26 results on '"Karolina Z. Milowska"'
Search Results
2. Doping Engineering of Single-Walled Carbon Nanotubes by Nitrogen Compounds Using Basicity and Alignment
- Author
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Bogumiła Kumanek, Karolina Z. Milowska, Łukasz Przypis, Grzegorz Stando, Karolina Matuszek, Douglas MacFarlane, Mike C. Payne, Dawid Janas, Przypis, Łukasz [0000-0001-5195-8751], Matuszek, Karolina [0000-0001-8979-5927], Janas, Dawid [0000-0002-6003-3520], and Apollo - University of Cambridge Repository
- Subjects
carbon nanotubes ,electrical properties ,General Materials Science ,doping ,nitrogen compounds ,thermoelectric properties - Abstract
Charge transport properties in single-walled carbon nanotubes (SWCNTs) can be significantly modified through doping, tuning their electrical and thermoelectric properties. In our study, we used more than 40 nitrogen-bearing compounds as dopants and determined their impact on the material's electrical conductivity. The application of nitrogen compounds of diverse structures and electronic configurations enabled us to determine how the dopant nature affects the SWCNTs. The results reveal that the impact of these dopants can often be anticipated by considering their Hammett's constants and pKa values. Furthermore, the empirical observations supported by first-principles calculations indicate that the doping level can be tuned not only by changing the type and the concentration of dopants but also by varying the orientation of nitrogen compounds around SWCNTs.
- Published
- 2022
3. Effective doping of single-walled carbon nanotube films with bromine under ultrasound
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Karolina Z. Milowska, Maciej Krzywiecki, Mike C. Payne, and Dawid Janas
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Ultrasounds ,Mechanics of Materials ,Mechanical Engineering ,Carbon nanotubes ,Doping ,TA401-492 ,General Materials Science ,Bromine ,Materials of engineering and construction. Mechanics of materials - Abstract
Carbon nanomaterials such as graphene and carbon nanotubes (CNTs) have attracted considerable interest from the scientific community over the past decades. Due to the extraordinary properties they are envisioned to play a key role in a wide spectrum of applications in the upcoming future. An interesting property of carbon nanostructures is the sensitivity of their electronic properties to a range of chemical stimuli. Consequently, their capabilities for charge propagation may be significantly enhanced upon appropriate combination with a chemical compound, which can affect the Fermi level of the material. In this work, the impact of addition of bromine to single-walled CNT (SWCNT) films on their electrical and thermoelectric properties was investigated. The experimental results revealed that thermoelectric capabilities of the material may be enhanced by two orders of magnitude by sonication-assisted introduction of Br2 into a SWCNT network. Conducted computations unravelled how the dopant affects the electronic properties of the SWCNT host and its charge transport properties.
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- 2022
4. The Origin of Amphipathic Nature of Short and Thin Pristine Carbon Nanotubes—Fully Recyclable 1D Water‐in‐Oil Emulsion Stabilizers
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Anna W. Blacha, Karolina Z. Milowska, Mike C. Payne, Heather F. Greer, Artur P. Terzyk, Emil Korczeniewski, Aleksandra Cyganiuk, and Sławomir Boncel
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Mechanics of Materials ,Mechanical Engineering - Published
- 2023
5. The True Amphipathic Nature of Graphene Flakes: A Versatile 2D Stabilizer
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Pak-Lee Chau, Krzysztof K. K. Koziol, Mike C. Payne, Noorhana Yahya, Karolina Z. Milowska, Anna W Kuziel, Sławomir Boncel, Cranfield University, Silesian University of Technology, University of Cambridge [UK] (CAM), Bioinformatique structurale - Structural Bioinformatics, Institut Pasteur [Paris]-Centre National de la Recherche Scientifique (CNRS), Centre de Bioinformatique, Biostatistique et Biologie Intégrative (C3BI), Universiti Teknologi PETRONAS (UTP), A.W.K. and K.K.K. acknowledge Cranfield University Grant EME/3022Z. K.Z.M. and M.C.P. acknowledge EPSRC Grant EP/P034616/1. S.B. is very grateful for the financial support from the National Science Centre (Poland) Grant No. 2019/33/B/ST5/01412 in the framework of OPUS program. S.B. also greatly acknowledges financial support in the area of fundamental sciences and R&D from Silesian University of Technology Rector's Grant No. 892/RN2/RR42019. P.-L.C. was partly supported by the INCEPTION project ANR-16-CONV-0005., ANR-16-CONV-0005,INCEPTION,Institut Convergences pour l'étude de l'Emergence des Pathologies au Travers des Individus et des populatiONs(2016), and Institut Pasteur [Paris] (IP)-Centre National de la Recherche Scientifique (CNRS)
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Materials science ,Oxide ,Nanotechnology ,Pickering emulsions ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,law.invention ,Molecular dynamics ,chemistry.chemical_compound ,Colloid ,law ,interfacial self‐assembly ,Amphiphile ,General Materials Science ,interfacial self-assembly ,[PHYS]Physics [physics] ,Graphene ,Mechanical Engineering ,graphene flakes ,021001 nanoscience & nanotechnology ,Pickering emulsion ,0104 chemical sciences ,stabilizers ,chemistry ,Mechanics of Materials ,Density functional theory ,0210 nano-technology ,Stabilizer (chemistry) - Abstract
