Organic-inorganic metal halide perovskites have recently attracted increasing attention as highly efficient light harvesting materials for photovoltaic applications. However, the precise control of crystallization and morphology of organometallic perovskites deposited from solution, considered crucial for enhancing the final photovoltaic performance, remains challenging. In this context, here, we report on growing microcrystalline deposits of CH3NH3PbI3 (MAPbI3), by one-step solution casting on cylinde-shaped quartz substrates (rods). We show that the substrate curvature has a strong influence on morphology of the obtained polycrystalline deposits of MAPbI3. Although the crystalline width and length markedly decreased for substrates with higher curvatures, the photoluminescence (PL) spectral peak positions did not significantly evolve for MAPbI3 deposits on substrates with different diameters. The crystalline size reduction and denser coverage of microcrystalline MAPbI3 deposits on cylinder-shaped substrates with higher curvatures were attributed to two major contributions, both related to the annealing step of the MAPbI3 deposits. In particular, the diameter-dependent variability of the heat capacities and the substrate curvature-enhanced solvent evaporation rate seemed to contribute the most to the crystallization process and the resulting morphology changes of MAPbI3 deposits on cylinder-shaped quartz substrates with various diameters. The longitudinal geometry of cylinder-shaped substrates provided also a facile solution for checking the PL response of the deposits of MAPbI3 exposed to the flow of various gaseous media, such as oxygen, nitrogen and argon. Overall, the approach reported herein inspires novel, cylinder-shaped geometries of MAPbI3 deposits, which can find applications in low-cost photo-optical devices, including gas sensors.

A combined resistivity and hard x-ray diffraction study of superconductivity and charge ordering in $\mathrm{Ir_{1-x}Pt_xTe_2}$ as a function of Pt substitution and externally applied hydrostatic pressure is presented. Experiments are focused on samples near the critical composition $x_c\sim 0.045$ where competition and switching between charge order and superconductivity is established. We show that charge order as a function of pressure in $\mathrm{Ir_{0.95}Pt_{0.05}Te_{2}}$ is preempted - and hence triggered - by a structural transition. Charge ordering appears uniaxially along the short crystallographic (1,0,1) domain axis with a $\mathrm{(\frac{1}{5},0,\frac{1}{5})}$ modulation. Based on these results we draw a charge-order phase diagram and argue that the stripe ordering constrains superconductivity in two-dimensional sheets.

A combined resistivity and hard x-ray diffraction study of superconductivity and charge ordering in Ir Ir(1-x)PtxTe(2), as a function of Pt substitution and externally applied hydrostatic pressure, is presented. Experiments are focused on samples near the critical composition x(c)-0.045 where competition and switching between charge order and superconductivity is established. We show that charge order as a function of pressure in Ir0.95Pt0.05Te2 is preempted-and hence triggered - by a structural transition. Charge ordering appears uniaxially along the short crystallographic (1, 0, 1) domain axis with a (1/5, 0, 1/5) modulation. Based on these results we draw a charge-order phase diagram and discuss the relation between stripe ordering and superconductivity.

A combined resistivity and hard x-ray diffraction study of superconductivity and charge ordering in Ir1−xPtxTe2, as a function of Pt substitution and externally applied hydrostatic pressure, is presented. Experiments are focused on samples near the critical composition xc ∼ 0.045 where competition and switching between charge order and superconductivity is established. We show that charge order as a function of pressure in Ir0.95Pt0.05Te2 is preempted — and hence triggered — by a structural transition. Charge ordering appears uniaxially along the short crystallographic (1,0,1) domain axis with a (1/5,0,1/5) modulation. Based on these results we draw a charge-order phase diagram and discuss the relation between stripe ordering and superconductivity.

