Sum decomposition of Mueller matrices of biological nanostructures
Roger Magnusson, Kenneth Järrendahl, Hans Arwin (IFM, LiU)
A Muller matrix M provides a full description of the specular reflection properties of a surface and includes irradiance reflectance, polarization and depolarization properties. Experimental M are obtained by spectroscopic ellipsometry. Here the objective is to sum decompose a depolarizing Muller matrix according to
where Mi are non-depolarizing matrices with relative weights λi. For a non-depolarizing reflector only one of the four terms is non-zero whereas for a depolarizing M two or more terms are non-zero. An eigenvector analysis of the covariance matrix of M, gives a hint to the appropriate set of matrices Mi to use and the λI’s, are eigenvalues of the covariance matrix. Once the set of Mi is found, a regression decomposition (e.g. in MATLAB) can be performed. As an example, a decomposition of M measured on the beetle Cetonia aurata is shown below. Only two eigenvalues are non-zero and a possible decomposition is as a mirror and a left-handed circular polarizer. The last two terms do not contribute as λ3 and λ4 are zero, but would correspond to a left-handed circular polarizer and a halfwave plate for more complex reflectors.
Once the decomposition strategies are settled, a classification scheme can be established. One strategy is to introduce four major classes of reflectors corresponding to the number of non-zero λi. The spectral and angular dependence should then be condensed to a single parameter, e.g. by averaging each λi over the visible spectrum, or by defining other measures which uniquely describe the reflector. For colors we have color systems like the RGB, L*a*b*, etc. The ultimate goal in this project is to find a corresponding system with polarization coordinates describing a reflector.
Interface coherency studies in c-Ti1-xCrxN/h-AlN and c-Ti1-xZrxN/h-AlN (x=0-1) multilayers
Siva Phani Kumar Yalamanchili, Fei Wang, Naureen Ghafoor, Ferenc Tasnádi (IFM, LiU)
Our aim is to revisit the long existing concept of favorable isostructural decomposition in TiAlN hard coatings and reveals a novel research route for hard multicomponent nanostructured materials. Recent high resolution structural investigation on atomistic scale indicates, that formation of hexagonal AlN is not necessarily detrimental for mechanical properties as long as interface coherence upholds (see Fig.). We study coherent cubic to hexagonal interface in hard coating multilayers, such as c-Ti1-xMxN/h-AlN (M:Cr, Zr, x=0-1). Our major interest is to prove the novel concept by energetic arguments, explore the impact of interface composition on the thermodynamic properties (stability) and also to utilize the knowledge for developing new hard coatings.
Eu-doped Gd2O3 nanoparticles for specific dual-modal biomedical imaging
Andreas Skallberg, Zhangjun Hu (IFM, LiU)
This project has been aimed to design and synthesize the ligands, which contain exceptional chelate sites (for grafting the surface of Eu-doped GO NPs), screened water-soluble moieties (for stabilizing NPs and enhancing biocompatibility); conjugated aromatic parts (for sensitizing Eu luminescence via antenna effects) and pre-reserved reactive sites (for further decorating with the targeting molecules). This final aim is to optimize the preparation and modification of the titled NPs by using the synthesized ligands; and evaluate the property aspects and targeting imaging capacities of NPs. We will evaluate the probe performance as both preparative MRI and intraoperative tumor paint for optical tumor delineation.
Surface diffusion studies of non-carbide forming adatoms on graphene surfaces
Chamseddine Bouhafs, Linda Karlsson, Vanya Darakchieva, Per Persson (IFM, LiU)
This project will investigate the kinetics and interactions of non-carbide forming metal adatoms on the surface of the 2D material graphene. The purpose is to address original and significant surface physics, to determine metal-graphene interfaces and explore binary phase diagrams of two-dimensional structures.
Use and functionalization of graphene for electronic devices requires the successful attachment of metal atoms and contacts to the graphene sheets. Growth of thin metal sheets onto graphene films have however not been investigated in detail, but rather in macroscopic perspectives, neglecting the atomic arrangement at the interface and the consequence on e.g. charge transfer and electronic states the arrangement may have.
Hence, the aim of this project is to deposit a sub monolayer of select elements (non-carbide forming) on graphene, and to investigate the behavior of the adatoms as they migrate in-situ. The assembly will be heated, also in-situ, using a high temperature annealing holder inside the electron microscope, and the progress, kinetics and ripening details will be monitored live.
