TY - JOUR A1 - Fischer, Eric W. A1 - Werther, Michael A1 - Bouakline, Foudhil A1 - Saalfrank, Peter T1 - A hierarchical effective mode approach to phonon-driven multilevel vibrational relaxation dynamics at surfaces JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry N2 - We discuss an efficient Hierarchical Effective Mode (HEM) representation of a high-dimensional harmonic oscillator bath, which describes phonon-driven vibrational relaxation of an adsorbate-surface system, namely, deuterium adsorbed on Si(100). Starting from the original Hamiltonian of the adsorbate-surface system, the HEM representation is constructed via iterative orthogonal transformations, which are efficiently implemented with Householder matrices. The detailed description of the HEM representation and its construction are given in the second quantization representation. The hierarchical nature of this representation allows access to the exact quantum dynamics of the adsorbate-surface system over finite time intervals, controllable via the truncation order of the hierarchy. To study the convergence properties of the effective mode representation, we solve the time-dependent Schrodinger equation of the truncated system-bath HEM Hamiltonian, with the help of the multilayer extension of the Multiconfigurational Time-Dependent Hartree (ML-MCTDH) method. The results of the HEM representation are compared with those obtained with a quantum-mechanical tier-model. The convergence of the HEM representation with respect to the truncation order of the hierarchy is discussed for different initial conditions of the adsorbate-surface system. The combination of the HEM representation with the ML-MCTDH method provides information on the time evolution of the system (adsorbate) and multiple effective modes of the bath (surface). This permits insight into mechanisms of vibration-phonon coupling of the adsorbate-surface system, as well as inter-mode couplings of the effective bath. Y1 - 2020 U6 - https://doi.org/10.1063/5.0017716 SN - 0021-9606 SN - 1089-7690 VL - 153 IS - 6 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Fischer, Eric W. A1 - Saalfrank, Peter T1 - A thermofield-based multilayer multiconfigurational time-dependent Hartree approach to non-adiabatic quantum dynamics at finite temperature JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry N2 - We introduce a thermofield-based formulation of the multilayer multiconfigurational time-dependent Hartree (MCTDH) method to study finite temperature effects on non-adiabatic quantum dynamics from a non-stochastic, wave function perspective. Our approach is based on the formal equivalence of bosonic many-body theory at zero temperature with a doubled number of degrees of freedom and the thermal quasi-particle representation of bosonic thermofield dynamics (TFD). This equivalence allows for a transfer of bosonic many-body MCTDH as introduced by Wang and Thoss to the finite temperature framework of thermal quasi-particle TFD. As an application, we study temperature effects on the ultrafast internal conversion dynamics in pyrazine. We show that finite temperature effects can be efficiently accounted for in the construction of multilayer expansions of thermofield states in the framework presented herein. Furthermore, we find our results to agree well with existing studies on the pyrazine model based on the pMCTDH method. Y1 - 2021 U6 - https://doi.org/10.1063/5.0064013 SN - 0021-9606 SN - 1089-7690 VL - 155 IS - 13 PB - American Institute of Physics CY - Melville ER - TY - GEN A1 - Li, Hongguang A1 - Babu, Sukumaran Santhosh A1 - Turner, Sarah T. A1 - Neher, Dieter A1 - Hollamby, Martin J. A1 - Seki, Tomohiro A1 - Yagai, Shiki A1 - Deguchi, Yonekazu A1 - Möhwald, Helmuth A1 - Nakanishi, Takashi T1 - Alkylated-C60 based soft materials BT - regulation of selfassembly and optoelectronic properties by chain branching N2 - Derivatization of fullerene (C60) with branched aliphatic chains softens C60-based materials and enables the formation of thermotropic liquid crystals and room temperature nonvolatile liquids. This work demonstrates that by carefully tuning parameters such as type, number and substituent position of the branched chains, liquid crystalline C60 materials with mesophase temperatures suited for photovoltaic cell fabrication and room temperature nonvolatile liquid fullerenes with tunable viscosity can be obtained. In particular, compound 1, with branched chains, exhibits a smectic liquid crystalline phase extending from 84 °C to room temperature. Analysis of bulk heterojunction (BHJ) organic solar cells with a ca. 100 nm active layer of compound 1 and poly(3-hexylthiophene) (P3HT) as an electron acceptor and an electron donor, respectively, reveals an improved performance (power conversion efficiency, PCE: 1.6 ± 0.1%) in comparison with another compound, 10 (PCE: 0.5 ± 0.1%). The latter, in contrast to 1, carries linear aliphatic chains and thus forms a highly ordered solid lamellar phase at room temperature. The solar cell performance of 1 blended with P3HT approaches that of PCBM/P3HT for the same active layer thickness. This indicates that C60 derivatives bearing branched tails are a promising class of electron acceptors in soft (flexible) photovoltaic devices. