MARCH 2013 -

Angew. Chem. Int. Ed. 2013, 52, 2038 –2041.

Enhancement of Activity and Selectivity in Acid-Catalyzed Reactions by Dealuminated Hierarchical Zeolites.
Petr Sazama, Zdeněk Sobalik, Jiří Dědeček, Ivo Jakubec, Vasile Parvulescu, Zdeněk Bastl, Jiří Rathouský, and Hana Jirglová.

Abstract: Shape-selective reactions: Highly selective catalysts are obtained by alkaline and subsequent acid leaching of conventionally prepared zeolites. Active sites that are located in the shape-selective environment of micropores and accessible through mesopores (see picture) provide high selectivity and activity in acid-catalyzed reactions (more read in article).

Faraday Discuss., 2013, 160, 341-358.

Interactions of monovalent salts with cationic lipid bilayers.
Šárka Pokorná, Piotr Jurkiewicz, Lukasz Cwiklik, Mario Vazdar and Martin
Hof.

Abstract: The influence of monovalent salts (NaF, NaCl, NaBr, NaClO₄, KCl) on the properties of lipid bilayers composed of binary mixtures of zwitterionic DOPC (dioleoylphosphatidylcholine) and cationic DOTAP dioleoyltrimethylammoniumpropane) is experimentally measured and numerically simulated. Both approaches report a specific adsorption of the studied anions at the cationic bilayer. The adsorption is enhanced for higher content of DOTAP in DOPC/DOTAP mixtures and for larger anions (Br⁻and ClO₄⁻).... (read more in article).


ARCHIVE 2009-2013......

FEBRUARY 2013 -

Journal of Catalysis, 2013, 299, 109–118.

Pulsed laser deposition of bimetallic gold–platinum nanoparticles on cerium oxide and their characterisation by X-ray photoelectron spectroscopy and temperature-programmed desorption of isotopically labelled carbon monoxide.
Plšek, Jan; Bastl, Zdeněk.

Abstract: Bimetallic Au–Pt nanoparticles on cerium oxide supports were prepared using pulsed laser deposition (PLD) at room temperature and investigated using X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) of isotopically labelled carbon monoxide ¹³C¹⁸O. The metal deposition caused a partial reduction of Ce₄⁺ to Ce₃⁺. Two components in the spectra of Au (4f) and Pt (4f) photoelectrons were observed and assigned to the charged and metallic state of metals in the nanodeposits. The abundance of the charged species decreased with an increasing amount of the deposited metals and with thermal treatment of the samples... (read more).

J. Phys. Chem. Lett. , 2013, (4), 589-595.

Single-Molecule Conductance in a Series of Extended Viologen Molecules.
V. Kolivoška, M. Valášek, M. Gál, R. Sokolová, J. Bulíčková, L. Pospíšil,
G. Meszáros, M. Hromadová.

Abstract: Single-molecule conductance in a series of extended viologen molecules was measured at room temperature using a gold–molecule–gold scanning tunneling microscopy break junction arrangement. Conductance values for individual molecules change from 4.8 ± 1.2 nS for the shortest compound to 2.9 ± 1.0 nS for the compound with six repeating units and length of 11 nm. The latter value is almost 3 orders of magnitude higher than that reported for all-carbon-based aromatic molecular wires of comparable length. On the basis of the length of the molecules, an attenuation factor of only 0.06 ± 0.004 nm^–1 (0.006 ± 0.0004 Å^–1) was obtained. To the best of our knowledge, this is the smallest value reported for the conductance attenuation in a series of molecular wires (read more).

JANUARY 2013 -

Journal of Catalysis, 299, 2013, pp. 188-203.

Structure and critical function of Fe and acid sites in Fe-ZSM-5 in propane
oxidative dehydrogenation with N₂O and N₂O decomposition.
Petr Sazama, Naveen K. Sathu, Edyta Tabor, Blanka Wichterlová, Štěpán Sklenák, Zdeněk Sobalík.

