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Allali, N., Urbanova, V., Etienne, M., Devaux, X., Mallet, M., Vigolo, B., . . . Mamane, V. (2018). Accurate control of the covalent functionalization of single-walled carbon nanotubes for the electro-enzymatically controlled oxidation of biomolecules. Beilstein Journal of Nanotechnology, 9, 2750-2762
Open this publication in new window or tab >>Accurate control of the covalent functionalization of single-walled carbon nanotubes for the electro-enzymatically controlled oxidation of biomolecules
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2018 (English)In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 9, p. 2750-2762Article in journal (Refereed) Published
Abstract [en]

Single-walled carbon nanotubes (SWCNTs) were functionalized by ferrocene through ethyleneglycol chains of different lengths (FcETGn) and the functionalized SWCNTs (f-SWCNTs) were characterized by different complementary analytical techniques. In particular, high-resolution scanning electron transmission microscopy (HRSTEM) and electron energy loss spectroscopy (EELS) analyses support that the outer tubes of the carbon-nanotube bundles were covalently grafted with FcETGn groups. This result confirms that the electrocatalytic effect observed during the oxidation of the reduced form of nicotinamide adenine dinucleotide (NADH) co-factor by the f-SWCNTs is due to the presence of grafted ferrocene derivatives playing the role of a mediator. This work clearly proves that residual impurities present in our SWCNT sample (below 5 wt. %) play no role in the electrocatalytic oxidation of NADH. Moreover, molecular dynamic simulations confirm the essential role of the PEG linker in the efficiency of the bioelectrochemical device in water, due to the favorable interaction between the ETG units and water molecules that prevents π-stacking of the ferrocene unit on the surface of the CNTs. This system can be applied to biosensing, as exemplified for glucose detection. The well-controlled and well-characterized functionalization of essentially clean SWCNTs enabled us to establish the maximum level of impurity content, below which the f-SWCNT intrinsic electrochemical activity is not jeopardized.

Place, publisher, year, edition, pages
Beilstein-Institut, 2018
Keywords
biosensing, carbon nanotubes, covalent functionalization, electrocatalysis, ferrocene
National Category
Other Physics Topics
Research subject
Experimental Physics; Applied Physics
Identifiers
urn:nbn:se:ltu:diva-71587 (URN)10.3762/bjnano.9.257 (DOI)000448782500001 ()30416926 (PubMedID)2-s2.0-85056284634 (Scopus ID)
Note

Validerad;2018;Nivå 2;2018-11-15 (johcin)

Available from: 2018-11-15 Created: 2018-11-15 Last updated: 2019-04-11Bibliographically approved
Berezovsky, V. & Öberg, S. (2018). Computational study of the CO adsorption and diffusion in zeolites: validating the Reed–Ehrlich model. Adsorption, 24(4), 403-413
Open this publication in new window or tab >>Computational study of the CO adsorption and diffusion in zeolites: validating the Reed–Ehrlich model
2018 (English)In: Adsorption, ISSN 0929-5607, E-ISSN 1572-8757, Vol. 24, no 4, p. 403-413Article in journal (Refereed) Published
Abstract [en]

Molecular simulations have been employed to explore at the microscopic scale the adsorption of CO in zeolites (MFI, CHA and DDR). On the basis of classical force fields, grand canonical Monte Carlo simulations are performed to predict the adsorption properties (isotherms) of these types of zeolites up to high pressure. Subsequent careful analysis yields details the microscopic mechanism in play, along the whole adsorption process, together with a considering of the arrangements of CO in MFI at high pressure. This work also summarizes an approach which uses single component diffusion data in prediction of multicomponent diffusion.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Condensed Matter Physics Physical Chemistry Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-68541 (URN)10.1007/s10450-018-9948-z (DOI)000432610800006 ()2-s2.0-85046018279 (Scopus ID)
Funder
Swedish National Infrastructure for Computing (SNIC)Swedish Foundation for Strategic Research
Note

Validerad;2018;Nivå 2;2018-08-07 (rokbeg)

Available from: 2018-04-28 Created: 2018-04-28 Last updated: 2019-01-18Bibliographically approved
Santos, P., Coutinho, J. & Öberg, S. (2018). First-principles calculations of iron-hydrogen reactions in silicon. Journal of Applied Physics, 123(24), Article ID 245703.
Open this publication in new window or tab >>First-principles calculations of iron-hydrogen reactions in silicon
2018 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, no 24, article id 245703Article in journal (Refereed) Published
Abstract [en]