International audience; The fundamental colloidal properties of pristine graphene flakes remain incompletely understood, with conflicting reports about their chemical character, hindering potential applications that could exploit the extraordinary electronic, thermal, and mechanical properties of graphene. Here, the true amphipathic nature of pristine graphene flakes is demonstrated through wet-chemistry testing, optical microscopy, electron microscopy, and density functional theory, molecular dynamics, and Monte Carlo calculations, and it is shown how this fact paves the way for the formation of ultrastable water/oil emulsions. In contrast to commonly used graphene oxide flakes, pristine graphene flakes possess well-defined hydrophobic and hydrophilic regions: the basal plane and edges, respectively, the interplay of which allows small flakes to be utilized as stabilizers with an amphipathic strength that depends on the edge-to-surface ratio. The interactions between flakes can be also controlled by varying the oil-to-water ratio. In addition, it is predicted that graphene flakes can be efficiently used as a new-generation stabilizer that is active under high pressure, high temperature, and in saline solutions, greatly enhancing the efficiency and functionality of applications based on this material.
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- 2020
6. Carbon nanotube functionalization as a route to enhancing the electrical and mechanical properties of Cu-CNT composites
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Lidia Wolanicka, Paul D. Bristowe, Krzysztof K. K. Koziol, Karolina Z. Milowska, and Marek Burda
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Nanotube ,Materials science ,Dopant ,Doping ,Composite number ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,Electrical resistance and conductance ,law ,Surface modification ,General Materials Science ,Composite material ,0210 nano-technology ,Electrical conductor - Abstract
Copper–CNT (carbon nanotube) composite materials are promising alternatives to conventional conductors in applications ranging from interconnects in microelectronics to electrical cabling in aircraft and vehicles. Unfortunately, exploiting the full potential of these composites is difficult due to the poor Cu–CNT electro-mechanical interface. We demonstrate through large-scale ab initio calculations and sonication experiments that this problem can be addressed by CNT surface modification. Our calculations show that covalent functionalization of CNTs below 6.7 at% significantly improves Cu–CNT wetting and the mechanical properties of the composite. Oxidative pre-treatment of CNTs enhances the Young's modulus of the composite by nearly a factor 3 above that of pure Cu, whereas amination slightly improves the electrical current density with respect to the unmodified Cu–CNT system in the high bias regime. However, only nitrogen doping can effectively improve both the mechanical and electrical properties of the composite. As the experiments show, consistent with the calculations, substitutional doping with nitrogen effectively improves adhesion of the CNT to the Cu matrix. We also predict an improvement in the mechanical properties for the composite containing doped double-wall CNTs. Moreover, the calculations indicate that the presence of nitrogen dopants almost doubles locally the transmission through the nanotube and reduces the back scattering in the Cu matrix around the CNT. The computed electrical conductance of N-doped Cu–CNT “carpets” exceeds that of an undoped system by ∼160%.
- Published
- 2018
7. Highly Luminescent Cesium Lead Halide Perovskite Nanocrystals with Tunable Composition and Thickness by Ultrasonication
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Jochen Feldmann, Verena A. Hintermayr, Yu Tong, Alexander S. Urban, Karolina Z. Milowska, Aurora Manzi, Pablo Docampo, Sara Bals, Meltem F. Aygüler, Eva Bladt, and Lakshminarayana Polavarapu
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Photoluminescence ,Chemistry ,Analytical chemistry ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Cubic crystal system ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Dark field microscopy ,Catalysis ,0104 chemical sciences ,Nanocrystal ,Quantum dot ,Scanning transmission electron microscopy ,0210 nano-technology ,Luminescence ,Perovskite (structure) - Abstract
We describe the simple, scalable, single-step, and polar-solvent-free synthesis of high-quality colloidal CsPbX3 (X=Cl, Br, and I) perovskite nanocrystals (NCs) with tunable halide ion composition and thickness by direct ultrasonication of the corresponding precursor solutions in the presence of organic capping molecules. High angle annular dark field scanning transmission electron microscopy (HAADF-STEM) revealed the cubic crystal structure and surface termination of the NCs with atomic resolution. The NCs exhibit high photoluminescence quantum yields, narrow emission line widths, and considerable air stability. Furthermore, we investigated the quantum size effects in CsPbBr3 and CsPbI3 nanoplatelets by tuning their thickness down to only three to six monolayers. The high quality of the prepared NCs (CsPbBr3) was confirmed by amplified spontaneous emission with low thresholds. The versatility of this synthesis approach was demonstrated by synthesizing different perovskite NCs.
