| 1. |
- Crispin, Xavier, et al.
(författare)
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Semiconducting Polymers : Probing the solid-liquid interface
- 2017
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Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 16:7, s. 704-705
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Exploring the minute mechanical deformations induced by electrical bias at the interface with electrolytes allows the identification of local crystallinity and distinguishing adsorption and intercalation of ions in electroactive polymers.
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| 2. |
- French, Roger H., et al.
(författare)
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Long range interactions in nanoscale science
- 2010
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Ingår i: Reviews of Modern Physics. - 0034-6861. ; 82:2, s. 1887-1944
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Forskningsöversikt (refereegranskat)abstract
- Our understanding of the “long range” electrodynamic, electrostatic, and polar interactions that dominate the organization of small objects at separations beyond an interatomic bond length is reviewed. From this basic-forces perspective, a large number of systems are described from which one can learn about these organizing forces and how to modulate them. The many practical systems that harness these nanoscale forces are then surveyed. The survey reveals not only the promise of new devices and materials, but also the possibility of designing them more effectively.
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| 3. |
- Isaksson, Mikael, et al.
(författare)
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An environmental-sensitive BODIPY®-derivative with bioapplication : spectral and photophysical properties
- 2003
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Ingår i: Journal of Fluorescence. - 1053-0509 .- 1573-4994. ; 13:5, s. 379-84
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Tidskriftsartikel (refereegranskat)abstract
- A previously synthesised derivative of BODIPY aimed for sulfhydryl specific labelling of cysteine residues in proteins was studied. The spectral and photophysical properties of this derivative, N-(4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene-2-yl) iodoacetamide (NBDY) were characterised, and found to be considerably different from those of commonly used derivatives of BODIPY, e.g. N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-yl)methyl iodoacetamide. The absorption and fluorescence spectra, as well as fluorescence lifetimes and quantum yields of NBDY are quite sensitive to solvent properties. The fluorescence is effectively quenched by I– when NBDY is free in water or attached to Cys in different mutants of plasminogen activator inhibitor type 2 (PAI-2). A ground-state dimer forms when two NBDY groups are closely spaced in plasminogen activator inhibitor type 1 (PAI-1).
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| 4. |
- Isaksson, Mikael, et al.
(författare)
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Partial donor-donor energy migration (PDDEM) : a novel fluorescence method for internal protein distance measurements
- 2004
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 6:11, s. 3001-3008
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Tidskriftsartikel (refereegranskat)abstract
- We show that the photophysics of chemically identical but photophysically non-identical fluorescent pairs can be used for measuring distances within proteins. For this purpose, the theory of partial donor-donor energy migration (PDDEM, S. Kalinin, J. G. Molotkovsky and L. B.-Angstrom. Johansson, Spectrochim. Acta, Part A, 2002, 58, 1057-1097) was applied for distance measurements between BODIPY groups covalently linked to cystein residues in plasminogen activator inhibitor of type 2 (PAI-2). Two sulfhydryl specific derivatives of BODIPY were used namely: N-(4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene-2-yl) iodoacetamide and N-(4.4-difluoro-5.7-ditriethyl-4-bona-3a,4a-diaza-s-indacene-3-yl) methyl iodoacetamide. To determine distances, the time-resolved fluorescence relaxation for two singly labelled forms of PAI-2, as well as the corresponding doubly labelled protein were combined and analysed in a global manner. Fluorescence depolarisation experiments on the labelled mutants were also analysed. The distances determined by PDDEM were in good agreement to those obtained from donor-donor energy migration (DDEM) experiments and structural data on PAI-2. The PDDEM approach allows for the use of very different fluorescent probes, which enables wide range of distances to be measured. The PDDEM model also provides a rational explanation to why previous observations of polyfluorophore-labelled proteins exhibit a shorter average fluorescence lifetime compared to the arithmetic average of lifetimes obtained for the corresponding single labelled proteins.
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| 5. |
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| 6. |
- Lindgren, Gustav, et al.