Controlling the contamination of silicon materials by iron, especially dissolved interstitial iron (Fe-i), is a longstanding problem with recent developments and several open issues. Among these, we have the question whether hydrogen can assist iron diffusion or if significant amounts of substitutional iron (Fe-s) can be created. Using density functional calculations, we explore the structure, formation energies, binding energies, migration, and electronic levels of several FeH complexes in Si. We find that a weakly bound FeiH pair has a migration barrier close to that of isolated Fe-i and a donor level at E-v + 0.5 eV. Conversely, FeiH2 (0/+) is estimated at E-v + 0.33 eV. These findings suggest that the hole trap at E-v + 0.32 eV obtained by capacitance measurements should be assigned to FeiH2 . FesH-related complexes show only deep acceptor activity and are expected to have little effect on minority carrier life-time in p-type Si. The opposite conclusion can be drawn for n-type Si. We find that while in H-free material Fe i defects have lower formation energy than Fe-s , in hydrogenated samples Fe-s -related defects become considerably more stable. This would explain the observation of an electron paramagnetic resonance signal attributed to a FesH-related complex in hydrogenated Si, which was quenched from above 1000 degrees C to iced-water temperature.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-70160 (URN)10.1063/1.5039647 (DOI)000437034500044 ()2-s2.0-85049239103 (Scopus ID)
Note

Validerad;2018;Nivå 2; 2018-07-25 (inah)

Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2018-08-08Bibliographically approved
Wright, E., Coutinho, J., Öberg, S. & Torres, V. (2017). A first-principles model of copper-boron interactions in Si: for the light-induced degradation of solar Si. Journal of Physics: Condensed Matter, 29(6), Article ID 065701.
Open this publication in new window or tab >>A first-principles model of copper-boron interactions in Si: for the light-induced degradation of solar Si
2017 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 6, article id 065701Article in journal (Refereed) Published
Abstract [en]

The recent discovery that Cu contamination of Si combined with light exposure has a significant detrimental impact on carrier life-time has drawn much concern within the solar-Si community. The effect, known as the copper-related light-induced degradation (Cu-LID) of Si solar cells, has been connected to the release of Cu interstitials within the bulk (2016 Sol. Energy Mater. Sol. Cells 147 115-26). In this paper, we describe a comprehensive analysis of the formation/dissociation process of the CuB pair in Si by means of first-principles modelling, as well as the interaction of CuB defects with photo-excited minority carriers. We confirm that the long-range interaction between the Cu-i(+) cation and the B-s(-) anion has a Coulomb-like behaviour, in line with the trapping-limited diffusivity of Cu observed by transient ion drift measurements. On the other hand, the short-range interaction between the d-electrons of Cu and the excess of negative charge on B-s(-) produces a repulsive effect, thereby decreasing the binding energy of the pair when compared to the ideal point-charge Coulomb model. We also find that metastable CuB pairs produce acceptor states just below the conduction band minimum, which arise from the Cu level emptied by the B acceptor. Based on these results, we argue that photo-generated minority carriers trapped by the metastable pairs can switch off the Coulomb interaction that holds the pairs together, enhancing the release of Cu interstitials, and acting as a catalyst for Cu-LID.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2017
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-61817 (URN)10.1088/1361-648X/aa4d78 (DOI)000391564700001 ()2-s2.0-85011968739 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-02-03 (andbra)

Available from: 2017-02-03 Created: 2017-02-03 Last updated: 2018-11-16Bibliographically approved
Pinto, H., Haapasilta, V., Lokhandwala, M., Öberg, S. & Foster, A. S. (2017). Adsorption and migration of single metal atoms on the calcite (10.4) surface. Journal of Physics: Condensed Matter, 29(13), Article ID 135001.
Open this publication in new window or tab >>Adsorption and migration of single metal atoms on the calcite (10.4) surface
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2017 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 13, article id 135001Article in journal (Refereed) Published
Abstract [en]

Transition metal atoms are one of the key ingredients in the formation of functional 2D metal organic coordination networks. Additionally, the co-deposition of metal atoms can play an important role in anchoring the molecular structures to the surface at room temperature. To gain control of such processes requires the understanding of adsorption and diffusion properties of the different transition metals on the target surface. Here, we used density functional theory to investigate the adsorption of 3d (Ti, Cr, Fe, Ni, Cu), 4d (Zr, Nb, Mo, Pd, Ag) and 5d (Hf, W, Ir, Pt, Au) transition metal adatoms on the insulating calcite (10.4) surface. We identified the most stable adsorption sites and calculated binding energies and corresponding ground state structures. We find that the preferential adsorption sites are the Ca–Ca bridge sites. Apart from the Cr, Mo, Cu, Ag and Au all the studied metals bind strongly to the calcite surface. The calculated migration barriers for the representative Ag and Fe atoms indicates that the metal adatoms are mobile on the calcite surface at room temperature. Bader analysis suggests that there is no significant charge transfer between the metal adatoms and the calcite surface.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2017
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-62127 (URN)10.1088/1361-648X/aa5bd9 (DOI)000425246600001 ()2-s2.0-85015159437 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-02-22 (andbra)