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- 2016
8. Starke Lumineszenz in Nanokristallen aus Caesiumbleihalogenid- Perowskit mit durchstimmbarer Zusammensetzung und Dicke mittels Ultraschalldispersion
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Lakshminarayana Polavarapu, Jochen Feldmann, Verena A. Hintermayr, Karolina Z. Milowska, Yu Tong, Sara Bals, Eva Bladt, Meltem F. Aygüler, Aurora Manzi, Pablo Docampo, and Alexander S. Urban
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02 engineering and technology ,General Medicine ,010402 general chemistry ,021001 nanoscience & nanotechnology ,0210 nano-technology ,01 natural sciences ,0104 chemical sciences - Abstract
Wir berichten uber eine einfache, skalierbare, einstufige Synthese von kolloidalen Perowskit-Nanokristallen (NCs) aus CsPbX3 (X=Cl, Br und I) mit durchstimmbarer Halogenidionenzusammensetzung und Dicke mittels Ultraschalldispersion der entsprechenden Eduktlosungen im Gegenwart von organischen Liganden und ohne Verwendung von polaren Losungsmitteln. Die kubische Kristallstruktur sowie Oberflachenterminierung wurden mittels HAADF-STEM mit atomarer Prazision aufgelost. Die NCs weisen hohen Photoluminenszenzquantenausbeuten, schmale Emissionslinien und hohe Stabilitat gegenuber Luft auf. Zusatzlich untersuchen wir die Quanteneinschrankungseffekte in Nanoplattchen aus CsPbBr3 und CsPbI3 mit reduzierten Dicken von 3 bis 6 Monolagen. Die hohe optische Qualitat der NCs (CsPbBr3) wird durch verstarkter Spontanemission (ASE) mit extrem niedrigen Schwellen gezeigt. Weiterhin wird durch den Einsatz an verschiedenen Perowskiten die Flexibilitat der Synthesemethode demonstriert.
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- 2016
9. Role of ligand–ligand vs. core–core interactions in gold nanoclusters
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Jacek K. Stolarczyk and Karolina Z. Milowska
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Steric effects ,Ligand ,Chemistry ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Nanoclusters ,Crystal ,Colloid ,symbols.namesake ,Computational chemistry ,Chemical physics ,symbols ,Nanomedicine ,Density functional theory ,Physical and Theoretical Chemistry ,van der Waals force ,0210 nano-technology - Abstract
The controlled assembly of ligand-coated gold nanoclusters (NCs) into larger structures paves the way for new applications ranging from electronics to nanomedicine. Here, we demonstrate through rigorous density functional theory (DFT) calculations employing novel functionals accounting for van der Waals forces that the ligand-ligand interactions determine whether stable assemblies can be formed. The study of NCs with different core sizes, symmetry forms, ligand lengths, mutual crystal orientations, and in the presence of a solvent suggests that core-to-core van der Waals interactions play a lesser role in the assembly. The dominant interactions originate from combination of steric effects, augmented by ligand bundling on NC facets, and related to them changes in electronic properties induced by neighbouring NCs. We also show that, in contrast to standard colloidal theory approach, DFT correctly reproduces the surprising experimental trends in the strength of the inter-particle interaction observed when varying the length of the ligands. The results underpin the importance of understanding NC interactions in designing gold NCs for a specific function.
- Published
- 2016
10. Influence of Carboxylation on Structural and Mechanical Properties of Carbon Nanotubes: Composite Reinforcement and Toxicity Reduction Perspectives
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Karolina Z. Milowska
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Materials science ,Physics::Medical Physics ,Composite number ,Mechanical properties of carbon nanotubes ,Nanotechnology ,Carbon nanotube ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Condensed Matter::Materials Science ,General Energy ,Carboxylation ,Chemical engineering ,Ab initio quantum chemistry methods ,law ,Vacancy defect ,Physics::Atomic and Molecular Clusters ,Density functional theory ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Elastic modulus - Abstract
Carboxylation of carbon nanotubes (CNTs) is an important process that is applied routinely for various applications, in particular for biomedical usage and the manufacturing of next-generation composite materials. This study investigates the influence of carboxylation on the structural and mechanical properties of CNTs. Ab initio calculations were performed within the density functional theory framework for metallic and semiconducting single- and multiwalled CNTs, imperfect and carboxylated at various concentrations, including disorder. The morphologies were analyzed, the stabilities of the carboxylated CNTs were determined, relevant electronic properties were evaluated, and elastic moduli were calculated (Young’s, shear, and bulk moduli, as well as Poisson’s ratio). The properties of grafted (—COOH, —OH, ═O) and imperfect (vacancy defects) CNTs were compared with those of carboxylated CNTs. In particular, both the structural and elastic properties were found to exhibit significant differences between —CO...
