| 1. |
- Abrahamsson, Maria, 1975, et al.
(författare)
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High Extinction Coefficient Ru-Sensitizers that Promote Hole Transfer on Nanocrystalline TiO2
- 2014
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 15:6, s. 1154-1163
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Tidskriftsartikel (refereegranskat)abstract
- Two series of Ru-II polypyridyl compounds with formulas [(bpy)(2)RuL](PF6)(2) and [(deeb)(2)RuL](PF6)(2), where bpy is 2,2-bipyridine, deeb is 4,4-diethylester-2,2-bpy, and L is one of several substituted 9-(1,3-dithiole-2-ylidene)-4,5-diazafluorene ligands, were studied as potential photosensitizers for TiO2. These compounds possess notably high extinction coefficients (40000M(-1)cm(-1) @470 nm) which are shown by time-dependent density functional theory (TD-DFT) calculations to result from overlapping metal-to-ligand charge transfer (MLCT) and ligand-localized transitions. Low-temperature absorption and photoluminescence measurements were suggestive of a short-lived MLCT excited state. When adsorbed onto TiO2 thin films, both the free ligands (L) and their corresponding [(deeb)(2)RuL](2+) complexes exhibited rapid excited-state electron injection into TiO2; in the case of the complexes, this was followed by rapid (k>10(8) s(-1)) hole transfer from Ru-III to the 1,3-dithiole ring of the L ligand. Observation of diffusion-limited reductive quenching of the [Ru(bpz)(3)](2+)* (bpz is 2,2-bipyrazine) excited state by the L ligands in solution supported the occurrence of intramolecular hole transfer following electron injection by the TiO2-anchored complexes.
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| 2. |
- Ahmed, Mukhtiar, et al.
(författare)
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Pyrrolidium- and Imidazolium-Based Ionic Liquids and Electrolytes with Flexible Oligoether Anions
- 2024
-
Ingår i: ChemPhysChem. - : John Wiley & Sons. - 1439-7641 .- 1439-4235. ; 25:9
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Tidskriftsartikel (refereegranskat)abstract
- A new class of fluorine-free ionic liquids (ILs) and electrolytes based on aliphatic flexible oligoether anions, 2-(2-methoxyethoxy)acetate (MEA) and 2-[2-(2-methoxyethoxy)ethoxy]acetate (MEEA), coupled with pyrrolidinium and imidazolium cations is introduced. For the ILs with MEEA anions, Li+ conducting electrolytes are created by doping the ILs with 30 mol % of LiMEEA. The structural flexibility of the oligoether functionality in the anion results in glass transition temperatures (Tg) as low as −60 °C for the neat ILs and the electrolytes. The imidazolium-based ILs and electrolytes reveal better thermal stabilities but higher Tg and lower electrochemical stabilities than the corresponding pyrrolidinium-based analogues. All neat ILs show comparable transport properties for the cations and these decrease by the addition of lithium salt – the pyrrolidinium-based electrolyte being affected the most.
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| 3. |
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| 4. |
- Alipour, Mohammad, et al.
(författare)
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Improved Battery Cycle Life Prediction Using a Hybrid Data-Driven Model Incorporating Linear Support Vector Regression and Gaussian
- 2022
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 23:7
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to accurately predict lithium-ion battery life-time already at an early stage of battery usage is critical for ensuring safe operation, accelerating technology development, and enabling battery second-life applications. Many models are unable to effectively predict battery life-time at early cycles due to the complex and nonlinear degrading behavior of lithium-ion batteries. In this study, two hybrid data-driven models, incorporating a traditional linear support vector regression (LSVR) and a Gaussian process regression (GPR), were developed to estimate battery life-time at an early stage, before more severe capacity fading, utilizing a data set of 124 battery cells with lifetimes ranging from 150 to 2300 cycles. Two type of hybrid models, here denoted as A and B, were proposed. For each of the models, we achieved 1.1 % (A) and 1.4 % (B) training error, and similarly, 8.3 % (A) and 8.2 % (B) test error. The two key advantages are that the error percentage is kept below 10 % and that very low error values for the training and test sets were observed when utilizing data from only the first 100 cycles.The proposed method thus appears highly promising for predicting battery life during early cycles.
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| 5. |
- Almeida, Roseley, et al.
(författare)
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Theoretical Evidence behind Bifunctional Catalytic Activity in Pristine and Functionalized Al2C Monolayers
- 2018
-
Ingår i: ChemPhysChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-4235 .- 1439-7641. ; 19:1, s. 148-152
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Tidskriftsartikel (refereegranskat)abstract
- First principles electronic structure calculations based on the density functional theory (DFT) framework are performed to investigate hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on two-dimensional Al2C monolayers. In addition to the pristine Al2C monolayer, monolayers doped with Nitrogen (N), Phosphorous (P), Boron (B), and Sulphur (S) are also investigated. After determining the individual adsorption energy of hydrogen and oxygen on the different functionalized Al2C monolayers, the adsorption free energies are predicted for each of the functionalized monolayers in order to assess their suitability for HER or OER. The density of states and optical absorption spectra calculations along with the work function of the functionalized Al2C monolayers enable us to gain a profound understanding of the electronic structure for the individual system and their relation to the water splitting mechanism.
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| 6. |
- Alvelid, Jonatan, et al.
(författare)
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Far Red‐Shifted CdTe Quantum Dots for Multicolour Stimulated Emission Depletion Nanoscopy
- 2022
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 24:3
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Tidskriftsartikel (refereegranskat)abstract
- Stimulated emission depletion (STED) nanoscopy is a widely used nanoscopy technique. Two-colour STED imaging in fixed and living cells is standardised today utilising both fluorescent dyes and fluorescent proteins. Solutions to image additional colours have been demonstrated using spectral unmixing, photobleaching steps, or long-Stokes-shift dyes. However, these approaches often compromise speed, spatial resolution, and image quality, and increase complexity. Here, we present multicolour STED nanoscopy with far red-shifted semiconductor CdTe quantum dots (QDs). STED imaging of the QDs is optimized to minimize blinking effects and maximize the number of detected photons. The far-red and compact emission spectra of the investigated QDs free spectral space for the simultaneous use of fluorescent dyes, enabling straightforward three-colour STED imaging with a single depletion beam. We use our method to study the internalization of QDs in cells, opening up the way for future super-resolution studies of particle uptake and internalization.
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| 7. |
- Andersson, Magnus, et al.