Abstract: The structure and population of ion-exchanged Fe ions, Fe-oxo species, and Fe-oxo oligomers and Fe₂O₃ oxide particles and the concentration of acid sites in non-steamed and steamed Fe-ZSM-5 were elucidated using semi-quantitative Mössbauer and FTIR analysis supplemented by UV–Vis and H2-TPR. Differences in the concentration of the individual Fe species and acid sites were related to the activity and time-on-stream behavior of Fe-zeolites in decomposition of N₂O and oxidative dehydrogenation of propane to propene with N₂O. The evacuated non-steamed FeH-ZSM-5 contained high concentration of Brønsted sites and predominantly bare Fe(II) ions (72%), and less mono- and dinuclear Fe(III) (16–19%) and oligomeric Fe(III)-oxo species (9–12%). The steamed Fe(H)-ZSM-5st zeolites were greatly reorganized, resulting in a low concentration of both the Brønsted sites and bare Fe(II) ions, and the Td-coordinated Fe(III) ions in the Fesingle bondAlsingle bondSi extra-framework species (43–47%) and Fe-oxide-like particles (30–33%) prevailed. .. (read more).


J. Am. Chem. Soc., 2012, 134 (51), pp 20788–20796.

On the Road from Formamide Ices to Nucleobases: IR-Spectroscopic Observation of a Direct Reaction between Cyano Radicals and Formamide in a High-Energy Impact Event (article here).
Ferus M., Civiš S., Mládek A., Šponer J., Juha L., Šponer J.E..

Abstract: The formamide-based synthesis of nucleic acids is considered as a onaqueous scenario for the emergence of biomolecules from inorganic matter. In the current study, we scrutinized the chemical composition of formamide ices mixed with an FeNi meteorite material treated with laser-induced dielectric breakdown plasma created in nitrogen buffer gas. These experiments aimed to capture the first steps of those chemical transformations that may lead to the formation of nucleobases during the impact of an extraterrestrial icy body containing formamide on an early Earth atmosphere. High-resolution FT-IR spectroscopy combined with quantum chemical calculations was used to analyze the volatile fraction of the products formed during such an event. We have found that the spectrum of the evaporated formamide ices is dominated by the spectral signatures of the dimeric form of formamide. Upon exposure to laser sparks, new well-defined bands appear in the spectrum centered at 820, 995, and 1650 cm–1. On the basis of quantum chemical calculations, these bands can be assigned to the absorptions of 2-amino-2-hydroxy-acetonitrile and to 2-amino-2-hydroxy-malononitrile, which are formed in a direct reaction between formamide and CN• radicals upon the high-energy impact event. We also show that there is an exergonic reaction route via these intermediates leading to iaminomaleonitrile, which is generally considered to play a key role in the synthesis of nucleobases.

DECEMBER 2012 -

Electrochemistry Communications, 24, 2012, 25-27 (article here).

Transfer of heparin polyion across a polarized water/ionic liquid membrane interface.
Langmaier Jan, Samec Zdeněk, Samcová Eva, Tůma Per.

Abstract: Cyclic voltammetry is used to investigate the transfer of heparin polyion across the interface between water and the ionic liquid (IL) membrane composed of tridodecylmethylammonium cation (TDMA(+)) and tetrakis[3,5-bis(trifluoromethyl) phenyl]borate anion (TFPB-). Study reveals a tunable effect of the semihydrophobic tetraalkylammonium cations (TAA(+)) present at trace concentrations in the aqueous solution containing heparin. Theoretical considerations based on the mixed-potential concept and experimental evidence suggest that the TAA(+) cations promote the extraction of heparin into the IL phase, from which heparin can be stripped off by applied potential providing a well-separated current signal. A new method for the amperometric detection of heparin is proposed.


Chemistry - A European Journal, 18 (43), 2012, 13877-13884.

Effects of Heat Treatment on Raman Spectra of Two-Layer ¹²C/¹³C Graphene (article here).
Kalbáč Martin, Frank Otakar, Kavan Ladislav.

Abstract: The Raman spectra of two-layered graphene on a silicon substrate were studied in the temperature range from 298 to 1073 K in an inert atmosphere. Isotopic engineering was used to fabricate two-layer graphene specimens containing ¹³C atoms in the top layer and ¹²C atoms in the bottom layer, which allowed the behavior of each particular layer to be distinguished as a function of temperature. It is demonstrated that the top layer exhibits much lower Raman temperature coefficients than the bottom one for both the G and the G' modes. We suggest that the changes in the Raman spectra of graphene observed during thermal cycling are predominantly caused by a superposition of two effects, namely, the mechanical stress in graphene exerted by the substrate and the intrinsic changes in the graphene lattice caused by the temperature itself. The top graphene layer is proposed to be more relaxed than the bottom graphene layer and thus reflects almost exclusively the temperature variations as a freestanding graphene layer would.

