bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic Properties of Endohedral Metallofullerenes: Single-Molecular Magnetism and Anisotropy
Authors: Popov Alexey A. , Zhang Yang , Dunsch Lothar , Greber Thomas , Westerstöm Rasmus , Yang Shangfeng 
Published: February 2020

Endohedral metallofullerenes (EMFs) encapsulating lanthanide ions (Ln) are of particular interest because of the specific magnetic properties resulting from the combination of the partially filled 4f shell of metal ions, their exchange interactions in endohedral clusters, and shielding role of the carbon cage, which protects endohedral spin states from the outer environment. Inhomogeneous environment of Ln ions inside clusterfullerenes induces magnetic anisotropy and results in a number of magnetic phenomena. In particular, Dy-based nitride clusterfullerenes are the first EMFs to exhibit single molecular magnet (SMM) behaviour.1 Furthermore, completely different SMM behaviour of DySc2N@C80, Dy2ScN@C80, and Dy3N@C80 molecules shows that exchange interactions between Ln ions in EMFs has strong influence on the magnetic properties.2 Results of the SQUID and XMCD studies of different EMFs at low temperatures will be discussed in this contribution. Whereas SQUID and XMCD are of particular use for the study of the low-temperature effects, magnetic properties of EMFs at room-temperature are conveniently addressed by paramagnetic NMR spectroscopy,3 since paramagnetic chemical shift is proportional to the anisotropy of magnetic susceptibility. New results on the NMR studies for a series of LnSc2N@C80molecules will be reported.
1. R. Westerström, J. Dreiser, C. Piamonteze, M. Muntwiler, S. Weyeneth, H. Brune, S. Rusponi, F. Nolting, A. Popov, S. Yang, L. Dunsch and T. Greber, J. Am. Chem. Soc., 2012, 134, 9840-9843.
2. R. Westerström, J. Dreiser, C. Piamonteze, M. Muntwiler, S. Weyeneth, K. Krämer, S.-X. Liu, S. Decurtins, A. Popov, S. Yang, L. Dunsch and T. Greber, arXiv:cond-mat/0604365v1, 2013, 1310.5040.
3. Y. Zhang, A. A. Popov, S. Schiemenz and L. Dunsch, Chem.-Eur. J., 2012, 18, 9691-9698.
Photophysical and Electrochemical Properties of Functionalized Benzo[ghi]perylene and Coronene Derivatives
Authors: Hasobe Taku 
Published: February 2020

Planar polycyclic aromatic hydrocarbons (PAHs) such as benzo[ghi]perylene (Bp) and coronene (Cor) are expected for electronic device applications and solar energy conversion because of their π-conjugated structures and ordered aggregate properties. In this work, a series of Bp and Cor derivatives substituted by methoxycarbonyl (COOMe: electron-withdrawing unit) and methoxy (MeO: electron-donating unit) groups were systematically synthesized considering the differences in types and numbers of substituent groups (Figure 1).
The electrochemical, spectroscopic and photophysical properties of these molecules were investigated in full detail by cyclic voltammetry, steady-state and time-resolved spectroscopy and quantum yield measurements of fluorescence and intersystem crossing. The synthetic introduction of proper substituents on the aromatic ring therefore enables us to successfully control the electrochemical behavior. For example, with increasing the number of COOMe groups, the reduction and oxidation potentials are significantly shifted to positive direction. On the other hand, the steady-state absorption and fluorescence spectra also become red-shifted and broadened as compared to those of unsubstituted Bp and Cor.
Additionally, a systematic comparison of quantum yields and rate constants of the excited-state dynamics also reveals that the fluorescence quantum yields dramatically increase with an increase of the number of COOMe groups in both Bp and Cor derivatives. The fabrication and measurement of filed effect transistors (FET) utilizing these derivatives are also discussed in this presentation.
A Supramolecular Photosynthetic Model Made of a Multi-Porphyrinic Array Constructed Around a C60 Core and a C60-Imidazole Derivative
Authors: Armaroli Nicola , Nierengarten Jean-François , Yoosaf K. , Iehl Julian , Nierengarten Iwona , Hmadeh Mohamed , Albrecht-Gary Anne-Marie 
Published: February 2020

