Prof. Maxim S. Pchenitchnikov

Structure and Thermoelectric Performance of Copper-rich Cu2+xSe Doped with Rare-earth Elements

Supervisor: Prof. Graeme Blake

Solid-State Materials for Electronics Group

Sustainability is vital for the new century, and thermoelectric (TE) materials, which convert heat and electricity into one another, are the area of tremendous interest as a source of clean and sustainable energy. With the recent development of phonon-liquid electron crystals (PLECs), the most prevalent of which are copper chalcogenides, considerable breakthroughs have been made in the field of thermoelectric materials. Because of the liquid-like features of highly mobile copper ions in these materials, heat-carrying phonons are effectively scattered, and PLECs have a high thermoelectric figure of merit ZT. This project focuses on studying the effect of doping copper-rich Cu2+xSe with rare earth elements.

Structural Insights of Amino-acid Based Hydrogel using Small-angle X-ray Scattering (SAXS) Technique

Supervisor: Prof. Giuseppe Portale

Macromolecular Chemistry and New Polymeric Materials Group

Hydrogels are highly absorbent insoluble three-dimensional (3D) networks of hydrophilic polymers. They maintain a very well-defined structure due to physical or chemical cross-linking of individual polymer chains. They have existed for almost a century, and nowadays, they have a huge number of applications in numerous processes ranging from biological to industrial. In this project, we are studying hydrogels based on a low molecular weight gelator (LMWG) called Fmoc-k(Fmoc) [Fmoc: fluorenylmethoxycarbonyl, k: L-lysine] using the small-angle x-ray scattering technique (SAXS). Fmoc-k(Fmoc) is particularly interesting because hydrogels based on it possess several advantages and properties like low minimum gelation concentration (MGC), high mechanical strength, high thermal stability, and thixotropic property. Furthermore, they are also biocompatible and biodegradable, which make them ideal for drug delivery. SAXS is employed because it gives us the structural information at the nanoscale and sub-microscale. From these information, we can understand the supramolecular structure and design new architectures tailored to specific needs depending on biological or non-biological applications.

3D Printing of Drug Delivery Scaffolds

Supervisor: Prof. Marleen Kamperman

Polymer Science Group

Musculoskeletal tissues are prone to injuries as they make up the region where stress concentration occurs. These injuries are the leading contributor to disability around the world due to their poor healing process. To overcome this problem, 3D-printed scaffolds, commonly used in tissue engineering, are essential elements in the treatment of these conditions as they provide a suitable microenvironment for cells to proliferate and differentiate. To further boost cell differentiation and/or add antibacterial properties, drug-delivery systems can be introduced. These, however, usually present a burst release of the drug in the first few hours. In our project, a new approach was evaluated, including drug nanocarriers. We have produced and characterized poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with hydrophilic drugs. Next, we mixed the drug-loaded PLGA NPs with polycaprolactone (PCL) microparticles before melting and studied the printability using Melt Electrowriting. We aim to control the drug release by producing 3D scaffolds with encapsulated PLGA nanoparticles in the PCL matrix.

Polarization-resolved Excitation Spectroscopy on C8S3 Nanotubes

Supervisor: Prof. Maxim Pchenitchikov

Optical Condensed Matter Physics Group

Artificial light-harvesting complexes provide an effective base for investigating the energy transport mechanisms in natural light-harvesting complexes via self-assembled supramolecular structures. One such structure arises from the amphiphillic C8S3 molecules which self-assemble into double-walled cylindrical nanotubes reminiscent of the photosynthetic structures found in green sulphur bacteria. While the optical properties of C8S3 nanotubes in bulk solution have been extensively studied, very little work has been done to optically characterise individual nanotubes. My project focuses on isolating individual nanotubes and obtaining their polarization-resolved excitation spectra to see how they compare to the absorption in bulk samples.

