350 results on '"Hans Ågren"'
Search Results
2. Optical Properties of Few-Layer Ti3CN MXene: From Experimental Observations to Theoretical Calculations
- Author
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Lingfeng Gao, Hualong Chen, Artem V. Kuklin, Swelm Wageh, Ahmed A. Al-Ghamdi, Hans Ågren, and Han Zhang
- Subjects
Z-scan ,Materials Chemistry ,General Engineering ,transient absorption ,Materialkemi ,General Physics and Astronomy ,General Materials Science ,density functional theory calculations ,MXene ,Ti3CN - Abstract
Despite the emerging interest in research and development of Ti3CN MXene nanosheet (NS)-based optoelectronic devices, there is still a lack of in-depth studies of the underlying photophysical processes, like carrier relaxation dynamics and nonlinear photon absorption, operating in such devices, hindering their further and precise design. In this paper, we attempt to remedy the situation by fabricating few-layer Ti3CN NSs via combining selective etching and molecular intercalation and by investigating the carrier relaxation possesses and broadband nonlinear optical responses via transient absorption and Z-scan techniques. These results are complemented by first-principle theoretical analyses of the optical properties. Both saturable absorption and reverse saturable absorption phenomena are observed due to multiphoton absorption effects. The analysis of these results adds to the understanding of the basic photophysical processes, which is anticipated to be beneficial for the further design of MXene-based devices.
- Published
- 2022
3. Medium dependent optical response in ultra-fine plasmonic nanoparticles
- Author
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Lasse K. Sørensen, Daniil E. Khrennikov, Valeriy S. Gerasimov, Alexander E. Ershov, Sergey P. Polyutov, Sergey V. Karpov, and Hans Ågren
- Subjects
General Physics and Astronomy ,Physical and Theoretical Chemistry - Abstract
We study the influence of media on the interaction of ultra-fine plasmonic nanoparticles (≤ 8 nm) with radiation. The important role of the surface layer of the nanoparticles, with properties that differ from the ones in the inner part, is established. Using an atomistic representation of the nanoparticle material and its interaction with light, we find a highly inhomogeneous distribution of the electric field inside and around the particles. It is predicted that with an increase in the refractive index of the ambient medium, the extension of the surface layer of atoms increases, something that also is accompanied by an enhanced red shift of the plasmon resonance band compared to large particles in which the influence of this layer and its relative volume is reduced. It is shown that the physical origin for the formation of a surface layer of atoms near the nanoparticle boundary is related to the anisotropy of the local environment of atoms in this layer which changes the conditions for the interaction of neighboring atoms with each other and with the incident radiation. It is shown that a growth of the refractive index of the ambient medium results in an increase in the local field in the dielectric cavity in which a plasmonic nanoparticle is embedded and which is accompanied by a growth of the amplitude of the plasmon resonance. We predict that in the ultra-fine regime the refractive index sensitivity shows a decreasing trend with respect to size which is opposite to that for larger particles. With the applied atomistic model this work demonstrates close relations between field distributions and properties of ultra-fine nanoparticles.
- Published
- 2022
4. Charge-transfer plasmons of complex nanoparticle arrays connected by conductive molecular bridges
- Author
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Aleksandr S. Fedorov, Maxim A. Visotin, Egor V. Eremkin, Pavel O. Krasnov, Hans Ågren, and Sergey P. Polyutov
- Subjects
General Physics and Astronomy ,Physical and Theoretical Chemistry - Abstract
Charge-transfer plasmons (CTP) in complexes of metal nanoparticles bridged by conductive molecular linkers are theoretically analysed using a statistic approach. The applied model takes into account the kinetic energy of carriers inside the linkers including its dissipation and the Coulomb energy of the charged nanoparticles. The plasmons are statistically investigated for systems containing a large number of complexes of bridged nanoparticles of realistic sizes generated using a simplified molecular dynamics algorithm, where the geometries of the complexes are dependent on the rate of connection of the linkers with the nanoparticles. As illustrated, the distribution of CTP frequencies in the generated nanoparticle complexes is very inhomogeneous. It has a narrow peak, corresponding to CTP plasmons in dimers, and two broad peaks, corresponding mainly to low and high-frequency oscillations in chains of connected nanoparticles. It is found that in general the plasmon frequencies depend inversely on the value of the complex dipole moment of the plasmon oscillation, where the assumption follows that low-frequency plasmons will be more efficiently excited in an external electromagnetic field. To calculate the CTP energy absorption in this field two model modifications are proposed: a system-external electromagnetic field interaction model and a simplified broadening plasmon peak model where the plasmons are calculated at first without damping and where the delta-shaped oscillation peaks are broadened then due to the damping. It is demonstrated that both modifications lead to a wide and almost monotonic absorption in the IR region for all generated systems containing a large number of bridged nanoparticles due to the presence of a large number of CTPs in this region.
- Published
- 2022
5. An atomistic explanation of the ethanol-water azeotrope
- Author
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Vincenzo Carravetta, Anderson Herbert de Abreu Gomes, Ricardo dos Reis Teixeira Marinho, Gunnar Öhrwall, Hans Ågren, Olle Björneholm, and Arnaldo Naves de Brito
- Subjects
General Physics and Astronomy ,Physical and Theoretical Chemistry - Abstract
Above ethanol–water azeotrope water molecules (red) migrate toward the surface and ethanol surface concentration never comes to a complete saturation.
- Published
- 2022
6. The molecular structure of the surface of water–ethanol mixtures
- Author
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Arnaldo Naves de Brito, Anderson Herbert de Abreu Gomes, Huib J. Bakker, Johannes Kirschner, R. R. T. Marinho, Hans Ågren, Vincenzo Carravetta, Niklas Ottosson, and Olle Björneholm
- Subjects
chemistry.chemical_compound ,Ethanol ,chemistry ,X-ray photoelectron spectroscopy ,Chemical engineering ,Amphiphile ,General Physics and Astronomy ,Molecule ,Alcohol ,Physical and Theoretical Chemistry ,Surface concentration ,Spectroscopy ,Mole fraction - Abstract
Mixtures of water and alcohol exhibit an excess surface concentration of alcohol as a result of the amphiphilic nature of the alcohol molecule, which has important consequences for the physico-chemical properties of water-alcohol mixtures. Here we use a combination of intensity vibrational sum-frequency generation (VSFG) spectroscopy, heterodyne-detected VSFG (HD-VSFG), and core-level photoelectron spectroscopy (PES) to investigate the molecular properties of water-ethanol mixtures at the air-liquid interface. We find that increasing the ethanol concentration up to a molar fraction (MF) of 0.1 leads to a steep increase of the surface density of the ethanol molecules, and an increased ordering of the ethanol molecules at the surface. When the ethanol concentration is further increased, the surface density of ethanol remains more or less constant, while the orientation of the ethanol molecules becomes increasingly disordered. The used techniques of PES and VSFG provide complementary information on the density and orientation of ethanol molecules at the surface of water, thus providing new information on the molecular-scale properties of the surface of water-alcohol mixtures over a wide range of compositions. This information is invaluable in understanding the chemical and physical properties of water-alcohol mixtures.
- Published
- 2021
7. Prediction of new spin-forbidden transitions in the N2 molecule—the electric dipole A′5Σg+ → A3Σu+ and magnetic dipole a′1Σu−← A3Σu+ transitions
- Author
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Boris Minaev, Ramon S. da Silva, Olexander Panchenko, and Hans Ågren
- Subjects
General Physics and Astronomy ,Physical and Theoretical Chemistry - Abstract
On the ground of multi-reference configuration interaction calculations with an account of spin–orbit coupling, we have predicted the probability of two unknown spin-forbidden transitions in the spectrum of the N2 molecule: the electric dipole A′5Σg+ → A3Σu+ emission system and the magnetic dipole a′1Σu− ← A3Σu+ transition. The radiative lifetime of the lowest A′5Σg+ sublevel is less than a microsecond; the magnetic transition induced by the spin current in the triplet state is predicted with relatively low oscillator strength (f = 10−10), which still could be detectable.
- Published
- 2023
8. Ultraefficient Singlet Oxygen Generation from Manganese-Doped Cesium Lead Chloride Perovskite Quantum Dots
- Author
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Deyang Li, Qun Zhang, Xiyu Li, Haichun Liu, Tianyu Zhao, Shenlong Jiang, Hans Ågren, and Guanying Chen
- Subjects
Materials science ,Singlet oxygen ,General Engineering ,General Physics and Astronomy ,chemistry.chemical_element ,Halide ,Quantum yield ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Oxygen ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Nanocrystal ,Quantum dot ,General Materials Science ,0210 nano-technology ,Photodegradation ,Perovskite (structure) - Abstract
Lead halide perovskites hold promise for photovoltaics, lasers, and light-emitting diode (LED) applications, being known as light-harvesting or -emitting materials. Here we show that colloidal lead halide CsPbCl3 perovskite quantum dots (PQDs), when incorporating divalent manganese (Mn2+) ions, are able to produce spin-paired singlet oxygen molecules with over-unit quantum yield (∼1.08) in air conditions. Our mechanistic studies and atomic-level density functional theory calculations endorse an energy-migration-mediated quantum cutting process favoring multiple singlet oxygen generation (MSOG), in which one exciton-activated bulk Mn2+ ion (∼2.0 eV) inside the nanocrystal migrates its energy among the Mn2+ sublattice to two surface Mn2+ defect states (∼1.0 eV), followed by nonradiative energy transfers to two surrounding oxygen molecules. Moreover, superhydrophobicization of MSOG PQDs through silica-mediated polystyrene encapsulation prevents them from disintegrating in aqueous medium, enabling photodegradation of methyl orange at a rate even higher than that of the canonical titanium oxide photocatalyst. The observation of ultraefficient singlet oxygen generation in PQDs has implications for fields ranging from photodynamic therapy to photocatalytic applications.