(författare)
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Physical Properties of Biopolymers Assessed by Optical Tweezers : Analysis of folding and refolding of bacterial pili
- 2008
-
Ingår i: ChemPhysChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-4235 .- 1439-7641. ; 9:2, s. 221-235
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial adhesion to surfaces mediated by specific adhesion organelles that promote infections, as exemplified by the pili of uropathogenic E. coli, is studied mostly at the level of cell-cell interactions and thereby reflects the averaged behavior of multiple pili. The role of pilus rod structure has therefore only been estimated from the outcome of experiments involving large numbers of organelles at the same time. It has, however, lately become clear that the biomechanical behavior of the pilus shafts play an important, albeit hitherto rather unrecognized, role in the adhesion process. For example, it has been observed that shafts from two different strains, even though they are similar in structure, result in large differences in the ability of the bacteria to adhere to their host tissue. However, in order to identify all properties of pilus structures that are of importance in the adhesion process, the biomechanical properties of pili must be assessed at the single-molecule level. Due to the low range of forces of these structures, until recently it was not possible to obtain such information. However, with the development of force-measuring optical tweezers (FMOT) with force resolution in the low piconewton range, it has lately become possible to assess forces mediated by individual pili on single living bacteria in real time. FMOT allows for a more or less detailed mapping of the biomechanical properties of individual pilus shafts, in particular those that are associated with their elongation and contraction under stress. This Mi- nireview presents the FMOT technique, the biological model system, and results from assessment of the biomechanical properties of bacterial pili. The information retrieved is also compared with that obtained by atomic force microscopy.
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| 8. |
- Andersson, Per Ola, et al.
(författare)
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A Novel ATR-FTIR Approach for Characterisation and Identification of Ex Situ Immobilised Species
- 2007
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Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 8:5, s. 712-722
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a novel method to analyse ex situ prepared protein chips by attenuated total reflection Fourier IR spectroscopy (ATR-FTIR), which circumvents tedious functionalisation steps of internal reflection elements (IREs), and simultaneously allows for complementary measurements by other analytical techniques. This concept is proven by utilising immobilised metal affinity capture (IMACTM) chips containing about 10 m thick films of copolymers coated with nitrilotriacetic acid (NTA) groups, which originally was manufactured for surface enhanced laser desorption ionisation (SELDI) spectrometry. Three immobilisation steps were analysed by ATR-FTIR spectroscopy: 1) NTA complexation with nickel(II) ions 2) binding of two histidine (His)-tagged synthetic peptides of 25 (25-His6) and 48 (48-His6) amino acids to the NTA-groups and 3) attachment of a ligand, mesyl amide, to the surface-bound 48-His6. Despite interference from H2O, both amide I and II were well resolved. Utilising peptide adsorption in the thick copolymer matrix yields a high saturation peptide concentration of 100 mg mL-1 and a dissociation constant of 116±11 M, as determined by a detailed analysis of the Langmuir adsorption isotherm. The mesyl amide ligand was directly seen in the raw ATR-FTIR spectrum with specific peaks in the fingerprint region at 1172 and 1350 cm-1. Several aspects of the fine structure of the amide I band of the peptide were analysed: influences from secondary structure, amino side chains and competing contamination product. We believe that this approach has great potential as a stand-alone or complementary analytical tool for determination of the chemical composition of functionalised surfaces. We emphasise further that with this approach no chemical treatment of IREs is needed; the chips can be regenerated and reused, and applied in other experimental set-ups.
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| 9. |
- Andrejic, Milica, et al.
(författare)
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Coupled-Cluster Interaction Energies for 200-Atom Host-Guest Systems
- 2014
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 15:15, s. 3270-3281
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a method to calculate interaction energies of large systems (such as host-guest or even protein-ligand systems) at the local coupled-cluster with singles, doubles, and perturbative triples level, and with extrapolation to the limit of a complete basis set. The method is based on the polarizable multipole interactions with supermolecular pairs molecular fractionation approach, which combines a pairwise quantum-mechanical evaluation of the short-range interactions with a polarizable multipole treatment of many-body effects. The method is tested for nine guest molecules binding to an octa-acid host (in total 198-207 atoms), as part of the SAMPL4 blind challenge. From the test calculations, the accuracy of the approach is found to be 10 kJ mol(-1) or better. Comparison with dispersion-corrected density functional theory reveals that the latter underestimates the dispersion contribution for this type of system, which leads to a difference in the ranking of the ligands.
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| 10. |
- Anoshkin, Ilya, et al.
(författare)
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Coronene Encapsulation in Single-Walled Carbon Nanotubes : Stacked Columns, Peapods, and Nanoribbons
- 2014
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 15:8, s. 1660-1665
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Tidskriftsartikel (refereegranskat)abstract
- Encapsulation of coronene inside single-walled carbon nanotubes (SWNTs) was studied under various conditions. Under high vacuum, two main types of molecular encapsulation were observed by using transmission electron microscopy: coronene dimers and molecular stacking columns perpendicular or tilted (45-608) with regard to the axis of the SWNTs. A relatively small number of short nanoribbons or polymerized coronene molecular chains were observed. However, experiments performed under an argon atmosphere (0.17 MPa) revealed reactions between the coronene molecules and the formation of hydrogen-terminated graphene nanoribbons. It was also observed that the morphology of the encapsulated products depend on the diameter of the SWNTs. The experimental results are explained by using density functional theory calculations through the energies of the coronene molecules inside the SWNTs, which depend on the orientation of the molecules and the diameter of the tubes.
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| 11. |
- Atak, Kaan, et al.
(författare)
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The Chemical Bond in Carbonyl and Sulfinyl Groups Studied by Soft X-ray Spectroscopy and ab Initio Calculations
- 2012
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 13:13, s. 3106-3111
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Tidskriftsartikel (refereegranskat)abstract
- The polar character of the sulfinyl bond, which determines many of the properties of dimethyl sulfoxide (DMSO), is a result of charge transfer in low-lying π-type orbitals. This characteristic—together with the wide energy gap between the highest occupied and the lowest unoccupied molecular orbitals of this substance—makes DMSO a relatively inert aprotic solvent with strong nucleophilicity and electrophilicity.
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| 12. |
- Bagger, Alexander, et al.
(författare)
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Ab Initio Cyclic Voltammetry on Cu(111), Cu(100) and Cu(110) in Acidic, Neutral and Alkaline Solutions
- 2019
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 20
-
Tidskriftsartikel (refereegranskat)abstract
- Electrochemical reactions depend on the electrochemical interface between the electrode surfaces and the electrolytes. To control and advance electrochemical reactions there is a need to develop realistic simulation models of the electrochemical interface to understand the interface from an atomistic point-of-view. Here we present a method for obtaining thermodynamic realistic interface structures, a procedure we use to derive specific coverages and to obtain ab initio simulated cyclic voltammograms. As a case study, the method and procedure is applied in a matrix study of three Cu facets in three different electrolytes. The results have been validated by direct comparison to experimental cyclic voltammograms. The alkaline (NaOH) cyclic voltammograms are described by H* and OH*, while in neutral medium (KHCO3) the CO3* species are dominating and in acidic (KCl) the Cl* species prevail. An almost one-to-one mapping is observed from simulation to experiments giving an atomistic understanding of the interface structure of the Cu facets. Atomistic understanding of the interface at relevant eletrolyte conditions will further allow realistic modelling of electrochemical reactions of importance for future eletrocatalytic studies.