Available from: 2017-02-22 Created: 2017-02-22 Last updated: 2018-11-16Bibliographically approved
Vaqueiro-Contreras, M., Markevich, V. P., Halsall, M. P., Peaker, A. R., Santos, P., Coutinho, J., . . . Svensson, B. (2017). Powerful recombination centers resulting from reactions of hydrogen with carbon–oxygen defects in n-type Czochralski-grown silicon. Physica Status Solidi. Rapid Research Letters, 11(8), Article ID 1700133.
Open this publication in new window or tab >>Powerful recombination centers resulting from reactions of hydrogen with carbon–oxygen defects in n-type Czochralski-grown silicon
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2017 (English)In: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 11, no 8, article id 1700133Article in journal (Refereed) Published
Abstract [en]

It has been acknowledged for over 50 years that treatments with hydrogen can improve silicon semiconductor devices. In recent years, these have been used to an advantage in silicon solar cells reducing the loss of photo-generated carriers at the silicon surface or at the silicon interface with dielectrics. However, we have found that in some types of silicon the in-diffusion of hydrogen can result in the formation of powerful recombination centers composed of carbon, oxygen, and hydrogen which reduce the carrier lifetime and ultimately the efficiency of solar cells made from such material

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-65354 (URN)10.1002/pssr.201700133 (DOI)000407919400003 ()2-s2.0-85021346191 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-08-28 (andbra)

Available from: 2017-08-28 Created: 2017-08-28 Last updated: 2018-07-10Bibliographically approved
Talwelkarshimpi, M., Öberg, S., Giri, L. & Pedireddi, V. R. (2017). Some hydrated molecular complexes of 4-cyanophenylboronic acid: Significance of water in the structure stabilization by theoretical investigation. Crystal Growth & Design, 17(12), 6247-6254
Open this publication in new window or tab >>Some hydrated molecular complexes of 4-cyanophenylboronic acid: Significance of water in the structure stabilization by theoretical investigation
2017 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 17, no 12, p. 6247-6254Article in journal (Refereed) Published
Abstract [en]

Molecular complexes 1a – 1c, of 4-cyanophenylboronic acid, 1, with N-donor compounds, 4,4'-bipyridine (a), 1,2-bis(4-pyridyl)ethene (b) and melamine (c), respectively, have been prepared, in the form of single crystals, by slow solvent evaporation method. Three-dimensional structures of all the complexes have been determined by X-ray diffraction technique. All the complexes 1a – 1c were noted to be crystallized as hydrates. Variations in the patterns of intermolecular interactions amongst the complexes and also the geometrical features of 1 have been analysed comparing with the features found in the native structure of 1 by determining its crystal structure also. -B(OH)2 moiety in the native form of 1 and also in the molecular complexes, 1a – 1c, adopts syn - anti conformation. Further, calculations were performed, using DFT-D3 method, to rationalize the propensity of formation of hydrate structures and to deliberate the observed structural features with respect to the strength of the intermolecular interactions, for instance, hydrogen bonds.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-66157 (URN)10.1021/acs.cgd.7b00798 (DOI)000417669900013 ()
Note

Validerad;2017;Nivå 2;2017-12-06 (rokbeg)

Available from: 2017-10-17 Created: 2017-10-17 Last updated: 2018-01-11Bibliographically approved
TalwelkarShimpi, M., Öberg, S., Giri, L. & Pedireddi, V. R. (2017). Some Hydrated Molecular Complexes of 4-Cyanophenylboronic acid: Significanceof Water in the Structure Stabilization by Theoretical Investigations. In: : . Paper presented at 17th International Conference on Density-Functional Theory and its Applications, Tällberg, Sweden, 21-25 August 2017.
Open this publication in new window or tab >>Some Hydrated Molecular Complexes of 4-Cyanophenylboronic acid: Significanceof Water in the Structure Stabilization by Theoretical Investigations
2017 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-66273 (URN)
Conference
17th International Conference on Density-Functional Theory and its Applications, Tällberg, Sweden, 21-25 August 2017
Projects
223110
Available from: 2017-10-26 Created: 2017-10-26 Last updated: 2017-11-24Bibliographically approved
Santos, P., Coutinho, J., Öberg, S., Vaqueiro-Contreras, M., Markevich, V. P., Halsall, M. P. & Peaker, A. R. (2017). Theory of a carbon-oxygen-hydrogen recombination center in n-type Si. Paper presented at 17th International Conference on Gettering and Defect Engineering in Semiconductor Technology (GADEST), Lopota, Georgia, Oct 01-06, 2017. Physica status solidi. A, Applied research, 214(7), Article ID 1700309.
Open this publication in new window or tab >>Theory of a carbon-oxygen-hydrogen recombination center in n-type Si
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2017 (English)In: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 214, no 7, article id 1700309Article in journal (Refereed) Published
Abstract [en]