- Published
- 2020
9. Two-dimensional MXenes: From morphological to optical, electric, and magnetic properties and applications
- Author
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Yanqi Ge, Alexander Baev, Paras N. Prasad, Artem V. Kuklin, Hans Ågren, Xiantao Jiang, and Han Zhang
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Physics ,Elemental composition ,010308 nuclear & particles physics ,0103 physical sciences ,General Physics and Astronomy ,Nanotechnology ,010306 general physics ,MXenes ,01 natural sciences ,Electronic properties - Abstract
MXenes, generally referring to two-dimensional (2D) transition-metal carbides, nitrides, and carbonitrides, have received tremendous attention since the first report in 2011. Extensive experimental and theoretical studies have unveiled their enormous potential for applications in optoelectronics, photonics, catalysis, and many other areas. Because of their intriguing mechanical and electronic properties, together with the richness of elemental composition and chemical decoration, MXenes are poised to provide a new 2D nanoplatform for advanced optoelectronics. This comprehensive review, intended for a broad multidisciplinary readership, highlights the state-of-the-art progress on MXene theory, materials synthesis techniques, morphology modifications, opto-electro-magnetic properties, and their applications. The efforts exploring the device performance limits, steric configurations, physical mechanisms, and novel application boundaries are comprehensively discussed. The review is concluded with a compelling perspective, outlook as well as non-trivial challenges in future investigation of MXene-based nano-optoelectronics.
- Published
- 2020
10. Engineering stable radicals using photochromic triggers
- Author
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Hans Ågren, Michael L. Steigerwald, Liangliang Zhu, Gleb V. Baryshnikov, Jian Gu, Yunyun Zhou, Wandong Zhao, Xuanying Chen, Qi Zou, and Wenbo Chen
- Subjects
Steric effects ,Radical ,Science ,General Physics and Astronomy ,Synthetic chemistry methodology ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Redox ,Peroxide ,General Biochemistry, Genetics and Molecular Biology ,Article ,chemistry.chemical_compound ,Photochromism ,Photocatalysis ,Hydrogen peroxide ,lcsh:Science ,Multidisciplinary ,Chloroform ,010405 organic chemistry ,Chemistry ,Excited states ,General Chemistry ,0104 chemical sciences ,lcsh:Q - Abstract
Long-standing radical species have raised noteworthy concerns in organic functional chemistry and materials. However, there remains a substantial challenge to produce long-standing radicals by light, because of the structural dilemmas between photoproduction and stabilization. Herein, we present a pyrrole and chloride assisted photochromic structure to address this issue. In this well-selected system, production and stabilization of a radical species were simultaneously found accompanied by a photochemical process in chloroform. Theoretical study and mechanism construction indicate that the designed π-system provides a superior spin-delocalization effect and a large steric effect, mostly avoiding possible consumptions and making the radical stable for hours even under an oxygen-saturated condition. Moreover, this radical system can be applied for a visualized and quantitative detection towards peroxides, such as 2,2,6,6-tetramethylpiperidine-1-oxyl, hydrogen peroxide, and ozone. As the detection relies on a radical capturing mechanism, a higher sensing rate was achieved compared to traditional redox techniques for peroxide detection., Long-standing radical species have raised noteworthy concerns in organic chemistry and but there remains a substantial challenge to produce long-standing radicals by light. Here, the authors demonstrate a stable dithienylethene derived photochromic radical for detection of peroxides and ozone.
- Published
- 2020
11. Structural stability of single-layer PdSe2 with pentagonal puckered morphology and its nanotubes
- Author
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Pavel V. Avramov, Hans Ågren, and Artem V. Kuklin
- Subjects
Materials science ,Condensed matter physics ,Band gap ,business.industry ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Nanoclusters ,Semiconductor ,Planar ,Structural stability ,Monolayer ,Periodic boundary conditions ,Direct and indirect band gaps ,Physical and Theoretical Chemistry ,0210 nano-technology ,business - Abstract
Two-dimensional (2D) materials have gained a lot of attention being a new class of materials with unique properties that could influence future technologies. Concomitant computational design and discovery of new two-dimensional materials have therefore become a significant part of modern materials research. The stability of these predicted materials has emerged as the main issue due to drawbacks of the periodic boundary condition approximation that allow one to pass common criteria of stability. Here, based on first-principle calculations, we demonstrate structural stability and instability of several recently proposed 2D materials with pentagonal morphology including the experimentally exfoliated single-layer PdSe2. It is found that an appropriate orientation of the central Pd sublattice with respect to Se2 dimers effectively compensates all mechanical stress and preserves the planar structure of the PdSe2 nanoclusters, while the flakes of all other materials having pentagonal morphology exhibit non-zero curvature induced by excessive interatomic forces. The relative energies of the PdSe2 monolayer and nanotubes per formula unit also confirm that the planar monolayer is a global energy minimum. Like the monolayer, (n,0) PdSe2 tubes are indirect band gap semiconductors with similar band gaps, while (n,n) tubes reveal indirect–direct band gap transitions following the increase of the tube diameter. Small strain energies of large diameter tubes propose their possible experimental realization for various optoelectronic applications.
- Published
- 2020
12. Perovskite photonic crystal photoelectric devices
- Author
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Yanan Ji, Wen Xu, Ilia L. Rasskazov, Haichun Liu, Junhua Hu, Mao Liu, Donglei Zhou, Xue Bai, Hans Ågren, and Hongwei Song
- Subjects
Materials Chemistry ,Materialkemi ,General Physics and Astronomy - Abstract
Metal halide perovskite materials have been extensively explored in modern photonic devices. Photonic crystals (PCs) are periodic structures with specific optical properties, such as photonic stop bands and “slow photon” effects, which can tailor the propagation and distribution of photons in photoelectric devices. PCs have in recent years been widely explored to significantly improve the performance of perovskite luminescent materials and/or photoelectric devices. Therefore, a full understanding of the key role of PCs and a further learning of the correct use of PCs in perovskite photonic/photoelectric devices are essential for realizing the inherent potential of the superior performance of such devices. By means of this first review, we aim at offering a comprehensive framework description for PCs suitable for high-performance perovskite photoelectric devices. We start with a brief introduction to the basic aspects of PCs. Then, we summarize the influences of PCs on emission/absorption for perovskite luminescent materials. Subsequently, we systematically discuss concepts like light extraction, light trapping, slow-light effects, and structural effects of PCs for perovskite devices, with a particular emphasis on their theoretical descriptions. We argue that the marriage of perovskite materials with PCs can open up a novel frontier in photoelectric devices that potentially can spawn many exciting new fields.
- Published
- 2022
13. Aromaticity and photophysics of tetrasila- and tetragerma-annelated tetrathienylenes as new representatives of the hetero[8]circulene family
- Author
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Victor N. Cherepanov, Nataliya N. Karaush-Karmazin, Rashid R. Valiev, Gleb V. Baryshnikov, Valentina A. Minaeva, B. F. Minaev, Hans Ågren, and Department
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Materials science ,Absorption spectroscopy ,116 Chemical sciences ,Circulene ,BASIS-SET ,General Physics and Astronomy ,гетеро[8]циркулены ,02 engineering and technology ,Electronic structure ,Ring (chemistry) ,114 Physical sciences ,01 natural sciences ,DENSITY-FUNCTIONAL THEORY ,chemistry.chemical_compound ,RAMAN ,FRANCK-CONDON ,DESIGN ,SULFLOWER ,0103 physical sciences ,SPECTRA ,Physical and Theoretical Chemistry ,ароматичность ,010304 chemical physics ,PHOSPHORESCENCE ,Aromaticity ,021001 nanoscience & nanotechnology ,Internal conversion (chemistry) ,фотофизическое поведение ,MOLECULAR-ORBITAL METHODS ,Crystallography ,электронные спектры поглощения ,SINGLE ,chemistry ,Excited state ,0210 nano-technology ,Sulflower - Abstract
The electronic structure, absorption and emission spectra, aromaticity and photophysical behavior of the recently synthesized tetrasilatetrathia[8]circulene and tetragermatetrathia[8]circulene compounds have been studied computationally. Both compounds demonstrate a specific bifacial aromaticity, which is unusual for hetero[8]circulenes; the inner eight-membered core sustains an expected strong paratropic magnetically-induced ring current, while the outer perimeter contains saturated Si(Et)2 and Ge(Et)2 moieties which break the conjugation between the thiophene rings. The overall magnetically-induced ring current for both studied circulenes is close to zero because of the strong local diatropic currents in each thiophene ring that compensate the paratropic counterpart. The electronic absorption and emission spectra of tetrasilatetrathia[8]circulene and tetragermatetrathia[8]circulene demonstrate a clear visible vibronic progression. The 0–0 band is the most active one in the absorption spectra, while in the fluorescence spectra the 0–1 band composed of several normal vibrations is more intense compared with the 0–0 band in excellent agreement with experiment. Accounting for spin–orbit coupling effects, an analysis of the photophysical constants for the two compounds demonstrates: (1) a clear manifestation of the internal heavy atom effect on the inter-system crossing efficiency; (2) one to two order domination of non-radiative rates over the fluorescence rate; and (3) that the S1–S0 internal conversion is extremely slow and can not compete with the fluorescence, while the S1–Tn inter-system crossing is a main deactivation channel of the S1 excited state. These results provide new insight into the electronic structure and photophysics of tetrasilatetrathia[8]circulene and tetragermatetrathia[8]circulene as novel standalone representatives of hetero[8]circulenes – tetraannelated derivatives of tetrathienylene.