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- 2015
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11. Carbon Dots: A Unique Fluorescent Cocktail of Polycyclic Aromatic Hydrocarbons
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Alexander S. Urban, Jacek K. Stolarczyk, Ming Fu, Yu Wang, Karolina Z. Milowska, Andrey L. Rogach, Jochen Feldmann, Claas J. Reckmeier, and Florian Ehrat
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chemistry.chemical_classification ,Materials science ,Photoluminescence ,Mechanical Engineering ,Exciton ,chemistry.chemical_element ,Polycyclic aromatic hydrocarbon ,Bioengineering ,Nanotechnology ,General Chemistry ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Fluorescence ,Condensed Matter::Materials Science ,symbols.namesake ,chemistry ,Chemical physics ,Stokes shift ,symbols ,General Materials Science ,Spectroscopy ,Carbon ,Astrophysics::Galaxy Astrophysics ,Excitation - Abstract
Carbon dots (CDs) have attracted rapidly growing interest in recent years due to their unique and tunable optical properties, the low cost of fabrication, and their widespread uses. However, due to the complex structure of CDs, both the molecular ingredients and the intrinsic mechanisms governing photoluminescence of CDs are poorly understood. Among other features, a large Stokes shift of over 100 nm and a photoluminescence spectrally dependent on the excitation wavelength have so far not been adequately explained. In this Letter we investigate CDs and develop a model system to mimic their optical properties. This system comprised three types of polycyclic aromatic hydrocarbon (PAH) molecules with fine-tuned concentrations embedded in a polymer matrix. The model suggests that the Stokes shift in CDs is due to the self-trapping of an exciton in the PAH network. The width and the excitation dependence of the emission comes from a selective excitation of PAHs with slightly different energy gaps and from energy transfer between them. These insights will help to tailor the optical properties of CDs and help their implementation into applications, e.g., light-emitting devices and biomarkers. This could also lead to "artificial" tunable carbon dots by locally modifying the composition and consequently the optical properties of composite PAH films.
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- 2015
12. Breaking the electrical barrier between copper and carbon nanotubes
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Nordin Ćatić, Lidia Wolanicka, Marek Burda, Krzysztof K. K. Koziol, Karolina Z. Milowska, Paul D. Bristowe, and Mahdi Ghorbani-Asl
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Materials science ,business.industry ,Contact resistance ,Composite number ,Conductance ,Nanotechnology ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,Bimetal ,law ,Microelectronics ,General Materials Science ,Electrical measurements ,Composite material ,0210 nano-technology ,business ,Current density - Abstract
Improving the interface between copper and carbon nanotubes (CNTs) offers a straightforward strategy for the effective manufacturing and utilisation of Cu–CNT composite material that could be used in various industries including microelectronics, aerospace and transportation. Motivated by a combination of structural and electrical measurements on Cu–M–CNT bimetal systems (M = Ni, Cr) we show, using first principles calculations, that the conductance of this composite can exceed that of a pure Cu–CNT system and that the current density can even reach 1011 A cm−2. The results show that the proper choice of alloying element (M) and type of contact facilitate the fabrication of ultra-conductive Cu–M–CNT systems by creating a favourable interface geometry, increasing the interface electronic density of states and reducing the contact resistance. In particular, a small concentration of Ni between the Cu matrix and the CNT using either an “end contact” and or a “dot contact” can significantly improve the electrical performance of the composite. Furthermore the predicted conductance of Ni-doped Cu–CNT “carpets” exceeds that of an undoped system by ∼200%. Cr is shown to improve CNT integration and composite conductance over a wide temperature range while Al, at low voltages, can enhance the conductance beyond that of Cr.
