@article{FischerAndersSaalfrank2022,
  author    = {Fischer, Eric Wolfgang and Anders, Janet and Saalfrank, Peter},
  title     = {Cavity-altered thermal isomerization rates and dynamical resonant localization in vibro-polaritonic chemistry},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {156},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {15},
  publisher = {American Institute of Physics},
  address   = {Melville, NY},
  issn      = {0021-9606},
  doi       = {10.1063/5.0076434},
  pages     = {16},
  year      = {2022},
  abstract  = {It has been experimentally demonstrated that reaction rates for molecules embedded in microfluidic optical cavities are altered when compared to rates observed under "ordinary" reaction conditions. However, precise mechanisms of how strong coupling of an optical cavity mode to molecular vibrations affects the reactivity and how resonance behavior emerges are still under dispute. In the present work, we approach these mechanistic issues from the perspective of a thermal model reaction, the inversion of ammonia along the umbrella mode, in the presence of a single-cavity mode of varying frequency and coupling strength. A topological analysis of the related cavity Born-Oppenheimer potential energy surface in combination with quantum mechanical and transition state theory rate calculations reveals two quantum effects, leading to decelerated reaction rates in qualitative agreement with experiments: the stiffening of quantized modes perpendicular to the reaction path at the transition state, which reduces the number of thermally accessible reaction channels, and the broadening of the barrier region, which attenuates tunneling. We find these two effects to be very robust in a fluctuating environment, causing statistical variations of potential parameters, such as the barrier height. Furthermore, by solving the time-dependent Schrodinger equation in the vibrational strong coupling regime, we identify a resonance behavior, in qualitative agreement with experimental and earlier theoretical work. The latter manifests as reduced reaction probability when the cavity frequency omega(c) is tuned resonant to a molecular reactant frequency. We find this effect to be based on the dynamical localization of the vibro-polaritonic wavepacket in the reactant well.},
  language  = {en}
}
@article{SchuermannNagelJuergensenetal.2022,
  author    = {Sch{\"u}rmann, Robin and Nagel, Alessandro and Juergensen, Sabrina and Pathak, Anisha and Reich, Stephanie and Pacholski, Claudia and Bald, Ilko},
  title     = {Microscopic understanding of reaction rates observed in plasmon chemistry of nanoparticle-ligand systems},
  series = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  volume    = {126},
  journal   = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  number    = {11},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1932-7447},
  doi       = {10.1021/acs.jpcc.2c00278},
  pages     = {5333 -- 5342},
  year      = {2022},
  abstract  = {Surface-enhanced Raman scattering (SERS) is an effective and widely used technique to study chemical reactions induced or catalyzed by plasmonic substrates, since the experimental setup allows us to trigger and track the reaction simultaneously and identify the products. However, on substrates with plasmonic hotspots, the total signal mainly originates from these nanoscopic volumes with high reactivity and the information about the overall consumption remains obscure in SERS measurements. This has important implications; for example, the apparent reaction order in SERS measurements does not correlate with the real reaction order, whereas the apparent reaction rates are proportional to the real reaction rates as demonstrated by finite-difference time-domain (FDTD) simulations. We determined the electric field enhancement distribution of a gold nanoparticle (AuNP) monolayer and calculated the SERS intensities in light-driven reactions in an adsorbed self-assembled molecular monolayer on the AuNP surface. Accordingly, even if a high conversion is observed in SERS due to the high reactivity in the hotspots, most of the adsorbed molecules on the AuNP surface remain unreacted. The theoretical findings are compared with the hot-electron-induced dehalogenation of 4-bromothiophenol, indicating a time dependency of the hot-carrier concentration in plasmon-mediated reactions. To fit the kinetics of plasmon-mediated reactions in plasmonic hotspots, fractal-like kinetics are well suited to account for the inhomogeneity of reactive sites on the substrates, whereas also modified standard kinetics model allows equally well fits. The outcomes of this study are on the one hand essential to derive a mechanistic understanding of reactions on plasmonic substrates by SERS measurements and on the other hand to drive plasmonic reactions with high local precision and facilitate the engineering of chemistry on a nanoscale.},
  language  = {en}
}
@article{DoeringGrigorievTapioetal.2022,
  author    = {Doering, Ulrike and Grigoriev, Dmitry and Tapio, Kosti and Bald, Ilko and B{\"o}ker, Alexander},
  title     = {Synthesis of nanostructured protein-mineral-microcapsules by sonication},
  series = {Soft matter},
  volume    = {18},
  journal   = {Soft matter},
  number    = {13},
  publisher = {Royal Society of Chemistry},
  address   = {London},
  issn      = {1744-6848},
  doi       = {10.1039/d1sm01638e},
  pages     = {2558 -- 2568},
  year      = {2022},