Quantification of the ordering of PbSe Quantum-Dot Super-Lattices (QD-SLs) using Advanced X-Ray Techniques

Supervisor: Prof. Giuseppe Portale

Macromolecular Chemistry and New Polymeric Materials Group

Colloidal QDs can self-assemble and can result in the formation of periodic superstructures (2D/3D). This periodic arrangement of QDs is known as a superlattice (SL) and similar to atomic lattices, these SLs also diffract light with a wavelength comparable to that of the periodicity of their arrangement. The orientation of the QDs on both the atomic level and super-structure level influences the transport properties of devices fabricated using such structures. Poor orientation of such SLs is an obstacle to improving the transport properties of such arrays. The development of experimental techniques to quantify such orientations at both atomic and the super-structure length scale is crucial to circumvent this hurdle. My project focuses on studying both the orientations: namely the orientation of the PbSe atomic lattice (AL) and that of the SL formed with respect to the substrate using X-Ray characterization techniques such as Small Angle X-Ray Scattering and Wide Angle X-Ray Scattering (SAXS/WAXS). It also focuses on quantifying the orientations of the formed QD-SLs.

Transport Properties of PbSe Colloidal Quantum Dot Superlattices

Supervisor: Prof. Maria Loi

Photophysics and Opto-Electronics Group

For the miniaturisation and efficiency improvement of semiconductor devices, the exploitation of electrical properties of new classes of nanomaterials namely quantum dots (QDs) is quite important. The careful control on the self-assembly of these QDs in solution phase can create their superlattices. These superlattices of QDs show very promising device performance in the field-effect configuration. In this work, we deposited the supperlatices of Lead Selenide (PbSe) QDs as an active channel layer of field-effect transistors to study the transport properties in these structures. By characterising the crystal structure we examined the ordering of nanocrystals in superlattices. Furthermore, we performed low-temperature measurements in order to understand the behaviour of these superstructures towards the transport of charges.

Robust Photoactuating Artificial Muscles from Amino Acid Modified Molecular Motor Amphiphiles

Supervisor: Prof. Ben Feringa

Synthetic Organic Chemistry Group

As technology progresses, engineering on the molecular scale to create stimuli responsive functional materials becomes increasingly important. Taking inspiration from nature for the development of such stimuli responsive materials capable of converting molecular motion into macroscopic movement, it is of paramount importance to be able to precisely control molecular organization to allow for the amplification of motion by many orders of magnitude. By modifying light-driven molecular motors, versatile responsive molecular systems can be synthesized through self-assembly. One such system was presented by the Feringa group in 2016, where a photoactuating molecular muscle was synthesized from amphiphilic molecular motors. The artificial motor introduced in this work does suffer from drying effects that result in the loss of actuation, and the strings are relatively weak. In our work we address these issues by modifying the motor by introducing amino acid groups and investigating the effect of different cationic species on the self-assembly and photoactuation of the system.

Non-linear Hall Effect in MoTe2

Supervisor: Prof. Marcos Guimarães

Opto-Spintronics of Nanostructures Group

Second harmonic Hall-voltage is observed in a symmetry-broken system to show the direct measurement of Berry-curvature dipole. The experiment material is MoTe2 with 1T’ phase, whose 2D nature facilities the observation of Hall voltage and the symmetry broken in such a way to allow a large and quadratic transversal voltage response to current. The measurements are operated on a device with dimensions of micrometers in plane and nanometers between layers, and geometry of a Hall bar. The fabrication procedure is carried out in Fabrication-of-Nanodevices（FND）labs. In FND labs, the mesoscopic behaviour of electrons, in terms of transport and interaction with electric or magnetic field, is studied on devices with dimensions of micrometers and nanometers. Quantum effects are discovered and proved through delicate design of the geometry of devices and crystals with specific crystal structures and magnetic orders.