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- 2017
13. Improving the electrical properties of carbon nanotubes with interhalogen compounds
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Dawid Janas, Paul D. Bristowe, Krzysztof K. K. Koziol, and Karolina Z. Milowska
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Materials science ,Graphene ,Doping ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Iodine monobromide ,Carbon nanotube ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,Iodine monochloride ,chemistry.chemical_compound ,chemistry ,Electrical resistance and conductance ,law ,General Materials Science ,0210 nano-technology ,Carbon ,Interhalogen - Abstract
The electronic properties of carbon nanostructures such as carbon nanotubes (CNTs) or graphene can easily be tuned by the action of various doping agents. We present an experimental study and numerical analysis of how and why metallic and semiconductive CNTs can be p-doped by exposing them to two interhalogens: iodine monochloride and iodine monobromide. Simple application of these compounds was found to reduce the electrical resistance by as much as 2/3 without causing any unfavorable chemical modification, which could disrupt the highly conductive network of sp2 carbon atoms. To gain better insight into the underlying mechanism of the observed experimental results, we provide a first principles indication of how interhalogens interact with model metallic (5,5) and semiconductive (10,0) CNTs.
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- 2017
14. Hole -character and delocalization in (Ga,Mn)As revised with pSIC and MLWF approaches – Newly found spin-unpolarized gap states of s-type below 1 of Mn
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Karolina Z. Milowska and Małgorzata Wierzbowska
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Wannier function ,Condensed matter physics ,Band gap ,Chemistry ,General Physics and Astronomy ,02 engineering and technology ,Magnetic semiconductor ,021001 nanoscience & nanotechnology ,01 natural sciences ,Pseudopotential ,Delocalized electron ,Ferromagnetism ,0103 physical sciences ,Density functional theory ,Physical and Theoretical Chemistry ,010306 general physics ,0210 nano-technology ,Spin (physics) - Abstract
The dilute magnetic semiconductor (Ga, Mn)As is ferromagnetic in accordance with the p–d Zener model. Hole density function (HDF) localization has been previously studied by means of the density functional theory (DFT) and non-standard DFT methods; however not for dopings near 1 % . We have revised (Ga, Mn)As using the DFT with the pseudopotential self-interaction correction (pSIC) and maximally-localized Wannier functions (MLWFs), which show the sp 3 character of a HDF. Nature of HDF is extended – for low dopings and the pSIC, 70 % of the HDF is located within the inter-impurities region, and contribution of the 3d-Mn states is 3–5 % for 1–3 % of Mn with the pSIC, and 11 % with the DFT. We found that for dopings below 1 % , the spin-unpolarized s-type impurity states segregate from the conduction band to the energy gap – in contrast to earlier publications. This implies that donor co-doped dilute samples would be both insulating and nonmagnetic.
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- 2014
15. Stability and electronic structure of covalently functionalized graphene layers
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Karolina Z. Milowska and Jacek A. Majewski
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Materials science ,Band gap ,Graphene ,Electronic structure ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Chemical physics ,law ,Covalent bond ,Monolayer ,Surface modification ,Density functional theory ,HOMO/LUMO - Abstract
We present exemplary results of extensive studies of mechanical, electronic, and transport properties of covalent functionalization of graphene monolayers (GML) with –NH2. We report new results of ab initio studies of covalent functionalization of GML with –NH2 groups up to 12.5% concentration. Our studies are performed in the framework of the density functional theory (DFT) and non-equilibrium Green's function (NEGF). We discuss the stability (adsorption energy), elastic moduli, electronic structure, band gaps, and effective electron masses as a function of the density of the adsorbed molecules. We also show the conductance and I(V) characteristic of these systems. Generally, the stability of the functionalized graphene layers decreases with the growing concentration of attachments and we determine the critical density of the molecules that can be chemisorbed on the surface of GLs. Because of local deformations of GLs and sp3 rehybridization of the bonds induced by fragments, elastic moduli decrease with increasing number of groups. Simultaneously, we observe that the functionalizing molecules stretch the graphene's lattice, the effect being more pronounced for higher concentration of adsorbed molecules. We find out that the GLs functionalization leads in many cases to the opening of the graphene band gap (up to 0.5302 eV for 12.5% concentration) and can be therefore utilized in graphene devices. The new HOMO and LUMO originate mostly from the impurity bands induced by the functionalization and they exhibit parabolic dispersion with electron effective masses comparable to ones in silicon or gallium nitride.
