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Zakomirnyi, V., Rasskazov, I. L., Gerasimov, V. S., Ershov, A. E., Polyutov, S. P., Karpov, S. V. & Ågren, H. (2018). Titanium nitride nanoparticles as an alternative platform for plasmonic waveguides in the visible and telecommunication wavelength ranges. Photonics and Nanostructures - Fundamentals and Applications, 30, 50-56
Open this publication in new window or tab >>Titanium nitride nanoparticles as an alternative platform for plasmonic waveguides in the visible and telecommunication wavelength ranges
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2018 (English)In: Photonics and Nanostructures - Fundamentals and Applications, ISSN 1569-4410, Vol. 30, p. 50-56Article in journal (Refereed) Published
Abstract [en]

We propose to utilize titanium nitride (TiN) as an alternative material for linear periodic chains (LPCs) of nanoparticles (NPs) which support surface plasmon polariton (SPP) propagation. Dispersion and transmission properties of LPCs have been examined within the framework of the dipole approximation for NPs with various shapes: spheres, prolate and oblate spheroids. It is shown that LPCs of TiN NPs support high-Q eigenmodes for an SPP attenuation that is comparable with LPCs from conventional plasmonic materials such as Au or Ag, with the advantage that the refractory properties and cheap fabrication of TiN nanostructures are more preferable in practical implementations compared to Au and Ag. We show that the SPP decay in TiN LPCs remains almost the same even at extremely high temperatures which is impossible to reach with conventional plasmonic materials. Finally, we show that the bandwidth of TiN LPCs from non-spherical particles can be tuned from the visible to the telecommunication wavelength range by switching the SPP polarization, which is an attractive feature for integrating these structures into modern photonic devices.

Place, publisher, year, edition, pages
Elsevier, 2018
Keyword
Nanoparticle, Plasmon waveguide, Refractory plasmonics, Surface plasmon polariton, Titanium nitride
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-229236 (URN)10.1016/j.photonics.2018.04.005 (DOI)2-s2.0-85046117367 (Scopus ID)
Note

QC 20180601

Available from: 2018-06-01 Created: 2018-06-01 Last updated: 2018-06-01Bibliographically approved
Baryshnikov, G. V., Valiev, R. R., Minaev, B. F. & Ågren, H. (2017). A computational study of aromaticity and photophysical properties of unsymmetrical azatrioxa[8]circulenes. New Journal of Chemistry, 41(7), 2717-2723
Open this publication in new window or tab >>A computational study of aromaticity and photophysical properties of unsymmetrical azatrioxa[8]circulenes
2017 (English)In: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 41, no 7, p. 2717-2723Article in journal (Refereed) Published
Abstract [en]

Owing to their potential use in organic light-emitting diodes and field-effect transistors we present a theoretical study of a series of unsymmetrical azatrioxa[8]circulenes in order to explain the impact of outer substituents and benzoannelation on photophysical constants and aromaticity of these compounds in terms of spin-orbit coupling perturbation and magnetically-induced ring currents. It is argued that the S1-Tn inter-system crossing processes constitute the main deactivation pathways for the fluorescence quenching, something that is supported by a good agreement obtained with experimental data on fluorescence quantum yields. The concept of the gauge-including magnetically induced currents has been applied in order to estimate the role of substituents and benzoannelated fragments on the aromaticity and particularly on the overall balance between the diatropic “aromatic” and paratropic “antiaromatic” current strengths. While a variation of the substituents in the outer perimeter of the studied circulenes does not provide a clear effect on their aromaticity, it is demonstrated that an additional benzoannelation (π-extension) of the azatrioxa[8]circulene macrocycle induces a significant aromaticity enhancement.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-207398 (URN)10.1039/c6nj03925a (DOI)000401528400021 ()2-s2.0-85016316941 (Scopus ID)
Note

Funding details: 0115U000637, MESU, Ministry of Education and Science of Ukraine; Funding text: The calculations were performed using the computational resources provided by the Swedish National Infrastructure for Computing (SNIC) at the Parallel Computer Center (PDC) through the project “Multiphysics Modeling of Molecular Materials” SNIC 020/11-23. This work has been supported by the Academy of Finland through project 275845. CSC, Finnish IT Center for Science, is acknowledged for computer time. This research was also supported by the Ministry of Education and Science of Ukraine (project number 0115U000637).

