Gd-Ce nanoprobes, surface functionalization and the dynamics of protein corona formation
Filip Genander, Maria Assenhöj
Introduction of nanoparticles (NPs) into an in-vivo environment, poses challenges as proteins likely interact and attaches to the NP’s surface, forming a protein corona. Depending on the pristine NP’s properties, different proteins will form the corona. The corona plays a key part in the interactions between the NP and the in-vivo environment, e.g., immunogenic responses. We have integrated gadolinium in cerium oxide NPs (Gd-CeNPs), to obtain dual functionality, i.e., superior contrast enhancing properties for magnetic resonance imaging (MRI) and remarkable capabilities for scavenging reactive oxygen species (ROS).
In this CeNano project small sized Gd-CeNPs different step-by-step functionalization silanisation strategies will be compared. The systems will be investigated by using a full set of material characterization tools and detailed evaluation of the protein corona formation. This work is done to investigate how the biological response correlates to the choice of surface functionalization strategies and further to explore the potential of NPs in biomedical imaging applications.
Schematic picture of protein corona formation on a rare-earth oxide nanoparticle (not in scale)
Optimizing ionics and oxygen electrocatalysis for electrolytic hydrogen peroxide synthesis
Zhixing Wu, Mikhail Vagin
The continuation of the project is dedicated to the development of electrogenerator for sustainable H2O2 production operating with air and water only.
The key aspect of the technology is the membrane electrolysis performed on efficient organic electrocatalyst of peroxide-liberating oxygen reduction in combination with electrocatalytic oxygen evolution reaction as auxiliary process. Both processes are under investigation in a frame of two coherent PhD projects.
Scheme of the H2O2 electrogenerator.
Quest for Single-photon Emitters in Silicon Carbide: A combined effort between Data Science and Material Science
Material defects and defect properties engineered on the atomic scale can exhibit optical and spin properties that could be powerful tools for miniaturizing sensors, communication, and data processing. The point defects engineered in silicon carbide (SiC) can act as single-photon sources and possess states with a lifetime long enough to construct a quantum memory. However, transmission losses over optical fibers present a fundamental challenge for long-range quantum networks. Single-photon sources must emit at an optimal frequency to achieve minimum losses at telecom frequency bands while fulfilling growth, stability, and state control demands. It has become clear that finding suitable defect emitters will require interdisciplinary efforts.
Recent efforts have introduced high-throughput techniques and the construction of extensive defect property databases for SiC, which allows for data-driven approaches to defect search and identification. Combining this with modern high-accuracy first-principle calculations will accelerate the search for defects with suitable properties. Meanwhile, experiments using state-of-the-art techniques of photoluminescence (PL) and optically detected magnetic resonance (ODMR) can effectively pinpoint and characterize the components and properties of observed defects.
In this project, we will study defects in SiC that can act as candidate single-photon emitters in future nanodevices. This will be facilitated by investigating PL emission in the range of interest, filtering and cross-referencing of available database data, and given result, a detailed examination of defect properties by sample manipulation or additional measurement techniques such as ODMR and highly accurate computer simulation of candidate structures. With this, we aim to identify and provide a detailed theoretical and experimental characterization of point defects fitting as optical emitters in SiC.
Targetable fluorescent nanoprobes towards precise fluorescence-guided surgery
Docent Zhangjun Hu, Xin Zhang (IFM), Prof. Oliver Gimm, Ervin Beka (BKV)
Fluorescent nanomaterials are increasingly enabling applications ranging from deep tissue imaging in vivo to point-of-care diagnostics due to their beneficial capabilities. Many nanomaterials with near-infrared (NIR) emission have shown huge potentials in vivo clinical applications including fluorescence-guided surgery due to their proper tissue penetrating wavelengths. Hypoparathyroidism is one of the most frequent complications of thyroid surgery, especially when associated with lymph node dissection in cases of thyroid cancer. Fluorescence-guided thyroidectomy has been demonstrated very useful for preventing post-thyroidectomy hypoparathyroidism. However, so far, only organic fluorophores have been applied to reach this purpose but typically suffer from low photostability, strong background noise, and poor specific accumulation. In this interdisciplinary collaborated project, photostable ultrasmall high bright red fluorescent nanoparticles will be fabricated based on a versatile nano scaffold that has been demonstrated in our previous work. The rational surface engineering will further endow the nanoparticles with intended functionalities including high biocompatibility and specificity for minimizing the toxicity and maximizing the visuality, respectively. To realize the targeting, a new tag will be developed based on calcimimetic agents, which are specific ligands to target calcium-sensing receptor (CaSR), a demonstrated suitable target for hyperparathyroidism. Parathyroid tissue will be used for the evaluation of the specificity of the fabricated FL-NPs towards parathyroid glands.