At LiU, the Electron Microscopy of Materials are advancing low-kV methods for imaging of structures at atomic resolution, e.g. by annular bright field scanning TEM and by improved aberration corrected imaging at low-kV. The former is a new technique which we have implemented to visualize both heavy and light elements simultaneously. Together, these methods constitute the key elements for a successful outcome.
Two figures of MXene (another 2D material) on which we can determine the movement and coalescence of Ti adatoms on the MXene surface.
Developing a smart electronic paper based on piezoelectric nanowires
Eiman S. Nour, Hatim Alnoor, Mats O. Sandberg*, Omer Nour (ITN, LiU) (*also at Acreo AB)
Zinc oxide (ZnO) is a semiconductor possessing a strong piezoelectric effect and is characterized by many other interesting chemical and physical properties. ZnO also possesses self-organized growth, a fact that makes it possible to synthesize it on any substrate, even those of amorphous nature, like e.g. paper. In addition, its nanostructures which can be synthesized by low temperature methods (˂100 oC) constitute one of the richest families of nano-morphologies. In this project we utilize the piezoelectric properties of ZnO nanowires synthesized on paper substrate to develop a ‘’smart electronic’’ paper which harvest mechanical energy provide by writing pressure to electrical signals. The concept can be of potential for many applications, like signature verification, mobile electronic keyboard etc.. So far the preliminary results are encouraging and we have obtained an open circuit harvested voltage of up to 4.8 V.
Registration of nanoparticle-microelectrode collisions: electroanalysis for nanomaterials characterization and environmental monitoring
Alina Sekretaryova, Onur Parlak, Mikhail Vagin, Martin Mak (IFM, LiU)The extensive industrial usage the nanoparticles (NP) leads to their release into the environment with yearly exponential increase due to use intensification(1). In particular, Silver NP are in extensive use in variety of products due to their biocide activities(2) and are perhaps the most worrying of industrially-manufactured NP because of inherent toxicity to mammalians(3) and aquatic life(4), while these commercial products are a major and growing source of silver NP to the environment(5, 6). However, the behavior of NP in the environment as well as in the sewage treatment and waste incineration plants is largely unknown due to the lack of experimental data of the NP environmental detection. Appeared recently(7, 8), direct electrochemical detection of nanoparticles by means of the registration of their single collisions with microelectrode surface represents one of the most advanced techniques of NP real-time quantification and characterization(9, 10). The main objective of the Project is the development of new platform for NP characterization, to generate new knowledge in electrochemical behavior of NP and to explore the potential application of NP. The main goals are NP quantification and characterization with collision detection for water quality monitoring. The Project will promote the synergetic research interactions based on ongoing PhD Projects between A. Sekretaryova (supervisor: Dr. M. Vagin) working on electrochemical environmental monitoring and O. Parlak (supervisor: Dr. M. Mak) working on NP fabrication.
1. J. Fabrega et al., Environ.Int., 2011, 37, 517; 2. H. Lara et al., J.Nanobiotechnol., 2011, 9; 3. M. Ahamed et al., Clin.Chim.Acta, 2010, 411, 1841; 4. A. Hinther et al., Environ.Sci.Technol, 2010, 44, 1841; 5. M. Eckelman et al., Environ.Sci.Technol, 2007, 41, 6283; 6. Y. Ju-Nam et al., Sci.TotalEnviron., 2008, 400, 396; 7. M. Heyrovsky et al., Langmuir, 1995, 11, 4293; 8. X. Y. Xiao et al., JACS, 2007, 129, 9610; 9. E. Stuart et al., Nanoscale, 2013, 5, 174; 10. Y. Zhou et al., Angew.Chem.Int.Ed., 2011, 50, 4219.
The missing link between theory and experiment for the understanding of the nanostructure of amorphous boron carbide
Annop Ektarawong, Mewlude Imam, Henrik Pedersen, Björn Alling (IFM, LiU)Boron carbide thin films are the material of choice for a new generation of neutron detectors at the European Spallation Source (ESS) in Lund. When grown with physical and vapour deposition techniques amorphous B4C is obtained. The atomic and nanoscale structure of these coatings determine their mechanical, electrical, and chemical properties, but are currently unknown. In this project these amorphous materials are investigated with combined theoretical and experimental methods. On the theoretical side we will use quantum molecular dynamics meltquench and structure prediction methods to obtain candidate amorphous structure models including radial distribution functions, average coordination numbers and boron-carbon configuration preferences. These will then be compared with the structural information of our films using pair distribution function analysis of synchrotron X-ray total scattering, nuclear magnetic resonance, and neutron scattering techniques.