We report the synthesis, structure, and superconducting properties of single crystals of SmFeAsOHx. The crystals were grown at high pressure and high temperature using a cubic anvil technique. H-1-NMR studies confirm the presence of H atoms in the samples. Single crystal x-ray diffraction analyses demonstrate a remarkable disorder in the Sm2O2 layers induced by hydrogen incorporation and reveal that the H positions are compatible with a H2O-like geometry inside the crystals. We have measured the magnetotransport properties of SmFeAsOHx single crystals with x = 0.07, 0.11, and 0.16 in magnetic field up to 16 T, oriented along the two main crystallographic directions. The results show an increase of the critical temperature with hydrogen content. The zero-temperature upper critical fields and the magnetic anisotropy are calculated as a function of the hydrogen content. SmFeAsOHx crystals present significantly higher upper critical fields and magnetic anisotropies compared to SmFeAsO1-x F-x compounds.

Understanding the relationship between the superconducting, the neighboring insulating, and the normal metallic state above T-c is a major challenge for all unconventional superconductors. The molecular A(3)C(60) fulleride superconductors have a parent antiferromagnetic insulator in common with the atom-based cuprates, but here, the C(60)(3-)electronic structure controls the geometry and spin state of the structural building unit via the on-molecule JahnTeller effect. We identify the Jahn-Teller metal as a fluctuating microscopically heterogeneous coexistence of both localized Jahn-Teller-active and itinerant electrons that connects the insulating and superconducting states of fullerides. The balance between these molecular and extended lattice features of the electrons at the Fermi level gives a dome-shaped variation of T-c with interfulleride separation, demonstrating molecular electronic structure control of superconductivity.

The hybrid halide perovskites, the very performant compounds in photovoltaic applications, possess large Seebeck coefficient and low thermal conductivity making them potentially interesting high figure of merit (ZT) materials. For this purpose one needs to tune the electrical conductivity of these semiconductors to higher values. We have studied the CH_3NH_3MI_3 (M=Pb,Sn) samples in pristine form showing very low ZT values for both materials; however, photoinduced doping (in M=Pb) and chemical doping (in M=Sn) indicate that, by further doping optimization, ZT can be enhanced toward unity and reach the performance level of the presently most efficient thermoelectric materials.

Hybrid assemblies based on conducting polymers and carbon nanomaterials with organized nanoscale structure are excellent candidates for various application schemes ranging from thermal management to electrochemical energy conversion and storage. In the case of macroscopic samples, however, precise control of the nanoscale structure has remained a major challenge to be solved for the scientific community. In this study we demonstrate possible routes to homogeneously infiltrate poly(3-hexylthiophene), poly(3,4-ethylenedioxythiophene), and polyaniline into macroscopic arrays of vertically aligned multiwalled carbon nanotubes (MWCNTAs). Electron microscopic images and Raman spectroscopic analysis (performed along the longitudinal dimension of the hybrid samples) both confirmed that optimization of the electropolymerization circumstances allowed fine tuning of the hybrid structure towards the targeted application. In this vein, three different application avenues were tested. The remarkable anisotropy in both the electrical and thermal conductivity of the nanocomposites makes them eminently attractive candidates to be deployed in thermal management. Thermoelectric studies, aimed to understand the effect of organized nanoscale morphology on the important parameters (Seebeck coefficient, electrical-, and thermal conductivity) compared to their non-organized hybrid counterparts. Finally, extraordinary high charge storage capacity values were registered for the MWCNTA/PANI hybrids (500 F g(-1) and 1-3 F cm(-2)). (C) 2015 Wiley Periodicals, Inc.

Human nucleolar phosphoprotein p140 (hNopp 140) is a highly phosphorylated protein inhibitor of casein kinase 2 (CK2). As in the case of many kinase-inhibitor systems, the inhibitor has been described to belong to the family of intrinsically disordered proteins (IDPs), which often utilize transient structural elements to bind their cognate enzyme. Here we investigated the structural status of this protein both to provide distinct lines of evidence for its disorder and to point out its transient structure potentially involved in interactions and also its tendency to aggregate. Structural disorder of hNopp140 is apparent by its anomalous electrophoretic mobility, protease sensitivity, heat stability, hydrodynamic behavior on size-exclusion chromatography, 1H NMR spectrum and differential scanning calorimetry scan. hNopp140 has a significant tendency to aggregate and the change of its circular dichroism spectrum in the presence of 0–80% TFE suggests a tendency to form local helical structures. Wide-line NMR measurements suggest the overall disordered character of the protein. In all, our data suggest that this protein falls into the pre-molten globule state of IDPs, with a significant tendency to become ordered in the presence of its partner as demonstrated in the presence of transcription factor IIB (TFIIB).