Towards a predictive model for surface-controlled deposition of nanometer thin films
Anton Persson (IEI), Pamburayi Mpofu (IFM), Henrik Pedersen (IFM), Matts Karlsson (IEI)
Nanometer thin films of materials play a crucial role in all modern nano-scaled electronic devices. The method for materials synthesis offering the highest level of control on the sub-nanometer scale is atomic layer deposition (ALD). ALD is a time-resolved form of chemical vapor deposition (CVD) where volatile precursor molecules, containing the atoms needed for the film material are introduced in a deposition chamber in pulses separated by inert gas purges. The time-resolved precursor supply renders a self-limiting surface chemistry since the chemical reactions stops when all surface sites are occupied by a chemisorbed precursor. This makes ALD fully surface-controlled and allows for deposition of conformal films on topographically complex surfaces. The surface-controlled deposition chemistry has formed the common notion that ALD is very simple; molecules react to form a film via simple surface reactions. However, ALD spans ten orders of magnitude in both time and space, making a true model of the ALD process, and thus a high level of process understanding very challenging to achieve. From our on-going and previous work on modelling ALD and CVD, we are now in a position to construct such a model for ALD. This project aims at forming a predictive, multi-scale model to increase the understanding of materials synthesis at the sub-nanometer scale.
Can annealing enhance the crystalline quality in diboride superlattices?
Artificial superlattices are nano-layered structures of two different materials that do not occur in nature. Superlattices, when carefully designed and synthesized, have demonstrated properties that cannot be obtained in the natural form of crystals. One approach to grow single crystal superlattices is by magnetron sputter epitaxy.
We have recently grown CrBx/TiBy superlattices by DC magnetron sputtering from compound CrB2 and TiB2 targets (non-reactive sputtering) as a first-ever such an experiment on diborides. We obtained the deposition parameters to grow promising superlattices; however, high-resolution microscopy shows that the achieved nanostructures are still not ideal due to boron segregation in the nanostructure (Fig. 1), which is more pronounced in the TiBy layers. This segregation is attributed to excess boron, as sputter-deposited TM diboride thin films are often over-stoichiometric (B/TM ratio > 2).
One strategy to resolve this issue and increase the crystal quality can be engineering their nanostructure by a post-annealing process. It is expected that a controlled post-annealing process can lead to an atomic re-arrangement, in the direction of thermodynamic equilibrium and consequently, influence the huge as-grown boron segregation. To assist in finding the right post-annealing approach in terms of temperatures and even initial as-grown layers design, theoretical calculations will be applied. This theory will also answer questions of two kinds: about the thermodynamic equilibrium, in terms of Free energy minima, towards which the as-grown material will strive, and about the kinetics of boron and metal diffusion in and between the layers governing the hierarchy and time scales of various kinds of transformations in the layers.Fig. 1. (a) HAADF-STEM of CrBx/TiBy superlattices with modulation period Λ = 5.3 nm, (b) Ti, Cr, and B (EELS) maps from a similar neighboring area
Sputtered insulating-oxide interlayer for organic photovoltaic devices
Jianwei Yu, Rui Shu, Per Eklund, Feng Gao
Organic solar cells (OSCs) are a promising technology to utilize solar energy because of its low-cost, lightweight physical characteristics, and the lucrative possibility of integration directly into flexible and wearable electronic devices. Recent development in non-fullerene acceptors (NFAs) have successfully boosted power conversion efficiencies (PCEs) of OSCs to high values over 18%, approaching the commercially viable efficiency goal. However, the large donor/acceptor (D/A) interface in bulk heterojunction structure can not only render exciton formation and dissociation, but also increase the energy loss, which limits the further improvement in the OSCs. The energy is believed to loss from extra non-radiative recombination in both charge transfer and transport process. Therefore, it is important to undersantand the mechanism and influencing factors of the charge recombination at D/A interface in the OSCs.