(författare)
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Polarization-dependent local conductivity and activation energy in KTiOPO4
- 2019
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 114:19
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Tidskriftsartikel (refereegranskat)abstract
- We study the local conductivity properties of KTiOPO4 using conductive atomic force microscopy in ultrahigh vacuum (UHV). We show that domains with opposite orientations have different conductivity values. We investigate the temperature dependence of the local conductivity and report a difference in the activation energy of 25% between different domains. Furthermore, we show that the local conductivity increases with the number of biased-scans. Finally, it is found that the domain wall conductivity previously observed at ambient conditions vanishes in UHV. Our results are discussed in terms of the screening effects and surface conditions.
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| 7. |
- Neumayer, Sabine M., et al.
(författare)
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Surface Chemistry Controls Anomalous Ferroelectric Behavior in Lithium Niobate
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:34, s. 29153-29160
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Tidskriftsartikel (refereegranskat)abstract
- Polarization switching in ferroelectric materials underpins a multitude of applications ranging from nonvolatile memories to data storage to ferroelectric lithography. While traditionally considered to be a functionality of the material only, basic theoretical considerations suggest that switching is expected to be intrinsically linked to changes in the electrochemical state of the surface. Hence, the properties and dynamics of the screening charges can affect or control the switching dynamics. Despite being recognized for over 50 years, analysis of these phenomena remained largely speculative. Here, we explore polarization switching on the prototypical LiNbO3 surface using the combination of contact mode Kelvin probe force microscopy and chemical imaging by time-of-flight mass-spectrometry and demonstrate pronounced chemical differences between the domains. These studies provide a consistent explanation to the anomalous polarization and surface charge behavior observed in LiNbO3 and point to new opportunities in chemical control of polarization dynamics in thin films and crystals via control of surface chemistry, complementing traditional routes via bulk doping, and substrate-induced strain and tilt systems.
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| 8. |
- Neumayer, Sabine M., et al.
(författare)
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Thickness, humidity, and polarization dependent ferroelectric switching and conductivity in Mg doped lithium niobate
- 2015
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 118:24
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Tidskriftsartikel (refereegranskat)abstract
- Mg doped lithium niobate (Mg:LN) exhibits several advantages over undoped LN such as resistance to photorefraction, lower coercive fields, and p-type conductivity that is particularly pronounced at domain walls and opens up a range of applications, e.g., in domain wall electronics. Engineering of precise domain patterns necessitates well founded knowledge of switching kinetics, which can differ significantly from that of undoped LN. In this work, the role of humidity and sample composition in polarization reversal has been investigated under application of the same voltage waveform. Control over domain sizes has been achieved by varying the sample thickness and initial polarization as well as atmospheric conditions. In addition, local introduction of proton exchanged phases allows for inhibition of domain nucleation or destabilization, which can be utilized to modify domain patterns. Polarization dependent current flow, attributed to charged domain walls and band bending, demonstrates the rectifying ability of Mg: LN in combination with suitable metal electrodes that allow for further tailoring of conductivity.
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| 9. |
- Shin, Junsoo, et al.
(författare)
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Atomistic Screening Mechanism of Ferroelectric Surfaces : An In Situ Study of the Polar Phase in Ultrathin BaTiO3 Films Exposed to H2O
- 2009
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 9:11, s. 3720-3725
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Tidskriftsartikel (refereegranskat)abstract
- The polarization screening mechanism and ferroelectric phase stability of ultrathin BaTiO3 films exposed to water molecules is determined by first principles theory and in situ experiment. Surface crystallography data from electron diffraction combined with density functional theory calculations demonstrate that small water vapor exposures do not affect surface structure or polarization. Large exposures result in surface hydroxylation and rippling, formation of surface oxygen vacancies, and reversal of the polarization direction. Understanding interplay between ferroelectric phase stability, screening, and atomistic processes at surfaces is a key to control low-dimensional ferroelectricity.
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