- Published
- 2013
16. Mechanical and electrical properties of carbon nanotubes and graphene layers functionalized with amines
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Karolina Z. Milowska, Magdalena Birowska, and Jacek A. Majewski
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Materials science ,Graphene ,Band gap ,Mechanical Engineering ,Nanotechnology ,Mechanical properties of carbon nanotubes ,General Chemistry ,Carbon nanotube ,Electronic, Optical and Magnetic Materials ,law.invention ,Chemical engineering ,law ,Monolayer ,Materials Chemistry ,Molecule ,Surface modification ,Electrical and Electronic Engineering ,Electronic band structure - Abstract
In the present paper, we study the effects of functionalization of graphene monolayers (GL) and single carbon nanotubes (CNT) with two types of amines NH, and NH2, analyzing structural, elastic and electronic properties of the structures. We have performed DFT calculations for GL and CNT with various densities of the attached amine molecules. We have determined the changes in the geometry, adsorption and binding energies, the Young's modulus, and the band structure as a function of the density of the adsorbed molecules. We observe characteristic effects such as rehybridization of the bonds induced by fragments attached to graphene and nanotubes and deformation of systems that results further in decrease of the Young's modulus. We also show that the band gap in GLs increases with the density of adsorbed molecules, whereas it decreases in CNTs. Our calculations reveal that the amines exhibit the strong cohesion to GLs and CNTs. Further, we determine the critical density of the NH fragments that leads to the closing of the band gap in functionalized CNT. We also show how to engineer the magnitude of the band gap by functionalizing graphene with NH2 and NH groups of various concentrations.
- Published
- 2012
17. Van Der Waals Density Functionals for Graphene Layers and Graphite
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Jacek A. Majewski, Magdalena Birowska, and Karolina Z. Milowska
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Materials science ,Condensed matter physics ,Graphene ,Van der Waals strain ,Ab initio ,General Physics and Astronomy ,chemistry.chemical_element ,law.invention ,symbols.namesake ,chemistry ,law ,symbols ,Van der Waals radius ,Density functional theory ,Graphite ,van der Waals force ,Carbon - Abstract
In this communication, we present results of theoretical studies of various systems where Van der Waals interaction plays a considerable role. In the first-principle calculations performed in the density functional theory framework we implement novel functionals accounting for Van der Waals forces and employ to the test cases of graphite and graphene layers. It turns out that this approach provides a solution to the long standing problem of overbinding between graphene layers in bulk graphite, giving the distance between the carbon layers in excellent agreement with experiment. In graphene bilayers, Van der Waals functionals lead to energetic barriers for A–B to A–A ordering of graphene bilayers that are by a factor of two smaller than the barriers obtained with standard functionals. It may be of crucial importance, particularly, if one uses atomistic ab initio methods as a starting point for multi-scale modeling of materials and for determination of effective potentials.
- Published
- 2011
18. Ab Initio Modeling of Graphene Functionalized with Boron and Nitrogen
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Magdalena Woińska, Jacek A. Majewski, and Karolina Z. Milowska
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Materials science ,chemistry ,Graphene ,law ,Ab initio ,General Physics and Astronomy ,chemistry.chemical_element ,Physical chemistry ,Boron ,Nitrogen ,law.invention - Published
- 2012
19. Graphene based sensors: theoretical study
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Karolina Z. Milowska and Jacek A. Majewski
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Condensed Matter - Materials Science ,Materials science ,Graphene ,Charge density ,Functionalized graphene ,chemistry.chemical_element ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Nanotechnology ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,General Energy ,chemistry ,law ,Covalent bond ,Monolayer ,Density of states ,Density functional theory ,Physical and Theoretical Chemistry ,Carbon - Abstract
Graphene, a 2-dimensional monolayer form of sp2 hybridizated carbon atoms, is attracting increasing attention due to its unique and superior physicochemical properties. Covalently functionalized graphene layers, with their modifiable chemical functionality and usefull electrical properties, are excellent candidates for broad range of sensors, suitable for biomedical, optoelectronic and environmental applications. Here, we present extensive study of transport properties of sensors based on covalently functionalized graphene monolayer (GML) with graphene electrodes. The transmissions, density of states and current-voltage characterisctics supported by analysis of charge distribution of GML functionalized by -CH3, -CH2, -NH2, -NH and -OH fragments have been calculated by means of density functional theory (DFT) and non-equilibrium Green's function (NEGF). Further, we demonstrate how to control the device sensitivity by manipulating: (i) concentration, (ii) particular arrangement, and (iii) type of surface groups. We explain the underlying detection physical mechanisms. Comparisons of the theoretical results to available experimental data are provided are made and show good agreement., Comment: 3 figures