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| 13. |
- Bast, Radovan, et al.
(författare)
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Static and frequency-dependent dipole-dipole polarizabilities of all closed-shell atoms up to radium : A four-component relativistic DFT study
- 2008
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 9:3, s. 445-453
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Tidskriftsartikel (refereegranskat)abstract
- We test the performance of four-component relativistic density functional theory by calculating the static and frequency-dependent electric dipole-dipole polarizabilities of all (ground-state) closed-shell atoms-up to Ra. We consider 12 nonrelativistic functionals, including three asymptotically, shape-corrected functionals, by using two smooth interpolation schemes introduced by the Baerends group: the gradient-regulated asymptotic connection (GRAC) procedure and the statistical averaging of (model) orbital potentials (SAOP). Basis sets of doubly augmented triple-zeta quality are used. The results are compared to experimental data or to accurate ob initio results. The reference static electric dipole polarizability of palladium has been obtained by finite-field calculations using the coupled-cluster singles, doubles, and perturbative triples method within this work. The best overall performance is obtained using hybrid functionals and their GRAC shape-corrected versions. The performance of SAOP is among the best for nonhybrid functionals for Group 18 atoms but its precision degrades when considering the full set of atoms. In general, we find that conclusions based on results obtained for the rare-gas atoms are not necessarily representative of the complete set of atoms. GRAC cannot be used with effective core potentials since the asymptomatic correction is switched on in the core region.
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| 14. |
- Bergström, Lars Magnus
(författare)
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Bending energetics of tablet-shaped micelles : A novel approach to rationalize micellar systems
- 2007
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 8:3, s. 462-472
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Tidskriftsartikel (refereegranskat)abstract
- A novel approach to rationalize micellar systems is expounded in which the structural behaviour of tablet-shaped micelles is theoretically investigated as a function of the three bending elasticity constants: spontaneous curvature (H-0), bending rigidity (k(c)), and saddle-splay constant (k(c)). As a result, experimentally accessible micellar properties, such as aggregation number, length-to-width ratio, and polydispersity, may be relation to the different bending elasticity constants. Is it demonstrated that discrete micelles or connected cylinders form when H-0 > 1/4 xi where xi is the thickness of a surfacant monolayer, whereas various bilayer structures are expected to predominate when H-0 > 1/4 xi. Our theory predicts, in agreement with experiments, a transition from discrete globular (tablet-shaped) micelles to a phase of ordered, or disordered, connected cylinders above a critital surfactant concentration. Moreover, a novel explanation for the mechanism of growth, from small globular to long rodlike or wormlike micelles, follows as a consequence from the theory. In accordance, polydiperse elongated micelles (large length-to-width ratio) for as the bending rigidity is lowered, approaching the critical point at k(c) - 0, whereas monodisperse globular micelles (small length-to-width ratio) are expected to be present at larg k(c) values. The spontaneous curvature mainly determines the width of tablet-shaped or ribbonlike micelles, or the radius of dislike micelles, whereas the saddle-splay constant primarily influences the size but not the shape of the micelles.
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| 15. |
- Björk, Jonas, et al.
(författare)
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Adsorption of large hydrocarbons on coinage metals : a van der Waals density functional study
- 2014
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Ingår i: ChemPhysChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-4235 .- 1439-7641. ; 15:13, s. 2851-2858
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of organic molecules onto the close-packed facets of coinage metals is studied, and how accurately adsorption heights can be described by using recent advances of the van der Waals density functional (vdWDF), with optPBE/vdWDF, optB86b/vdWDF, vdWDF2, and rev/vdWDF2 functionals is illustrated. The adsorption of two prototypical aromatic hydrocarbons is investigated, and the calculated adsorption heights are compared to experimental literature values from normal incident X-ray standing wave absorption and a state-of-the-art semi-empirical method. It is shown that both the optB86b/vdWDF and rev/vdWDF2 functionals describe adsorption heights with an accuracy of 0.1 Å, compared to experimental values, and are concluded as reliable methods of choice for related systems.
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| 16. |
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| 17. |
- Blaudeck, Thomas, et al.
(författare)
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Formation Principles and Ligand Dynamics of Nanoassemblies of CdSe Quantum Dots and Functionalised Dye Molecules
- 2012
-
Ingår i: ChemPhysChem. - : Wiley-Blackwell / Wiley-VCH Verlag Berlin. - 1439-4235 .- 1439-7641. ; 13:4, s. 959-972
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Tidskriftsartikel (refereegranskat)abstract
- Functional dye molecules, such as porphyrins, attached to CdSe quantum dots (QDs) through anchoring meso-pyridyl substituents, form quasi-stable nanoassemblies. This fact results in photoluminescence (PL) quenching of the QDs both due to Forster resonance energy transfer (FRET) and the formation of non-radiative surface states under conditions of quantum confinement (non-FRET). The formation process is in competition with the ligand dynamics. At least two timescales are found for the formation of the assemblies: 1) one faster than 60 s attributed to saturation of empty attachment sites and 2) one slower than 600 s, which is attributed to a reorganisation of the tri-n-octylphosphine oxide (TOPO) ligand shell. Finally, this process results in almost complete exchange of the TOPO shell by porphyrin dye molecules. Following a SternVolmer analysis, we established a microscopic description of PL quenching and assembly formation. Based on this formalism, we determined the equilibrium constant for assembly formation between QDs and the pyridyl-functionalised dye molecules to be K approximate to 10(5)-10(7) M-1, which is several orders of magnitude larger than that of the TOPO ligands. Our results give additional insights into the non-FRET PL quenching processes involved and show that the QD surface is inhomogeneous with respect to the involved attachment and detachment processes. In comparison with other methods, such as NMR spectroscopy, the advantage of our approach is that ligand dynamics can be investigated at extremely low ratios of dye molecules to QDs.
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| 18. |
- Borg, Mikael, et al.
(författare)
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Density of configurational states from first-principles calculations: The phase diagram of Al-Na surface alloys
- 2005
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Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 6:9, s. 1923-1928
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Tidskriftsartikel (refereegranskat)abstract
- The structural phases of AlxNa1-x surface alloys have been investigated theoretically and experimentally. We describe the system using a lattice gas Hamiltonian, determined from density functional theory together with Monte Carlo (MC) calculations. The obtained phase diagram reproduces the experiment on a quantitative level. From calculation of the (configurational) density of states by recently introduced Wang-Landau MC algorithm, we derive thermodynamic quantities such as free energy and entropy which are not directly accessible from conventional MC simulations. We accurately reproduce the stoichiometry, as well as the temperature at which an order-disorder phase transition occurs, and demonstrate the crucial role, and magnitude of the configurational entropy.
