the chemical functionalization of the catalyst surfaces will inevitably affect the reaction processes, and is considered to be one of the effective strategies to tune the electro-catalytic performance of noble metals and colloidal nanocrystals. Recently, colloidal nanocrystal-based electrocatalysts have drawn enormous attention due to their exceptional catalytic selectivity/activity and durability relative to the existing bulk electrocatalysts.

In this research, the electrochemical reduction of 50 mM of 5-hydroxymethylfurfural (HMF) will be investigated at a current density range of 10-50 mA/cm2 and pH = 9.2, over Nickel boride (NixB) nanocrystals and Ni foam electrocatalysts. The electrochemical measurements including; Electrochemical Impedance  Spectroscopy (EIS), Linear Sweep Voltammetry (LSV), and Chronopotentiometry will be employed to study the behaviours of the electrochemical systems. The conversion, selectivity towards the formation of 2,5-bis(hydroxymethyl)furan (BHMF) and 2,5-dimethylfuran (DMF) and Faradaic efficiency (FE) will then be calculated after the analysis with High-Performance Liquid Chromatography (HPLC) and Solid-state NMR. Overall, the study will justify the claim that colloidal nanocrystals are an excellent emerging class of electrocatalysts due to their high surface/volume ratio.