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 250 Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95358 SP - 1943 EP - 1951 ER - TY - JOUR A1 - Bastian, Philipp U. A1 - Yu, Leixiao A1 - de Guereñu Kurganova, Anna Lopez A1 - Haag, Rainer A1 - Kumke, Michael Uwe T1 - Bioinspired confinement of upconversion nanoparticles for improved performance in aqueous solution JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - The resonance energy transfer (RET) from NaYF4:Yb,Er upconverting nanoparticles (UNCPs) to a dye (5-carboxytetramethylrhodamine (TAMRA)) was investigated by photoluminescence experiments and microscale thermophoresis (MST). The dye was excited via RET from the UCNPs which was excited in the near-infrared (NIR). The change of the dye diffusion speed (free vs coupled) was investigated by MST. RET shows significant changes in the decay times of the dye as well as of the UCNPs. MST reveals significant changes in the diffusion speed. A unique amphiphilic coating polymer (customized mussel protein (CMP) polymer) for UCNP surface coating was used, which mimics blood protein adsorption and mussel food protein adhesion to transfer the UCNP into the aqueous phase and to allow surface functionalization. The CMP provides very good water dispersibility to the UCNPs and minimizes ligand exchange and subsequent UCNP aging reactions because of the interlinkage of the CMP on the UCNP surface. Moreover, CMP provides N-3-functional groups for dick chemistry-based functionalization demonstrated with the dye 5-carboxytetramethylrhodamine (TAMRA). This establishes the principle coupling scheme for suitable biomarkers such as antibodies. The CMP provides very stable aqueous UCNP dispersions that are storable up to 3 years in a fridge at 5 degrees C without dissolution or coagulation. The outstanding properties of CMP in shielding the UCNP from unwanted solvent effects is reflected in the distinct increase of the photoluminescence decay times after UCNP functionalization. The UCNP-to-TAMRA energy transfer is also spectroscopically investigated at low temperatures (4-200 K), revealing that one of the two green Er(III) emission bands contributes the major part to the energy transfer. The TAMRA fluorescence decay time increases by a factor of 9500 from 2.28 ns up to 22 mu s due to radiationless energy transfer from the UCNP after NIR excitation of the latter. This underlines the unique properties of CMP as a versatile capping ligand for distinctly improving the UCNPs' performance in aqueous solutions, for coupling of biomolecules, and for applications for in vitro and in vivo experiments using UCNPs as optical probes in life science applications. Y1 - 2020 U6 - https://doi.org/10.1021/acs.jpcc.0c09798 SN - 1932-7447 SN - 1932-7455 VL - 124 IS - 52 SP - 28623 EP - 28635 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Fischer, Eric Wolfgang A1 - Anders, Janet A1 - Saalfrank, Peter T1 - Cavity-altered thermal isomerization rates and dynamical resonant localization in vibro-polaritonic chemistry JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - 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. Y1 - 2022 U6 - https://doi.org/10.1063/5.0076434 SN - 0021-9606 SN - 1089-7690 VL - 156 IS - 15 PB - American Institute of Physics CY - Melville, NY ER - TY - JOUR A1 - Erler, Alexander A1 - Riebe, Daniel A1 - Beitz, Toralf A1 - Löhmannsröben, Hans-Gerd A1 - Grothusheitkamp, Daniela A1 - Kunz, Thomas A1 - Methner, Frank-Jürgen T1 - Characterization of volatile metabolites formed by molds on barley by mass and ion mobility spectrometry JF - Journal of mass spectrometr N2 - The contamination of barley by molds on the field or in storage leads to the spoilage of grain and the production of mycotoxins, which causes major economic losses in malting facilities and breweries. Therefore, on-site detection of hidden fungus contaminations in grain storages based on the detection of volatile marker compounds is of high interest. In this work, the volatile metabolites of 10 different fungus species are identified by gas chromatography (GC) combined with two complementary mass spectrometric methods, namely, electron impact (EI) and chemical ionization at atmospheric pressure (APCI)-mass spectrometry (MS). The APCI source utilizes soft X-radiation, which enables the selective protonation of the volatile metabolites largely without side reactions. Nearly 80 volatile or semivolatile compounds from different substance classes, namely, alcohols, aldehydes, ketones, carboxylic acids, esters, substituted aromatic compounds, alkenes, terpenes, oxidized terpenes, sesquiterpenes, and oxidized sesquiterpenes, could be identified. The profiles of volatile and semivolatile metabolites of the different fungus species are characteristic of them and allow their safe differentiation. The application of the same GC parameters and APCI source allows a simple method transfer from MS to ion mobility spectrometry (IMS), which permits on-site analyses of grain stores. Characterization of IMS yields limits of detection very similar to those of APCI-MS. Accordingly, more than 90% of the volatile metabolites found by APCI-MS were also detected in IMS. In addition to different fungus genera, different species of one fungus genus could also be differentiated by GC-IMS. KW - APCI KW - fungus KW - gas chromatography KW - ion mobility spectrometry