NOVEMBER 2012 -

Journal of American Chemical Society, 134 (40), 2012, 16671-16692.

Ruthenium Stilbenyl and Diruthenium Distyrylethene Complexes: Aspects of
Electron Delocalization and Electrocatalyzed Isomerization of the Z-Isomer
Linseis, Michael; Záliš, Stanislav; Zabel, Manfred; et al.

Abstract: Regio- and stereoselective insertion of the terminal ethynyl functions of 4-ethynylstilbene, the E and Z isomers of 4,4^′-bis(ethynylphenyl)ethene and a backbone-rigidified cyclohexenyl derivative of the Z isomer into the Ru–H bond of the complex RuClH(CO)(PⁱPr₃)₂provides the corresponding vinyl ruthenium complexes, which have been characterized spectroscopically and by X-ray crystallography. Large red shifts of the UV/vis absorption bands evidence efficient incorporation of the vinyl metal subunit(s) into the conjugated π-system. All complexes oxidize at low potentials. The various oxidized forms of all complexes were generated and characterized by UV/vis/NIR, IR and EPR spectroscopies. These studies indicated electrocatalytic Z→E isomerization of the oxidized Z-distyrylethene complex Ru-Z2, which is prevented in its backbone-rigidified derivative Ru-Z2fix (read more...)


small 8 (20), 2012, 3185–3191.

Microscopic Origin of the Fast Blue-Green Luminescence of Chemically Synthesized Non-oxidized Silicon Quantum Dots (article here).

Kateřina Dohnalová, Anna Fučíková , Chinnaswamy P. Umesh , Jana Humpolíčková , Jos M. J. Paulusse , Jan Valenta , Han Zuilhof , Martin Hof , and Tom Gregorkiewicz.

Abstract: The microscopic origin of the bright nanosecond blue-green photoluminescence (PL), frequently reported for synthesized organically terminated Si quantum dots (Si- QDs), has not been fully resolved, hampering potential applications of this interesting material. Here a comprehensive study of the PL from alkyl-terminated Si-QDs of 2–3 nm size, prepared by wet chemical synthesis is reported. Results obtained on the ensemble and those from the single nano-object level are compared, and they provide conclusive evidence that effi cient and tunable emission arises due to radiative recombination of electron–hole pairs confi ned in the Si-QDs. This understanding paves the way towards applications of chemical synthesis for the development of Si-QDs with tunable sizes and bandgaps.



OCTOBER 2012 -

Journal of Physical Chemistry C, 2012, 116 (35), pp 19046-19050 .

Raman Spectroscopy as a Tool to Address Individual Graphene Layers
in Few-Layer Graphene (article here).
Kalbáč, Martin; Kong, Jing; Dresselhaus, Mildred S.

Abstract: We developed a new general approach to address individual graphene sheets in few-layer graphene by Raman spectroscopy. Our method is based on isotope labeling of individual layers during their synthesis and subsequent transfer to form multilayered graphene. The power of the procedure is demonstrated in the analysis of the interactions of individual layers with the substrate and with the environment. In addition, we measured Raman spectra of individual graphene layers in 3-LG during electrochemical doping. We show that they do not exhibit the same level of doping as one another and the doping level is dependent on layer position with respect to the substrate.



J. Phys. Chem. Lett., 2012, 3, pp 3096–3101.
Nucleation of Mixed Nitric Acid–Water Ice Nanoparticles in Molecular Beams that Starts with a HNO₃ Molecule (article here).
J. Lengyel, A. Pysanenko, J. Kočišek, V. Poterya, Ch. Pradzynski, T. Zeuch, P.Slavíček, and Michal Fárník.

Abstract: Mixed (HNO₃)_m(H₂O)_n clusters generated in supersonic expansion of nitric acid vapor are investigated in two different experiments, time-of-flight mass spectrometry after electron ionization and Na doping and photoionization. This combination of complementary methods reveals that only clusters containing at least one acid molecule are generated, that is, the acid molecule serves as the nucleation center in the expansion. The experiments also suggest that at least four water molecules are needed for HNO₃ acidic dissociation. The clusters are undoubtedly generated, as proved by electron ionization; however, they are not detected by the Na doping due to a fast charge-transfer reaction between the Na atom and HNO₃. This points to limitations of the Na doping recently advocated as a general method for atmospheric aerosol detection. On the other hand, the combination of the two methods introduces a tool for detecting molecules with sizable electron affinity in clusters.

