Search results for " NANO"
showing 10 items of 10430 documents
Spectroscopic studies of semiconducting single-walled carbon nanotubes
2010
The unique nature of optical properties of single-walled carbon nanotubes (SWCNT), together with their promising potential applications, have created enormous interest towards the photophysics of SWCNT. Many aspects of carbon nanotubes originate from the electronic structure of carbon honeycomb lattice and one-dimensionality. SWCNTs exist in various chiral structures and diameters, which the optical and electrical properties are dependent on. It has been discovered that SWCNT excited states are excitonic with strong Coulomb interaction between the electron and the hole. However, many features of excitons are not yet well defined, such as absorption cross-sections, fluorescence quantum yield…
Optical properties of conductive carbon-based nanomaterials
2016
The interaction of light with carbon nanomaterials is the main focus of this thesis. I explore several nanostructured systems involving different allotropes of carbon, and characterize them both electrically, if applicable, and optically. Special attention is paid to search for plasmon-like excitations on the systems, or utilizing surface plasmons on characterization. The first objective is to achieve control of carbon nanotube (CNT) conductivity with surface plasmon polaritons (SPPs), which resulted in the first CNT field-effect transistor (FET) that can be gated definitively with SPPs. The second objective is the investigation of optical properties of various thin carbon-based molecular n…
Photodynamics studies of ligand-protected gold nanoclusters by using ultrafast transient infrared spectroscopy
2015
Highly monodisperse samples of three ligand-protected gold nanoclusters Au102(pMBA)44, Au144(SC2H4Ph)60, and a cluster tentatively identified as Au130(pMBA)50, were characterized by UV/vis and infrared spectroscopy, and their photodynamics was studied by transient absorption spectroscopy. The dynamics study for each cluster was performed by electronically exciting the cluster with a pump pulse in the visible or near infrared region and by monitoring the transient absorption of vibrational modes of the ligands with a mid-IR probe pulse. The photodynamics studies were used to determine the molecular or metallic behavior of the cluster, and also to gain important size dependent information abo…
Exotic Spin-Orbital Physics in Hybrid Oxides
2016
We compare the effective spin-orbital super\-exchange triggered by magnetic $3d$ impurities with $d^3$ and $d^2$ configurations and either no orbital degree of freedom (orbital dilution) or hole replacing a doublon (charge dilution) in a $4d^4$ Mott insulator with $S=1$ spins. Impurities causing orbital dilution act either as spin defects decoupled from the surrounding ions, or generate orbital polarons along $d^3$-$d^4$ hybrid bonds. The exchange on these bonds determines which orbital is occupied by a doublon on the host site. In case of charge dilution by $3d^2$ impurities additional $\propto T_i^+T_j^+$ terms arise which enhance orbital fluctuations. We show that such terms may radicall…
Design Scheme of New Tetragonal Heusler Compounds for Spin-Transfer Torque Applications and its Experimental Realization
2012
Band Jahn-Teller type structural instabilities of cubic Mn(2)YZ Heusler compounds causing tetragonal distortions can be predicted by ab initio band-structure calculations. This allows for identification of new Heusler materials with tunable magnetic and structural properties that can satisfy the demands for spintronic applications, such as in spin-transfer torque-based devices.
Spin caloric transport from density-functional theory
2019
Spin caloric transport refers to the coupling of heat with spin transport. Its applications primarily concern the generation of spin currents and control of magnetisation by temperature gradients for information technology, known by the synonym spin caloritronics. Within the framework of ab initio theory, new tools are being developed to provide an additional understanding of these phenomena in realistic materials, accounting for the complexity of the electronic structure without adjustable parameters. Here, we review this progress, summarising the principles of the density-functional-based approaches in the field and presenting a number of application highlights. Our discussion includes th…
Multi-functional Stabilizers-functionalized Carbon Nanotubes for advanced Ultra-High Molecular Weight Polyethylene-based Nanocomposites
2015
Stabilizing molecules, such as hindered phenols (both synthetic and naturally occurring), polyphenols and hindered amine light stabilizers, were covalently linked or physically absorbed onto outer surface of multi-walled carbon nanotubes (CNTs) and the obtained multi-functional fillers (Stab-f-CNTs) were dispersed in Ultra High Molecular Weight Polyethylene (UHMWPE) aiming at obtaining advanced nanocomposites with enhanced thermo- and/or photo-oxidative stability, electrical and mechanical properties. The chemical grafting or physical absorption of stabilizing molecules is confirmed by spectroscopic, spectrometric and thermo-gravimetric analyses, and the influence of the multi-functional na…
Heterogeneous photocatalysis: guidelines on experimental setup, catalyst characterization, interpretation, and assessment of reactivity
2019
Soon after the publication of the first pioneering works on heterogeneous photocatalysis, the number of papers on this topic continuously increased. This intriguing field of research is very complex as it endows with an interdisciplinary overview that involves different aspects of chemistry, physics, material and environmental sciences. Even if photocatalytic applications in real processes are often difficult to be implemented and scaled-up, investigations at laboratory scale are easy to be performed, and in some cases they may give rise to misconceptions. For this reason, the present work aims to sum up most of the common experimental techniques and procedures generally used in heterogeneo…
Photoluminescence and Electron Spin Resonance of Silicon Dioxide Crystal with Rutile Structure (Stishovite)
2018
This work was supported by ERANET MYND. Also, financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ/2017/2 realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. The authors express our gratitude to R.I. Mashkovtsev for help in ESR signal interpretation. The authors are appreciative to T.I. Dyuzheva, L.M. Lityagina, N.A. Bendeliani for stishovite single crystals and to K. Hubner and H.-J. Fitting for stishovite powder of Barringer Meteor Crater.
Experimental Investigation on Stiffness and Strength of Single-Lap Z-Pinned Joints in a Laminated CFRP Stress-Ribbon Strip
2016
Carbon fiber-reinforced polymer (carbon-polymer) is an advanced lightweight composite material with high strength and excellent resistance to corrosion and fatigue. Over the past decades, application of fiber-reinforced polymers has been spread from the aerospace to other branches of industry such as automobile and civil engineering. Unidirectional carbon-polymers have a high potential for replacing steel in tensile members. Recently, the first carbonpolymer stress-ribbon bridge has been constructed in Germany. The non-laminated strip-loop carbon-polymer thin strips were used as the load bearing components in this bridge. In comparison with the laminated components, the applied cables are c…