The photophysical properties of a supramolecular fullerene-porphyrin ensemble resulting from the self-assembly of a pyrrolidinofullerene-imidazole derivative (F1) with a multi-metalloporphyrin array constructed around a hexa-substituted fullerene core (F(ZnP)12
) have been investigated. The fullerene hexa-adduct core of the host system does not play any active role in the cascade of photoinduced events of the supramolecular ensemble, indeed no intercomponent photoinduced processes could be observed in host F(ZnP)12
. In contrast, upon axial coordination with the mono-substituted fullerene guest F1, a quantitative quenching of the fluorescence signal of the metalloporphyrins was observed for the supramolecular complex [F(ZnP)12 (F1)n] both in polar and non polar solvents. In toluene, the supramolecular ensemble exhibits a charge transfer emission centered around 930 nm suggesting the occurrence of intramolecular face-to-face interactions of F1 with neighboring metalloporphyrin moieties within the self-assembled photoactive array. This mechanism is supported by the fact that a one order of magnitude increase in the binding constant was observed for the supramolecular complex [F(ZnP)12 (F1)n] when compared to a reference system lacking the pyrrolidino-fullerene unit. In benzonitrile, a long-lived charge separated state (τ = 0.3 μs) has been detected for the supramolecular adduct.
References
K. Yoosaf, J. Iehl, I. Nierengarten, M. Hmadeh, A.-M. Albrecht-Gary, J.-F. Nierengarten, N. Armaroli, Chem. Eur. J., 2014, in press
Graphene Growth on Electrodeposited Polycrystalline Metals and Alloys
Authors: Pigliafreddo Dario , Tocchio Marco , Livolsi Federica , Nobili Luca , Carraro Carlo , Maboudian Roya , Magagnin Luca 
Published: February 2020

Graphene grown by CVD on Cu foils has generated interest due to low cost and the prospect of large-area monolayer coverage. The initial nucleation and growth dynamics of graphene play a critical role in determining the final film quality. However, such characteristics are dependent on Cu surface structure, suggesting that the underlying Cu substrate has a detailed influence on the nucleating carbon species during growth [1,2]. Graphene synthesis on freestanding metallic foils was carried out in a hot-wall tube furnace with CH4 and H2 gases at about 1000 °C.
In this work, we investigate the effects of the electrochemical synthesis onto graphene quality, showing the influence of the Cu-Ru interdiffusion. Copper (about 40 mm thick) and ruthenium coated (about 1 mm thick) copper foils were prepared by electrodeposition in acid electrolyte. The growth of good quality graphene layers is also discussed in terms of the role played by grain boundaries and diffusion at the grain boundaries. Our results demonstrate the synthesis of graphene on Cu with presence of the D-peak and with the 2D-peak not higher than the G-peak (shifting of the 2D-peak) and on Ru with a high D-peak but with the 2D-peak still higher than the G-peak. Graphene on Ru coated copper has a negligible D-peak and the 2D-peak is higher than the G-peak. As alternative substrate, graphene was grown on Ni-Cu electrodeposited alloys with increasing copper content, showing a different behavior from the Cu-Ru system and function of the amount of copper. The Ni-Cu system was used to grow graphene layers on porous substrates obtained by electrochemical de-alloying of copper.

References

[1] X. Li, W. Cai, J. An, S. Kim, J. Nah, D. Yang, R. Piner, A. Velamakanni, I. Jung, E. Tutuc, S.K. Banerjee, L. Colombo, R.S. Ruoff, Science 2009, 1312–1314.
[2] J.D. Wood, S.W. Schmucker, A.S. Lyons, E. Pop, J.W. Lyding, Nano Lett. 2011, 11, 4547–4554.
Hydrogen Incorporation and Reaction with Graphene on SiO2
Authors: Soares Gabriel Vieira , Bom Nicolau Molina , Oliveira Myriano , Lopes João Marcelo , Riechert Henning , Radtke Cláudio 
Published: February 2020