QC 20170608

Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2017-06-08Bibliographically approved
Shao, W., Chen, G., Ohulchanskyy, T. Y., Yang, C., Ågren, H. & Prasad, P. N. (2017). A core-multiple shell nanostructure enabling concurrent upconversion and quantum cutting for photon management. Nanoscale, 9(5), 1934-1941
Open this publication in new window or tab >>A core-multiple shell nanostructure enabling concurrent upconversion and quantum cutting for photon management
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2017 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, no 5, p. 1934-1941Article in journal (Refereed) Published
Abstract [en]

Photon management enables the manipulation of the number of input photons by conversion of two or more light quanta into one (upconversion) or vice versa (quantum cutting). Simultaneous realization of both these processes in a single unit provides unique opportunities of efficient utilization of photons throughout a broad spectral range. Yet, concurrent realization of these two parallel optical processes in one single unit remains elusive, limiting its impact on many existing or possible future applications such as for panchromatic photovoltaics. Here, we describe an epitaxial active core/inert shell/active shell/inert shell fluoride nanostructure to implement upconversion and quantum cutting within spatially confined and isolated rare-earth-doped active domains. The core area transforms infrared photons through trivalent erbium (Er3+) ions into three-and two-photon upconverted visible and near infrared luminescence, while the second shell domain splits an excitation photon into two near infrared photons through cooperative quantum cutting from one trivalent terbium ion (Tb3+) to two trivalent ytterbium ions (Yb3+). The inert layer in between the active domains is able to effectively suppress the destructive interference between upconversion and quantum cutting, while the outermost inert shell is able to eliminate surfacerelated quenching. This design enables the colloidal core/multishell nanoparticles to have an upconversion quantum yield of similar to 1.6%, and to have a luminescence yield of the quantum cutting process as high as similar to 130%. This work constitutes a solid step for flexible photon management in a single nanostructure, and has an implication for photonic applications beyond photovoltaics.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-204732 (URN)10.1039/c6nr09713h (DOI)000395594300022 ()28098308 (PubMedID)2-s2.0-85011387426 (Scopus ID)
Note

QC 20170601

Available from: 2017-06-01 Created: 2017-06-01 Last updated: 2017-06-01Bibliographically approved
Vaz da Cruz, V., Ertan, E., C. Couto, R., Eckert, S., Fondell, M., Dantz, M., . . . Kimberg, V. (2017). A study of the water molecule using frequency control over nuclear dynamics in resonant X-ray scattering. Physical Chemistry, Chemical Physics - PCCP, 19(30), 19573-19589
Open this publication in new window or tab >>A study of the water molecule using frequency control over nuclear dynamics in resonant X-ray scattering
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2017 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 30, p. 19573-19589Article in journal (Refereed) Published
Abstract [en]

In this combined theoretical and experimental study we report a full analysis of the resonant inelastic X-ray scattering (RIXS) spectra of H2O, D2O and HDO. We demonstrate that electronically-elastic RIXS has an inherent capability to map the potential energy surface and to perform vibrational analysis of the electronic ground state in multimode systems. We show that the control and selection of vibrational excitation can be performed by tuning the X-ray frequency across core-excited molecular bands and that this is clearly reflected in the RIXS spectra. Using high level ab initio electronic structure and quantum nuclear wave packet calculations together with high resolution RIXS measurements, we discuss in detail the mode coupling, mode localization and anharmonicity in the studied systems.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
Keyword
RIXS, water, quantum dynamics, x-ray
National Category
Atom and Molecular Physics and Optics
Research subject
Theoretical Chemistry and Biology
Identifiers
urn:nbn:se:kth:diva-187012 (URN)10.1039/C7CP01215B (DOI)000407053000006 ()28352891 (PubMedID)2-s2.0-85027313711 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation, KAW-2013.0020Carl Tryggers foundation , CTS 15:266Swedish Research Council
Note

QC 20160516

Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2018-05-15Bibliographically approved
Bu, L., Chen, J., Wei, X., Li, X., Ågren, H. & Xie, Y. (2017). An AIE and ICT based NIR florescent probe for cysteine and homocysteine. Dyes and pigments, 136, 724-731
Open this publication in new window or tab >>An AIE and ICT based NIR florescent probe for cysteine and homocysteine
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2017 (English)In: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 136, p. 724-731Article in journal (Refereed) Published
Abstract [en]