- Published
- 2019
14. Overtone Vibrational Transition-Induced Lanthanide Excited-State Quenching in Yb3+/Er3+-Doped Upconversion Nanocrystals
- Author
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Haichun Liu, Bingru Huang, Sai Duan, Jan Bergstrand, Jerker Widengren, Qiuqiang Zhan, and Hans Ågren
- Subjects
Lanthanide ,Materials science ,Quenching (fluorescence) ,Overtone ,Doping ,General Engineering ,Physics::Optics ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Photon upconversion ,0104 chemical sciences ,Condensed Matter::Materials Science ,Nanocrystal ,Excited state ,Physics::Atomic and Molecular Clusters ,Astrophysics::Solar and Stellar Astrophysics ,General Materials Science ,Physics::Chemical Physics ,0210 nano-technology - Abstract
Overtone Vibrational Transition-Induced Lanthanide Excited-State Quenching in Yb3+/Er3+-Doped Upconversion Nanocrystals
- Published
- 2018
15. Applications of Few-Layer Nb2C MXene : Narrow-Band Photodetectors and Femtosecond Mode-Locked Fiber Lasers
- Author
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Chunyang Ma, Songrui Wei, Lingfeng Gao, Han Zhang, Hans Ågren, and Artem V. Kuklin
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Materials science ,General Physics and Astronomy ,Photodetector ,Materialkemi ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Optical switch ,chemistry.chemical_compound ,Fiber laser ,mode-locker ,Materials Chemistry ,Nb2C ,General Materials Science ,photodetector ,business.industry ,General Engineering ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Wavelength ,chemistry ,Femtosecond ,Optoelectronics ,Niobium carbide ,Density functional theory ,density functional theory calculations ,0210 nano-technology ,business ,MXenes ,MXene - Abstract
Although the physicochemical properties of niobium carbide (Nb2C) have been widely investigated, their exploration in the field of photoelectronics is still at the infancy stage with many potential applications that remain to be exploited. Hence, it is demonstrated here that few-layer Nb2C MXene can serve as an excellent building block for both photoelectrochemical-type photodetectors (PDs) and mode-lockers. We show that the photoresponse performance can be readily adjusted by external conditions and that Nb2C NSs exhibit a great potential for narrow-band PDs. The demonstrated mechanism was further confirmed by work functions predicted by density functional theory calculations. In addition, as an optical switch for passively mode-locked fiber lasers, ultrastable pulses can be demonstrated in the telecommunication and mid-infrared regions for Nb2C MXene, and as high as the 69th harmonic order with 411 MHz at the center wavelength of 1882 nm can be achieved. These intriguing results indicate that few-layer Nb2C nanosheets can be used as building blocks for various photoelectronic devices, further broadening the application prospects of two-dimensional MXenes.
- Published
- 2021
16. Breaking inversion symmetry by protonation : experimental and theoretical NEXAFS study of the diazynium ion, N2H+
- Author
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Weijie Hua, Vincenzo Carravetta, Rebecka Lindblad, Hans Ågren, Christine Bülow, V. Zamudio-Bayer, Jan-Erik Rubensson, Rafael C. Couto, Martin Timm, Bernd von Issendorff, Markus Kubin, Stacey L. Sorensen, J. Tobias Lau, Ludvig Kjellsson, and Johan Söderström
- Subjects
Physics ,Absorption spectroscopy ,General Physics and Astronomy ,Large scale facilities for research with photons neutrons and ions ,Charge (physics) ,Protonation ,Electronic structure ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Spectral line ,0104 chemical sciences ,Ion ,Ab initio quantum chemistry methods ,0103 physical sciences ,Teoretisk kemi ,Symmetry breaking ,Physical and Theoretical Chemistry ,010306 general physics ,Theoretical Chemistry - Abstract
As an example of symmetry breaking in NEXAFS spectra of protonated species we present a high resolution NEXAFS spectrum of protonated dinitrogen, the diazynium ion N2H . By ab initio calculations we show that the spectrum consists of a superposition of two nitrogen 1s absorption spectra, each including a amp; 960; band, and a nitrogen 1s to H charge transfer band followed by a weak irregular progression of high energy excitations. Calculations also show that, as an effect of symmetry breaking by protonation, the amp; 960; transitions are separated by 0.23 eV, only slightly exceeding the difference in the corresponding dark symmetry forbidden and bright symmetry allowed core excitations of neutral N2. By DFT and calculations and vibrational analysis, the complex amp; 960; excitation band of N2H is understood as due to the superposition of the significantly different vibrational progressions of excitations from terminal and central nitrogen atoms, both leading to bent final state geometries. We also show computationally that the electronic structure of the charge transfer excitation smoothly depends on the nitrogen proton distance and that there is a clear extension of the spectra going from infinity to close nitrogen proton distance where fine structures show some, although not fully detailed, similarities. An interesting feature of partial localization of the nitrogen core orbitals, with a strong, non monotonous, variation with nitrogen proton distance could be highlighted. Specific effects could be unraveled when comparing molecular cation NEXAFS spectra, as represented by recently recorded spectra of N2 and CO , and spectra of protonated molecules as represented here by the N2H ion. Both types containing rich physical effects not represented in NEXAFS of neutral molecules because of the positive charge, whereas protonation also breaks the symmetry. The effect of the protonation on dinitrogen can be separated in charge, which extends the high energy part of the spectrum, and symmetry breaking, which is most clearly seen in the low energy amp; 960; transition
- Published
- 2021
17. Lighting up solid states using a rubber
- Author
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Gleb V. Baryshnikov, Yanjie Wang, Zhongyu Li, Hans Ågren, Qi Zou, Man Zhang, Shen Shen, and Liangliang Zhu
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Work (thermodynamics) ,Materials science ,Polymers ,Science ,General Physics and Astronomy ,Quantum yield ,Materialkemi ,02 engineering and technology ,010402 general chemistry ,Smart material ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,Natural rubber ,Materials Chemistry ,Triboelectric effect ,Multidisciplinary ,General Chemistry ,Organic molecules in materials science ,021001 nanoscience & nanotechnology ,Tautomer ,0104 chemical sciences ,Rubbing ,Chemical physics ,visual_art ,visual_art.visual_art_medium ,0210 nano-technology ,Material properties - Abstract
It is crucial and desirable to develop green and high-efficient strategies to regulate solid-state structures and their related material properties. However, relative to solution, it is more difficult to break and generate chemical bonds in solid states. In this work, a rubbing-induced photoluminescence on the solid states of ortho-pyridinil phenol family was achieved. This rubbing response relied on an accurately designed topochemical tautomerism, where a negative charge, exactly provided by the triboelectric effect of a rubber, can induce a proton transfer in a double H-bonded dimeric structure. This process instantaneously led to a bright-form tautomer that can be stabilized in the solid-state settings, leading to an up to over 450-fold increase of the fluorescent quantum yield of the materials. The property can be repeatedly used due to the reversibility of the tautomerism, enabling encrypted applications. Moreover, a further modification to the structure can be accomplished to achieve different properties, opening up more possibilities for the design of new-generation smart materials., Changes in molecular properties due to stimuli response are critically important for the development of new materials. However, most processes are slow or inefficient in the solid state. Here the authors demonstrate property switching in the solid state using a rubbing-induced tautomerism in multiple hydrogen-bonded donor-acceptor couples.
- Published
- 2021
18. Atomistic description of plasmonic generation in alloys and core shell nanoparticles
- Author
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Lasse Kragh Sørensen, Hans Ågren, Vadim I. Zakomirnyi, and Anton D. Utyushev
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Quenching ,Materials science ,Condensed matter physics ,Surface plasmon ,Physics::Optics ,General Physics and Astronomy ,Nanoparticle ,02 engineering and technology ,Dielectric ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Polarizability ,Physics::Atomic and Molecular Clusters ,Nanorod ,Physical and Theoretical Chemistry ,Surface plasmon resonance ,0210 nano-technology ,Plasmon - Abstract
Using the extended discrete interaction model we investigate the tunabilty of surface plasmon resonances in alloys and core–shell nanoparticles made from silver and gold in the small (1–15 nm) nanoscale regime where classical models based on the bulk dielectric constant may not apply. We show that the surface plasmon resonance of these alloys and core–shell particles to a large extent follow Vegard's law irrespective of the geometry of the nanoparticle. The evolution of the polarizability with size demonstrates a highly non-linear behaviour of the polarizability with the ratio of the constituents and geometry in alloys and core–shell nanoparticles, with the exception of the longitudinal surface plasmon resonance in nanorods and, partly, nanodisc alloys. We here show that the non-linear behaviour can be explained in terms of the difference in polarizability of the mixing constituents and local effects causing a quenching of the dipoles for geometries with a low aspect ratio. A thorough statistical investigation reveals that there is only a small dependence of the surface plasmon resonance on atomic arrangement and exact distribution in a nanoparticle and that the standard deviation decreases rapidly with the size of the nanoparticles. The physical ground for the random distribution algorithm for alloys in discrete interaction models is explained in detail and verified by a statistical analysis. For nanoparticles below 4 nm a sampling strategy is recommended.
- Published
- 2020
19. First-principles calculations of anharmonic and deuteration effects on the photophysical properties of polyacenes and porphyrinoids
- Author
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Theo Kurtén, Boris F. Minaev, Glib V. Baryshnikov, Hans Ågren, Dage Sundholm, Victor N. Cherepanov, Rinat T. Nasibullin, Rashid R. Valiev, and Department of Chemistry
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Materials science ,116 Chemical sciences ,Circulene ,INTERNAL-CONVERSION ,General Physics and Astronomy ,Quantum yield ,010402 general chemistry ,01 natural sciences ,Molecular physics ,114 Physical sciences ,chemistry.chemical_compound ,Reaction rate constant ,MATRIX-ELEMENTS ,RATE CONSTANTS ,0103 physical sciences ,Tetraphenylporphyrin ,MORSE OSCILLATOR MODEL ,RATES ,Physical and Theoretical Chemistry ,FLUORESCENCE ,Anthracene ,COMPLEX ,010304 chemical physics ,RADIATIONLESS ELECTRONIC-TRANSITIONS ,Anharmonicity ,Internal conversion (chemistry) ,Porphyrin ,0104 chemical sciences ,chemistry ,13. Climate action ,ORGANIC-MOLECULES ,SPIN-ORBIT - Abstract
A new method for calculating internal conversion rate constants (k[combining low line]IC), including anharmonic effects and using the Lagrangian multiplier technique, is proposed. The deuteration effect on k[combining low line]IC is investigated for naphthalene, anthracene, free-base porphyrin (H2P) and tetraphenylporphyrin (H2TPP). The results show that anharmonic effects are important when calculating k[combining low line]IC for transitions between electronic states that are energetically separated (ΔE) by more than 20 000-25 000 cm-1. Anharmonic effects are also important when ΔE20 000-25 000 cm-1 and when the accepting modes are X-H stretching vibrations with a frequency larger than 2000 cm-1. The calculations show that there is mixing between the S1 and S2 states of naphthalene induced by non-adiabatic interactions. The non-adiabatic interaction matrix element between the S1 and S2 states is 250 cm-1 and 50 cm-1 for the normal and fully deuterated naphthalene structure and this difference significantly affects the estimated fluorescence quantum yield. Besides aromatic hydrocarbons H2P and H2TPP, the k[combining low line]IC rate constant is also calculated for pyrometene (PM567) and tetraoxa[8]circulene (4B) with a detailed analysis of the effect of the vibrational anharmonicity.