Owing to its unique properties with respect to charge transport, graphene is one of the most promising candidates for future nanoelectronic devices. However, the processing and modification of graphene properties for technological purposes is still a challenge. In this context, gases adsorption in graphene is of central importance. It has been already reported that oxygen (O) and hydrogen (H) incorporation in graphene layers have a strong influence in their transport and structural characteristics [1,2]. For instance, hydrogenation of graphene can give rise to a bang gap around 1 eV, where in some cases H incorporation leads to a reduction in carrier mobility. Therefore, understanding the interaction of H with these structures and related chemical modifications are fundamental issues. In the present work, we investigate the incorporation of H in graphene layers upon hydrogen annealing.
Starting samples consisted of monolayer graphene grown by chemical vapor deposition (CVD) on copper and then transferred to SiO2 films (285 nm thick) on Si. Bare SiO2 films of the same thickness on Si were also submitted to the same experiments for the sake of comparison. Samples were loaded in a static pressure and resistively heated quartz tube furnace, which was initially pumped down to 2 x 10-7 mbar. Hereafter, they were annealed at temperatures ranging from 100 up to 1000 ºC, for 1 h, in a 1000 mbar H2 atmosphere enriched in the 2H (D) rare isotope. This rare isotope was chosen in order to distinguish H incorporated during experiment from those incorporated due to air exposure. As references, samples annealed at the same temperatures but in ultra high vacuum (UHV) were also investigated. D quantification was accomplished by nuclear reaction analyses (NRA), using the D(3He,p)4He nuclear reaction at 700 keV (1012 D/cm2 sensitivity and 5% accuracy). In addition, Raman scattering and X-ray photoelectron spectroscopy (XPS) were used for the characterization of the graphene.
Distinct D incorporation behavior was observed for samples with and without graphene overlayer. For annealing temperature above 100ºC, we observed a higher incorporation of species in graphene when compared to bare SiO2 samples. This incorporation reaches saturation for temperature around 400ºC. XPS measurements suggest the formation of C-H on graphene, increasing its relative concentration with temperature until 800ºC. At higher annealing temperatures, the etching of graphene layer takes place introducing bonding configurations related to defective states. Mechanisms of hydrogen reaction and incorporation based on the observed results will be discussed.
References
[1] S. Ryu, L. Liu, S. Berciaud, Y. You, H. Liu, P. Kim, G. W. Flynn, and L. E. Brus, Nano Lett. 10, (2010) 4944.
[2] D. C. Elias, R. R. Nair, T. M. G. Mohiuddin, S. V. Morozov, P. Blake, M. P. Halsall, A. C. Ferrari, D. W. Boukhvalov, M. I. Katnelson, A. K. Geim, and K. S. Novoselov, Science 233 (2009), 610.
Visible Plasmon-Enhanced Water Splitting
Authors: Misawa Hiroaki 
Published: February 2020

The interaction between photon and molecule is weak. The probability of interaction between photon and molecule is roughly estimated as low as 10-7 because the focal spot size of visible light (~1×10-8 cm2) is 107 times larger than the general molecular absorption cross-section (~1×10-15 cm2) due to the relationship between the diffraction limit of the light and the molecular size. Thus far, the number of excited-state molecules has been increased by photon density using a laser as an excitation source, although there is a loss of energy since the probability of interaction does not change. We have recently found that metallic nanostructures exhibiting localized plasmon resonance are promising in the photochemical reaction field, which make it possible to increase the interaction between photons and molecules. As one of the most important achievements, we have observed significant photopolymerization via two-photon absorption in photoinitiator molecules of negative photoresists in the nanogaps of closely spaced gold nanoparticles irradiated by a weak incoherent light source [1]. The key technology and outstanding feature of our photochemical reaction fields is the fabrication of nanogap metallic nanostructures with nanometric accuracy and use of the localization of electromagnetic waves within nanogaps. Near-field enhancement effects localized on nanogap gold structures were studied by two-photon photoluminescence from gold [2], surface-enhanced Raman scattering [3] and plasmon-enhanced photochemical reactions [4,5]. Thus, gold nanostructures are useful in photochemical reaction fields, which make it possible to promote strong coupling between photons and molecules with the aim of effectively using photons. From this standpoint, we have recently demonstrated plasmonic photoelectric conversion from visible to near-infrared wavelengths using electrodes in which gold nanorods are arrayed on TiO2single-crystal and photocatalytic water splitting [6,7].
References
[1] K. Ueno, H. Misawa et al. J. Am. Chem. Soc.
2008, 130, 6928.
[2] K. Ueno, H. Misawa et al. Adv. Mater.
2008, 20, 26.
[3] Y. Yokota, K. Ueno, H. Misawa, Chem. Commun.
2011, 3505.
[4] K. Ueno, H. Misawa et al. J. Phys. Chem. Lett.
2010, 1, 657.
[5] B. Wu, K. Ueno, H. Misawa et al. J. Phys. Chem. Lett.
2012, 3, 1443.
[6] Y. Nishijima, K. Ueno, H. Misawa et al. J. Phys. Chem. Lett.
2010, 1, 2031.
[7] Y. Nishijima, K. Ueno, H. Misawa et al. J. Phys. Chem. Lett.
2012, 3, 1248.
Nanostructured Palladium-Graphene Materials for Energy Conversion
Authors: Serov Alexey , Andersen Nalin , Artyushkova Kateryna , Atanassov Plamen 
Published: February 2020

Carbon nanostructured materials are widely used in different energy applications: fuel cells, supercapacitors, Li-ion batteries etc [1, 2]. Several synthetic approaches can be used for preparation of CNTs, graphene etc, such as: CVD, exfoliation. At the present work we adopted the sacrificial support method (SSM) developed at UNM group [3-12].
Several types of 3D structured graphene materials were synthesized by modified SSM. The morphology control was achieved by variation of silica types, graphene oxide to silica ratio etc. After successful synthesis of graphenes the sacrificial support was leatched by means of concentrated HF.
Figure 1 represents SEM image of 3D structured graphene synthesized by SSM.