A combination of aggregation-induced emission and intramolecular charge transfer was achieved by using a triphenylamine analogue and a dicyanovinyl moiety as the electron donating and accepting units, respectively. Hence, we designed and synthesized a probe with a D-π-A framework as a near-infrared fluorescence turn-on probe for biothiols (cysteine and homocysteine). Owing to the remarkable intramolecular charge transfer effect as well as intramolecular rotations associated with the donor moiety, the probe exhibits extremely weak fluorescence, which becomes a good starting point for developing fluorescence “turn-on” probes. Upon reaction with cysteine or homocysteine utilizing the dicyanovinyl moiety, the intramolecular charge transfer character was weakened, and the reacting products were observed to aggregate in aqueous solutions, resulting in the aggregation-induced emission effect with red fluorescence at 651 and 656 nm, respectively. Hence, the probe could be used as a fluorescence “turn-on” sensor for cysteine and homocysteine, with the sensing time of less than 4 min and the detection limits of 8.4 μM and 5.7 μM towards cysteine and homocysteine, respectively. The probe could distinguish cysteine and homocysteine from glutathione. The sensing mechanism was systematically investigated by employing high resolution mass spectrometry, 1H NMR and density functional theory calculations as well as checking the solvent viscosity dependent fluorescence, and thus the nucleophilic addition products, the intramolecular charge transfer character, and the aggregation-induced emission behaviour were clearly elucidated. It is noteworthy that the low cytotoxicity, the intrinsic aggregation-induced emission nature and near-infrared emissions enable the application of the probe in living cell imaging. © 2016 Elsevier Ltd

Keyword
AIE, Biothiols, Cell imaging, Fluorescent probes, ICT, Addition reactions, Amino acids, Charge transfer, Density functional theory, Fluorescence, Infrared devices, Lanthanum compounds, Mass spectrometry, Solutions, Aggregation-induced emissions, High resolution mass spectrometry, Intra-molecular charge transfer, Near-infrared emissions, Near-infrared fluorescence, Probes
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-195127 (URN)10.1016/j.dyepig.2016.09.032 (DOI)000387837200087 ()2-s2.0-84988524950 (Scopus ID)
Note

Funding Details: 91227201, NSFC, National Natural Science Foundation of China. QC 20161107

Available from: 2016-11-07 Created: 2016-11-02 Last updated: 2017-11-29Bibliographically approved
Jena, N. K., Lyne, Å., Natarajan Arul, M., Ågren, H. & Birgisson, B. (2017). Atomic level simulations of the interaction of asphaltene with quartz surfaces: role of chemical modifications and aqueous environment. Materials and Structures, 50(1), Article ID 99.
Open this publication in new window or tab >>Atomic level simulations of the interaction of asphaltene with quartz surfaces: role of chemical modifications and aqueous environment
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2017 (English)In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 50, no 1, article id 99Article in journal (Refereed) Published
Abstract [en]

Understanding the properties of bitumen and its interaction with mineral aggregates is crucial for future strategies to improve roads and highways. Knowledge of basic molecular and electronic structures of bitumen, one out of the two main components of asphalt, poses a major step towards achieving such a goal. In the present work we employ atomistic simulation techniques to study the interaction of asphaltenes, a major constituent of bitumen, with quartz surfaces. As an effective means to tune adhesion or cohesion properties of asphaltenes and mineral surfaces, we propose chemical modification of the pristine asphaltene structure. By the choice of substituent and site of substitution we find that adhesion between the asphaltene molecule and the quartz surface can easily be improved at the same time as the cohesive interaction between the asphaltene units is reduced, while other substituents may lead to the opposite effect. We also provide insight at the molecular level into how water molecules affect interactions between asphaltenes and quartz. Our approach emphasizes a future role for advanced atomistic modeling to understand the properties of bitumen and suggest further improvements.

Place, publisher, year, edition, pages
Kluwer Academic Publishers, 2017
Keyword
Adhesion, Bitumen, Cohesion, Molecular dynamics, Quartz, Bituminous materials, Chemical modification, Electronic structure, Molecules, Aqueous environment, Atomic level simulations, Atomistic modeling, Atomistic simulations, Cohesion properties, Cohesive interactions, Asphaltenes
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-201948 (URN)10.1617/s11527-016-0880-y (DOI)000405071300013 ()2-s2.0-84994500697 (Scopus ID)
Note