- Published
- 2020
20. Correction: The molecular structure of the surface of water–ethanol mixtures
- Author
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Johannes Kirschner, Anderson H. A. Gomes, Ricardo R. T. Marinho, Olle Björneholm, Hans Ågren, Vincenzo Carravetta, Niklas Ottosson, Arnaldo Naves de Brito, and Huib J. Bakker
- Subjects
General Physics and Astronomy ,Physical and Theoretical Chemistry - Abstract
Correction for ‘The molecular structure of the surface of water–ethanol mixtures’ by Johannes Kirschner et al., Phys. Chem. Chem. Phys., 2021, 23, 11568–11578, DOI: 10.1039/D0CP06387H.
- Published
- 2022
21. Plasmonic nano-shells: atomistic discrete interaction versus classic electrodynamics models
- Author
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P. Scott Carney, Zilvinas Rinkevicius, Hans Ågren, Lasse Kragh Sørensen, Ilia L. Rasskazov, and Vadim I. Zakomirnyi
- Subjects
Permittivity ,Physics ,Mie scattering ,Physics::Optics ,General Physics and Astronomy ,Semiclassical physics ,Radius ,Plasma oscillation ,Molecular physics ,Polarizability ,Physics::Atomic and Molecular Clusters ,Physical and Theoretical Chemistry ,Plasmon ,Harmonic oscillator - Abstract
Using the extended discrete interaction model and Mie theory, we investigate the tunability of the optical polarizability of small metallic nano-shells. We show that the spectral positions of symmetric and antisymmetric dipolar plasmon resonances vary with the ratio of particle radius to hole radius in a manner similar to one predicted for uniform metallic nano-shells using a semiclassical approach of two coupled harmonic oscillators. We show that, according to the extended discrete interaction model, the dipolar plasmon resonances are also present for nano-shells in the 2–13 nm size region and show the same functional dependence seen for larger nano-shells. Using previously fitted data from experiment, we can predict the size-dependence of the plasma frequency for nano-shells in the 1–15 nm size region. We find that Mie theory, which utilizes the electron mean free path correction for the permittivity, is not able to reproduce the same functional form of the dipolar modes for the nano-shells of the same sizes.
- Published
- 2020
22. Twisted-Planar-Twisted expanded porphyrinoid dimer as a rudimentary reaction-based methanol indicator
- Author
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Yongshu Xie, Weihua Zhu, Xu Liang, Glib V. Baryshnikov, Chengjie Li, Hans Ågren, Feng Sha, Xin-Yan Wu, Qizhao Li, Tingting Gu, Jonathan L. Sessler, Yubin Ding, and Chengxi Zhao
- Subjects
Science ,Dimer ,General Physics and Astronomy ,Synthetic chemistry methodology ,Dihedral angle ,010402 general chemistry ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,chemistry.chemical_compound ,Moiety ,Reactivity (chemistry) ,lcsh:Science ,Multidisciplinary ,010405 organic chemistry ,Sensors ,technology, industry, and agriculture ,General Chemistry ,Self-assembly ,Porphyrin ,Planarity testing ,0104 chemical sciences ,Crystallography ,Monomer ,chemistry ,lcsh:Q ,Methanol - Abstract
Directly linked porphyrin dimers have attracted considerable attention because of their intriguing electronic features. Most emphasis has been placed on either dimers with large dihedral angles between the constituent planar monomeric subunits or those with overall planarity, referred to as “Planar-Twisted-Planar” and “Planar-Planar-Planar”, respectively. Herein, we report a “Twisted-Planar-Twisted” framework, the hexaphyrin dimer D that exists in a trans configuration. Treatment of D with MeOH affords two isomeric dimers, MD1 and MD2, both of which incorporate a methoxy moiety and exist in cis orientations with respect to the tethering linkage. The methanol-promoted conversion is accompanied by a readily discernible color change from green to brown and is not induced to an appreciable level by other alcohols. Dimer D thus acts as a rudimentary, albeit highly selective, reaction-based methanol indicator. This work provides a promising approach for constructing reaction-based chemosensors using porphyrinoid dimers of nonplanar subunits with biased reactivity., Directly linked porphyrin dimers show intriguing electronic features but emphasis has been placed on planar monomeric units. Here, the authors report a Twisted-Planar-Twisted framework which can undergo a cis-trans transformation accompanied by a colour change in presence of methanol, making this framework applicable as a methanol sensor.
- Published
- 2020
23. X-Ray Absorption Spectrum of the N2+ Molecular Ion
- Author
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Rebecka Lindblad, Ludvig Kjellsson, Marcus Lundberg, S. L. Sorensen, V. Zamudio-Bayer, Hans Ågren, B. von Issendorff, J. T. Lau, Rafael C. Couto, Martin Timm, C. Bulow, Jan-Erik Rubensson, and Vincenzo Carravetta
- Subjects
Physics ,X-ray absorption spectroscopy ,Absorption spectroscopy ,Atom and Molecular Physics and Optics ,Polyatomic ion ,General Physics and Astronomy ,Large scale facilities for research with photons neutrons and ions ,Charge (physics) ,Coupling (probability) ,01 natural sciences ,Ion ,Teoretisk kemi ,0103 physical sciences ,Atom- och molekylfysik och optik ,Atomic physics ,Theoretical Chemistry ,010306 general physics ,Spin (physics) ,Ground state - Abstract
The x-ray absorption spectrum of ${\mathrm{N}}_{2}^{+}$ in the K-edge region has been measured by irradiation of ions stored in a cryogenic radio frequency ion trap with synchrotron radiation. We interpret the experimental results with the help of restricted active space multiconfiguration theory. Spectroscopic constants of the $1{\ensuremath{\sigma}}_{u}^{\ensuremath{-}1}\text{ }{^{2}\mathrm{\ensuremath{\Sigma}}}_{u}^{+}$ state, and the two $1{\ensuremath{\sigma}}_{u}^{\ensuremath{-}1}3{\ensuremath{\sigma}}_{g}^{\ensuremath{-}1}1{\ensuremath{\pi}}_{g}\text{ }{^{2}\mathrm{\ensuremath{\Pi}}}_{u}$ states are determined from the measurements. The charge of the ground state together with spin coupling involving several open shells give rise to double excitations and configuration mixing, and a complete breakdown of the orbital picture for higher lying core-excited states.
- Published
- 2020
24. Vibronic absorption spectra of the angular fused bisindolo- and biscarbazoloanthracene blue fluorophores for OLED applications
- Author
-
Gleb V. Baryshnikov, Rashid R. Valiev, Boris F. Minaev, Dmitry A. Sunchugashev, and Hans Ågren
- Subjects
Anthracene ,010304 chemical physics ,Absorption spectroscopy ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,OLED ,Vibronic spectroscopy ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
An in-depth analysis of the vibronic absorption spectra for the recently synthesized blue-fluorescent OLED emitters bis[(1,2)(5,6)]indoloanthracene and biscarbazolo[3,4-a:3â²,4â²-h]anthracene has ...
- Published
- 2018
25. Computational study of aromaticity, 1H NMR spectra and intermolecular interactions of twisted thia-norhexaphyrin and its multiply annulated polypyrrolic derivatives
- Author
-
Rashid R. Valiev, Chengjie Li, Hans Ågren, Yongshu Xie, Gleb V. Baryshnikov, Qizhao Li, and Department of Chemistry
- Subjects
Proton ,Chemistry ,Hydrogen bond ,Chemical shift ,Atoms in molecules ,Intermolecular force ,116 Chemical sciences ,General Physics and Astronomy ,Aromaticity ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Computational chemistry ,Intramolecular force ,Proton NMR ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
The recently synthesized twisted thia-norhexaphyrin and its multiply annulated polypyrrolic derivatives have been studied computationally. Gauge-including magnetically induced current calculations predict a global nonaromatic character of the initial thia-norhexaphyrin due to the highly-twisted conformation of the macrocycle. Upon the oxidation of the thia-norhexaphyrin the four multiply annulated polypyrrolic aromatic macrocycles are formed for which the global aromatic character is confirmed in agreement with experimentally measured 1H NMR spectra. The calculations of the proton chemical shifts for the studied compounds by direct comparison with the tetramethylsilane standard leads to a significant mean absolute error. At the same time a linear regression procedure for the two selected groups of protons (CH and NH protons) provides much better values of calculated chemical shifts and tight correlation with experiment. The separate consideration of NH protons is motivated by the numerous intermolecular hydrogen bonds in which the protons are involved that induce considerable upfield shifts leading to the significant underestimation of corresponding chemical shifts. Such a selected correlation can be used for accurate estimation of proton chemical shifts of the related porphyrinoids. Bader's theory of Atoms in Molecules has been applied for the studied twisted thia-norhexaphyrin and its multiply annulated polypyrrolic derivatives to characterize the intramolecular H-bonds and other non-covalent interactions.