Figure 1: SEM image of 3D structured graphene.
TEM analysis confirmed the formation of multi-stacks of graphene layers (Fig. 2).
The later step involved the deposition on the graphene surface Pd-based materials. Two methods: thermal or chemical reduction of Pd-precursors was used in order to synthesize highly active catalysts for alcohols electrooxidation.
It has been observed that Pd-Cu was evenly dispersed on the graphene sheets (Fig.3).
Electrochemical performance of Pd-based catalysts in the reaction of alcohols electrooxidation is shown on Figure 4. It was found that addition of second oxophilic metal to the palladium substantially improved it is activity. Peak current generated by Pd-Cu deposited onto the surface of 3D structured graphene was found to be ~1800 A gpd
-1.

Figure 2: TEM image of 3D structured graphene.

Figure 3: TEM image of Pd-Cu/3D structured graphene.

Figure 4: Electrooxidation of EtOH in alkaline media by Pd-based catalysts.

References:

E. Antolini Appl. Catal. B. 88 (2009) 1.

G. Kucinskis, G. Bajars, J. Kleperis J. Power Sources 240 (2013) 66–79.

A. Serov, U. Martinez, A. Falase, P. Atanassov, Electrochem. Comm. 22 (2012) 193-196.

A. Falase, M. Main, K. Garcia, A. Serov, C. Lau, P. Atanassov, Electrochim. Acta 66 (2012) 295-301.

S. Pylypenko, S. Mukherjee, T. S. Olson, P. Atanassov, Electrochim. Acta 53 (2008) 7875-7883.

M. H. Robson, A. Serov, K. Artyushkova, P. Atanassov Electrochim. Acta, 90 (2013) 656–665.

S. Brocato, A. Serov, P. Atanassov Electrochim. Acta, 87 (2013) 361-365

A. Serov, M. H. Robson, K. Artyushkova, P. Atanassov Appl. Catal. B 127 (2012) 300-306.

A. Serov, M. H. Robson, M. Smolnik, P. Atanassov Electrochim. Acta 80 (2012) 213-218.

A. Serov, M. H. Robson, B. Halevi, K. Artyushkova, P. Atanassov Electrochem. Comm. 22 (2012) 53-56.

A. Serov, U. Martinez, P. Atanassov Electrochem. Comm. 34 (2013) 185-188.

A. Serov, M. H. Robson, M. Smolnik, P. Atanassov, Electrochim. Acta 109 (2013) 433-439.
Phenolic Porphyrins Assembled at Surfaces: Hydrogen-Bonding and Binary Systems
Authors: Hill Jonathan P. , Wakayama Yutaka , Xie Yongshu , Ji Qingmin , Ariga Katsuhiko 
Published: February 2020