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- 2014
20. Electronic structure of graphene functionalized with boron and nitrogen
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Magdalena Woińska, Jacek A. Majewski, and Karolina Z. Milowska
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Condensed Matter - Materials Science ,Materials science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Band gap ,Graphene ,Binding energy ,Substituent ,chemistry.chemical_element ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Electronic structure ,Condensed Matter Physics ,law.invention ,chemistry.chemical_compound ,Condensed Matter::Materials Science ,chemistry ,Chemical physics ,law ,Ab initio quantum chemistry methods ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Physics::Atomic and Molecular Clusters ,Density functional theory ,Boron - Abstract
We present a theoretical study of the structural and electronic properties of graphene monolayer functionalized with boron and nitrogen atoms substituting carbon atoms. Our study is based on the ab initio calculations in the framework of the density functional theory. We calculate the binding energies of the functionalized systems, changes in the morphology caused by functionalization, and further the band gap energy as a function of the concentration of dopants. Moreover, we address the problem of possible clustering of dopants at a given concentration. We define the clustering parameter to quantify the dependence of the properties of the functionalized systems on the distribution of B/N atoms. We show that clustering of B/N atoms in graphene is energetically unfavorable in comparison to the homogenous distribution of dopants. For most of the structures, we observe a nonzero energy gap that is only slightly dependent on the concentration of the substituent atoms., Comment: accepted in Physica Status Solidi
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- 2013
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21. Mechanical, electronic, and transport properties of functionalized graphene monolayers from ab initio studies
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Magdalena Birowska, Jacek A. Majewski, and Karolina Z. Milowska
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Band gap ,Chemistry ,Graphene ,Ab initio ,Conductance ,Electronic structure ,law.invention ,Condensed Matter::Materials Science ,Chemical physics ,Computational chemistry ,law ,Monolayer ,Molecule ,Density functional theory ,Physics::Chemical Physics - Abstract
We present exemplary results of extensive studies of mechanical, electronic and transport properties of covalent functionalization of graphene monolayers (GML). We report new results of ab initio studies for covalent functionalization of GML with −NH2 groups up to 12.5 % concentration. Our studies are performed in the framework of the density functional theory (DFT) and non-equilibrium Green’s function (NEGF). We discuss the stability (adsorption energy), elastic moduli, electronic structure, band gaps, and effective electron masses as a function of the density of the adsorbed molecules. We also show the conductance and current – voltage I(V) characteristics for these systems.
- Published
- 2013
22. Ab initio modeling of graphene layer functionalized with boron and nitrogen
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Jacek A. Majewski, Karolina Z. Milowska, and Magdalena Woińska
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Materials science ,Graphene ,Band gap ,Ab initio ,Substituent ,chemistry.chemical_element ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Computational chemistry ,Chemical physics ,Physics::Atomic and Molecular Clusters ,Bilayer graphene ,Boron ,Elastic modulus ,Graphene nanoribbons - Abstract
We present a computational study of the phenomenon of opening the band gap in graphene by means of functionalization with boron and nitrogen atoms. For most of the considered structures, we observe a nonzero energy gap with the width slightly dependent on the concentration of the substituent atoms. Additionally, elastic properties for graphene functionalized with B/N atoms for concentrations of 2% and 4% have been predicted. N-substitution almost does not influence the elastic moduli of graphene, while changes caused by B-substitution are more remarkable.
- Published
- 2013
23. Ab-initio study of structural, mechanical and electronic properties of functionalized carbon nanotubes
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Magdalena Birowska, Karolina Z. Milowska, and Jacek A. Majewski
- Subjects
Materials science ,Selective chemistry of single-walled nanotubes ,Ab initio ,Nanotechnology ,Mechanical properties of carbon nanotubes ,Electronic structure ,Carbon nanotube ,law.invention ,Optical properties of carbon nanotubes ,Condensed Matter::Materials Science ,Carbon nanobud ,Chemical engineering ,law ,Density functional theory - Abstract
We present exemplary results of extensive studies of structural, mechanical and electronic properties of covalent functionalization of carbon nanotubes (CNTs). We report new results for metallic (9,0), and semiconducting (10,0) single-wall carbon nanotubes (CNT) functionalized with -COOH, -OH, and both groups with concentration up to 12.5%. Our studies are performed in the framework of the density functional theory (DFT). We discuss here the stability, local and global changes in structure, elastic moduli (Young's, Shear, and Bulk), electronic structure and resulting band gaps, as a function of the density of the adsorbed molecules.