- Published
- 2019
26. Helicity Inversion of Supramolecular Hydrogels Induced by Achiral Substituents
- Author
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Soo Zeng Fiona Phua, Pei-Zhou Li, Hans Ågren, Jianhui Sheng, Guofeng Liu, Xin Li, Yanli Zhao, Liangliang Zhu, Wee Kong Ong, School of Materials Science and Engineering, and School of Physical and Mathematical Sciences
- Subjects
inorganic chemicals ,Supramolecular chirality ,Circular dichroism ,Chemistry ,Stereochemistry ,technology, industry, and agriculture ,General Engineering ,Supramolecular chemistry ,Stacking ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Helicity Inversion ,Crystallography ,Molecular dynamics ,Achiral Substituent ,Chemistry [Science] ,Self-healing hydrogels ,General Materials Science ,Self-assembly ,0210 nano-technology ,Chirality (chemistry) - Abstract
Probing the supramolecular chirality of assemblies and controlling their handedness are closely related to the origin of chirality at the supramolecular level and the development of smart materials with desired handedness. However, it remains unclear how achiral residues covalently bonded to chiral amino acids can function in the chirality inversion of supramolecular assemblies. Herein, we report macroscopic chirality and dynamic manipulation of chiroptical activity of hydrogels self-assembled from phenylalanine derivatives, together with the inversion of their handedness achieved solely by exchanging achiral substituents between oligo(ethylene glycol) and carboxylic acid groups. This helicity inversion is mainly induced by distinct stacking mode of the self-assembled building blocks, as collectively confirmed by scanning electron microscopy, circular dichroism, crystallography, and molecular dynamics calculations. Through this straightforward approach, we were able to invert the handedness of helical assemblies by merely exchanging achiral substituents at the terminal of chiral gelators. This work not only presents a feasible strategy to achieve the handedness inversion of helical nanostructures for better understanding of chiral self-assembly process in supramolecular chemistry but also facilities the development of smart materials with controllable handedness in materials science. MOE (Min. of Education, S’pore)
- Published
- 2017
27. Achieving high-efficiency emission depletion nanoscopy by employing cross relaxation in upconversion nanoparticles
- Author
-
Rui Pu, Bingru Huang, Haichun Liu, Sailing He, Qiuqiang Zhan, Chao Zhou, Xingyun Peng, Baoju Wang, Hans Ågren, and Qiusheng Wu
- Subjects
Luminescence ,Materials science ,Science ,Color ,General Physics and Astronomy ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,Microscopy, Electron, Transmission ,Microscopy ,Humans ,Stimulated emission ,lcsh:Science ,Cytoskeleton ,Multidisciplinary ,Super-resolution microscopy ,Nonlinear optics ,General Chemistry ,021001 nanoscience & nanotechnology ,Fluorescence ,0104 chemical sciences ,Light intensity ,Microscopy, Fluorescence ,Molecular Probes ,Thulium ,Nanoparticles ,lcsh:Q ,0210 nano-technology ,HeLa Cells - Abstract
Stimulated emission depletion microscopy provides a powerful sub-diffraction imaging modality for life science studies. Conventionally, stimulated emission depletion requires a relatively high light intensity to obtain an adequate depletion efficiency through only light–matter interaction. Here we show efficient emission depletion for a class of lanthanide-doped upconversion nanoparticles with the assistance of interionic cross relaxation, which significantly lowers the laser intensity requirements of optical depletion. We demonstrate two-color super-resolution imaging using upconversion nanoparticles (resolution ~ 66 nm) with a single pair of excitation/depletion beams. In addition, we show super-resolution imaging of immunostained cytoskeleton structures of fixed cells (resolution ~ 82 nm) using upconversion nanoparticles. These achievements provide a new perspective for the development of photoswitchable luminescent probes and will broaden the applications of lanthanide-doped nanoparticles for sub-diffraction microscopic imaging., Upconversion nanoparticles, which do not suffer from the photophysical artifacts that limit fluorescent molecules, offer an exciting opportunity for biological super-resolution imaging. Here, Zhan et al. develop an efficient STED mechanism using optimized lanthanide upconversion nanoparticles, enabling cytoskeleton nanoscopic imaging.
- Published
- 2017
28. A computational study of structural and magnetic properties of bi- and trinuclear Cu(II) complexes with extremely long Cu---Cu distances
- Author
-
Gleb V. Baryshnikov, Boris F. Minaev, Hans Ågren, and Alina T. Baryshnikova
- Subjects
chemistry ,010405 organic chemistry ,Computational chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,Physical chemistry ,Symmetry breaking ,Physical and Theoretical Chemistry ,010402 general chemistry ,01 natural sciences ,Copper ,0104 chemical sciences - Abstract
Three recently synthesized copper(II) complexes with aroylhydrazones of trifluoroacetic and benzenecarboxylic acids (Dalton Trans., 2013, 42, 16878) have been computationally investigated by densit ...
- Published
- 2017
29. Swelling and dimensional stability of xyloglucan/montmorillonite nanocomposites in moist conditions from molecular dynamics simulations
- Author
-
Yaoquan Tu, Jakob Wohlert, Lars Berglund, Hans Ågren, Malin Bergenstråhle-Wohlert, and Yan Wang
- Subjects
Materials science ,General Computer Science ,Composite number ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,complex mixtures ,01 natural sciences ,chemistry.chemical_compound ,medicine ,General Materials Science ,Hemicellulose ,Relative humidity ,Composite material ,Nanocomposite ,General Chemistry ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Xyloglucan ,Computational Mathematics ,Montmorillonite ,chemistry ,Mechanics of Materials ,Swelling ,medicine.symptom ,Biocomposite ,0210 nano-technology - Abstract
Nacre-mimetic biocomposites made from the combination of montmorillonite clay and the hemicellulose xyloglucan give materials that retain much of their material properties even at high relative humidity. Here, a model composite system consisting of two clay platelets intercalated by xyloglucan oligomers was studied at different levels of hydration using molecular dynamics simulations, and compared to the pure clay. It was found that xyloglucan inhibits swelling of the clay at low water contents by promoting the formation of nano-sized voids that fill with water without affecting the material’s dimensions. At higher water contents the XG itself swells, but at the same time maintaining contact with both platelets across the gallery, thereby acting as a physical cross-linker in a manner similar to the role of XG in the plant cell wall.
- Published
- 2017
30. Two-photon absorption of BF2-carrying compounds: insights from theory and experiment
- Author
-
Małgorzata Wielgus, Robert Zaleśny, Wojciech Bartkowiak, Hans Ågren, Rakesh Puttreddy, Joanna Bednarska, Beata Jędrzejewska, Kari Rissanen, and Borys Ośmiałowski
- Subjects
010405 organic chemistry ,structure-property study ,General Physics and Astronomy ,Nanotechnology ,010402 general chemistry ,01 natural sciences ,Fluorescence ,Two-photon absorption ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical physics ,Pyridine ,compounds ,Physical and Theoretical Chemistry ,ta116 - Abstract
This communication presents a structure–property study of a few novel pyridine-based difluoroborate compounds with a N–BF2–O core, which exhibit outstanding fluorescence properties. To exploit their potential for two-photon bioimaging, relationships between the two-photon action cross section and systematic structural modifications have been investigated and unravelled.
- Published
- 2017
31. Design, synthesis and evaluation of a new Mn – Contrast agent for MR imaging of myocardium based on the DTPA-phenylpentadecanoic acid complex
- Author
-
Rashid R. Valiev, Victor D. Filimonov, Vladimir Y. Usov, Hans Ågren, M. L. Belyanin, Elena V. Stepanova, and Oleg Y. Borodin
- Subjects
магнитно-резонансная томография ,chemistry.chemical_classification ,010405 organic chemistry ,Stereochemistry ,Chemistry ,media_common.quotation_subject ,гадолиний ,General Physics and Astronomy ,Fatty acid ,теория функционала плотности ,010402 general chemistry ,01 natural sciences ,Mr imaging ,марганец ,0104 chemical sciences ,Nuclear magnetic resonance ,Design synthesis ,Contrast (vision) ,Moiety ,Physical and Theoretical Chemistry ,media_common - Abstract
In the present paper we describe the first synthesis and evaluation of a novel Mn (II) complex (DTPA-PPDA Mn (II)) which contains a C-15 fatty acid moiety that has high affinity to the heart muscle. The complexation energy of DTPA-PPDA Mn (II) evaluated by quantum chemistry methodology indicates that it essentially exceeds the corresponding value for the known DTPA Mn (II) complex. Molecular docking revealed that the affinity of the designed complex to the heart-type transport protein H-FABP well exceeds that of lauric acid. Phantom experiments in low-field MRI the designed contrast agent provides MR imaging comparable to gadopentetic acid.
- Published
- 2016
32. A three-dimensional ratiometric sensing strategy on unimolecular fluorescence–thermally activated delayed fluorescence dual emission
- Author
-
Chao Deng, Xiaoyan Bao, Gleb V. Baryshnikov, Liangliang Zhu, Xuping Li, Bin Wu, Hans Ågren, and Yunyun Zhou
- Subjects
0301 basic medicine ,Multidisciplinary ,Materials science ,Science ,Atom and Molecular Physics and Optics ,Dual emission ,General Physics and Astronomy ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,Fluorescence ,Article ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,030104 developmental biology ,lcsh:Q ,Atom- och molekylfysik och optik ,lcsh:Science ,0210 nano-technology ,Molecular probe - Abstract
Visualized sensing through fluorescence signals is a powerful method for chemical and physical detection. However, the utilization of fluorescent molecular probes still suffers from lack of precise signal self-calibration in practical use. Here we show that fluorescence and thermally activated delayed fluorescence can be simultaneously produced at the single-molecular level. The thermally activated delayed fluorescence serves as a sensing signal with its wavelength and lifetime both altered correlating to polarity, whereas the fluorescence always remains unchanged as an internal reference. Upon the establishment of a three-dimensional working curve upon the ratiometric wavelength and photoluminescence lifetime vs. polarity, disturbance factors during a relevant sensing process can be largely minimized by such a multiple self-calibration. This strategy was further applied into a precise detection of the microenvironmental polarity variation in complex phospholipid systems, towards providing new insights for convenient and accurate diagnosis of membrane lesions., New photoluminescent strategies are required to realize high-performance ratiometric sensors for bio-sensing applications. Here, the authors demonstrate a fluorescence-thermally activated delayed fluorescence dual emission strategy for ratiometric sensors with high precision.
- Published
- 2019
33. Decomposition of molecular properties
- Author
-
Ignat Harczuk, Olav Vahtras, and Hans Ågren
- Subjects
Models, Molecular ,Work (thermodynamics) ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Physical Phenomena ,symbols.namesake ,Physics::Atomic and Molecular Clusters ,Decomposition (computer science) ,Theoretical chemistry ,Molecule ,Physics::Atomic Physics ,Physical and Theoretical Chemistry ,Rayleigh scattering ,Quantum ,Quantum chemical ,Physics ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Models, Chemical ,symbols ,Nanoparticles ,Quantum Theory ,Collagen ,0210 nano-technology ,Dispersion (chemistry) - Abstract
We review recent work on property decomposition techniques using quantum chemical methods and discuss some topical applications in terms of quantum mechanics-molecular mechanics calculations and the constructing of properties of large molecules and clusters. Starting out from the so-called LoProp decomposition scheme [Gagliardi et al., J. Chem. Phys., 2004, 121, 4994] for extracting atomic and inter-atomic contributions to molecular properties we show how this method can be generalized to localized frequency-dependent polarizabilities, to localized hyperpolarizabilities and to localized dispersion coefficients. Some applications of the generalized decomposition technique are reviewed - calculations of frequency-dependent polarizabilities, Rayleigh scattering of large clusters, and calculations of hyperpolarizabilities of proteins.
