Front Cover (Phys. Status Solidi B 11‐12/2009)Boehme, C.; McCamey, D. R.; van Schooten, K. J.; Baker, W. J.; Lee, S.‐Y.; Paik, S.‐Y.; Lupton, J. M.
doi: 10.1002/pssb.200990015pmid: N/A
The illustration depicted on the front cover refers to the article by Christoph Boehme and collaborators (University of Utah, USA) on pp. 2750–2755. Their article deals with organic light emitting diodes fabricated with the organic semiconductor poly(2‐methoxy‐5‐(20‐ethyl‐hexyloxy)‐1,4‐phenylene vinylene) (MEH‐PPV). By observing the change in current through such a device following electron spin resonance, they are able to observe coherent spin effects in these technologically important materials.
Inside Back Cover (Phys. Status Solidi B 11‐12/2009)Güttinger, J.; Stampfer, C.; Frey, T.; Ihn, T.; Ensslin, K.
doi: 10.1002/pssb.200990016pmid: N/A
The inside back cover depicts the schematic of an etched graphene quantum dot with rough edges. By measuring the current through the dot and changing gate voltage and source‐drain bias, Coulomb blockade diamonds can be recorded and are shown for zero magnetic field (top right) and B = 13 T (lower left). In the paper the evolution of a large number of Coulomb peaks in perpendicular field are interpreted based on the formation of the unique E = 0 Landau level in graphene, giving rise to the electron‐hole crossover in the center of the region where the current is pinched off. The diamonds shown have been recorded around the electron‐hole crossover, displaying a rich zoo of excited states and co‐tunneling features within and outside the diamonds with pronounced magnetic field dependences. For further details see the article by Güttinger et al. starting on p. 2553.
Control of p‐doping on single‐walled carbon nanotubes with nitronium hexafluoroantimonate in liquid phaseKim, Ki Kang; Bae, Jung Jun; Kim, Soo Min; Park, Hyeon Ki; An, Kay Hyeok; Lee, Young Hee
doi: 10.1002/pssb.200982318pmid: N/A
We report that nitronium hexafluoroantimonate (NHFA) can be used as a strong p‐type dopant on single‐walled carbon nanotubes (SWCNTs). The diameter range of SWCNTs in this work ranged from 1.2 to 1.8 nm. The NHFA was dissolved in a mixed solution of tetramethylsilane/1,2‐dichloroethane (1:1 by weight) with SWCNTs. The treated samples in liquid phase were characterized by UV–VIS–NIR absorption and Raman spectroscopies. We found that with increasing the NHFA concentration, the van Hove singularity‐related transitions (${\rm E}_{11}^{\rm S}$, ${\rm E}_{22}^{\rm S}$, and ${\rm E}_{11}^{\rm M}$) in the optical absorption spectra disappeared gradually and a new transition peak was clearly observed near 1.33 eV. G‐band in the Raman spectra was upshifted to 1618 cm−1 from 1587 cm−1 of the pristine peak due to the phonon stiffening, an evidence of p‐type doping. The sheet resistance of the SWCNT film was reduced up to 90%. After thermal annealing, the Raman spectra were recovered, similar to those of the pristine sample without any damage.
In vitro effects of SWCNT: Role of treatment durationBruinink, Arie; Manser, Pius; Hasler, Sabrina
doi: 10.1002/pssb.200982319pmid: N/A
Despite the growing interest in single carbon nanotubes (SWCNT) for consumer products still little is known about their toxic potential and toxicomechanism. The present study was performed to elucidate the role of treatment duration and catalyst contamination in SWCNT induced effects. For this SWCNT of two different purities were evaluated: SWCNT raw material (SWCNTrm) and purified SWCNT (SWCNTpur). Our data suggest that the presence of an increased quantity of SWCNT contaminants has a negative impact on lung epithelial A549 cell functionality. Evidence was found that the cellular effects of SWCNTpur are based on accumulation within the target compartment of the cell. In case of SWCNTrm adaptations of the cell to the SWCNT exposure may occur reducing the importance of accumulation regarding the observed effects.
The reaction of lithium metal vapor with single walled carbon nanotubes of large diametersKalbac, Martin; Kavan, Ladislav; Dunsch, Lothar
doi: 10.1002/pssb.200982251pmid: N/A
Raman spectroscopy was used to evaluate the effect of lithium vapor on single walled carbon nanotubes (SWCNTs) having diameters from 1.2 to 1.6 nm. The Raman spectra were excited by five different laser lines. A strong doping of SWCNTs after the reaction with Li vapor was confirmed by the corresponding attenuation of the Raman signal. The relative intensities and frequencies of the radial breathing mode of the Li vapor treated SWCNT were recovered after subsequent reaction with water. Our data demonstrate that the reaction of Li with large diameter SWCNTs is reversible, which is different from previous results showing irreversible changes for SWCNT samples containing both large diameter and small diameter tubes. The subsequent in situ Raman spectroelectrochemical measurement of our sample confirmed that after water treatment of the Li etched sample there is no significant residual doping of the SWCNT sample.
Boron, nitrogen and phosphorous substitutionally doped single‐wall carbon nanotubes studied by resonance Raman spectroscopyMaciel, I. O.; Campos‐Delgado, J.; Pimenta, M. A.; Terrones, M.; Terrones, H.; Rao, A. M.; Jorio, A.
doi: 10.1002/pssb.200982254pmid: N/A
Substitutional doping on single‐wall an on multi‐wall carbon nanotubes is possible by adding new atoms during the growing process. In this work we analyze the changes in the Raman spectra of SWNT samples substitutionaly doped with boron, nitrogen, and phosphorous. We find that small amounts of dopants are not enough to change the frequency of the tangential G mode, but there is a doping‐dependent shift in ωG when the P‐doped SWNTs are measured at high laser power, indicating that doping can change the thermal properties of SWNT bundles. This result seems to hold also for B‐doped samples, but not for N‐doped SWNTs, showing a different behavior for donors (P‐ and N‐ doping). The ID/IG ratio analysis to provide information about the doping level in the SWNT samples is also discussed.