Polimerizáció szén nanoszerkezetekben = Polymerization in carbon nanostructures

Háromfajta szén nanoszerkezettel foglalkoztunk: fullerének és fulleridsók, szén nanocsövek, valamint szén nanocsövek és szerves molekulák alkotta hibrid rendszerek. Az első csoportba tartozó anyagokat hőmérséklet- és nyomásfüggő rezgési spektroszkópiával vizsgáltuk, és kimutattuk a molekuláris jellemzők és a kristályok makroszkopikus tulajdonságai közti összefüggéseket. A mikroszkopikus effektusok a molekulák közti polimerizációs reakció követése (C70), molekuláris Jahn-Teller torzulás (tetrafenil-foszfónium-C60), valamint Mott-lokalizáció által okozott elektronkorreláció és Jahn-Teller effektus kombinációja (Cs3C60). Szén nanocsövek széles sávú optikai spektrumából az elektronszerkezetre, nagy érzékenységgel mért infravörös spektrumukból a csövek rezgési módusaira következtettünk. Mivel különböző átmérőjű csövekből álló mintasorozatokat vizsgáltunk, meg tudtuk állapítani ezeknek a mennyiségeknek a csövek geometriájától való függését. Szén nanocső-szerves molekula hibridek kötési állapotát infravörös és optikai spektroszkópia segítségével határoztuk meg. Eredményeinket nemzetközi folyóiratokban publikáltuk, ezek közül legfontosabbak két Physical Review B, két Journal of Physical Chemistry C, egy Journal of Applied Physics, egy Journal of Physical Chemistry Letters, egy Nature Communications folyóiratcikk, továbbá hét meghívott előadás nemzetközi konferenciákon. | 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

Breakdown of diameter selectivity in a reductive hydrogenation reaction of single-walled carbon nanotubes

Reductive hydrogenation was applied to two types of single-walled carbon nanotubes with different diameter range. Alkali metal intercalation, followed by reaction with methanol, led to hydrogenated products. Both yield and selectivity of this reaction showed strong dependence on diameter, contrary to expectation based on simple curvature effects. The observed yield, as detected by thermogravimetry-mass spectrometry and 1H-NMR, is drastically reduced in small-diameter tubes where the alkali dopant does not reach the inside of the bundles. Wide range optical transmission measurements were employed to determine the selectivity and indicate that besides higher yield, lower diameter selectivity occurs above a critical diameter

Encapsulation of the Graphene Nanoribbon Precursor 1,2,4-trichlorobenzene in Boron Nitride Nanotubes at Room Temperature

Graphene nanoribbons are prepared inside boron nitride nanotubes by liquid phase encapsulation and subsequent annealing of 1,2,4-trichlorobenzene. The product is imaged with high resolution transmission electron microscopy, and characterized by optical absorption and Raman spectroscopy. Carbon-containing material is detected inside the boron nitride nanotubes with energy-dispersive x-ray spectroscopy (EDS) and scanning transmission electron microscopy (STEM). The observed structures twist under the electron beam and the characteristic features of nanoribbons appear in the Raman spectra.Comment: 8 pages, 4 figure

Óriás mágneses ellenállás (GMR) elektrolitikus multirétegekben = Giant magnetoresistance (GMR) in electrodeposited multilayers