Haromfajta szen nanoszerkezettel foglalkoztunk: fullerenek es fulleridsok, szen nanocsovek, valamint szen nanocsovek es szerves molekulak alkotta hibrid rendszerek. Az első csoportba tartozo anyagokat hőmerseklet- es nyomasfuggő rezgesi spektroszkopiaval vizsgaltuk, es kimutattuk a molekularis jellemzők es a kristalyok makroszkopikus tulajdonsagai kozti osszefuggeseket. A mikroszkopikus effektusok a molekulak kozti polimerizacios reakcio kovetese (C70), molekularis Jahn-Teller torzulas (tetrafenil-foszfonium-C60), valamint Mott-lokalizacio altal okozott elektronkorrelacio es Jahn-Teller effektus kombinacioja (Cs3C60). Szen nanocsovek szeles savu optikai spektrumabol az elektronszerkezetre, nagy erzekenyseggel mert infravoros spektrumukbol a csovek rezgesi modusaira kovetkeztettunk. Mivel kulonboző atmerőjű csovekből allo mintasorozatokat vizsgaltunk, meg tudtuk allapitani ezeknek a mennyisegeknek a csovek geometriajatol valo fuggeset. Szen nanocső-szerves molekula hibridek kotesi allapotat infravoros es optikai spektroszkopia segitsegevel hataroztuk meg. Eredmenyeinket nemzetkozi folyoiratokban publikaltuk, ezek kozul legfontosabbak ket Physical Review B, ket Journal of Physical Chemistry C, egy Journal of Applied Physics, egy Journal of Physical Chemistry Letters, egy Nature Communications folyoiratcikk, tovabba het meghivott előadas nemzetkozi konferenciakon. | We investigated three types of carbon nanostructures: fullerenes and fulleride salts, carbon nanotubes and hybrid systems composed of carbon nanotubes and organic molecules. Materials belonging to the first group were studied by temperature- and pressure-dependent vibrational spectroscopy, and determined the relationship between molecular features and macroscopic crystal properties. Such microscopic effects are molecular polimerization reactions (C70), molecular Jahn-Teller distortion (tetraphenylphosphonium-C60), and the combination of electron correlations due to Mott localization and the Jahn-Teller effect (Cs3C60). From the wide-range optical spectra of carbon nanotubes we could determine the electronic structure, and from measuring their infrared spectra with high sensitivity, their vibrational modes. Having studied series of samples with different tube diameter, the dependence of these quantities on the geometry of the tubes could be established. The bonding configuration in carbon nanotube-organic molecule hybrids was determined by infrared and optical spectroscopy as well. Our results were published in international journals, of which the most important are four papers in Physical Review B, two in Journal of Physical Chemistry, one in Science and one in Nature Materials, in addition to seven invited lectures at international conferences.

Cs3C60 is a correlated superconductor under pressure, but an insulator under ambient conditions. The mechanism causing this insulating behavior is the combination of Mott localization and the dynamic Jahn-Teller effect. We show evidence from infrared spectroscopy for the dynamic Jahn-Teller distortion. The continuous change with temperature of the splitting of infrared lines is typical Jahn-Teller behavior, reflecting the change in population of solid-state conformers. We conclude that the electronic and magnetic solid-state properties of the insulating state are controlled by molecular phenomena. We estimate the time scale of the dynamic JahnTeller effect to be above 10(-11) s and the energy difference between the conformers less than 20 cm(-1).