QC 20170306

Available from: 2017-03-06 Created: 2017-03-06 Last updated: 2017-08-01Bibliographically approved
Song, H., Li, X., Ågren, H. & Xie, Y. (2017). Branched and linear alkoxy chains-wrapped push-pull porphyrins for developing efficient dye-sensitized solar cells. Dyes and pigments, 137, 421-429
Open this publication in new window or tab >>Branched and linear alkoxy chains-wrapped push-pull porphyrins for developing efficient dye-sensitized solar cells
2017 (English)In: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 137, p. 421-429Article in journal (Refereed) Published
Abstract [en]

Four alkoxy-wrapped push-pull porphyrin dyes containing the phenothiazine derived donor and the ethynylbenzoic acid acceptor have been designed, synthesized and used as sensitizers for fabricating efficient dye-sensitized solar cells (DSSCs). Branched or linear alkoxy chains were introduced to the ortho-positions of the meso-phenyl moieties to suppress the dye aggregation and charge recombination. The effect of alkoxy chains were investigated in the absence and presence of an additional electron withdrawing benzothiadiazole unit. In the former cases, almost identical photovoltaic efficiencies of similar to 8.3% were achieved for both the branched and the linear alkoxy chains, while in the latter cases, the planar benzothiadiazole unit induces serious dye aggregation and charge recombination, resulting in lower efficiencies of 6.46% and 7.50% for the linear and branched chains, respectively, even though broader absorption was achieved. The relatively higher efficiency achieved for the dyes with branched chains may be related to the better effect of suppressing the dye aggregation and charge recombination. Furthermore, the coadsorption approach was employed, and a highest efficiency of 9.62% was achieved for the dye that features branched chains and the benzothiadiazole unit. These results compose a novel approach for developing efficient DSSCs by combining the coadsorbent with a porphyrin dye containing both the additional benzothiadiazole acceptor and branched alkoxy chains.

Keyword
Dye-sensitized solar cells, Porphyrin, Sensitizer, Push-pull structure, Branched chains
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-199725 (URN)10.1016/j.dyepig.2016.10.041 (DOI)000390182700049 ()2-s2.0-85002694348 (Scopus ID)
Note

QC 20170126

Available from: 2017-01-26 Created: 2017-01-16 Last updated: 2017-11-29Bibliographically approved
Monti, S., Barcaro, G., Sementa, L., Carravetta, V. & Ågren, H. (2017). Characterization of the adsorption dynamics of trisodium citrate on gold in water solution. RSC Advances, 7(78), 49655-49663
Open this publication in new window or tab >>Characterization of the adsorption dynamics of trisodium citrate on gold in water solution
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2017 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 78, p. 49655-49663Article in journal (Refereed) Published
Abstract [en]

Molecular dynamics simulations (MDs) based on a reactive force field (ReaxFF) are carried out to investigate typical adsorption modes of trisodium citrate (CIT) on gold nanoparticles (AuNPs). All possible configurations of CIT on a model AuNP in solution are identified and the stabilizing role played by the adsorbate on the AuNP structure is disclosed by analyzing protonation state, dynamics and interactions of the molecules with the surrounding environment. A realistic scenario is created by sampling extensively the conformational space of citrate and by validating the simulation results against data extracted from the literature. Carboxyl moieties are found in contact with the gold substrate through one or both oxygens and Na+ ions are present in the adsorbed citrate layer. Citrate binding is relatively strong and its action as a chelator stabilizes surface reconstructions. The molecules have the tendency to self-assemble and form a stable cover, which is reinforced by adatoms. All the results are in perfect agreement with experimental observations and theoretical data.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-217967 (URN)10.1039/c7ra10759e (DOI)000413893000057 ()2-s2.0-85032467372 (Scopus ID)
Note

QC 20171121

Available from: 2017-11-21 Created: 2017-11-21 Last updated: 2017-11-29Bibliographically approved
Kuang, G., Zhou, Y., Zou, R., Halldin, C., Nordberg, A., Långström, B., . . . Tu, Y. (2017). Characterization of the binding mode of the PET tracer [18F]ASEM to a chimera structure of the α7 nicotinic acetylcholine receptor. RSC Advances, 7(32), 19787-19793
Open this publication in new window or tab >>Characterization of the binding mode of the PET tracer [18F]ASEM to a chimera structure of the α7 nicotinic acetylcholine receptor
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2017 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 32, p. 19787-19793Article in journal (Refereed) Published
Abstract [en]

