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- Fedorov, Aleksandr S., et al.
(författare)
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Charge-transfer plasmons of complex nanoparticle arrays connected by conductive molecular bridges
- 2022
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:32, s. 19531-19540
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Tidskriftsartikel (refereegranskat)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.
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| 2. |
- Ottosson, Niklas, et al.
(författare)
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Molecular Sinkers : X-ray Photoemission and Atomistic Simulations of Benzoic Acid and Benzoate at the Aqueous Solution/Vapor Interface
- 2012
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 116:43, s. 13017-13023
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Tidskriftsartikel (refereegranskat)abstract
- In this work we, for the first time, provide a detailed microscopic picture of the behavior of benzoic acid at the aqueous solution/vapor interface in its neutral as well as in its dissociated form (benzoate). This is achieved through a combination of highly surface-sensitive X-ray photoelectron spectroscopy experiments and fully atomistic molecular simulations. We show that drastic changes occur in the interface behavior of the neutral acid upon release of the proton. The benzoic acid molecules are found to be strongly adsorbed in the interface layer with the planes of the aromatic rings oriented almost parallel to the water surface. In contrast, in the benzoate form the carboxylate group shows a sinker-like behavior while the aromatic ring acts as a buoy, oriented nearly perpendicular to the surface. Furthermore, a significant fraction of the molecular ions move from the interface layer into the bulk of the solution. We rationalize these findings in terms of the very different hydration properties of benzoic acid's carboxylic group in the two charge states. The molecule has an amphiphilic nature and the deprotonation thus changes the hydrophobic/hydrophilic balance between the nonpolar aromatic and the polar carboxylic parts of the molecule. That, consequently, leads to a pronounced reorientation of the molecule at the interface.
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