The 'expanded fulleride' Cs(3)C(60) is an antiferromagnetic insulator in its normal state and becomes a molecular superconductor with T(c) as high as 38 K under pressure. There is mounting evidence that superconductivity is not of the conventional BCS type and electron-electron interactions are essential for its explanation. Here we present evidence for the dynamic Jahn-Teller effect as the source of the dramatic change in electronic structure occurring during the transition from the metallic to the localized state. We apply infrared spectroscopy, which can detect subtle changes in the shape of the C(60)3- ion due to the Jahn-Teller distortion. The temperature dependence of the spectra in the insulating phase can be explained by the gradual transformation from two temperature-dependent solid-state conformers to a single one, typical and unique for Jahn-Teller systems. These results unequivocally establish the relevance of the dynamic Jahn-Teller effect to overcoming Hund's rule and forming a low-spin state, leading to a magnetic Mott-Jahn-Teller insulator.

Elmeleti vizsgalatainkban az kerdeztuk, hogyan vezethetnek a geometriai kenyszerek, a magasabb spinkicserelődes, illetve az anizotrop kolcsonhatasok szokatlan tulajdonsagu magneses fazisokhoz. Megmutattuk, hogy 1-es spinű kvantumrendszerekben nemmagneses, megis O(3) szimmetriat sertő kvadrupolaris rend johet letre bikvadratikus kolcsonhatas jelenleteben haromszog- es negyzetracson. Az erősen frusztralt piroklor racson klasszikus spinekre megmutattuk, hogy a bikvadratikus tag egyutt az elsőszomszed Heisenberg-kolcsonhatassal nematikus fazist eredmenyezhet algebrai spinkorrelaciokkal. Kiterjedt Monte-Carlo-szimulaciokkal megmutattuk egy valodi gap nelkuli spinfolyadek letezeset kvantumdimer-rendszerekben. Tovabbfejlesztettuk 9 T-s szilardtest-NMR spektrometerunket egy korszerű radiofrekvencias konzol uzembehelyezesevel es szamos a molekularis magnesek es kapcsolok csaladjaba tartozo cianid-hidas atmenetifem-komplex NMR tulajdonsagait vizsgaltuk. Berlini kek analog vegyuletben az atmeneti femion-osszetetel fuggvenyeben valtozo magneses tulajdonsagokat kovettuk a kristalyviz protonjait felhasznalva. Kvazi ketdimenzios ferromagneses vegyuletben szerkezetileg azonositottuk es jellemeztuk a kulonboző eredetű (viz ill. szerves) protonjeleket. Egy masik NMR vizsgalatunkban sikeresen leirtuk egy izolalt kuban molekula proton-NMR spektrumat a kolcsonhato 8-spin rendszer Hamilton-operatoranak numerikus diagonalizalasaval. | On the theoretical side, we have studied how geometrical, higher spin exchange, or DM interaction induced frustration can lead to exotic phases. We found nonmagnetic, yet O(3) breaking quadrupolar phases in quantum spin-one system with biquadratic exchange on triangular and square lattices. On the highly frustrated pyrochlore lattice with classical spins, we have shown that biquadratic term next to a nearest neighbor Heisenberg exchange may stabilize nematic order with algebraic decay of spin correlations. Using Monte-Carlo simulations, we have shown the appearance of a true gapless spin-liquid state in three-dimension on a quantum-dimer model. We have shown that the anisotropy may induce Ising-like degeneracy in dimer systems. On the NMR side, we have installed a new radiofrequency console in our 9-T solid state NMR spectrometer. We have investigated cyanide-bridge transition metal complexes belonging to the family of molecular magnets and switches. Using the proton signals of the water in the lattice, we have traced the changes of magnetic properties due to changing transition metal ion composition in a Preussian blue analogue compound. We identified and characterized from structural aspects the proton signals of different origin (water or organic) in a quasi two-dimensional ferromagnetic compound. In another NMR study, we have successfully modelled the proton NMR line shape of isolated cubane molecules with exact diagonalization of the interacting 8-spin Hamiltonian.