SEPTEMBER 2012 -

Carbon, 2012, Vol. 50 (10), 3682 - 3687.
The control of graphene double-layer formation in copper-catalyzed chemical vapor deposition (article here).

Kalbáč, M.; Frank, O.; Kavan, L.

Abstract: The growth of graphene during Cu-catalyzed chemical vapor deposition was studied using ¹²CH₄ and ¹³CH₄ precursor gasses. We suggest that the growth egins by the formation of a multilayer cluster. This seed increases its size but the growth speed of a particular layer depends on its proximity to the copper surface. The layer closest to the substrate grows fastest and thus further limits the growth rate of the upper layers. Nevertheless, the growth of the upper layers continues until the copper surface is completely blocked. It is shown that the upper layers can be removed by modification of the conditions of the growth by hydrogen etching.

Astronomy and Astrophysics, 2012, 545, A61, 10 pages.

Li I spectra in the 4.65–8.33 micron range: high-L states and oscillator strengths.
S. Civiš, M. Ferus, P. Kubelík, V. E. Chernov and E. M. Zanozina.

Abstract: Infrared (IR) astronomy capacities have rapidly developed in recent years thanks to several ground- and space-based facilities. To take advantage of these capabilities efficiently, a large amount of atomic data (such as line wavenumber, excited-level energy values, and oscillator strengths) are needed. These data are incomplete, in particular, for lithium whose abundances are important for several astrophysical problems.
Aims: No laboratory-measured spectra of Li I have been reported for wavelengths longward of 6.6 microns. We aim to find new Li I lines in the 4.65–8.33 microns range due to transitions between states with high orbital momentum (l ≥ 4) and to determine the excitation energies of these states... (more in article).

AUGUST 2012 -

Chemistry of Materials 24 (16), 2012, 3231-3239.

Synthesis of ZSM-5 Zeolites with Defined Distribution of Al Atoms in the Framework and Multinuclear MAS NMR Analysis of the Control of Al Distribution (article here).
Dedecek J., Balgová V., Pashkova V., Klein P., and Wichterlová B.


J. of Chemical Physics 137, 2012, 034304.
(article chosen as a Research Highlight featured on the journal website home page).

Uptake of atmospheric molecules by ice nanoparticles: Pickup cross sections (article here).
Jozef Lengyel, Jaroslav Kočišek, Viktoriya Poterya, Andriy Pysanenko, Pavla Svrčková, Michal Fárník, Dimitrios Zaouris, and Juraj Fedor.

Abstract: Uptake of several atmospheric molecules on free ice nanoparticles was investigated. Typical examples were chosen: water, methane, NOx species (NO, NO₂), hydrogen halides (HCl, HBr), and volatile organic compounds (CH₃OH, CH₃CH₂OH). The cross sections for pickup of these molecules on ice nanoparticles (H₂O)_N with the mean size of math ≈ 260 (diameter ∼2.3 nm) were measured in a molecular beam experiment. These cross sections were determined from the cluster beam velocity decrease due to the momentum transfer during the pickup process. For water molecules molecular dynamics simulations were performed to learn the details of the pickup process. The experimental results for water are in good agreement with the simulations. The pickup cross sections of ice particles of several nanometers in diameter can be more than 3 times larger than the geometrical cross sections of these particles. This can have significant consequences in modelling of atmospheric ice nanoparticles, e.g., their growth.

Publication has been identified on the list of Top 20 Most Read in July and in August 2012 !

JULY 2012 -

Inorganic Chemistry, 2012, 51 , 5128-5137.
Measured and Calculated Oxidation Potentials of 1-X-12-Y-CB₁₁Me₁₀^– Anions (article here).
Abdul Wahab, Brian Stepp, Christos Douvris, Michal Valášek, Jan Štursa, Jiřı́ Klı́ma, Mari-Carmen Piqueras, Raül Crespo, Jiřı́ Ludvı́k, and Josef Michl.

