Search results for "pintailmiöt"
showing 10 items of 12 documents
Theory for the stationary polariton response in the presence of vibrations
2019
We construct a model describing the response of a hybrid system where the electromagnetic field - in particular, surface plasmon polaritons - couples strongly with electronic excitations of atoms or molecules. Our approach is based on the input-output theory of quantum optics, and in particular it takes into account the thermal and quantum vibrations of the molecules. The latter is described within the $P(E)$ theory analogous to that used in the theory of dynamical Coulomb blockade. As a result, we are able to include the effect of the molecular Stokes shift on the strongly coupled response of the system. Our model then accounts for the asymmetric emission from upper and lower polariton mod…
Novel Methodologies to Model Charge Transport in Metal-Air Batteries
2018
Experimental evidence on photo-assisted O$^-$ ion production from Al$_2$O$_3$ cathode in cesium sputter negative ion source
2020
The production of negative ions in cesium sputter ion sources is generally considered to be a pure surface process. It has been recently proposed that ion pair production could explain the higher-than-expected beam currents extracted from these ion sources, therefore opening the door for laser-assisted enhancement of the negative ion yield. We have tested this hypothesis by measuring the effect of various pulsed diode lasers on the O$^-$ beam current produced from Al$_2$O$_3$ cathode of a cesium sputter ion source. It is expected that the ion pair production of O$^-$ requires populating the 5d electronic states of neutral cesium, thus implying that the process should be provoked only with s…
Unraveling the Role of the Rh–ZrO2 Interface in the Water–Gas-Shift Reaction via a First-Principles Microkinetic Study
2018
The industrially important water–gas-shift (WGS) reaction is a complex network of competing elementary reactions in which the catalyst is a multicomponent system consisting of distinct domains. Herein, we have combined density functional theory calculations with microkinetic modeling to explore the active phase, kinetics, and reaction mechanism of the WGS over the Rh–ZrO2 interface. We have explicitly considered the support and metal and their interface and find that the Rh–ZrO2 interface is far more active toward WGS than Rh(111) facets, which are susceptible to CO poisoning. CO2 forming on the zirconia support rapidly transforms into formate. These findings demonstrate the central role of…
Electric-field-controlled reversible order-disorder switching of a metal tip surface
2018
While it is well established that elevated temperatures can induce surface roughening of metal surfaces, the effect of a high electric field on the atomic structure at ambient temperature has not been investigated in detail. Here we show with atomic resolution using in situ transmission electron microscopy how intense electric fields induce reversible switching between perfect crystalline and disordered phases of gold surfaces at room temperature. Ab initio molecular dynamics simulations reveal that the mechanism behind the structural change can be attributed to a vanishing energy cost in forming surface defects in high electric fields. Our results demonstrate how surface processes can be d…
Grand-canonical approach to density functional theory of electrocatalytic systems: Thermodynamics of solid-liquid interfaces at constant ion and elec…
2018
Properties of solid-liquid interfaces are of immense importance for electrocatalytic and electrochemical systems, but modeling such interfaces at the atomic level presents a serious challenge and approaches beyond standard methodologies are needed. An atomistic computational scheme needs to treat at least part of the system quantum mechanically to describe adsorption and reactions, while the entire system is in thermal equilibrium. The experimentally relevant macroscopic control variables are temperature, electrode potential, and the choice of the solvent and ions, and these need to be explicitly included in the computational model as well; this calls for a thermodynamic ensemble with fixed…
Diversity at the nanoscale : laser-oxidation of single-layer graphene affects Fmoc-phenylalanine surface-mediated self-assembly
2023
We report the effects of a laser-oxidized single layer graphene (SLG) surface on the self-assembly of amphiphilic gelator N-fluorenylmethoxycarbonyl-L-phenylalanine (Fmoc-Phe) towards an gel–SLG interface. Laser oxidation modulates the levels of hydrophobicity/hydrophilicity on the SLG surface. Atomic force, scanning electron, helium ion and scattering scanning nearfield optical microscopies (AFM, SEM, HIM, s-SNOM) were employed to assess the effects of surface properties on the secondary and tertiary organization of the formed Fmoc-Phe fibres at the SLG–gel interface. S-SNOM shows sheet-like secondary structures on both hydrophobic/hydrophilic areas of SLG and helical or disordered structu…
Experimental studies on carbon nanotubes and graphene functionalized via physical adsorption with cellulose and avidin
2018
In this Thesis I have experimentally studied structural, electronic, and optical properties of hybrids of nanocarbon materials, carbon nanotubes (CNT) and graphene, and certain biomacromolecules. The latter are especially xylan, a type of hemicellulose, and avidin, an important protein. Complexes of CNT with hemicellulose are attractive because the hybrid material is soluble in water. The conductive transport properties of thin films of CNT /hemicellulose have been systematically studied with different experimental tools. These are low temperature DC conduction measurements, Kelvin probe microscopy, and optical conductivity measurements at terahertz frequencies. The results clearly indicate …
Unraveling the prominent role of the Rh/ZrO2-interface in the water-gas shift reaction via a first principles microkinetic study
2018
The industrially important water–gas-shift (WGS) reaction is a complex network of competing elementary reactions in which the catalyst is a multicomponent system consisting of distinct domains. Herein, we have combined density functional theory calculations with microkinetic modeling to explore the active phase, kinetics, and reaction mechanism of the WGS over the Rh–ZrO2 interface. We have explicitly considered the support and metal and their interface and find that the Rh–ZrO2 interface is far more active toward WGS than Rh(111) facets, which are susceptible to CO poisoning. CO2 forming on the zirconia support rapidly transforms into formate. These findings demonstrate the central role of…
Spatial localization of hotspots in Fano-resonant plasmonic oligomers for surface-enhanced coherent anti-Stokes Raman scattering
2020
AbstractRealization of Fano resonance in plasmonic oligomers is often exploited to design efficient plasmonic substrates for surface-enhanced coherent anti-Stokes Raman scattering. Disk-type Fano-resonant plasmonic oligomers are widely used to enhance the Raman signal of the probe material. Generally, hot spots are generated in those oligomers at different spatial locations at different wavelengths and only a few spatially overlapping hot spots at multiple wavelengths can be achieved with oblique incidence of excitation light. In this work, we proposed hexagonal gold nanoparticle based Fano-resonant plasmonic oligomers that can yield higher number of spatially overlapped hot spots compared …