  abstract  = {We propose a simple and eco-friendly method for the formation of composite protein-mineral-microcapsules induced by ultrasound treatment. Protein- and nanoparticle-stabilized oil-in-water (O/W) emulsions loaded with different oils are prepared using high-intensity ultrasound. The formation of thin composite mineral proteinaceous shells is realized with various types of nanoparticles, which are pre-modified with Bovine Serum Albumin (BSA) and subsequently characterized by EDX, TGA, zeta potential measurements and Raman spectroscopy. Cryo-SEM and EDX mapping visualizations show the homogeneous distribution of the densely packed nanoparticles in the capsule shell. In contrast to the results reported in our previous paper,(1) the shell of those nanostructured composite microcapsules is not cross-linked by the intermolecular disulfide bonds between BSA molecules. Instead, a Pickering-Emulsion formation takes place because of the amphiphilicity-driven spontaneous attachment of the BSA-modified nanoparticles at the oil/water interface. Using colloidal particles for the formation of the shell of the microcapsules, in our case silica, hydroxyapatite and calcium carbonate nanoparticles, is promising for the creation of new functional materials. The nanoparticulate building blocks of the composite shell with different chemical, physical or morphological properties can contribute to additional, sometimes even multiple, features of the resulting capsules. Microcapsules with shells of densely packed nanoparticles could find interesting applications in pharmaceutical science, cosmetics or in food technology.},
  language  = {en}
}
@article{MayerPicconiRobinsonetal.2022,
  author    = {Mayer, Dennis and Picconi, David and Robinson, Matthew S. and G{\"u}hr, Markus},
  title     = {Experimental and theoretical gas-phase absorption spectra of thionated uracils},
  series = {Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature},
  volume    = {558},
  journal   = {Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0301-0104},
  doi       = {10.1016/j.chemphys.2022.111500},
  pages     = {9},
  year      = {2022},
  abstract  = {We present a comparative study of the gas-phase UV spectra of uracil and its thionated counterparts (2-thiouracil, 4-thiouracil and 2,4-dithiouracil), closely supported by time-dependent density functional theory calculations to assign the transitions observed. We systematically discuss pure gas-phase spectra for the (thio)uracils in the range of 200-400 nm (similar to 3.2-6.4 eV), and examine the spectra of all four species with a single theoretical approach. We note that specific vibrational modelling is needed to accurately determine the spectra across the examined wavelength range, and systematically model the transitions that appear at wavelengths shorter than 250 nm. Additionally, we find in the cases of 2-thiouracil and 2,4-dithiouracil, that the gas-phase spectra deviate significantly from some previously published solution-phase spectra, especially those collected in basic environments.},
  language  = {en}
}
@article{StefancuNanZhuetal.2022,
  author    = {Stefancu, Andrei and Nan, Lin and Zhu, Li and Chis, Vasile and Bald, Ilko and Liu, Min and Leopold, Nicolae and Maier, Stefan A. and Cortes, Emiliano},
  title     = {Controlling plasmonic chemistry pathways through specific ion effects},
  series = {Advanced optical materials},
  volume    = {10},
  journal   = {Advanced optical materials},
  number    = {14},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {2195-1071},
  doi       = {10.1002/adom.202200397},
  pages     = {10},
  year      = {2022},
  abstract  = {Plasmon-driven dehalogenation of brominated purines has been recently explored as a model system to understand fundamental aspects of plasmon-assisted chemical reactions. Here, it is shown that divalent Ca2+ ions strongly bridge the adsorption of bromoadenine (Br-Ade) to Ag surfaces. Such ion-mediated binding increases the molecule's adsorption energy leading to an overlap of the metal energy states and the molecular states, enabling the chemical interface damping (CID) of the plasmon modes of the Ag nanostructures (i.e., direct electron transfer from the metal to Br-Ade). Consequently, the conversion of Br-Ade to adenine almost doubles following the addition of Ca2+. These experimental results, supported by theoretical calculations of the local density of states of the Ag/Br-Ade complex, indicate a change of the charge transfer pathway driving the dehalogenation reaction, from Landau damping (in the lack of Ca2+ ions) to CID (after the addition of Ca2+). The results show that the surface dynamics of chemical species (including water molecules) play an essential role in charge transfer at plasmonic interfaces and cannot be ignored. It is envisioned that these results will help in designing more efficient nanoreactors, harnessing the full potential of plasmon-assisted chemistry.},
  language  = {en}
}
@article{MayerLeverPicconietal.2022,
  author    = {Mayer, Dennis and Lever, Fabiano and Picconi, David and Metje, Jan and Ališauskas, Skirmantas and Calegari, Francesca and D{\"u}sterer, Stefan and Ehlert, Christopher and Feifel, Raimund and Niebuhr, Mario and Manschwetus, Bastian and Kuhlmann, Marion and Mazza, Tommaso and Robinson, Matthew Scott and Squibb, Richard James and Trabattoni, Andrea and Wallner, M{\aa}ns and Saalfrank, Peter and Wolf, Thomas J. A. and G{\"u}hr, Markus},