Abstract: Cyclic voltammetry of 31 icosahedral carborane anions 1-X-12-Y-CB₁₁Me₁₀^– at a Pt electrode in liquid SO₂ revealed a completely reversible one-electron oxidation even at low scan rates, except for the anions with Y = I, which are oxidized irreversibly up to a scan rate of 5.0 V/s, and the anion with X = COOH and Y = H, whose oxidation is irreversible at scan rates below 1.0 V/s. Relative reversible oxidation potentials agree well with RI-B3LYP/TZVPP,COSMO and significantly less well with RI-BP86/TZVPP,COSMO or RI-HF/TZVPP,COSMO calculated adiabatic electron detachment energies. Correlations with HOMO energies of the anions are nearly as good, even though the oxidized forms are subject to considerable Jahn–Teller distortion. Except for the anion with X = F and Y = Me, the oxidation potentials vary linearly with substituent σ_p Hammett constants. The slopes (reaction constants) are 0.31 and 0.55 V for positions 1 and 12, respectively.


J. Am. Chem. Soc. 134, 2012, 8655-8661.

Dramatically Enhanced Cleavage of the C–C Bond Using an Electrocatalytically Coupled Reaction (article here).
Qinggang He, Badri Shyam, Kateřina Macounová, Petr Krtil, David Ramaker, and Sanjeev Mukerjee.

Abstract: This paper describes a generalized approach for the selective electrocatalytic C–C bond splitting in aliphatic alcohols at low temperature in aqueous state, with ethanol as an example. We show that selective C–C bond cleavage, leading to carbon dioxide, is possible in high pH aqueous media at low overpotentials. This improved selectivity and activity is achieved using a solution-born co-catalyst based on Pb(IV) acetate, which controls the mode of the ethanol adsorption so as to facilitate direct activation of the C–C bond. The simultaneously formed under-potentially deposited (UPD) Pb and surface lead hydroxide change the functionality of the catalyst surface for efficient promotion of CO oxidation. The resulting catalyst retains an unprecedented ability to sustain the full oxidation reaction pathway on an extended time scale of hours as opposed to minutes without addition of Pb(IV) acetate.

JUNE 2012 -

Analytical Chemistry, 2012, 84 (11), pp 4979-4983.
Real-Time Quantification of Traces of Biogenic Volatile Selenium Compounds in Humid Air by Selected Ion Flow Tube Mass Spectrometry (article here).
Sovová K., Shestivská V., Španěl, P.

Abstract: iological volatilization of selenium, Se, in a contaminated area is an economical and environmentally friendly approach to phytoremediation techniques, but analytical methods for monitoring and studying volatile compounds released in the process of phytovolatilization are currently limited in their performance. Thus, a new method for real time quantification of trace amounts of the vapors of hydrogen selenide (H₂Se), methylselenol (CH₃SeH), dimethylselenide ((CH₃)₂Se), and dimethyldiselenide ((CH₃)₂Se₂) present in ambient air adjacent to living plants has been developed. This involves the characterization of the mechanism and kinetics of the reaction of H₃O⁺, NO⁺, and O₂^+• reagent ions with molecules of these compounds and then use of the rate constants so obtained to determine their absolute concentrations in air by selected ion flow tube mass spectrometry, SIFT-MS. The results of experiments demonstrating this method on emissions from maize (Zea mays) seedlings cultivated in Se rich medium are also presented.


Biophysical Journal, Vol.102 (9), 2012, 2104–2113.
Dynamics and Size of Cross-Linking-Induced Lipid Nanodomains in Model Membranes (article here).
Štefl M., Šachl R., Humpolíčková J., Cebecauer M., Macháň R., Kolářová M., Johansson L. B.-Å. , Hof. M.

Abstract: Changes of membrane organization upon cross-linking of its components trigger cell signaling response to various exogenous factors. Cross-linking of raft gangliosides GM1 with cholera toxin (CTxB) was shown to cause microscopic phase separation in model membranes, and the CTxB-GM1 complexes forming a minimal lipid raft unit are the subject of ongoing cell membrane research. Yet, those subdiffraction sized rafts have never been described in terms of size and dynamics. By means of two-color z-scan fluorescence correlation spectroscopy, we show that the nanosized domains are formed in model membranes at lower sphingomyelin (Sph) content than needed for the large-scale phase separation and that the CTxB-GM1 complexes are confined in the domains poorly stabilized with Sph. Förster resonance energy transfer together with Monte Carlo modeling of the donor decay response reveal the domain radius of ∼8 nm, which increases at higher Sph content. We bserved two types of domains behaving differently, which suggests a dual role of the cross-linker: first, local transient condensation of the GM1 molecules compensating for a lack of Sph and second, coalescence of existing nanodomains ending in large-scale phase separation.