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| 19. |
- Brant, William R., et al.
(författare)
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Rapid Lithium Insertion and Location of Mobile Lithium in the Defect Perovskite Li0.18Sr0.66Ti0.5Nb0.5O3
- 2012
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Ingår i: ChemPhysChem. - : Wiley-Blackwell. - 1439-4235 .- 1439-7641. ; 13:9, s. 2293-2296
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Tidskriftsartikel (refereegranskat)abstract
- Fast and fancy: Lithium that was originally disordered within the structure of the perovskite Li0.18Sr0.66Ti0.5Nb0.5O3 can be induced into ordering within the yellow region of the unit cell by low temperatures and treatment with n-butyl-lithium. The fast kinetics of lithium insertion, in connection with a color change, make this nontoxic, air-stable material a suitable candidate for use in electrochromic systems or lithium-storage batteries.
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| 20. |
- Brea, Oriana, et al.
(författare)
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Molecular Modelling of the H-2-Adsorptive Properties of Tetrazolate-Based Metal-Organic Frameworks : From the Cluster Approach to Periodic Simulations
- 2018
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 19:11, s. 1349-1357
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen has been proposed as a long-term non-fossil fuel to be used in a future ideal carbon-neutral energetic economy. However, its low volumetric energy density hinders its storage and transportation. Metal-organic frameworks (MOFs) represent very promising materials for this purpose due to their very extended surface areas. Azolates, in particular tetrazolates, are - together with carboxylate functionalities - very common organic linkers connecting metallic secondary building units in MOFs. This study addresses, from a theoretical perspective, the H-2 adsorptive properties of tetrazolate linkers at the molecular level, following a size-progressive approach. Specifically, we have investigated how the physisorption energies and geometries are affected when changing the environment of the linker by considering the azolates in the gas phase, immersed in a finite cluster, or being part of an infinite extended crystal material. Furthermore, we also study the H-2 adsorptive capacity of these linkers within the cluster model.
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| 21. |
- Brändén, Magnus, 1971, et al.
(författare)
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Label-Free Measurements of Molecular Transport across Liposome Membranes using Evanescent-Wave Sensing
- 2008
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Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 9:17, s. 2480-2485
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Tidskriftsartikel (refereegranskat)abstract
- Pucker up! A novel approach enabling direct measurements of biomolecular transfer across lipid bilayer membranes, using surface plasmon resonance, is demonstrated. The figure shows the transfer of sucrose (S) through melittin pores formed in surface-attached liposomes. By measuring the shift in refractive index in the volume enclosed by the liposomes, the sucrose transfer can be time-resolved and quantified.
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| 22. |
- Cappel, Ute B., et al.
(författare)
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Electronic Structure Characterization of Cross-Linked Sulfur Polymers
- 2018
-
Ingår i: ChemPhysChem. - : WILEY-V C H VERLAG GMBH. - 1439-4235 .- 1439-7641. ; 19:9, s. 1041-1047
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Tidskriftsartikel (refereegranskat)abstract
- Cross-linked polymers of elemental sulfur are of potential interest for electronic applications as they enable facile thin-film processing of an abundant and inexpensive starting material. Here, we characterize the electronic structure of a cross-linked sulfur/diisopropenyl benzene (DIB) polymer by a combination of soft and hard X-ray photoelectron spectroscopy (SOXPES and HAXPES). Two different approaches for enhancing the conductivity of the polymer are compared: the addition of selenium in the polymer synthesis and the addition of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) during film preparation. For the former, we observe the incorporation of Se into the polymer structure resulting in a changed valence-band structure. For the latter, a Fermi level shift in agreement with p-type doping of the polymer is observed and also the formation of a surface layer consisting mostly of TFSI anions.
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| 23. |
- Castelain, Mickaël, et al.
(författare)
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Characterization of the Biomechanical Properties of T4 Pili Expressed by Streptococcus pneumoniae – A Comparison between Helix-like and Open Coil-like Pili
- 2009
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Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 10:9-10, s. 1533-1540
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial adhesion organelles, known as fimbria or pili, are expressed by Gram–positive as well as Gram–negative bacteria families. These appendages play a key role in the first steps of the invasion and infection processes, and they therefore provide bacteria with pathogenic abilities. To improve the knowledge of pili-mediated bacterial adhesion to host cells and how these pili behave under the presence of an external force, we first characterize, using force measuring optical tweezers, open coil-like T4 pili expressed by Gram–positive Streptococcus pneumoniae with respect to their biomechanicalproperties. It is shown that their elongation behavior can be well described by the worm-like chain model and that they possess a large degree of flexibility. Their properties are then compared with those of helix-like pili expressed by Gram–negative uropathogenic Escherichia coli (UPEC), which have different pili architecture. The differences suggest that these two types of pili have distinctly dissimilar mechanisms to adhere and sustain external forces. Helix-like pili expressed by UPEC bacteria adhere to host cells by single adhesins located at the distal end of the pili while their helix-like structures act as shock absorbers to dampen the irregularly shear forces induced by urine flow and to increase the cooperativity of the pili ensemble. Open coil-like pili expressed by S. pneumoniae adhere to cells by a multitude of adhesins distributed along the pili. It is hypothesized that these two types of pili represent different strategies of adhering to host cells in the presence of external forces. When exposed to significant forces, bacteria expressing helix-like pili remain attached bydistributing the external force among a multitude of pili, whereas bacteria expressing open coil-like pili sustain large forces primarily by their multitude of binding adhesins.
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| 24. |
- Chen, Shi-Lu, et al.
(författare)
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Phosphate Monoester Hydrolysis by Trinuclear Alkaline Phosphatase; DFT Study of Transition States and Reaction Mechanism
- 2014
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 15:11, s. 2321-2330
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Tidskriftsartikel (refereegranskat)abstract
- Alkaline phosphatase (AP) is a trinuclear metalloenzyme that catalyzes the hydrolysis of a broad range of phosphate monoesters to form inorganic phosphate and alcohol (or phenol). In this paper, by using density functional theory with a model based on a crystal structure, the AP-catalyzed hydrolysis of phosphate monoesters is investigated by calculating two substrates, that is, methyl and p-nitrophenyl phosphates, which represent alkyl and aryl phosphates, respectively. The calculations confirm that the AP reaction employs a ping-pong mechanism involving two chemical displacement steps, that is, the displacement of the substrate leaving group by a Ser102 alkoxide and the hydrolysis of the phosphoseryl intermediate by a Zn2-bound hydroxide. Both displacement steps proceed via a concerted associative pathway no matter which substrate is used. Other mechanistic aspects are also studied. Comparison of our calculations with linear free energy relationships experiments shows good agreement.