KW - mass KW - spectrometry KW - mold KW - soft X-ray Y1 - 2020 U6 - https://doi.org/10.1002/jms.4501 SN - 1076-5174 SN - 1096-9888 VL - 55 IS - 5 SP - 1 EP - 10 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Wojcik, Michal A1 - Brinkmann, Pia A1 - Zdunek, Rafał A1 - Riebe, Daniel A1 - Beitz, Toralf A1 - Merk, Sven A1 - Cieslik, Katarzyna A1 - Mory, David A1 - Antonczak, Arkadiusz T1 - Classification of copper minerals by handheld laser-induced breakdown spectroscopy and nonnegative tensor factorisation JF - Sensors N2 - Laser-induced breakdown spectroscopy (LIBS) analysers are becoming increasingly common for material classification purposes. However, to achieve good classification accuracy, mostly noncompact units are used based on their stability and reproducibility. In addition, computational algorithms that require significant hardware resources are commonly applied. For performing measurement campaigns in hard-to-access environments, such as mining sites, there is a need for compact, portable, or even handheld devices capable of reaching high measurement accuracy. The optics and hardware of small (i.e., handheld) devices are limited by space and power consumption and require a compromise of the achievable spectral quality. As long as the size of such a device is a major constraint, the software is the primary field for improvement. In this study, we propose a novel combination of handheld LIBS with non-negative tensor factorisation to investigate its classification capabilities of copper minerals. The proposed approach is based on the extraction of source spectra for each mineral (with the use of tensor methods) and their labelling based on the percentage contribution within the dataset. These latent spectra are then used in a regression model for validation purposes. The application of such an approach leads to an increase in the classification score by approximately 5% compared to that obtained using commonly used classifiers such as support vector machines, linear discriminant analysis, and the k-nearest neighbours algorithm. KW - LIBS KW - NTF KW - HALS KW - classification KW - copper minerals Y1 - 2020 U6 - https://doi.org/10.3390/s20185152 SN - 1424-8220 VL - 20 IS - 18 PB - MDPI CY - Basel ER - TY - GEN A1 - Wolff, Christian Michael A1 - Canil, Laura A1 - Rehermann, Carolin A1 - Nguyen, Ngoc Linh A1 - Zu, Fengshuo A1 - Ralaiarisoa, Maryline A1 - Caprioglio, Pietro A1 - Fiedler, Lukas A1 - Stolterfoht, Martin A1 - Kogikoski, Junior, Sergio A1 - Bald, Ilko A1 - Koch, Norbert A1 - Unger, Eva L. A1 - Dittrich, Thomas A1 - Abate, Antonio A1 - Neher, Dieter T1 - Correction to 'Perfluorinated self-assembled monolayers enhance the stability and efficiency of inverted perovskite solar cells' (2020, 14 (2), 1445−1456) T2 - ACS nano Y1 - 2020 U6 - https://doi.org/10.1021/acsnano.0c08081 SN - 1936-0851 SN - 1936-086X VL - 14 IS - 11 SP - 16156 EP - 16156 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Schilde, Uwe A1 - Kelling, Alexandra A1 - Umbreen, Sumaira A1 - Linker, Torsten T1 - Crystal structures of three bicyclic carbohydrate derivatives JF - Acta crystallographica Section E ; Crystallographic communications N2 - The title compounds, [(1R,3R,4R,5R,6S)-4,5-bis(acetyloxy)-7-oxo-2-oxabicyclo- [4.2.0]octan-3-yl]methyl acetate, C14H18O8, (I), [(1S,4R,5S,6R)-5-acetyloxy-7- hydroxyimino-2-oxobicyclo[4.2.0]octan-4-yl acetate, C11H15NO6, (II), and [(3aR,5R,6R,7R,7aS)-6,7-bis(acetyloxy)-2-oxooctahydropyrano[3,2-b]pyrrol-5- yl]methyl acetate, C14H19NO8, (III), are stable bicyclic carbohydrate derivatives. They can easily be synthesized in a few steps from commercially available glycals. As a result of the ring strain from the four-membered rings in (I) and (II), the conformations of the carbohydrates deviate strongly from the ideal chair form. Compound (II) occurs in the boat form. In the five-membered lactam (III), on the other hand, the carbohydrate adopts an almost ideal chair conformation. As a result of the distortion of the sugar rings, the configurations of the three bicyclic carbohydrate derivatives could not be determined from their NMR coupling constants. From our three crystal structure determinations, we were able to establish for the first time the absolute configurations of all new stereocenters of the carbohydrate rings. KW - crystal structure KW - carbohydrate deriv­atives KW - conformation KW - configuration Y1 - 2016 U6 - https://doi.org/10.1107/S2056989016018727 SN - 2056-9890 VL - 72 IS - 12 SP - 1839 EP - 1844 PB - IUCR CY - Chester ER - TY - JOUR A1 - Schmidt, Joachim T1 - Die Arbeit bei irreversibler Druck-Volumen-Änderung BT - Varianten der Berechnung N2 - For the calculation of the work in an irreversible pressure-volume change, we propose approxima-tions, which in contrast to the usual representation in the literature reflect the work performed during expansion and compression symmetrically. The calculations are based on the Reversible-Share-Theorem: Is used the force to overcome for calculating the work, so it captures only the configurational reversible work share. KW - physics KW - physical chemistry KW - thermodynamics KW - irreversible volume-change KW - reversible-share-theorem KW - total work KW - reversible work share KW - irreversible work share Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74931 ER -