MAY 2012 -

Astronomy & Astrophysics, 2012, 541, A125.
Potassium spectra in the 700–7000 cm^-1 domain: Transitions involving f-, g-, and h-states (article here).
S. Civiš, M. Ferus, P. Kubelík, P. Jelinek and V. E. Chernov.

Abstract:
Context - The infrared (IR) range is becoming increasingly important to astronomical studies of cool or dust-obscured objects, such as dwarfs, disks, or planets, and in the extended atmospheres of evolved stars. A general drawback of the IR spectral region is the much lower number of atomic lines available (relative to the visible and ultraviolet ranges).
Aims - We attempt to obtain new laboratory spectra to help us identify spectral lines in the IR. This may result in the discovery of new excited atomic levels that are difficult to compute theoretically with high accuracy, hence can be determined solely from IR lines.
Results - Precision laboratory measurements are presented for 38 KI lines in the infrared (including 25 lines not measured previously in the laboratory) range using time-resolved Fourier transform infrared spectroscopy. The 6g, 6h, and 7h levels of KI are observed for the first time, in addition to updated energy values of the other 23 KI levels and the f-values for the transitions involving these levels.
Conclusions - The recorded wave numbers are in good agreement with the data from the available solar spectrum atlases. Nevertheless, we correct their identification for three lines (1343.699, 1548.559, and 1556.986 cm^-1).


Catalysis Reviews:Science and Engineering, 2012, 54 (2), 135-223.

Siting and Distribution of Framework Aluminium Atoms in Silicon-Rich Zeolites and Impact on Catalysis (article here).
J. Dědeček, Z. Sobalík, B.Wichterlová.

Abstract:
Siting of Al atoms in the framework T sites, in zeolite rings and channel/cavity system, and the distribution of Al atoms between single Al atoms and close Al atoms in various Al-O-(Si-O)_n-Al sequences in Si-rich zeolites represent key parameters controlling properties of counter ion species. Framework Al siting and distribution is not random or controlled by simple rules and depends on the conditions of the zeolite synthesis. Al in Al-O-(Si-O)₂-Al in one 6-MR and single Al atoms predominate in Si-rich zeolites and their population can be varied to a large extent. The siting and distribution of framework Al atoms dramatically affect catalytic activity/selectivity both of protonic and transition metal ion-containing zeolite catalysts.

APRIL 2012 -

Chemical Communications, 2012, 48 (34), pp 4094-4096.
Competitive inhibition of a metal-free porphyrin oxygen-reduction catalyst by water (article here).
A.Trojánek, J. Langmaier, S. Záliš, Z. Samec.

Abstract:A stopped-flow method is used to study the effects of water and reactant acid anion TB⁻ = tetrakis(pentafluorophenyl)borate on the homogeneous oxygen reduction catalyzed by the protonated tetraphenylporphyrin. Observed competitive inhibition of the catalyst is linked to the DFT free energy of extraction of O₂, water, and TB⁻ from the porphyrin complex.

Nano Letters, 2012, 12 (2), pp 687-693 .
Phonon and Structural Changes in Deformed Bernal Stacked Bilayer Graphene (article here).
Frank, O., Bouša, M., Riaz, I., Jalil, R.,Novoselov, K. S., Tsoukleri, G., Parthenios, J., Kavan, L.,Papagelis, K., Galiotis, C.

Abstract: We present the first Raman spectroscopic study of Bernal bilayer graphene flakes under uniaxial tension. Apart from a purely mechanical behavior in flake regions where both layers are strained evenly, certain effects stem from inhomogeneous stress distribution across the layers. These phenomena such as the removal of inversion symmetry in bilayer graphene may have important implications in the band gap engineering, providing an alternative route to induce the formation of a band gap.

MARCH 2012 -

Chemical Communications, 2012, 48 (28), pp 3433-3435.
The oxidation of natural flavonoid quercetin (article here).
Sokolová, R., Ramešová, Š., Degano I., Hromadová, M., Gál, M., Žabka, J.

Abstract: This study explains the controversies in the literature concerning the number of electrons involved in the oxidation of quercetin. This stems from inappropriate
handling samples, which require strict anaerobic conditions. The redox potential of quercetin strongly depends on the pH and on the presence of dissociation forms in solution.

J. Chem. Theory Comput., 2012, 8 (2), pp 487–497.
Parallel Implementation of Multireference Coupled-Cluster Theories Based on the Reference-Level Parallelism (article here).
Jiří Brabec, Jiří Pittner, Hubertus J. J. van Dam, Edoardo Aprà, and Karol Kowalski.