 A. Ektarawong, S. I. Simak, L. Hultman, J. Birch, and B. Alling PRB 90, 024204 (2014)
The nanoscale of disordered B4C possibly built up of sub-nanometer sized B11C icosahedra and C-B-C linear chains. From ref .
Nanomechanical and nanodynamic properties of protein entities participating in dynamic conformational selection and multimodular recognition
Madhanagopal Anandapadamanaban, Maria Sunnerhagen (IFM, LiU)
From an engineering point of view, proteins are mechanical devises engineered to perform various tasks in the nano-dimensional range. Protein α-helices, the ’pistons’ of action, range from 1-50 nm in length and hundreds of nm when bundled, and protein β-sheets, which can be wrapped to form shapes of up to 100 nm and more, together form the structural framework where nanobiological functionality is encoded. Disordered regions have recently been recognized to function both as multirecognition elements in protein ’hubs’ and as flexible linkers organizing modular entities into multifunctional units. We are studying the structural and dynamic properties of proteins using both crystallography and NMR, together with other biophysical techniques such as CD, ITC, fluorescence and SPR, and apply this both to proteins involved in transcriptional activation (see our TBP-TAF1 complex in figure), but also in an ongoing study on the E3 ubiquitin ligase TRIM21 involved in autoimmune disease.
Electrostatic surface representation of yTBP, with the bound yTAF1 transcriptional regulator in green and with its TBP-anchoring residues annotated.
Biocompatibility studies of engineered nanoparticles aimed for use in biomedical applications
Natalia Abrikossova, Caroline Brommesson (IFM, LiU)
The demands on all nanomaterials aimed to be used in biological applications are extensive. Main focus in this project is to evaluate mechanisms of interaction between gadolinium oxide nanoparticles (Gd2O3) and inflammatory cells (in vitro). Gd2O3 nanoparticles are, due to their absorption and magnetic properties, promising for contrast enhancement during examinations with the clinically important diagnostic techniques computed tomography (CT) and magnetic resonance imaging (MRI). We use human isolated blood cells i.e. neutrophil granulocytes, platelets and monocytes as these are rapidly responding cells and also among the cells that will be the first to encounter intravenously administered nanoparticles. We evaluate cellular uptake of nanoparticles as well as functional responses following exposure to nanoparticles, e.g. cell aggregation and production of reaction oxygen species. Increased knowledge of the involved pathways and uptake mechanisms will be helpful in the future design of biocompatible nanoparticles.
Uptake of Gd2O3 nanoparticles in neutrophil granulocytes
Imaging strategies for dynamic and responsive supramolecular nanostructures by applying low-kV and in-situ transmission electron microscopy
Ingemar Persson, Camilla Sandén, Per Persson, Daniel Aili (IFM, LiU)
In this project we will investigate possible nondestructive routes for imaging of supramolecular assemblies and their response to external stimuli by applying electrons, accelerated at low voltages (60 kV) in the transmission electron microscope. Specifically, the intentions are to visualize molecules, supramolecular assemblies (peptides and lipid nanostructures) and gold nanoparticle hybrids and find methods to for low dose imaging where functionality and structure of molecular species are retained. Imaging will be carried out using the monochromated and double corrected Titan^3 microscope at LiU.
Investigating magnetron sputter epitaxy of ZrB2 on MOCVD grown GaN epi-layers for potential use in High Electron Mobility Transistors
Lina Tengdelius, Xun Li, Hans Högberg, Urban Forsberg (IFM, LiU)
ZrB2 is a refractory and conductive ceramic with high temperature stability and with potential use as a heat shield material for space vehicles. As thin film material the phase exhibits a good lattice match to GaN(0001) and 4H-SiC(0001) and has a 6:5 “magic” mismatch to Si(111). Recently, we demonstrated for the first time that epitaxial ZrB2 films can be sputtered from a compound target on 4H-SiC(0001) and Si(111) substrates (L. Tengdelius et al., physica status solidi A,211, 636-640 (2014)). However, epitaxial growth on GaN(0001) remains to be demonstrated as apparent from the selected area diffraction pattern in figure 1. For progress in the field, the project will grow and evaluate different templates, AlN, AlGaN and GaN on SiC substrates, see inset in figure 1. Previous investigations of sputtered ZrB2 on GaN have shown that the surface condition of the GaN template is of high importance, see interface between the substrate and the polycrystalline ZrB2 film in figure 1. Therefore, different surface pretreatment of the templates will be performed; both chemical cleaning as well as in situ hydrogen etching at an elevated temperature will be investigated.