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| 25. |
- Chen, Xing, et al.
(författare)
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Theoretical studies on the mechanism of α-santonin photo-induced rearrangement
- 2012
-
Ingår i: ChemPhysChem. - Germany : John Wiley & Sons. - 1439-4235 .- 1439-7641. ; 13:1, s. 353-362
-
Tidskriftsartikel (refereegranskat)abstract
- α-Santonin is the first organic compound observed to feature a photoinduced rearrangement and is now known to undergo a series of photochemical processes under UV irradiation. On the basis of the considerable interest of this system as a prototype, and of the yet limited insights reached for the basic photo mechanisms, we calculate the high-level electronic structures and explore the potential energy surfaces (PES) of α-santonin in the ground and lowest-lying excited states, their couplings, and the possible photoinduced isomerization pathways. The calculations identify the low-lying singlet excited state 1(nπ*) accessible under light irradiation, which decays to the low-energy 3(ππ*) state through an intersystem crossing in the Franck–Condon region to initiate the photoinduced rearrangement. The initial reaction from the C3C5 bond coupling, which takes place on the 3(ππ*) state potential energy surface, leads to a three-membered alkyl-ring compound intermediate state INT. The following photochemical reactions have the possibility to arise from two distinct CC bond cleavages, C4C5 and C3C4, denoted as path A and path B. Path A is favored both dynamically on the excited-state PES and thermodynamically on the ground-state PES in vacuo. Experiments show that it also becomes the dominant photoinduced rearrangement process in the crystal, which can be explained by considering the requirement for less space and the stacking effect under the confined environment. Path B is dynamical advantaged both on the ground- and excited-state PESs in a weak polar solvent, such as dioxane. Once the biradical intermediate B-INT is accessible on the ground-state PES, the formation of the product B-P is almost barrier free.
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| 26. |
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| 27. |
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| 28. |
- Das, Tisita, et al.
(författare)
-
TiS2 Monolayer as an Emerging Ultrathin Bifunctional Catalyst : Influence of Defects and Functionalization
- 2019
-
Ingår i: ChemPhysChem. - : Wiley-VCH Verlag. - 1439-4235 .- 1439-7641. ; 20:4, s. 608-617
-
Tidskriftsartikel (refereegranskat)abstract
- We have envisaged the hydrogen evolution and oxygen evolution reactions (HER and OER) on a two-dimensional (2D) noble-metal-free titanium disulfide (TiS2) monolayer, which belongs to the exciting family of transition metal dichalcogenides (TMDCs). Our theoretical investigation to probe the HER and OER on both the H and T phases of 2D TiS2 is based on electronic-structure calculations witihin the framework of density functional theory (DFT). Since TiS2 is the lightest compound among the group-IV TMDCs, it is worth exploring the catalytic activity of a TiS2 monolayer through the functionalization at the anion (S) site, substituting with P, N, and C dopants as well as by incorporating single sulfur vacancy defects. We have investigated the effect of functionalization and vacancy defects on the structural, electronic, and optical response of a TiS2 monolayer by determining the density of states, work-function, and optical absorption spectra. We have determined the HER and OER activities for the functionalized and defective TiS2 monolayers based on the reaction coordinate, which can be constructed from the adsorption free energies of the intermediates (H*, O*, OH* and OOH*, where * denotes the adosrbed state) in the HER and OER mechanisms. Finally, we have shown that TiS2 monolayers are emerging as a promising material for the HER and OER mechanisms under the influence of functionalization and defects.
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| 29. |
- Degerman, David, 1989-, et al.
(författare)
-
Demonstrating Pressure Jumping as a Tool to Address the Pressure Gap in High Pressure Photoelectron Spectroscopy of CO and CO2 Hydrogenation on Rh(211)
- 2024
-
Ingår i: ChemPhysChem. - 1439-4235 .- 1439-7641. ; 25:1
-
Tidskriftsartikel (refereegranskat)abstract
- Operando probing by x-ray photoelectron spectroscopy (XPS) of certain hydrogenation reactions are often limited by the scattering of photoelectrons in the gas phase. This work describes a method designed to partially circumvent this so called pressure gap. By performing a rapid switch from a high pressure (where acquisition is impossible) to a lower pressure we can for a short while probe a remnant of the high pressure surface as well as the time dynamics during the re-equilibration to the new pressure. This methodology is demonstrated using the CO2 and the CO hydrogenation reaction over Rh(211). In the CO2 hydrogenation reaction, the remnant surface of a 2 bar pressure shows an adsorbate distribution which favors chemisorbed CHx adsorbates over chemisorbed CO. This contrasts against previous static operando spectra acquired at lower pressures. Furthermore, the pressure jumping method yields a faster acquisition and more detailed spectra than static operando measurements above 1 bar. In the CO hydrogenation reaction, we observe that CHx accumulated faster during the 275 mbar low pressure regime, and different hypotheses are presented regarding this observation.
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| 30. |
- Delesma, Francisco A., et al.
(författare)
-
A Chemical View on X-ray Photoelectron Spectroscopy : the ESCA Molecule and Surface-to-Bulk XPS Shifts
- 2018
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 19:2, s. 169-174
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we remind the reader of a simple, intuitive picture of chemical shifts in X-ray photoelectron spectroscopy (XPS) as the difference in chemical bonding between the probed atom and its neighbor to the right in the periodic table, the so called Z + 1 approximation. We use the classical ESCA molecule, ethyl trifluoroacetate, and 4d-transition metals to explicitly demonstrate agreement between core-level shifts computed as differences between final core-hole states and the approach where each core-ionized atom is replaced by a Z + 1 atom. In this final state, or total energy picture, the XPS shift arises due to the more or less unfavorable chemical bonding of the effective nitrogen in the carbon geometry for the ESCA molecule. Surface core level shifts in metals are determined by whether the Z + 1 atom as an alloy segregates to the surface or is more soluble in the bulk. As further illustration of this more chemical picture, we compare the geometry of C 1s and O 1s core-ionized CO with that of, respectively, NO+ and CF+. The scope is not to propose a new method to compute XPS shifts but rather to stress the validity of this simple interpretation.
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| 31. |
- Devaux, Xavier, et al.
(författare)
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Covalent Functionalization of HiPco Single-Walled Carbon Nanotubes : Differences in the Oxidizing Action of H2SO4 and HNO3 during a Soft Oxidation Process
- 2015
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 16:12, s. 2692-2701
-
Tidskriftsartikel (refereegranskat)abstract
- The results of a study on the evolution of HiPco single-walled carbon nanotubes during the oxidizing action of H2SO4 and HNO3 are presented. The process conditions used have been chosen so as to avoid any significant damage to the nanotube structure. The type and level of functionalization, the location of the grafted functions on the surface of the nanotube and the changes in morphological characteristics of the samples were examined by using a wide and complementary range of analytical techniques. We propose an explanation for the differences in the oxidizing action of sulfuric and nitric acids. The combined results allow us to suggest possible reaction mechanisms that occur on the surface of the nanotube.