- Published
- 2013
24. Functionalization of carbon nanotubes with -CHn, -NHn fragments, -COOH and -OH groups
- Author
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Karolina Z. Milowska and Jacek A. Majewski
- Subjects
Condensed Matter - Materials Science ,Materials science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Band gap ,General Physics and Astronomy ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Carbon nanotube ,Photochemistry ,law.invention ,Ab initio quantum chemistry methods ,Covalent bond ,law ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Molecule ,Surface modification ,Density functional theory ,Physical and Theoretical Chemistry ,Electronic band structure - Abstract
We present results of extensive theoretical studies concerning stability, morphology, and band structure of single wall carbon nanotubes (CNTs) covalently functionalized by -CHn(for n=2,3,4),-NHn(for n=1,2,3,4),-COOH and -OH groups. Our studies are based on ab initio calculations in the framework of the density functional theory. We determine the dependence of the binding energies on the concentration of the adsorbed molecules, critical densities of adsorbed molecules, global and local changes in the morphology, and electronic structure paying particular attention to the functionalization induced changes of the band gaps. These studies reveal physical mechanisms that determine stability and electronic structure of those systems and also provide valuable theoretical predictions relevant for application. Functionalization of CNTs causes generally their elongation and locally sp2 -> sp3 rehybridization in the neighborhood of chemisorbed groups. For adsorbants making particularly strong covalent bonds with the CNTs(-CH2), we observe formation of the 5/7 defects. In CNTs functionalized with -CH2,-NH4, and -OH, we determine critical density of molecules that could be covalently bound to CNTs. Functionalization of CNTs can be utilized for band gap engineering and also lead to changes in their metallic/semiconductor character. In semiconducting CNTs, adsorbants such as -CH3,-NH2,-OH and -COOH, introduce 'impurity' bands in the band gap of pristine CNTs. In the case of -CH3,-NH2, the induced band gaps are typically smaller than in the pure CNT and depend strongly on the concentration of adsorbants. However, functionalization of semiconducting CNTs with -OH leads to the metallization of CNTs. On the other hand, the functionalization of semi-metallic (9,0)CNT with -CH2 causes the increase of the band gap and induces semi-metal to semiconductor transition., accepted in Journal of Chemical Physics
- Published
- 2012
25. Thioether-Functionalized Quinone-Based Resorcin[4]arene Cavitands: Electroswitchable Molecular Actuators
- Author
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François Diederich, Jovana V. Milić, Laurent Ruhlmann, Carlo Thilgen, Quy K. Ong, Thomas Schneeberger, Michal Zalibera, Nils Trapp, Karolina Z. Milowska, and Corinne Boudon
- Subjects
Chemistry ,electronics ,Organic Chemistry ,design ,Supramolecular chemistry ,electroswitches ,receptors ,Biochemistry ,Combinatorial chemistry ,Catalysis ,supramolecular chemistry ,Quinone ,Inorganic Chemistry ,chemistry.chemical_compound ,molecular devices ,monolayers ,Thioether ,motion ,Drug Discovery ,resorcin[4]arene cavitands ,molecular actuators ,Physical and Theoretical Chemistry - Abstract
The utility of molecular actuators in nanoelectronics requires activation of mechanical motion by electric charge at the interface with conductive surfaces. We functionalized redox-active resorcin[4]arene-quinone cavitands with thioethers as surface-anchoring groups at the lower rim and investigated their propensity to act as electroswitchable actuators that can adopt two different conformations in response to changes in applied potential. Molecular design was assessed by DFT calculations and X-ray analysis. Electronic properties were experimentally studied in solution and thin films electrochemically, as well as by X-ray photoelectron spectroscopy on gold substrates. The redox interconversion between the oxidized (quinone, Q) and the reduced (semiquinone, SQ) state was monitored by UV-Vis-NIR spectroelectrochemistry and EPR spectroscopy. Reduction to the SQ state induces a conformational change, providing the basis for potential voltage-controlled molecular actuating devices.
26. Structural and Electronic Properties of Functionalized Graphene
- Author
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Magdalena Birowska, Jacek A. Majewski, and Karolina Z. Milowska
- Subjects
Materials science ,Adsorption ,Band gap ,Graphene ,law ,Chemical physics ,General Physics and Astronomy ,Functionalized graphene ,Molecule ,Surface modification ,Electronic band structure ,Electronic properties ,law.invention - Abstract
In the present paper, we study the effects of functionalization of graphene with simple organic molecules OH, and NH2, focusing on the stability and band gaps of the structures. We have performed DFT calculations for graphene supercells with various numbers of the attached molecules. We have determined adsorption energies of the functionalized graphene monoand bilayers, the changes in the geometry, and the band structure. We observe the characteristic effects such as rehybridization of the bonds induced by fragments attached to graphene and opening of the graphene band gap by functionalization. We have also studied the dependence of the adsorption energies of the functionalized graphene on the density of the adsorbed molecules. Our calculations reveal that the –OH and –NH2 groups exhibit the strong cohesion to graphene layers. Further, we determine the critical density of the OH fragments which lead to the opening of the band gap. We also show how to engineer the magnitude of the band gap by functionalizing graphene with NH2 groups of various concentrations.
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