- Published
- 2019
34. Nuclear dynamics in resonant inelastic X-ray scattering and X-ray absorption of methanol
- Author
-
Raphael M. Jay, Victor Kimberg, Annette Pietzsch, Michael Odelius, Alexander Föhlisch, Sebastian Eckert, Thorsten Schmitt, Hans Ågren, Daniil A Fedotov, Dirk R. Rehn, Sergey Polyutov, Viktoriia Savchenko, Faris Gel'mukhanov, Mattis Fondell, Johannes Niskanen, Vinícius Vaz da Cruz, Rafael C. Couto, Nina Ignatova, and Patrick Norman
- Subjects
Materials science ,Absorption spectroscopy ,Atom and Molecular Physics and Optics ,Analytical chemistry ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,Physical Chemistry ,Spectral line ,chemistry.chemical_compound ,0103 physical sciences ,Teoretisk kemi ,Theoretical chemistry ,core excitation spectra of gas and liquid methanol, X ray absorption spectroscopy XAS , resonant inelastic X Ray scattering RIXS , Franck Condon amplitudes, valence excited states ,ddc:530 ,Physical and Theoretical Chemistry ,Absorption (electromagnetic radiation) ,Theoretical Chemistry ,Astrophysics::Galaxy Astrophysics ,Fysikalisk kemi ,X-ray absorption spectroscopy ,010304 chemical physics ,X-ray ,Institut für Physik und Astronomie ,0104 chemical sciences ,Resonant inelastic X-ray scattering ,chemistry ,Condensed Matter::Strongly Correlated Electrons ,Atom- och molekylfysik och optik ,Methanol - Abstract
We report on a combined theoretical and experimental study of core excitation spectra of gas and liquid phase methanol as obtained with the use of X ray absorption spectroscopy XAS and resonant inelastic X ray scattering RIXS . The electronic transitions are studied with computational methods that include strict and extended second order algebraic diagrammatic construction [ADC 2 and ADC 2 x], restricted active space second order perturbation theory, and time dependent density functional theory providing a complete assignment of the near oxygen K edge XAS. We show that multimode nuclear dynamics is of crucial importance for explaining the available experimental XAS and RIXS spectra. The multimode nuclear motion was considered in a recently developed mixed representation where dissociative states and highly excited vibrational modes are accurately treated with a time dependent wave packet technique, while the remaining active vibrational modes are described using Franck Condon amplitudes. Particular attention is paid to the polarization dependence of RIXS and the effects of the isotopic substitution on the RIXS profile in the case of dissociative core excited states. Our approach predicts the splitting of the 2a amp; 8243; RIXS peak to be due to an interplay between molecular and pseudo atomic features arising in the course of transitions between dissociative core and valence excited states. The dynamical nature of the splitting of the 2a amp; 8243; peak in RIXS of liquid methanol near pre edge core excitation is shown. The theoretical results are in good agreement with our liquid phase measurements and gas phase experimental data available from the literature
- Published
- 2019
35. Anion-induced exchange interactions in binuclear complexes of Cu(II) with flexible hexadentate bispicolylamidrazone ligands
- Author
-
Boris F. Minaev, Gleb V. Baryshnikov, Alina A. Baryshnikova, and Hans Ågren
- Subjects
010405 organic chemistry ,Exchange interaction ,General Physics and Astronomy ,chemistry.chemical_element ,теория функционала плотности ,010402 general chemistry ,01 natural sciences ,Copper ,0104 chemical sciences ,Ion ,Perchlorate ,chemistry.chemical_compound ,Crystallography ,chemistry ,Unpaired electron ,лиганды ,Computational chemistry ,медь ,Physics::Atomic and Molecular Clusters ,Density functional theory ,Singlet state ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Dispersion (chemistry) - Abstract
Two recently synthesized copper(II) complexes with spacer-armed bispicolylamidrazone ligands have been theoretically studied at the density functional theory (DFT) level accounting for empirical dispersion correction and intrinsic anionic environment by perchlorate ions. The exchange parameter between the open-shell singlet and triplet states of the studied complexes has been estimated by broken symmetry DFT calculations. The mechanism of spin-spin exchange interaction between the unpaired electrons via the σ-bond aliphatic chain (Gusev et al., 2015) is confirmed. Instead, a anion-induced mechanism is proposed which means that the anionic grid participates in the exchange interaction between the unpaired electrons.
- Published
- 2016
36. Hyperpolarizabilities of extended molecular mechanical systems
- Author
-
Hans Ågren, Olav Vahtras, and Ignat Harczuk
- Subjects
Physics ,Basis (linear algebra) ,General Physics and Astronomy ,Hyperpolarizability ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic units ,0104 chemical sciences ,Mechanical system ,Dipole ,Transformation (function) ,Quantum mechanics ,Physics::Atomic and Molecular Clusters ,Theoretical chemistry ,Density functional theory ,Physics::Atomic Physics ,Statistical physics ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
We propose and evaluate algorithms for the calculation of molecular polarizabilities and hyperpolarizabilities of extended chemical systems. These algorithms are generalizations of the Silberstein-Applequist procedure involving interacting induced classical dipoles through the localized polarizabilities and hyperpolarizabilities. The models are evaluated in terms of interacting molecular units as well as interacting atomic units that result from the atomic decomposition scheme known as the LoProp transformation. We introduce a generalized LoProp scheme which applies to hyperpolarizabilities as well as to polarizabilities. The accuracy of the second-order Applequist method is tested for the first hyperpolarizability for the TIP3P water model using both Hartree-Fock and density functional theory evaluated with different basis sets. Possible applications and ramifications of the scheme are discussed.
- Published
- 2016
37. Theoretical study of the binding profile of an allosteric modulator NS-1738 with a chimera structure of the α7 nicotinic acetylcholine receptor
- Author
-
Bengt Långström, Hans Ågren, Christer Halldin, Guanglin Kuang, Yaoquan Tu, Xu Wang, and Agneta Nordberg
- Subjects
0301 basic medicine ,Allosteric modulator ,alpha7 Nicotinic Acetylcholine Receptor ,Recombinant Fusion Proteins ,General Physics and Astronomy ,Molecular Dynamics Simulation ,Pharmacology ,03 medical and health sciences ,Chimera (genetics) ,Binding profile ,α7 nicotinic acetylcholine receptor ,Animals ,Humans ,Physical and Theoretical Chemistry ,Lymnaea ,biology ,Chemistry ,Phenylurea Compounds ,Hydrogen Bonding ,Long-term potentiation ,Molecular Docking Simulation ,Nicotinic acetylcholine receptor ,030104 developmental biology ,Allosteric enzyme ,Cholinergic system ,Biophysics ,biology.protein ,Allosteric Site - Abstract
Potentiation of the function of the α7 nicotinic acetylcholine receptor (α7-nAChR) is believed to provide a possible way for the treatment of cholinergic system dysfunctions such as Alzheimer's disease and schizophrenia. Positive allosteric modulators (PAMs) are able to augment the peak current response of the endogenous agonist of α7-nAChR by binding to some allosteric sites. In this study, the binding profile of a potent type I PAM, NS-1738, with a chimera structure (termed α7-AChBP) constructed from the extracellular domain of α7-nAChR and an acetylcholine binding protein was investigated with molecular docking, molecular dynamics simulation, and free energy calculation methods. We found that NS-1738 could bind to three allosteric sites of α7-AChBP, namely, the top pocket, the vestibule pocket and the agonist sub-pocket. NS-1738 has moderate binding affinities (-6.76 to -9.15 kcal mol
- Published
- 2016
38. Charge-transfer plasmons with narrow conductive molecular bridges: A quantum-classical theory
- Author
-
Alexander S. Fedorov, Sergey Polyutov, Pavel O. Krasnov, Felix N. Tomilin, Hans Ågren, and M.A. Visotin
- Subjects
chemistry.chemical_classification ,Materials science ,010304 chemical physics ,Physics::Optics ,General Physics and Astronomy ,Electron ,Polymer ,010402 general chemistry ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Polyacetylene ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Molecule ,Density functional theory ,Physical and Theoretical Chemistry ,Quantum ,Electrical conductor ,Plasmon - Abstract
We analyze a new type of plasmon system arising from small metal nanoparticles linked by narrow conductive molecular bridges. In contrast to the well-known charge-transfer plasmons, the bridge in these systems consists only of a narrow conductive molecule or polymer in which the electrons move in a ballistic mode, showing quantum effects. The plasmonic system is studied by an original hybrid quantum-classical model accounting for the quantum effects, with the main parameters obtained from first-principles density functional theory simulations. We have derived a general analytical expression for the modified frequency of the plasmons and have shown that its frequency lies in the near-infrared (IR) region and strongly depends on the conductivity of the molecule, on the nanoparticle-molecule interface, and on the size of the system. As illustrated, we explored the plasmons in a system consisting of two small gold nanoparticles linked by a conjugated polyacetylene molecule terminated by sulfur atoms. It is argued that applications of this novel type of plasmon may have wide ramifications in the areas of chemical sensing and IR deep tissue imaging.