The rotor–stator molecular cocrystal C60·C8H8 (fullerene–cubane) has been investigated by 13C nuclear magnetic resonance (NMR). The room‐temperature spectrum obtained using 1H–13C cross‐polarization technique shows two lines with chemical shifts identical with the shifts of the original molecular constituents demonstrating the lack of a strong electronic interaction between C60 and C8H8. The temperature dependence of the spin‐lattice relaxation time of the fullerene component confirms the existence of a first‐order orientational ordering transition around 145 K. The activation energies of large‐angle C60 reorientations above and below the ordering transitions are 260 K and 570 K, respectively. The transition temperature and the activation energies are significantly lower than in other C60 compounds. The 13C spectrum remains narrow down to 115 K indicating that similarly to pristine C60, the molecular reorientational motion is still fast in the ordered phase on the NMR time scale.

Tobb modszerrel vizsgaltuk az alkali fulleridsok Jahn-Teller torzulasat es kimutattuk, hogy az A4C60 alkali fulleridekben es a Na2C60 magas hőmersekletu fazisaban a torzulas szimmetriaja D3d/D5d, ez folyamatos pszeudorotacio soran, dinamikusan valosul meg. Hasonloan bizonyitottuk be, hogy a Na2C60 szobahőmersekleten szegregalodik nanomeretű femes Na3C60 es szigetelő C60 tartomanyokra. Fullerenekből es kubanbol allo rotor-sztator rendszerekben spektroszkopiai modszerekkel kimutattuk a fullerenmolekulak forgasat szobahőmersekleten, es a rezgesi spektrumok szimmetria-analiziseből kovetkeztettunk a C60-C8H8 polimer szerkezetere. Szen nanocsovekből allo atlatszo, onhordo vekonyretegek szeles savu optikai spektroszkopiai vizsgalataval meghataroztuk azok optikai allandoit es ateresztesi tartomanyat. Fotovezetes es optikai abszorpcio egyuttes merese alapjan arra kovetkeztettunk, hogy a fotovalasz bolometrikus. Magneses terben orientalt nanocsőmintak optikai reflexiojaban jelentős anizotropiat talaltunk. Az oldalfalon funkcionalizalt nanocsovek spektruma alapjan megallapitottuk, hogy a kisebb atmerőjű csovek reaktivitasa nagyobb. Eredmenyeinket nemzetkozi folyoiratokban publikaltuk, ezek kozul legfontosabbak negy Physical Review B, ket Journal of Physical Chemistry, egy Science es egy Nature Materials folyoiratcikk, tovabba ot meghivott előadas nemzetkozi konferenciakon. | We investigated the Jahn-Teller distortion in alkali fulleride salts by several methods and showed that the symmetry of the distortion is D3d/D5d in both the alkali fullerides A4C60 (A=K,Rb,Cs) and in the high-temperature phase of Na2C60, and it is realized during continous pseudorotation in a dynamic way. Likewise, we proved that Na2C60 is segregated at room temperature into nanometer size regions of metallic Na3C60 and insulating C60. In rotor-stator systems of fullerenes and cubane, we found spectroscopic proof of the rotation of the fullerene molecules at room temperature, and deducted the structure of the C60-C8H8 polymer from the symmetry analysis of the vibrational spectra. We determined the wide-range optical spectrum of transparent self-supporting nanotube films and calculated the optical constants and transmission windows of several types of nanotubes. From the measurement of photoconductivity and optical absorption on the same nanotube film we concluded that the photoresponse of the tubes is bolometric. We found optical anisotropy in magnetically oriented nanotubes. From the spectra of sidewall-functionalized nanotubes we found the smaller diameter ones to be more reactive. Our results were published in international journals, of which the most important are four papers in Physical Review B, two in Journal of Physical Chemistry, one in Science and one in Nature Materials, in addition to five invited lectures at international conferences.