The α7 nicotinic acetylcholine receptor (α7-nAChR) is assumed to be implicated in a variety of neurological disorders, such as schizophrenia and Alzheimer's disease (AD). The progress of these disorders can be studied through imaging α7-nAChR with positron emission tomography (PET). [18F]ASEM is a novel and potent α7-nAChR PET radioligand showing great promise in recent tests. However, the mechanism of the molecular interaction between [18F]ASEM and α7-nAChR is still unclear. In this paper, the binding profile of [18F]ASEM to a chimera structure of α7-nAChR was investigated with molecular docking, molecular dynamics, and metadynamics simulation methods. We found that [18F]ASEM binds at the same site as the crystallized agonist epibatidine but with a different binding mode. The dibenzo[b,d]thiophene ring has a different orientation compared to the pyridine ring of epibatidine and has van der Waals interactions with residues from loop C on one side and π-π stacking interaction with Trp53 on the other side. The conformation of Trp53 was found to have a great impact on the binding of [18F]ASEM. Six binding modes in terms of the side chain dihedral angles χ1 and χ2 of Trp53 were discovered by metadynamics simulation. In the most stable binding mode, Trp53 adopts a different conformation from that in the crystalline structure and has a rather favorable π-π stacking interaction with [18F]ASEM. We believe that these discoveries can be valuable for the development of novel PET radioligands.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
Keyword
Binding energy, Dihedral angle, Molecular dynamics, Neurodegenerative diseases, Positron emission tomography, Van der Waals forces, Alzheimer's disease, Crystalline structure, Metadynamics simulations, Molecular docking, Neurological disorders, Nicotinic acetylcholine receptors, Positron emission tomography (PET), Van Der Waals interactions, Bins
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-207402 (URN)10.1039/c7ra00496f (DOI)000399242100041 ()2-s2.0-85017176981 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , RB13-0192Stockholm County Council, K1764-2013Swedish National Infrastructure for Computing (SNIC), m.2015-1-396
Note

Funding details: CSC, China Scholarship Council; Funding text: The authors acknowledge support from the Swedish Foundation for Strategic Research (SSF) through the project “New imaging biomarkers in early diagnosis and treatment of Alzheimer's disease (RB13-0192)” and the support from the Stockholm Country Council through the project “Biomolecular profiling for early diagnosis of Alzheimer's disease (K1764-2013)”. Computer time for this work was awarded by a grant from the Swedish Infrastructure Committee (SNIC) for the project “Modeling of protein-ligand binding” (m.2015-1-396). The figures containing molecular structures were rendered with PyMol 1.3 (ref. 51) and VMD 1.9.2 (ref. 52). The work was partly sponsored by the China Scholarship Council (CSC).

QC 20170601

Available from: 2017-06-01 Created: 2017-06-01 Last updated: 2017-11-29Bibliographically approved
Wang, S., Li, X., Zhao, W., Chen, X., Zhang, J., Ågren, H., . . . Chen, W. (2017). Cu2+-Selectivity gated photochromism in Schiff-modified diarylethenes with a star-shaped structure. Journal of Materials Chemistry C, 5(2), 282-289
Open this publication in new window or tab >>Cu2+-Selectivity gated photochromism in Schiff-modified diarylethenes with a star-shaped structure
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2017 (English)In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 5, no 2, p. 282-289Article in journal (Refereed) Published
Abstract [en]

A great deal of effort has been devoted to developing gated photochromic systems due to their advantages in the smart materials and opto-electronic fields, whereas the gating function through certain ions has rarely been addressed. Since the photochromic materials gated by ions can be readily further processed into a multi-functional molecular switch and probe, we herein designed and conveniently synthesized a star-shaped Schiff-based diarylethene derivative showing typical photochromic properties in solution. This compound possesses two response channels (colorimetric and fluorogenic) to Cu2+ ions with photoswitching characteristics, making it a viable photochromic probe. It is noteworthy that its photochromic reactivity can be locked when Cu2+ ions are introduced into the solution. Moreover, the photoinactive and photoactive states can be interchanged reversibly by binding Cu2+ ions and unbinding Cu2+ ions using EDTA, which shows promise for application in multi-controlled molecular switches and smart materials. The mechanism of the photochromic properties locked by Cu2+ ions is reasonably proposed by theoretical simulations. These results could be valuable for the further development of molecular switching systems with multiple stimuli responses.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:kth:diva-202779 (URN)10.1039/c6tc04756d (DOI)000392813800005 ()
Note

QC 20170307

Available from: 2017-03-07 Created: 2017-03-07 Last updated: 2017-11-29Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1763-9383

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