Abstract: A novel algorithm for implementing a general type of multireference coupled-cluster (MRCC) theory based on the Jeziorski–Monkhorst exponential ansatz [Jeziorski, B.; Monkhorst, H. J. Phys. Rev. A1981, 24, 1668] is introduced. The proposed algorithm utilizes processor groups to calculate the equations for the MRCC amplitudes. In the basic formulation, each processor group constructs the equations related to a specific subset of references. By flexible choice of processor groups and subset of reference-specific sufficiency conditions designated to a given group, one can ensure optimum utilization of available computing resources. The performance of this algorithm is illustrated on the examples of the Brillouin–Wigner and Mukherjee MRCC methods with singles and doubles (BW-MRCCSD and Mk-MRCCSD). A significant improvement in scalability and in reduction of time to solution is reported with respect to recently reported parallel implementation of the BW-MRCCSD formalism [Brabec, J.; van Dam, H. J. J.; Kowalski, K.; Pittner, J. Chem. Phys. Lett.2011, 514, 347].

FEBRUARY 2012 -

J. Am. Chem. Soc. 134, 2012, 2691-2705.
Single-step versus Stepwise Two-electron Reduction of Polyarylpyridiniums: Insights from the Steric Switching of the Redox Potential Compression.
J. Fortage, C. Peltier, Ch. Perruchot, Y. Takemoto, Y. Teki, F. Bedioui, V. Marvaud, G. Dupeyre, L. Pospíšil, C. Adamo, M. Hromadová, I. Ciofini, Ph. Lainé.

Abstract: Contrary to 4,4′-dipyridinium (i.e., archetypal methyl viologen), which is reduced by two single-electron transfers (stepwise reduction), the 4,1′-dipyridinium isomer (so-called “head-to-tail” isomer) undergoes two electron transfers at apparently the same potential (single-step reduction). A combined theoretical and experimental study has been undertaken to establish that the latter electrochemical behavior, also observed for other polyarylpyridinium electrophores, is due to potential compression originating in a large structural rearrangement. (read more)

J. Phys. Chem. C 116 (5), 2012, 3379-3786 .
Electron Transfer Triggers Fast Dimer/Monomer Switching of Pyridinium and Quinolinium Cations (article here).
F. Teplý, M. Čížková, P. Slavíček, V. Kolivoška, J. Tarábek, M. Hromadová, L. Pospíšil.

Abstract: N-Heteroaromatic cations with quaternary pyridine-type nitrogen atoms have a rich application potential due to their bioactivity, fluorescence, and redox properties. Reactivityof radicals formed by reduction of such compounds is of key importance. We report the electron transfer mechanism of four novel compounds containing pyridinium, quinolinium, and benzothiazolium moiety. The reduction of pyridinium and quinolinium derivatives by one electron yields radicals that very rapidly form σ-dimers. Dimers can be converted to parent cations by oxidation, which proceeds at considerably higher potentials. Hence the dimerization can be reversibly switched by application of the appropriate electrode potential. In contrast, in benzothiazolium derivative the electron transfer yields a stable radical in which the follow-up dimerization reaction is completely blocked. Analysis of experimental data as well as theoretical models led to the identification of dimerization sites in reduced pyridinium and quinolinium species. We show the advantage of using the combination of electrochemical impedance data and simulation of cyclic voltammograms for estimation of kinetic parameters of the heterogeneous electron transfer rates and the coupled chemical reactions.

JANUARY 2012 -

Nano Letters, 11 (12), 2011, 5501–5506.
Graphene Nanoplatelets Outperforming Platinum as the Electrocatalyst in Co-Bipyridine-Mediated Dye-Sensitized Solar Cells (article here).
Kavan, L; Yum, JH; Gratzel, M.

Abstract: Graphene nanoplatelets (GNP) in the form of thin semitransparent films on F-doped SnO2 (FTO) exhibit high electrocatalytic activity for the Co(bpy)₃^3+/2+ redox couple in acetonitrile electrolyte solution. The GNP film is superior to the traditional electrocatalyst, that is, platinum, both in charge-transfer resistance (exchange current) and in electrochemical stability under prolonged potential cycling. The good electrochemical performance of GNP is readily applicable for dye-sensitized solar cells with Y123-sensitized TiO₂ photoanodes and Co(bpy)₃^3+/2+ as the redox shuttle. The dye-sensitized solar cell with GNP cathode is superior to that with the Pt-FTO cathode particularly in fill factor and in power conversion efficiency at higher illumination intensity.