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| 32. |
- Dietze, Elisabeth, 1993, et al.
(författare)
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Structure-Dependent Strain Effects
- 2020
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 21:21, s. 2407-2410
-
Tidskriftsartikel (refereegranskat)abstract
- Density functional theory calculations of atomic and molecular adsorption on (111) and (100) metal surfaces reveal marked surface and structure dependent effects of strain. Adsorption in three-fold hollow sites is found to be destabilized by compressive strain whereas the reversed trend is commonly valid for adsorption in four-fold sites. The effects, which are qualitatively explained using a simple two-orbital model, provide insights on how to modify chemical properties by strain design.
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| 33. |
- Dietzek, Benjamin, et al.
(författare)
-
Protochlorophyllide a: A Comprehensive Photophysical Picture
- 2009
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 10:1, s. 144-150
-
Tidskriftsartikel (refereegranskat)abstract
- The photochemistry of protochlorophyllide a, a precursor in the biosynthesis of chlorophyll and substrate of the light regulated enzyme protochlorophyllide oxidoreductase, is investigated by pump-probe spectroscopy. Upon excitation into the lowest lying Q-band the light induced changes ore recorded over a wide range of probe wavelengths in the visible and near-IR region between 500 and 1000 nm. Following excitation, an initial ultrafast 450 Is process is observed related to the motion out of the Franck-Condon region on the excited state surface; thus directly unraveling previous suggestions based on time-resolved fluorescence measurements (ChemPhysChem 2006, 7, 1727-1733). Furthermore, the data reveals a previously concealed photointermediate, whose formation on a nanosecond timescale matches the overall fluorescence decay and is assigned to a triplet state. The implications of this finding with respect to the photochemistry of NADPH.-protochlorophyllide oxidoreductase (POR) ore discussed.
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| 34. |
- Dietzek, Benjamin, et al.
(författare)
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The excited-state chemistry of protochlorophyllide a: A time-resolved fluorescence study
- 2006
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 7:8, s. 1727-1733
-
Tidskriftsartikel (refereegranskat)abstract
- The excited-state processes of protochlorophyllide a, the precursor of chlorophyll a in chlorophyll biosynthesis, are studied using picosecond time-resolved fluorescence spectroscopy. Following excitation into the Soret band, two distinct fluorescence components, with emission maxima at 640 and 647 nm, ore observed. The 640 nm emitting component appears within the time resolution of the experiment and then decays with a time constant of 27 ps. In contrast, the 647 nm emitting component is built up with a 3.5 ps rise time and undergoes a subsequent decay with a time constant of 3.5 ns. The 3.5 ps rise kinetics are attributed to relaxations in the electronically excited state preceding the nanosecond fluorescence, which is ascribed to emission out of the thermally equilibrated S, state. The 27 ps fluorescence, which appears within the experimental response of the streak camera, is suggested to originate from a second minimum on the excited-state potentiol-energy surface. The population of the secondary excited state is suggested to reflect a very fast motion out of the Franck-Condon region along a reaction coordinate different from the one connecting the Franck-Condon region with the S-1 potential-energy minimum. The 27 ps-component is an emissive intermediate on the reactive excited-state pathway, as its decay yields the intermediate photoproduct, which has been identified previously (J. Phys. Chem. B 2006, 110, 4399-4406). No emission of the photoproduct is observed. The results of the time-resolved fluorescence study allow a detailed spectral characterization of the emission of the excited states in protochlorophyllide a, and the refinement of the kinetic model deduced from ultrafast absorption measurements.
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| 35. |
- Driver, Gordon W
(författare)
-
Aqueous Brønsted–Lowry Chemistry of Ionic Liquid Ions
- 2015
-
Ingår i: ChemPhysChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-4235 .- 1439-7641. ; 16:11, s. 2432-2439
-
Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids have become commonplace materials found in research laboratories the world over, and are increasingly utilised in studies featuring water as co-solvent. It is reported herein that proton activities, aH+, originating from auto-protolysis of H2O molecules, are significantly altered in mixtures with common ionic liquids comprised of Cl−, [HSO4]−, [CH3SO4]−, [CH3COO]−, [BF4]−, relative to pure water. paH+ values, recorded in partially aqueous media as −log(aH+), are observed over a wide range (∼0–13) as a result of hydrolysis (or acid dissociation) of liquid salt ions to their associated parent molecules (or conjugate bases). Brønsted–Lowry acid–base character of ionic liquid ions observed is rooted in equilibria known to govern the highly developed aqueous chemistry of classical organic and inorganic salts, as their well-known aqueous pKs dictate. Classical salt behaviour observed for both protic and aprotic ions in the presence of water suggests appropriate attention need be given to relevant chemical systems in order to exploit, or avoid, the nature of the medium formed.
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| 36. |
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| 37. |
- Ewing, Andrew G, 1957, et al.
(författare)
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Frontiers in Neurochemistry
- 2018
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 19, s. 1121-1122
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 38. |
- Falk, Magnus, et al.
(författare)
-
Biofuel cells for biomedical applications : colonizing the animal kingdom
- 2013
-
Ingår i: ChemPhysChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-4235 .- 1439-7641. ; 14:10, s. 2045-2058
-
Forskningsöversikt (refereegranskat)abstract
- A review. Interdisciplinary research has combined the efforts of many scientists and engineers to gain an understanding of biotic and abiotic electrochem. processes, materials properties, biomedical, and engineering approaches for the development of alternative power-generating and/or energy-harvesting devices, aiming to solve health-related issues and to improve the quality of human life. This review intends to recapitulate the principles of biofuel cell development and the progress over the years, thanks to the contribution of cross-disciplinary researchers that have combined knowledge and innovative ideas to the field. The emergence of biofuel cells, as a response to the demand of elec. power devices that can operate under physiol. conditions, are reviewed. Implantable biofuel cells operating inside living organisms have been envisioned for over fifty years, but few reports of implanted devices have existed up until very recently. The very first report of an implanted biofuel cell (implanted in a grape) was published only in 2003 by Adam Heller and his coworkers. This work was a result of earlier scientific efforts of this group to "wire" enzymes to the electrode surface. The last couple of years have, however, seen a multitude of biofuel cells being implanted and operating in different living organisms, including mammals. Herein, the evolution of the biofuel concept, the understanding and employment of catalyst and biocatalyst processes to mimic biol. processes, are explored. These potentially green technol. biodevices are designed to be applied for biomedical applications to power nano- and microelectronic devices, drug delivery systems, biosensors, and many more.
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| 39. |
- Falklöf, Olle, et al.