- Published
- 2019
39. Unusual binding-site-specific photophysical properties of a benzothiazole-based optical probe in amyloid beta fibrils
- Author
-
Robert Zaleśny, Hans Ågren, and N. Arul Murugan
- Subjects
Amyloid ,Amyloid beta ,Atom and Molecular Physics and Optics ,General Physics and Astronomy ,Plasma protein binding ,010402 general chemistry ,Fibril ,01 natural sciences ,chemistry.chemical_compound ,Alzheimer Disease ,0103 physical sciences ,Humans ,Molecule ,Benzothiazoles ,Physical and Theoretical Chemistry ,Binding site ,Fluorescent Dyes ,Binding Sites ,010304 chemical physics ,biology ,0104 chemical sciences ,Molecular Docking Simulation ,Benzothiazole ,chemistry ,Absorption band ,biology.protein ,Biophysics ,Quantum Theory ,Thermodynamics ,Atom- och molekylfysik och optik ,Protein Binding - Abstract
Optical imaging of amyloid fibrils serves as a cost-effective route for the diagnosis of Alzheimer-like conformational diseases. However{,} the challenge here is to optimize the binding affinity and photophysical properties of the optical imaging agents in a way specific to certain types of amyloids. In a few occasions it is shown that novel optical imaging agents can be designed to bind to a particular type of amyloid fibril with larger binding affinity and specificity. There is also a recent report on photoluminescent polythiophenes which display photophysical properties that can be used to distinguish the variants or subtypes of amyloids (J. Rasmussen et al.{,} Proc. Natl. Acad. Sci. U. S. A.{,} 2017{,} 114(49){,} 13018â13023). Based on a multiscale modeling approach{,} here{,} we report on the complementary aspect that the photophysical properties of a benzothiazole based optical probe (referred to as BTA-3) can be specific to the binding sites in the same amyloid fibrils and we attribute this to its varying electronic structure in different sites. As reported experimentally from competitive binding assay studies for many amyloid staining molecules and tracers{,} we also show multiple binding sites in amyloid fibrils for this probe. In particular{,} BTA-3 displayed a red-shift in its low-frequency absorption band only in site-4{,} a surface site of amyloid fibrils when compared to the spectra in water solvent. In the remaining sites{,} it exhibited a less significant blue shift for the same absorption band.
- Published
- 2018
40. Dirac Magnons in Honeycomb Ferromagnets
- Author
-
Saikat Banerjee, Sergey S. Pershoguba, Gabriel Aeppli, Jason C. Lashley, Hans Ågren, Alexander V. Balatsky, and Jihwey Park
- Subjects
Materials science ,QC1-999 ,Dirac (software) ,General Physics and Astronomy ,FOS: Physical sciences ,02 engineering and technology ,Electron ,01 natural sciences ,law.invention ,Renormalization ,Spin wave ,law ,0103 physical sciences ,ddc:530 ,010306 general physics ,Electronic band structure ,Condensed Matter - Materials Science ,Condensed matter physics ,Graphene ,Magnon ,Physics ,Materials Science (cond-mat.mtrl-sci) ,021001 nanoscience & nanotechnology ,Quasiparticle ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology - Abstract
The discovery of the Dirac electron dispersion in graphene [A. H. Castro Neto, et al., The Electronic Properties of Graphene, Rev. Mod. Phys. 81, 109 (2009)] led to the question of the Dirac cone stability with respect to interactions. Coulomb interactions between electrons were shown to induce a logarithmic renormalization of the Dirac dispersion. With a rapid expansion of the list of compounds and quasiparticle bands with linear band touching [T. O. Wehling, et al., Dirac Materials, Adv. Phys. 63, 1 (2014)], the concept of bosonic Dirac materials has emerged. We consider a specific case of ferromagnets consisting of van der Waals-bonded stacks of honeycomb layers, e.g., chromium trihalides CrX3 (X=F, Cl, Br and I), that display two spin wave modes with energy dispersion similar to that for the electrons in graphene. At the single-particle level, these materials resemble their fermionic counterparts. However, how different particle statistics and interactions affect the stability of Dirac cones has yet to be determined. To address the role of interacting Dirac magnons, we expand the theory of ferromagnets beyond the standard Dyson theory [F. J. Dyson, General Theory of Spin-Wave Interactions, Phys. Rev. 102, 1217 (1956), F. J. Dyson, Thermodynamic Behavior of an Ideal Ferromagnet, Phys. Rev. 102, 1230 (1956)] to the case of non-Bravais honeycomb layers. We demonstrate that magnon-magnon interactions lead to a significant momentum-dependent renormalization of the bare band structure in addition to strongly momentum-dependent magnon lifetimes. We show that our theory qualitatively accounts for hitherto unexplained anomalies in nearly half-century-old magnetic neutron-scattering data for CrBr3 [W. B. Yelon and R. Silberglitt, Renormalization of Large-Wave-Vector Magnons in Ferromagnetic CrBr3 Studied by Inelastic Neutron Scattering: Spin-Wave Correlation Effects, Phys. Rev. B 4, 2280 (1971), E. J. Samuelsen, et al., Spin Waves in Ferromagnetic CrBr3 Studied by Inelastic Neutron Scattering, Phys. Rev. B 3, 157 (1971)]. We also show that honeycomb ferromagnets display dispersive surface and edge states, unlike their electronic analogs., Physical Review X, 8 (1), ISSN:2160-3308
- Published
- 2018
41. DFT simulation of the heteroannelated octatetraenes vibronic spectra with the Franck–Condon and Herzberg–Teller approaches including Duschinsky effect
- Author
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Boris F. Minaev, Nataliya N. Karaush, Hans Ågren, Rashid R. Valiev, and Gleb V. Baryshnikov
- Subjects
Герцберга-Теллера эффект ,Absorption spectroscopy ,Chemistry ,Circulene ,General Physics and Astronomy ,вибронные спектры ,Франка-Кондона принцип ,Molecular electronic transition ,Vibronic coupling ,Excited state ,Душинского эффект ,Vibronic spectroscopy ,Density functional theory ,Singlet state ,Physical and Theoretical Chemistry ,Atomic physics - Abstract
Calculations of vibronic structure in the electronic absorption spectra are carried out for the series of heteroannelated octatetraenes on the basis of density functional theory method. Both Franck-Condon and Herzberg-Teller approaches have been used for estimation of frequency and intensity of vibronic bands in the simulated absorption spectra with respect to the S-0 -> S-1 electronic transition. The key result discussed in this work is that the electronic transition into the first singlet excited states is vibronicallyactive in the absorption spectra for all studied circulenes in a good agreement with experimental observations. We have confirmed our previous assumption that the first (low-lying) weak absorption maximum in the spectra of tetra-tert-butyltetraoxa[8] circulene and dithieno[3,4-b: 3',4'-d]thiophene-annelated cyclooctatetraene can be assigned just for the S-0 -> S-1 transition which produce the next more intense vibronic satellite. In the case of aza[8] circulenes the S-0 -> S-1 transition is symmetry allowed and the corresponding vibronic bands are less intense relative to 0-0 band. (C) 2015 Elsevier B.V. All rights reserved.
- Published
- 2015
42. Metaphotonics: An emerging field with opportunities and challenges
- Author
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Marek Samoc, Alexander Baev, Martin Wegener, Paras N. Prasad, and Hans Ågren
- Subjects
Physics ,Field (physics) ,Scope (project management) ,Physics::Optics ,General Physics and Astronomy ,Metamaterial ,Cloaking ,Nanotechnology ,Nanoengineering ,Optical switch ,Realization (systems) ,Multiscale modeling - Abstract
Metaphotonics is an emerging multidisciplinary field that deals with manipulation of electro-magnetic fields in nanoengineered (meta)materials using both electric and magnetic interactions and their cross-coupling. It offers unprecedented control of both linear and nonlinear optical functions for applications ranging from optical switching, to negative- and near-zero refractive index metamaterials, to chiral bioimaging, to cloaking. However, realization of such applications requires physics-guided nanoengineering of appropriate artificial media with electro-magnetic properties at visible and infrared wavelengths that are tailored to surpass those of any naturally-occurring material. Here, we review metaphotonics with a broadened vision and scope, introduce potential applications, describe the role of theoretical physics through multiscale modeling, review the materials development and current status, and outline opportunities in this fertile emerging field.
- Published
- 2015
43. Origin of ion selectivity at the air/water interface
- Author
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Xin Li, Lu Sun, Hans Ågren, and Yaoquan Tu
- Subjects
chemistry.chemical_classification ,Hydrogen ,Inorganic chemistry ,General Physics and Astronomy ,Halide ,Ionic bonding ,chemistry.chemical_element ,Ion ,chemistry ,Chemical physics ,Molecule ,Physical and Theoretical Chemistry ,Counterion ,Polarization (electrochemistry) ,Surface water - Abstract
Among many characteristics of ions, their capability to accumulate at air/water interfaces is a particular issue that has been the subject of much research attention. For example, the accumulation of halide anions (Cl(-), Br(-), I(-)) at the water surface is of great importance to heterogeneous reactions that are of environmental concern. However, the actual mechanism that drives anions towards the air/water interface remains unclear. In this work, we have performed atomistic simulations using polarizable models to mimic ionic behavior under atmospheric conditions. We find that larger anions are abundant at the water surface and that the cations are pulled closer to the surface by the counterions. We propose that polarization effects stabilize the anions with large radii when approaching the surface. This energetically more favorable situation is caused by the fact that the more polarized anions at the surface attract water molecules more strongly. Of relevance is also the ordering of the surface water molecules with their hydrogen atoms pointing outwards which induce an external electronic field that leads to a different surface behavior of anions and cations. The water-water interaction is weakened by the distinct water-ion attraction, a point contradicting the proposition that F(-) is a kosmotrope. The simulation results thus allow us to obtain a more holistic understanding of the interfacial properties of ionic solutions and atmospheric aerosols.
- Published
- 2015
44. Frequency-dependent force fields for QMMM calculations
- Author
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Hans Ågren, Olav Vahtras, and Ignat Harczuk
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Physics ,Current (mathematics) ,Generalization ,Work (physics) ,Temperature ,Tryptophan ,Water ,General Physics and Astronomy ,Molecular Dynamics Simulation ,Test case ,Classical mechanics ,Polarizability ,Cluster (physics) ,Quantum Theory ,Physical and Theoretical Chemistry ,Focus (optics) ,Quantum - Abstract
We outline the construction of frequency-dependent polarizable force fields. The force fields are derived from analytic response theory for different frequencies using a generalization of the LoProp algorithm giving a decomposition of a molecular dynamical polarizability to localized atomic dynamical polarizabilities. These force fields can enter in a variety of applications - we focus on two such applications in this work: firstly, they can be incorporated in a physical, straightforward, way for current existing methods that use polarizable embeddings, and we can show, for the first time, the effect of the frequency dispersion within the classical environment of a quantum mechanics-molecular mechanics (QMMM) method. Our methodology is here evaluated for some test cases comprising water clusters and organic residues. Secondly, together with a modified Silberstein-Applequist procedure for interacting inducible point-dipoles, these frequency-dependent polarizable force fields can be used for a classical determination of frequency-dependent cluster polarizabilities. We evaluate this methodology by comparing with the corresponding results obtained from quantum mechanics or QMMM where the absolute mean [small alpha, Greek, macron] is determined with respect to the size of the QM and MM parts of the total system.