Stability Analysis of CsSnI3 Perovskite Nanocrystals Embedded in Polymer Matrices

Supervisor: Prof. Loredana Protesescu

Nanomaterials Chemistry Group

Metal halides perovskites with nanoscale geometries have revolutionised the field of solution processed photovoltaics and light-emitting devices due to their strong absorption and exceptional photoluminescence properties combined with a remarkable tolerance to structural defects. However, the further development of these materials to practical commercialization is hindered by their toxic components like lead, and by their inherent structural lability. Tin based perovskites have shown promise as a non-toxic alternative to their lead counterparts, but these tin structures still underperform their lead analogs in both performance and stability. CsSnI3 nanocrystals, specifically, last only several hours when kept in the ambient. This project aims to stabilise CsSnI3 nanocrystals in polymer matrices. To achieve this, a broad survey is performed on the effect of a wide range of polymers on the optical properties of CsSnI3.

Developing Biomedical Adhesives for Skin Transplants

Supervisor: Prof. Marleen Kamperman

Polymer Science Group

One of the limitations of current mesh graft techniques is the use of toxic glues applied to fasten the skin grafts to the wound bed. From the study of species such as the mussel and sandcastle worms, quite a lot is known about releasing biocompatible wet adhesion, but the highly modified polypeptides they employ are neither easy to make nor very practical for human use. This project focuses on the development of underwater biocompatible glue, using the design principle of polypeptide complex coacervate, with Hyaluronic acid (HA) and Chitosan (CH) as the anionic and cationic polymers respectively. The yield and properties of this complex coacervate are strongly dependent on the synthesis parameters, such as pH, polymer ratio, polymer concentration, and salt concentration.

Optical Spectroscopy of (Individual) Tin-Based Perovskite Nanocrystals

Supervisor Prof. Richard Hildner

Optical Spectroscopy of Functional Nanosystems Group

Inorganic perovskite CsPb nanocrystals (NCs) possess advantageous photoluminescence (PL) characteristics including higher quantum yield, narrower emission linewidth, as well as negligible influence of self-absorption and Förster resonance energy transfer. The facile access to the blue-green emitting light (410–530 nm) via a one-pot synthesis is a key practical advantage of CsPb NCs. Unfortunately, due to their inherent ionic nature, the fully-inorganic trihalide perovskite NCs can be degraded in polar solvents such as water. They also tend to degrade under exposure to high temperature or high-energy electron beams. The goals of the experiments are measuring the absorption and PL and blinking patterns of these perovskite NCs. Finally dilute the sample a few times to get single photon quantum dot.

Synthesis and Characterization of Chiral Polyoxometalates and Their Catalysis Applications

Supervisor Prof. Paolo Pescarmona

Sustainable Chemical Products and Catalysis Group

Polyoxometalates (POMs) are metal-oxygen clusters of early transition metals in high oxidation states. The structural diversity of POMs leads to equally diverse properties and applications in catalysis, magnetochemistry and medicine. The objective of this project is to synthesize and characterize new enantiomerically pure chiral polyoxometalates. There are several ways to synthesize chiral POMs including: chiral POMs with achiral linkers, achiral POMs with chiral organic ligands, self-assembly of achiral units yielding chiral helical structure (not enantiomerically pure) and self-assembling units resulting in other structures. The questions to answer with this project are: 1) Can we make a new class of chiral POMs? 2) Can we use them for asymmetric catalysis? 3) Can we measure their circular dichroism (CD) spectra?

Assessing Long-term Phototoxicity in Live-cell STED Microscopy

Supervisor: Prof. Rifka Vlijm

Molecular Biophysics Group

Stimulated Emission Depletion (STED) microscopy is one of the super-resolution techniques that overcome the diffraction limit of light. The high spatial and temporal resolutions of STED make this a suitable technique for imaging the cellular processes in living cells. However, the resolution of STED microscopy is dependent on the power of the STED laser, which is speculated to cause photodamage at high intensity. In this project, a framework is developed to determine the potential phototoxicity of STED. This framework includes control of the microscope through home-written python code. We evaluate not only whether instant cell death occurs (the common method) but also monitor the long-term effect on cell division. Cells only divide when they are in good condition, making them an excellent marker for detecting even small amounts of phototoxicity. We found similar rates of cell division for cells imaged with and without STED, showing that STED microscopy with low phototoxicity is possible.