(författare)
-
Steric Effects Govern the Photoactivation of Phytochromes
- 2016
-
Ingår i: ChemPhysChem. - : WILEY-V C H VERLAG GMBH. - 1439-4235 .- 1439-7641. ; 17:7, s. 954-957
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Tidskriftsartikel (refereegranskat)abstract
- Phytochromes constitute a superfamily of photoreceptor proteins existing in two forms that absorb red (Pr) and far-red (Pfr) light. Although it is well-known that the conversion of Pr into Pfr (the biologically active form) is triggered by a ZE photoisomerization of the linear tetrapyrrole chromophore, direct evidence is scarce as to why this reaction always occurs at the methine bridge between pyrrole rings C and D. Here, we present hybrid quantum mechanics/molecular mechanics calculations based on a high-resolution Pr crystal structure of Deinococcus radiodurans bacteriophytochrome to investigate the competition between all possible photoisomerizations at the three different (AB, BC and CD) methine bridges. The results demonstrate that steric interactions with the protein are a key discriminator between the different reaction channels. In particular, it is found that such interactions render photoisomerizations at the AB and BC bridges much less probable than photoisomerization at the CD bridge.
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| 40. |
- Farahani, Pooria, et al.
(författare)
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Mechanisms for the Breakdown of Halomethanes through Reactions with Ground-State Cyano Radicals
- 2015
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 16:1, s. 181-190
-
Tidskriftsartikel (refereegranskat)abstract
- One route to break down halomethanes is through reactions with radical species. The capability of the artificial force-induced reaction algorithm to efficiently explore a large number of radical reaction pathways has been illustrated for reactions between haloalkanes (CX3Y; X=H, F; Y=Cl, Br) and ground-state (2Σ+) cyano radicals (CN). For CH3Cl+CN, 71 stationary points in eight different pathways have been located and, in agreement with experiment, the highest rate constant (108 s−1 M−1 at 298 K) is obtained for hydrogen abstraction. For CH3Br, the rate constants for hydrogen and halogen abstraction are similar (109 s−1 M−1), whereas replacing hydrogen with fluorine eliminates the hydrogen-abstraction route and decreases the rate constants for halogen abstraction by 2–3 orders of magnitude. The detailed mapping of stationary points allows accurate calculations of product distributions, and the encouraging rate constants should motivate future studies with other radicals.
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| 41. |
- Farhat, Douaa, et al.
(författare)
-
Adiponitrile-Lithium Bis(trimethylsulfonyl)imide Solutions as Alkyl Carbonate-free Electrolytes for Li4Ti5O12 (LTO)/LiNi1/3Co1/3Mn1/3O2 (NMC) Li-Ion Batteries
- 2017
-
Ingår i: ChemPhysChem. - : WILEY-V C H VERLAG GMBH. - 1439-4235 .- 1439-7641. ; 18:10, s. 1333-1344
-
Tidskriftsartikel (refereegranskat)abstract
- Recently, dinitriles (NC(CH2)(n)CN) and especially adiponitrile (ADN, n = 4) have attracted attention as safe electrolyte solvents owing to their chemical stability, high boiling points, high flash points, and low vapor pressure. The good solvation properties of ADN toward lithium salts and its high electrochemical stability (approximate to 6 V vs. Li/Li+) make it suitable for safer Li-ions cells without performance loss. In this study, ADN is used as a single electrolyte solvent with lithium bis(trimethylsulfonyl) imide (LiTFSI). This electrolyte allows the use of aluminium collectors as almost no corrosion occurs at voltages up to 4.2 V. The physicochemical properties of the ADN-LiTFSI electrolyte, such as salt dissolution, conductivity, and viscosity, were determined. The cycling performances of batteries using Li4Ti5O12 (LTO) as the anode and LiNi1/3Co1/3Mn1/3O2 (NMC) as the cathode were determined. The results indicate that LTO/NMC batteries exhibit excellent rate capabilities with a columbic efficiency close to 100 %. As an example, cells were able to reach a capacity of 165 mAhg(-1) at 0.1C and a capacity retention of more than 98% after 200 cycles at 0.5 C. In addition, electrodes analyses by SEM, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy after cycling confirming minimal surface changes of the electrodes in the studied battery system.
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| 42. |
- Feng, Yingxin, 1994, et al.
(författare)
-
Kinetic Monte Carlo Simulations of Low-Temperature NH 3 -SCR over Cu-Exchanged Chabazite
- 2024
-
Ingår i: ChemPhysChem. - 1439-7641 .- 1439-4235. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- Cu-exchanged chabazite (Cu-CHA) is widely used for ammonia assisted selective catalytic reduction of nitrogen oxides (NH3-SCR). The Cu+ ions are at low temperatures solvated by NH3 forming mobile [Cu(NH3)2]+ complexes. The dynamic behaviour of the complexes is critical as O2 adsorption requires a pair of complexes to form a [Cu2(NH3)4O2]2+ peroxo-species over which NO couples with NH3. Here we introduce a first principles-based kinetic Monte Carlo approach to explore the effect of the Al-distribution on the reaction kinetics of NH3-SCR over Cu-CHA. The method allows us to scrutinize the interplay between the pairing of [Cu(NH3)2]+ complexes and the reaction landscape for the NH3-SCR reaction over the peroxo-complex. The Al-distribution affects the stability of the [Cu(NH3)2]+ pairs as well as the kinetic parameters of the SCR-reaction. The turn-over frequency is determined by the stability of the [Cu(NH3)2]+ pairs and the relative strength of NO and NH3 adsorption once a pair is present. The results establish the hierarchy of effects that influences the performance of Cu-CHA over NH3-SCR and provide a computational basis for further development of the Cu-CHA material.
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| 43. |
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| 44. |
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| 45. |
- Freitag, Marina, et al.
(författare)
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Supramolecular Hemicage Cobalt Mediators for Dye-Sensitized Solar Cells
- 2016
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 17:23, s. 3845-3852
-
Tidskriftsartikel (refereegranskat)abstract
- A new class of dye-sensitized solar cells (DSSCs) using the hemicage cobalt-based mediator [Co(ttb)](2+/3+) with the highly preorganized hexadentate ligand 5,5 '', 5 ''''-((2,4,6-triethyl benzene-1,3,5-triyl)tris(ethane-2,1-diyl))tri-2,2'-bipyridine (ttb) has been fully investigated. The performances of DSSCs sensitized with organic D-p-A dyes utilizing either [Co(ttb)](2+/3+) or the conventional [Co(bpy)(3)](2+/3+) (bpy = 2,2'-bipyridine) redox mediator are comparable under 1000 Wm(-2) AM 1.5 G illumination. However, the hemicage complexes exhibit exceptional stability under thermal and light stress. In particular, a 120-hour continuous light illumination stability test for DSSCs using [Co(ttb)](2+/3+) resulted in a 10% increase in the performance, whereas a 40% decrease in performance was found for [Co(bpy)(3)](2+/3+) electrolyte-based DSSCs under the same conditions. These results demonstrate the great promise of [Co(ttb)](2+/3+) complexes as redox mediators for efficient, cost-effective, large-scale DSSC devices.