- Published
- 2015
45. A theoretical study on the molecular determinants of the affibody protein ZAβ3bound to an amyloid β peptide
- Author
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Xianqiang Sun, Guanglin Kuang, Yaoquan Tu, Hans Ågren, and Xu Wang
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Amyloid beta-Peptides ,biology ,Chemistry ,Amyloid beta ,Stereochemistry ,Recombinant Fusion Proteins ,P3 peptide ,General Physics and Astronomy ,Hydrogen Bonding ,Peptide binding ,Molecular Dynamics Simulation ,Alanine scanning ,Molecular mechanics ,Hydrophobic effect ,Molecular dynamics ,Amyloid precursor protein ,biology.protein ,Thermodynamics ,Physical and Theoretical Chemistry ,Protein Binding - Abstract
Amyloid beta (Aβ) peptides are small cleavage products of the amyloid precursor protein. Aggregates of Aβ peptides are thought to be linked with Alzheimer's and other neurodegenerative diseases. Strategies aimed at inhibiting amyloid formation and promoting Aβ clearance have been proposed and investigated in in vitro experiments and in vivo therapies. A recent study indicated that a novel affibody protein ZAβ3, which binds to an Aβ40 monomer with a binding affinity of 17 nM, is able to prevent the aggregation of Aβ40. However, little is known about the energetic contribution of each residue in ZAβ3 to the formation of the (ZAβ3)2:Aβ complex. To address this issue, we carried out unbiased molecular dynamics simulations and molecular mechanics Poisson-Boltzmann surface area calculations. Through the per-residue decomposition scheme, we identified that the van der Waals interactions between the hydrophobic residues of (ZAβ3)2 and those at the exterior and interior faces of Aβ are the main contributors to the binding of (ZAβ3)2 to Aβ. Computational alanine scanning identified 5 hot spots, all residing in the binding interface and contributing to the binding of (ZAβ3)2 to Aβ through the hydrophobic effect. In addition, the amide hydrogen bonds in the 4-strand β-sheet and the π-π stacking were also analyzed. Overall, our study provides a theoretical basis for future experimental improvement of the ZAβ3 peptide binding to Aβ.
- Published
- 2015
46. Selective gating to vibrational modes through resonant X ray scattering
- Author
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Freddy Fernandes Guimarães, Brian Kennedy, Annette Pietzsch, Rafael C. Couto, Faris Gel'mukhanov, Victor Kimberg, Emelie Ertan, Thorsten Schmitt, Mattis Fondell, Marcus Dantz, Sebastian Eckert, Hans Ågren, Michael Odelius, Alexander Föhlisch, and Vinícius Vaz da Cruz
- Subjects
Materials science ,Science ,General Physics and Astronomy ,02 engineering and technology ,Gating ,Molecular systems ,01 natural sciences ,Molecular physics ,Article ,General Biochemistry, Genetics and Molecular Biology ,500 Naturwissenschaften und Mathematik ,Fragmentation (mass spectrometry) ,0103 physical sciences ,Theoretical chemistry ,ddc:530 ,Physics::Chemical Physics ,010306 general physics ,Multidisciplinary ,Scattering ,X-ray ,Institut für Physik und Astronomie ,General Chemistry ,021001 nanoscience & nanotechnology ,Vibration ,Molecular vibration ,Inhouse research on structure dynamics and function of matter ,ddc:500 ,Mathematisch-Naturwissenschaftliche Fakultät ,0210 nano-technology - Abstract
The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations., Investigating dynamics of polyatomic molecules is difficult as their potential energy surfaces are multidimensional due to coupled degrees of freedom. Here the authors demonstrate a spatial selective gating technique to probe the different vibrational modes of water upon core-level excitation with X-rays.
- Published
- 2017
47. A study of the water molecule using frequency control over nuclear dynamics in resonant X-ray scattering
- Author
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Annette Pietzsch, Michael Odelius, Thorsten Schmitt, Faris Gel'mukhanov, Emelie Ertan, Marcus Dantz, Brian Kennedy, Hans Ågren, Alexander Föhlisch, Freddy Fernandes Guimarães, Victor Kimberg, Sebastian Eckert, Mattis Fondell, Rafael C. Couto, and Vinícius Vaz da Cruz
- Subjects
Scattering ,Chemistry ,Wave packet ,Anharmonicity ,Ab initio ,General Physics and Astronomy ,Institut für Physik und Astronomie ,02 engineering and technology ,Electronic structure ,021001 nanoscience & nanotechnology ,01 natural sciences ,0103 physical sciences ,Potential energy surface ,ddc:540 ,Inhouse research on structure dynamics and function of matter ,Physical and Theoretical Chemistry ,Atomic physics ,Mathematisch-Naturwissenschaftliche Fakultät ,010306 general physics ,0210 nano-technology ,Ground state ,Excitation - Abstract
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., Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe, 781
- Published
- 2017
- Full Text
- View/download PDF
48. Local decomposition of imaginary polarizabilities and dispersion coefficients
- Author
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Olav Vahtras, Hans Ågren, Frank Jensen, Ignat Harczuk, and Balázs Nagy
- Subjects
010304 chemical physics ,Chemistry ,Isotropy ,Stacking ,General Physics and Astronomy ,Propagator ,010402 general chemistry ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Molecular dynamics ,Polarizability ,Quantum mechanics ,0103 physical sciences ,Dispersion (optics) ,Physics::Atomic and Molecular Clusters ,Physical and Theoretical Chemistry ,Anisotropy ,Multipole expansion - Abstract
We present a new way to compute the two-body contribution to the dispersion energy using ab initio theory. By combining the complex polarization propagator method and the LoProp transformation, local contributions to the Casimir-Polder interaction is obtained. The full dispersion energy in dimer systems consisting of pairs of molecules including H2, N2, CO, CH4, pyridine, and benzene is investigated, where anisotropic as well as isotropic models of dispersion are obtained using a decomposition scheme for the dipole-dipole polarizability. It is found that the local minima structure of the π-cloud stacking of the benzene dimer is underestimated by the total molecular dispersion, but is alleviated by the inclusion of atomic interactions via the decomposition scheme. The dispersion energy in the T-shaped benzene dimer system is greatly underestimated by all dispersion models, as compared to high-level quantum calculations. The generalization of the decomposition scheme to higher order multipole polarizability interactions, representing higher order dispersion coefficients, is briefly discussed. It is argued that the incorporation of atomic C6 coefficients in new atomic force fields may have important ramifications in molecular dynamics studies of biomolecular systems.
- Published
- 2017
49. Quantum-classical calculations of X-ray photoelectron spectra of polymers:polymethyl methacrylate revisited
- Author
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Kari Jänkälä, Ignat Harczuk, Olav Vahtras, Tuomas Löytynoja, and Hans Ågren
- Subjects
chemistry.chemical_classification ,X-ray photoelectron spectroscopy ,010304 chemical physics ,Polymers ,Chemical shift ,Relaxation (NMR) ,Binding energy ,General Physics and Astronomy ,02 engineering and technology ,Polymer ,021001 nanoscience & nanotechnology ,01 natural sciences ,Spectral line ,Carbon ,chemistry.chemical_compound ,Monomer ,chemistry ,Ionization ,Polarizability ,0103 physical sciences ,Density functional theory ,Physical and Theoretical Chemistry ,Atomic physics ,0210 nano-technology - Abstract
In this work, we apply quantum mechanics/molecular mechanics (QM/MM) approach to predict core-electron binding energies and chemical shifts of polymers, obtainable via X-ray photoelectron spectroscopy (XPS), using polymethyl methacrylate as a demonstration example. The results indicate that standard parametrizations of the quantum part (basis sets, level of correlation) and the molecular mechanics parts (decomposed charges, polarizabilities, and capping technique) are sufficient for the QM/MM model to be predictive for XPS of polymers. It is found that the polymer environment produces contributions to the XPS binding energies that are close to monotonous with the number of monomer units, totally amounting to approximately an eV decrease in binding energies. In most of the cases, the order of the shifts is maintained, and even the relative size of the differential shifts is largely preserved. The coupling of the internal core-hole relaxation to the polymer environment is found to be weak in each case, amounting only to one or two tenths of an eV. The main polymeric effect is actually well estimated already at the frozen orbital level of theory, which in turn implies a substantial computational simplification. These conclusions are best represented by the cases where the ionized monomer and its immediate surrounding are treated quantum mechanically. If the QM region includes only a single monomer, a couple of anomalies are spotted, which are referred to the QM/MM interface itself and to the neglect of a possible charge transfer.
- Published
- 2017
50. Principles of phosphorescent organic light emitting devices
- Author
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Gleb V. Baryshnikov, Hans Ågren, and Boris F. Minaev
- Subjects
Luminescent Agents ,Materials science ,Light ,Phosphorescent oleds ,business.industry ,Electrical Equipment and Supplies ,General Physics and Astronomy ,Nanotechnology ,Flat panel ,law.invention ,Solid-state lighting ,law ,OLED ,Optoelectronics ,Light emission ,Organic Chemicals ,Physical and Theoretical Chemistry ,business ,Phosphorescence ,Visible spectrum - Abstract
Organic light-emitting device (OLED) technology has found numerous applications in the development of solid state lighting, flat panel displays and flexible screens. These applications are already commercialized in mobile phones and TV sets. White OLEDs are of especial importance for lighting; they now use multilayer combinations of organic and elementoorganic dyes which emit various colors in the red, green and blue parts of the visible spectrum. At the same time the stability of phosphorescent blue emitters is still a major challenge for OLED applications. In this review we highlight the basic principles and the main mechanisms behind phosphorescent light emission of various classes of photofunctional OLED materials, like organic polymers and oligomers, electron and hole transport molecules, elementoorganic complexes with heavy metal central ions, and clarify connections between the main features of electronic structure and the photo-physical properties of the phosphorescent OLED materials.
- Published
- 2014
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