Biochimica et Biophysica Acta, 1818, 2012, 609–616.
Structure, dynamics, and hydration of POPC/POPS bilayers suspended in NaCl, KCl, and CsCl solutions
P.Jurkiewicz, L. Cwiklik, A.Vojtíšková, P.Jungwirth, M. Hof

Abstract: Effects of alkali metal chlorides on the properties of mixed negatively charged lipid bilayers are experimentally measured and numerically simulated. Addition of 20 mol% of negatively charged phosphatidylserine to zwitterionic phosphatidylcholine strengthens adsorption of monovalent cations revealing their specificity, in the following order: Cs⁺ K⁺ Na⁺. Time-resolved fluorescence solvent relaxation shows significant decrease both in mobility and hydration of the lipid carbonyls probed by Laurdan upon addition of the cations. The experimental findings are supported by molecular dynamics simulations, which show deep penetration of the cations down to the glycerol level of the lipid bilayer where they pair with oxygen atoms of carbonyl groups (with pairing with sn-2 carbonyl being about twice stronger than pairing with the sn-1 one). Moreover, the cations bridge neighboring lipids forming clusters of up to 4 lipid molecules, which decreases the area per lipid, thickens the membrane, causes rising of lipid headgroups, and hinders lipid dynamics. All these effects follow the same Hofmeister ordering as the cationic adsorption to the bilayer.

DECEMBER 2011 -


ACS NANO, 5 (11), 2011, 9171-9178.
Graphene Nanoplatelet Cathode for Co(III)/(II) Mediated Dye-Sensitized Solar Cells (article here).
Kavan, L; Yum, JH; Nazeeruddin, MK; Gratzel, M.

Abstract: Graphene nanoplatelets (GNP) in the form of thin semitransparent film on F-doped SnO₂(FTO) exhibit high electrocatalytic activity for Co(L)₂; where L is 6-(1H-pyrazol-1-yl)-2,2'-bipyridine.
The exchange current densities for the Co^2+/3+(L)₂ redox reaction scaled linearly with the GNP film's optical absorbance, and they were by 1-2 orders of magnitude larger than those for the l₃^-/l^- couple on the same electrode.
The electrocatalytic activity of GNP films with optical the Co^2+/3+(L)₂ redox reaction. Dye-sensitized solar cells with Y123 dye adsorbed on TiO₂ photoanode achieved energy conversion efficiencies between 8 and 10% for both GNP and Pt-based cathodes. However, the cell with GNP cathode is superior to that with Pt-FTO cathode particularly in fill factors and in the efficiency at higher illumination intensities.


Biophysical Journal, 101 (11), 2011, L60-L62.
Limitations of Electronic Energy Transfer in the Determination of Lipid Nanodomain Sizes.
R. Šachl, J. Humpolíčková, M. Štefl, L. B.-Å. Johansson, M. Hof.

Abstract: Even though superresolution microscopy indicates that size of plasma membrane rafts is <20 nm, those structures have never been observed. Förster resonance energy transfer (FRET) is therefore still the most powerful optical method for characterization of such domains. In this letter we investigate relation between nanodomain affinity of a donor-acceptor (D/A) pair and the detectable nanodomain size/area. We show that probes with high affinity to the liquid-ordered (Lo) phase are required for detecting domain sizes of a few nanometers, and/or domains that occupy a few percent of the bilayer area. A combination of donors and acceptors that prefer different phases is the more favorable approach. For instance, a D/A pair with the distribution constant of donors KD = 5 and acceptors KA = 0.01 can resolve a broad spectrum of nanodomain sizes. On the other hand, currently available donors and acceptors that prefer the same phase, either the liquid-disordered (Ld) or Lo phase, are not so convenient for determining domain sizes <20 nm. Here the detection limits of FRET experiments employing several commonly used D/A pairs have been investigated (read more).

NOVEMBER 2011 -

Low-Energy Electron Scattering from Molecules, Biomolecules and Surfaces.
Čársky P.; R. Čurík (Eds.).
1st Edition., 2011, 296 p., CRC Press. ISBN-10: 1439839107; ISBN-13: 978-1439839102

• CatalRevSciEng_ 54_2012_135_223.pdf (2.12MB)