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| 46. |
- Friedman, Ran
(författare)
-
Estimating the Gibbs Hydration Energies of Actinium and Trans-Plutonium Actinides
- 2023
-
Ingår i: ChemPhysChem. - : John Wiley & Sons. - 1439-4235 .- 1439-7641. ; 24:2
-
Tidskriftsartikel (refereegranskat)abstract
- The use of actinides for medical, scientific and technological purposes has gained momentum in the recent years. This creates a need to understand their interactions with biomolecules, both at the interface and as they become complexed. Calculation of the Gibbs binding energies of the ions to biomolecules, i. e., the Gibbs energy change associated with a transfer of an ion from the water phase to its binding site, could help to understand the actinides' toxicities and to design agents that bind them with high affinities. To this end, there is a need to obtain accurate reference values for actinide hydration, that for most actinides are not available from experiment. In this study, a set of ionic radii is developed that enables future calculations of binding energies for Pu3+ and five actinides with renewed scientific and technological interest: Ac3+, Am3+, Cm3+, Bk3+ and Cf3+. Reference hydration energies were calculated using quantum chemistry and ion solvation theory and agree well for all ions except Ac3+, where ion solvation theory seems to underestimate the magnitude of the Gibbs hydration energy. The set of radii and reference energies that are presented here provide means to calculate binding energies for actinides and biomolecules.
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| 47. |
- Friedman, Ran
(författare)
-
Specific Ion and Concentration Effects in Acetate Solutions with Na+, K+ and Cs
- 2019
-
Ingår i: ChemPhysChem. - : Wiley-Blackwell. - 1439-4235 .- 1439-7641. ; 20:8, s. 1006-1010
-
Tidskriftsartikel (refereegranskat)abstract
- How salt ions affect solutes and the water beyond the solvation shell is not well understood. Molecular dynamics simulations of alkali-acetate solutions were analysed here in order to examine if, and how, different cations and solute concentrations affect the water structure and the interactions between water and acetates. The results revealed that water structure is perturbed to more than 1 nm away from the acetates and that this effect is more pronounced in physiological than in molar electrolyte concentrations. Analysis of simulations of a soluble protein revealed that the water orientation is perturbed to at least 1.5 nm from the protein structure. Furthermore, modifications to the orientation of water around carboxylate side chains were shown to depend on the local environment on the protein surface, and could extend to well over 1 nm, which may have an effect on protein dynamics during MD simulations in small water boxes.
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| 48. |
- Garcia Cuesta, I, et al.
(författare)
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Carbon nanorings: A challenge to theoretical chemistry
- 2006
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 7:12, s. 2503-2507
-
Tidskriftsartikel (refereegranskat)abstract
- High-level quantum-chemical methods show that the binding in the inclusion complex of hexamethylbenzene (HMB) in 6-cycloparaphenitacetylene (6-CPPA) cannot be explained only in terms of electrostatic interactions-caused by the polarization associated to curved a-conjugated systems-and the inclusion of dispersion forces is definitely needed. The theoretical description of van der Wools interactions is notoriously complicated and in fact some DFT methods cannot even predict the existence of the relatively small supromolecular nonoring studied here. However, ab initio MP2 calculations agree with experimental data and show that, in the considered complex, the HMB fragment is placed at the center of the 6-CPPA ring. The binding energy, which is not available experimentally, is calculated to be around - 14 kcal mol(-1) with a lower limit of - 19 kcal mol(-1).
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| 49. |
- Gazdag, Tamás, et al.
(författare)
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An Exploration of Substituent Effects on the Photophysical Properties of Monobenzopentalenes
- 2024
-
Ingår i: ChemPhysChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-7641 .- 1439-4235. ; 25:7
-
Tidskriftsartikel (refereegranskat)abstract
- Monobenzopentalenes have received moderate attention compared to dibenzopentalenes, yet their accessibility as stable, non-symmetric structures with diverse substituents could be interesting for materials applications, including molecular photonics. Recently, monobenzopentalene was considered computationally as a potential chromophore for singlet fission (SF) photovoltaics. To advance this compound class towards photonics applications, the excited state energetics must be characterized, computationally and experimentally. In this report we synthesized a series of stable substituted monobenzopentalenes and provided the first experimental exploration of their photophysical properties. Structural and opto-electronic characterization revealed that all derivatives showed 1H NMR shifts in the olefinic region, bond length alternation in the pentalene unit, low-intensity absorptions reflecting the ground-state antiaromatic character and in turn the symmetry forbidden HOMO-to-LUMO transitions of ~2 eV and redox amphotericity. This was also supported by computed aromaticity indices (NICS, ACID, HOMA). Accordingly, substituents did not affect the fulfilment of the energetic criterion of SF, as the computed excited-state energy levels satisfied the required E(S1)/E(T1)>2 relationship. Further spectroscopic measurements revealed a concentration dependent quenching of the excited state and population of the S2 state on the nanosecond timescale, providing initial evidence for unusual photophysics and an alternative entry point for singlet fission with monobenzopentalenes.
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| 50. |
- Gedefaw, Desta, et al.
(författare)
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Design, Synthesis and Computational Study of Fluorinated Quinoxaline-Oligothiophene-based Conjugated Polymers with Broad Spectral Coverage
- 2018
-
Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 19:24, s. 3393-3400
-
Tidskriftsartikel (refereegranskat)abstract
- Donor-acceptor (D-A) copolymers typically show two absorption peaks in the visible region, flanking a valley region of limited absorptivity. One strategy for more panchromatic light harvesting is to incorporate side-groups orthogonal to the polymer backbone, which enable 2D pi conjugation and can give rise to additional absorption peaks. Here we design and synthesize two D-A polymers which both carry a fluorinated quinoxaline acceptor unit, but while P1 includes a benzodithiophene donor moiety with thiophene side-groups (2D-BDT), the P2 polymer lacks 2D conjugation in its simpler pentathiophene donor segment. The P1 polymer consequently shows an atypical absorption profile with more panchromatic absorption with no apparent valley in the spectrum. In order to understand the structure-electronic relations, the optical and electrochemical properties were predicted using a previously developed computational approach. The predicted optical properties show very good agreement with the experimental results. Solar cells made from P1 show a short-circuit current more than twice as large as P2, attributed to its enhanced spectral coverage. However, poor fill factors limit the preliminary power conversion efficiencies to 3.3 % for P1 and 1.0 % for P2 as blended with PCBM[70] in a 1 : 1.5 (w/w) ratio.
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