Organic/inorganic hybrid structures fabricated utilizing III-N nanorods
Mathias Forsberg, Galia Pozina (IFM, LiU)
Hybrid structures based on III-N semiconductor quantum well (QW) and organic polymers utilizing non-radiative resonant energy transfer (NRET) from excitations generated in QW to excitons in the fluorescent layer have potential applications as efficient emitters for down converting of UV and blue light. In this project a new design of hybrid will be used: organic polyfluorenes with emission in visible region deposited on heterostructured AlInN/GaN nanorods produced by DC magnetron sputtering.
Designed nanoparticles for graphene-based gas sensors
Rickard Gunnarsson, Jens Eriksson, Ulf Helmersson (IFM, LiU)
Graphene based gas sensors have a high sensitivity and are therefore a promising platform for detecting toxic vilotile organic compounds. However, these sensors lack selectivity and suffer from poor response and recovery time. The aim of this project is to coat graphene sensors with nanoparticles to circumvent these issues. The nanoparticles will be synthesized with a novel plasma based process, that allows for size and stoichiometry control of metal oxide nanoparticles. It is also possible to coat the nanoparticles with another metal which allows for a wider selection of material combinations to be used.
Boron Nitride – the ultimate substrate for graphene
Mihails Cubarovs, Anne Henry (IFM, LiU)
A chemical vapor deposition process has been developed for the growth of sp2 boron nitride (sp2-BN) on sapphire (Al2O3) with the need of an AlN buffer layer. We have shown that H2 should be used as carrier gas and the addition of small amount of Si in the gas mixture favors the growth of high quality rhombohedral layer. The epilayer surface is observed with nanosize features and when manipulating the material an exfoliation appears easy.
Polarizing properties and structural characteristics in the cuticle of the scarab beetle Chrysina gloriosa
Lia Fernandez del Rio, Hans Arwin, Kenneth Järrendahl (IFM, LiU)The scarab beetle Chrysina gloriosa has an eye catching metallic colouration originating from the refection of light on the exocuticle. The refected light is elliptically polarized and in some cases even circularly polarized. In this project the chiral exocuticle structure and its optical properties will be studied with SEM and Mueller-matrix ellipsometry and also optically modelled. Other scarab beetles with similar optical features will also be studied. The objective is to serve as inspiration in the production of bioinspired materials which would have metallic appearance, tunable optical properties and organic composition.
Tailoring the light emission efficiency of ZnO nanoparticles via polymer coating for optoelectronic applications
Martin Eriksson, Deping Qian, Volodymyr Khranovskyy, Fengling Zhang, Fredrik Karlsson (IFM, LiU)
ZnO is a semiconductor material with outstanding light emission properties. Due to its direct band gap and high exciton binding energy, it enables efficient UV light emission (λ ~375 nm) up to room temperature. However, the available surface states trap charge careers, which reduces the radiative recombination rate of the material. This is especially noticeable for nanoparticles, which have large surface-to-volume ratios. The aim of this study is to improve the light emission efficiency of ZnO nanoparticles by coating them with polymer. In this project we will investigate the light emission features of ZnO nanoparticles by microphotoluminescence spectroscopy and reveal how it can be influenced via coating by polymers. We plan to study both the time integrated and the time dependent photoluminescence of the ZnO nanoparticles coated by different polymers, such as PEO and PMMA, in comparison to bare ZnO nanoparticles. As a long term perspective, this study aims to contribute to applications such as inorganic nanoparticle/organic polymer based light emitting diodes (InOr-LEDs).
Low temperature time resolved photoluminescence spectra of ZnO nanoparticles
Ultrabright semiconducting polymer dots (Pdots) for specific cancer cell targeting
Peter Eriksson, Xuanjun Zhang (IFM, LiU)
Semiconducting polymer nanoparticles (Pdots) are a new class of fluorescent nanoprobe with superior characteristics such as low toxicity, ultra bright photoluminescence, nonblinking, and fast emission rates. We are now developing reliable methods to (1) functionalize the Pdot surface for specific bioconjugation with biomolecules such as proteins, cancer drugs, antibodies, etc; (2) tune emission to Near-Infrared (NIR) region for practical in vivo applications. The bright NIR fluorescent Pdots with specific targeting ligands are very promising for a variety of biological applications.