We have recently found that in-diffusion of hydrogen into n-type Si crystals containing oxygen and carbon impurities can result in the formation of powerful recombination centers (M. Vaqueiro-Contreras et al., to appear in PSS RRL). Here, we describe a combination of first-principles calculations and electrical measurements to investigate the composition, structure, electrical activity and recombination mechanism of a carbon-oxygen-hydrogen complex (COH) in Si. We found a defect comprising a carbon-oxygen complex connected to an H atom whose location depends on the charge state of the complex, and showing a calculated acceptor level at Ev+0.3eV, a few meV away from the observations. Bistable carbon-oxygen-hydrogen complex in silicon. Carbon, oxygen, hydrogen, and silicon atoms are shown in gray, red, black, and white, respectively

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-64823 (URN)10.1002/pssa.201700309 (DOI)000404974800029 ()2-s2.0-85020527524 (Scopus ID)
Conference
17th International Conference on Gettering and Defect Engineering in Semiconductor Technology (GADEST), Lopota, Georgia, Oct 01-06, 2017
Note

2017-08-16 (andbra);Konferensartikel i tidskrift

Available from: 2017-07-07 Created: 2017-07-07 Last updated: 2018-07-10Bibliographically approved
Coutinho, J., Torres, V. J. .., Demmouche, K. & Öberg, S. (2017). Theory of the carbon vacancy in 4H-SiC: Crystal field and pseudo-Jahn-Teller effects. Physical Review B, 96(17), Article ID 174105.
Open this publication in new window or tab >>Theory of the carbon vacancy in 4H-SiC: Crystal field and pseudo-Jahn-Teller effects
2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 17, article id 174105Article in journal (Refereed) Published
Abstract [en]

The carbon vacancy in 4H-SiC is a powerful minority carrier recombination center in as-grown material and a major cause of degradation of SiC-based devices. Despite the extensiveness and maturity of the literature regarding the characterization and modeling of the defect, many fundamental questions persist. Among them, we have the shaky connection of the EPR data to the electrical measurements lacking sublattice site resolution, the physical origin of the pseudo-Jahn-Teller effect, the reasoning for the observed sublattice dependence of the paramagnetic states, and the severe temperature dependence of some hyperfine signals, which cannot be accounted for by a thermally activated dynamic averaging between equivalent Jahn-Teller distorted structures. In this work, we address these problems by means of semilocal and hybrid density functional calculations. We start by inventorying a total of four different vacancy structures from the analysis of relative energies. Diamagnetic states have well defined low-energy structures, whereas paramagnetic states display metastability. The reasoning for the rich structural variety is traced back to the filling of electronic states which are shaped by a crystal-field-dependent (and therefore site-dependent) pseudo-Jahn-Teller effect. From calculated minimum energy paths for defect rotation and transformation mechanisms, combined with the calculated formation energies and electrical levels, we arrived at a configuration-coordinate diagram of the defect. The diagram provides us with a detailed first-principles picture of the defect when subject to thermal excitations. The calculated acceptor and donor transitions agree well with the binding energies of electrons emitted from the Z(1/2) and EH6/7 traps, respectively. From the comparison of calculated and measured U-values, and correlating the site-dependent formation energies with the relative intensity of the DLTS peaks in as-grown material, we assign Z(1) (EH6) and Z(2) (EH7) signals to acceptor (donor) transitions of carbon vacancies located on the h and k sublattice sites, respectively.

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Other Physics Topics
Research subject
Applied Physics
Identifiers
urn:nbn:se:ltu:diva-66604 (URN)10.1103/PhysRevB.96.174105 (DOI)000414395600002 ()2-s2.0-85039149462 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-11-16 (inah)

Available from: 2017-11-16 Created: 2017-11-16 Last updated: 2018-11-20Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0292-1159

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