  title     = {Following excited-state chemical shifts in molecular ultrafast x-ray photoelectron spectroscopy},
  series = {Nature Communications},
  volume    = {13},
  journal   = {Nature Communications},
  publisher = {Springer Nature},
  address   = {Berlin},
  issn      = {2041-1723},
  doi       = {10.1038/s41467-021-27908-y},
  pages     = {9},
  year      = {2022},
  abstract  = {The conversion of photon energy into other energetic forms in molecules is accompanied by charge moving on ultrafast timescales. We directly observe the charge motion at a specific site in an electronically excited molecule using time-resolved x-ray photoelectron spectroscopy (TR-XPS). We extend the concept of static chemical shift from conventional XPS by the excited-state chemical shift (ESCS), which is connected to the charge in the framework of a potential model. This allows us to invert TR-XPS spectra to the dynamic charge at a specific atom. We demonstrate the power of TR-XPS by using sulphur 2p-core-electron-emission probing to study the UV-excited dynamics of 2-thiouracil. The method allows us to discover that a major part of the population relaxes to the molecular ground state within 220-250 fs. In addition, a 250-fs oscillation, visible in the kinetic energy of the TR-XPS, reveals a coherent exchange of population among electronic states.},
  language  = {en}
}
@article{PruefertBeitzReichetal.2022,
  author    = {Pr{\"u}fert, Christian and Beitz, Toralf and Reich, Olaf and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {Inline process analysis of copper-bearing aerosols using laser-induced breakdown spectroscopy, laser-induced incandescence and optical imaging},
  series = {Spectrochimica acta, Part B, Atomic spectroscopy},
  volume    = {197},
  journal   = {Spectrochimica acta, Part B, Atomic spectroscopy},
  publisher = {Elsevier},
  address   = {Amsterdam [u.a.]},
  issn      = {0584-8547},
  doi       = {10.1016/j.sab.2022.106527},
  pages     = {11},
  year      = {2022},
  abstract  = {The quantification and identification of aerosols in industry plays a key role in process monitoring and control and lays the foundation for process automation aspired by the industry 4.0 initiative. However, measuring particulate matter's mass and number concentrations in harsh environments poses great analytical constraints. The presented approach comprises a comprehensive set of light-and imaging-based techniques, all contactless, in-line, and real-time. It includes, but is not limited to, stroboscopic imaging, laser-induced breakdown spectroscopy (LIBS) and laser-induced incandescence (LII). Stroboscopic imaging confirmed the particles sphericity and was used to measure the particle number density. A phase-selective LIBS setup with low fluence and 500 Hz repetition rate was used to classify each particle with a single-pulse and in real time. Simultaneously, the created plasma was captured by CCD imaging to determine the detection volume and hit rate of the LIBS setup. Both data sets combined were converted to a particle number density, which was consistent with the particle number density of the stroboscopic measurements. Furthermore, using a photodiode and microphone in parallel to the LIBS setup allowed for the photoacoustic normalization of the spectral line intensity at the laser repetition rate of 500 Hz. This was done as a partial photoacoustic normalization method with the cut-off based on the coefficient of variation (CV), reducing it by 25\%. Aside from that photodiode and microphone were proven to be valuable event counting with the advantage of the less spatially constricted. A second laser setup was used for laser -induced incandescence (LII) making it possible to classify the particles based on their incandescence tendency. Given its larger probing volume, LII could be employed at very low particle number densities. With respect to the current literature, this is the first approach of using LII as an in-line, real-time analytical technique for the compositional classification of metal-bearing aerosols.},
  language  = {en}
}
@article{RotheZhaoHalimetal.2022,
  author    = {Rothe, Martin and Zhao, Yuhang and Halim, Henry and Lu, Yan and Benson, Oliver},
  title     = {Spatial mapping of bleaching in a metal-organic plasmon converter},
  series = {Optics continuum},
  volume    = {1},
  journal   = {Optics continuum},
  number    = {8},
  publisher = {Optica Publishing Group},
  address   = {Washington},
  issn      = {2770-0208},
  doi       = {10.1364/OPTCON.454911},
  pages     = {1730 -- 1740},
  year      = {2022},
  abstract  = {Hybrid nanophotonic elements, fabricated by organic and inorganic materials, are going to be key components of modern devices. Coupled systems of photoemitters with a plasmonic waveguide serve the demand for nanoscopic frequency converters. However, processes like the degradation of the photoemitters via photobleaching occur and need to be monitored and controlled, to realize future successful devices. We introduce a hybrid perylene-diimide / silver nanowire as plasmon frequency converter. A versatile method is presented to monitor and analyze the bleaching process. It is based on a time series of photoluminescence images, during the operation of a single converter. An analytical model is applied on the data and unveils that the photobleaching rate is constant and independent of the operation of the plasmon converter.},
  language  = {en}
}