Teljesültek a projekt fő célkitűzései az elektrokémiailag előállított (ED) és óriás mágneses ellenállást (GMR) mutató mágneses/nemmágneses multirétegek gócképződési és rétegnövekedési folyamatainak tanulmányozására vonatkozólag. Eddig kilenc folyóirat közlemény jelent meg, köztük egy összefoglaló cikk a Progress in Materials Science-ben, egy beküldött cikk elbírálás alatt van, további 5 cikk pedig előkészületben van. Az ED Co/Cu multirétegek nemmágneses rétegéhez adalékolt Pb, Bi és Ag elemek közül a Pb esetén találtunk javulást a GMR-ben. A fürdő hőmérsékletének nem volt jelentős hatása a GMR-re ED Co(-Ni)/Cu multirétegek esetén. Atomerő mikroszkópiával (AFM) vizsgáltuk a felületi durvaság és a GMR korrelációját ED Co/Cu mulitrétegeknél, különösen a rétegnövekedés kezdeti szakaszában, valamint különböző körülmények között készült ED Ni-Co/Cu multirétegekben. A korábban alig vizsgált ED Fe-Co/Cu multiréteg rendszerre részletesen meghatároztuk a GMR jelenség megfigyeléséhez szükséges előállítási körülményeket. Megmutattuk, hogy ED Co/Cu, Ni-Co/Cu and Fe-Co/Cu multirétegek esetén nincs oszcilláló viselkedése a GMR-nek a nemmágneses réteg függvényében. Mélységprofil analízissel megállapítottuk, hogy ED Fe-Co-Ni and Ni-Fe rétegekben spontán összetételfluktuáció alakul ki leválásnál a hordozó közelében. Modelleztük a GMR változását a mágneses tér függvényében, hogy jobban megérthessük a kísérletileg megfigyelt GMR görbéket. | The major planned tasks of the project aimed mainly at studying the nucleation and growth processes of electrodeposited (ED) magnetic/non-magnetic multilayers with giant magnetoresistance (GMR) behavior were accomplished. A total of 9 papers including a review in Progress in Materials Science have already been published, 1 paper is under review and 5 more papers are under preparation. As to the influence non-magnetic elements (Pb, Ag and Bi) in the spacer layer on GMR in ED Co/Cu multilayers, a beneficial effect was found in the case of Ag. No significant influence of bath temperature on GMR could be demonstrated for ED Co(-Ni)/Cu multilayers. Atomic force microscopy (AFM) was used to investigate the surface roughness and its correlation with GMR in ED Co/Cu multilayers especially in the early stages of multilayer formation and in ED Ni-Co/Cu multilayers prepared under various conditions. The electrochemical preparation conditions for observing GMR were elaborated in detail for ED Fe-Co/Cu multilayers rarely investigated before. It could be shown that the GMR does not exhibit an oscillatory behavior as a function of the spacer layer thickness for ED Co/Cu, Ni-Co/Cu and Fe-Co/Cu multilayers. Depth profiling studies revealed a spontaneous composition vairation in the near substrate zone of ED Fe-Co-Ni and Ni-Fe layers. The magnetic field dependence of the GMR was modelled in order to better understand the experimentally observed GMR curves in multilayers

Polaritonic Enhancement of Near-Field Scattering of Small Molecules Encapsulated in Boron Nitride Nanotubes: Chemical Reactions in Confined Spaces

Nanotubes have been extensively utilized as nanocontainers for molecules and as nanoreactors for chemical reactions in confinement, with the potential for applications in hydrogen storage and catalysis. We show that phonon polaritons of boron nitride nanotubes (BNNTs) enhance the near-field vibrational spectra of molecules in close proximity to the surface. By encapsulating C60 fullerene in BNNTs, we reach a sensitivity level of a few hundred molecules. Furthermore, we show by the photopolymerization of C60 that products of chemical reactions inside the tubes can be identified, so long as their vibrational signatures lie in the reststrahlen band of the BNNT

Optical detection of charge dynamics in CH3NH3PbI3/carbon nanotube composites

This spectroscopic study of light-induced charge transfer in the methylammonium lead iodide/carbon nanotube composite confirms that carbon nanotubes can form efficient charge-transporting layers in organic perovskite based devices.</p

Molecular Encapsulation from the Liquid Phase and Graphene Nanoribbon Growth in Carbon Nanotubes

Growing graphene nanoribbons from small organic molecules encapsulated in carbon nanotubes can result in products with uniform width and chirality. We propose a method based on encapsulation of 1,2,4-trichlorobenzene from the liquid phase and subsequent annealing. This procedure results in graphene nanoribbons several tens of nanometers long. The presence of nanoribbons was proven by Raman spectra both on macroscopic samples and on the nanoscale by tip-enhanced Raman scattering and high-resolution transmission electron microscopic images

Near-field infrared microscopy of nanometer-sized nickel clusters inside single-walled carbon nanotubes

Nickel nanoclusters grown inside single-walled carbon nanotubes (SWCNT) were studied by infrared scattering-type scanning near-field optical microscopy (s-SNOM). The metal clusters give high local contrast enhancement in near-field phase maps caused by the excitation of free charge carriers. The experimental results are supported by calculations using the finite dipole model, approximating the clusters with elliptical nanoparticles. Compared to magnetic force microscopy, s-SNOM appears much more sensitive to detect metal clusters inside carbon nanotubes. We estimate that these clusters contain fewer than ~ 700 Ni atoms