In this project, we are aiming to explore transition metal oxides as interlayer for efficient and stable bilayer-heterojunction OSCs. The transition metal oxide interlayer with optimized band gap and morphology will be produced using magnetron sputtering. The interfacial stability of complete OSCs through tailoring the interlayer materials and the interfacial contacts will be further studied. Moreover, the mechanism of exciton diffusion will be revealed for paving a way to address the energy loss issue in OSCs.
Figure 1 Schematic illustration of sputtering process for transition metal oxide interlayer (left); the organic solar cell in bilayer heterojunction structure (right).
Exciton-Luminescent Lead-Free Halide Perovskites for Optoelectronic Devices
Muyi Zhang (IFM), Utkarsh Singh (IFM)
Metal halide perovskites are considered among the most promising semiconductors in the field of optoelectronics. However, the presence of toxic lead in high-performance metal halide perovskites is undesirable and this necessity has given rise to lead-free halide perovskites (LFHPs). One of the cutting-edge trends focuses on developing the exciton-luminescent LFHPs, which is widely recognized as the effective luminescence materials in optoelectronic devices such as light-emitting devices (LEDs) and scintillator detectors.
In this project, we aim to create optoelectronic devices with superior luminescence capacity based on our skills in device fabrications and ab initio simulations of functional materials. A collaboration of experimental and theoretical physics in nanoscale will be utilized for develop the LFHP materials and LED device. Hopefully, the result can break through the current efficiency record based on LFHPs. The multidisciplinary collaboration would also be instrumental in establishing design rules for nanoscale lead-free perovskite optoelectronics.
Sample Optimization for Waveguide-Enhanced Neutron Fluorescence Measurements on Gd2O3 Nanoparticles
Anna du Rietz, Molecular Surface Physics and Nanoscience, IFM, LiU
Bela Nagy, Biophysics and Bioengineering, IFM, LiU
We are working on the development of a method that combines Prompt Gamma Activation Analysis (PGAA) and Neutron Reflectometry (NR) for in situ monitoring of interactions between Gd-containing nanoparticles and biomimetic surfaces. The method requires the probed volume to be confined to a neutron waveguide structure formed by the gold layer on the surface, and the D2O solvent. This arrangement of layers gives rise to resonant absorption of neutrons. Within this CeNano project we will optimize this waveguide by tuning the size of the probed volume using variable length, poly(ethylene glycol) (PEG) spacer layers (Figure 1a). The aim is to determine the PEG chain lengths and deposition parameters to allow the excitation of higher harmonics in the waveguides leading to multiple resonances (Figure 1b). Measuring the gamma signal from multiple absorption peaks increases the precision of determining the amount and position of the Gd-containing nanoparticles within the probed volume. The deposited systems will be characterized using Spectroscopic Ellipsometry, X-ray Photoelectron Spectroscopy and X-ray Reflectometry, and the resulting structures will be used in simulations to determine the properties of the resonant absorption peaks.
Figure 1 a) Schematic illustration of the samples. The Au surface is coated with an alkylthiol self-assembled monolayer (SAM) with a PEG spacer layer attached on top. The Gd2O3 nanoparticles are deposited on or covalently bound to the PEG layer. The Gd atoms convert the incoming neutron radiation to gamma rays. b) Gamma photon intensities for different waveguide widths. The curves are offset with a factor of 104x for clarity. Inset: Scattering length density (SLD) and absorption cross section (orange) profiles of the different waveguide systems.