Supramolecular arrangement of porphyrins and other molecules has great potential in the fields of molecular information storage and sensing due to their ease of deposition and good chemical and thermal stabilities. In particular, porphyrins of relatively large molecular weights can be applied in thermal deposition while tetrapyrrole molecules have had an extensive synthetic chemistry developed, which enables synthesis of complex derivatives. In this work, we present complementary examples of porphyrin nanoarchitectonics. Starting from simple symmetrical phenol derivatives, we describe the effects of steric hindrance about the respective hydroxyl groups1,2 and also the effects of conformational variation on the self-assembly structures.3 We also investigated fabrication of binary molecular monolayers using two different porphyrin molecules tetrakis(3,5-di-t-butyl-4-hydroxyphenyl) porphyrin and tetrakis(4-pyridyl) porphyrin by deposition in ultrahigh vacuum.4 This leads to two unusual heteromolecular monolayer structures were observed with one exhibiting good separation of molecules within the monolayer. Meanwhile, a synthetic nanoarchitectonic approach was used to prepare self-assembled molecular nanowires at a mica substrate. The nanowires could be observed growing using atomic force microscopy (AFM) and the network structures of the nanowires can be influenced by manipulation using the AFM probe tip.4,5Formation of molecular monolayers with chromophores positioned remote from the substrate surface will also be discussed.
References
(1) J. P. Hill, Y. Wakayama, W. Schmitt, T. Tsuruoka, T. Nakanishi, P. A. Karr, M. L. Zandler, A. L. McCarty, F. D’Souza, L. R. Milgrom, K. Ariga, Chem. Commun. 2006, 2320–2322 (2) J. P. Hill, Y. Wakayama, M. Akada, Katsuhiko Ariga, J. Phys. Chem. C. 2007, 111, 16174–16180 (3) J. P. Hill, Y. Wakayama, K. Ariga, Phys. Chem. Chem. Phys. 2006, 8, 5034–5037 (4) J. P. Hill, Y. Xie, M. Akada, Y. Wakayama, L. K. Shrestha, Q. Ji, K. Ariga, Langmuir (2013) 29(24), 7291–7299 (5) Y. Xie, M. Akada, J. P. Hill, Q. Ji, R. Charvet K. Ariga, Chem. Commun. 2011, 47, 2285–2287.
Figure. Self-assembled phenol-substituted porphyrins on Cu(111) surface.
Electronic Transport Properties of Molecular Graphyne
Authors: Borguet Eric 
Published: February 2020

Thirty years ago there were two classic forms of carbon (diamond and graphite). Since then, three new carbon allotropes (buckyballs, carbon nanotubes and graphene), all involving only sp2 carbons, have been discovered. While there is much excitement about graphene, another interesting carbon-based material, graphyne, has been suggested.
Graphyne is a two dimensional network of sp and sp2 carbon centers. While this material is not known in nature, it has been the subject of theoretical calculations which suggest exciting properties for graphynes beyond those of graphene. While macroscopic samples of graphyne are not currently available, molecular units of graphyne, called carbo-benzenes, have been synthesized by our collaborators in Toulouse.
We report the single molecule electrical measurements on molecular carbo-benzenes, connected to gold electrodes via amine anchoring groups, determined using scanning tunneling microscope break junction (STM-BJ) methods. Our results show that these highly conjugated macro-aromatics with NH2 metal-anchoring functions are superior in conductivity (~100 nS) compared with molecules of similar length (1.94 nm). These experimental results are rationalized by high level calculations performed by our colleagues at Northwestern. Cutting one side of the macro-aromatic circuit results in a two orders of magnitude smaller junction conductance. Furthermore, single carbo-benzene-mediated junctions exhibit field-effect transistor behavior when an electrochemical gate potential is applied, opening the way for device applications.
Properties of Porphyrin- and Phthalocyanin-Monolayers at Metal-Electrolyte Interfaces
Authors: Wandelt Klaus R. 
Published: February 2020

The adsorption of organic layers on solid surfaces is a promising route to produce surfaces of designed functionality. In this lecture an overview will be given about state-of-the-art investigations of the structural and chemical properties of porphyrin- and phthalocyanin-monolayers adsorbed electrochemically in the form of their molecular cations on anion-modified single-crystal metal electrode surfaces as a function of the nature of the metal (copper, gold), the kind of the pread-sorbed anions (chloride, iodide, sulfate), the symmetry of the surface ((100), (111)), and the electro-chemical potential, using besides classical electrochemical methods Electrochemical Scanning Tunneling Microscopy (EC-STM), and ex-situ Synchrotron X-Ray Photoelectron Spectroscopy (S-XPS). Particular attention will be paid to the self-assembly- vs. template-effects in the structure formation process, to structural phase transitions as a function of electrochemical potential, as well as to the chemical reactivity of selected porphyrins and phthalocyanins. Fig. 1b shows 5,10,15,20-Tetrakis(4-trimethylammonio-phenyl)porphyrin molecules adsorbed on a Cl-precovered Cu(111) surface. Instead of the threefold symmetry of the substrate (Fig. 1a) the molecules self-assemble into a square molecular superlattice (Fig.1b) [1]. Fig.2 shows coexisting square and hexagonal structure domains of 3-pyridyloxy-appended phthalocyanine on iodide precovered Cu(100) [2].
References
[1] Thanh Hai Phan, Tomasz Kosmala, and Klaus Wandelt, in preparation
[2] Thanh Hai Phan, Stephan Breuer, Uwe Hahn, DucThanh Pham, Tomás Torres, and Klaus Wandelt,
J.Phys.Chem.C, submitted

Fig. 1 5,10,15,20-Tetrakis(4-trimethylammonio-phenyl)porphyrin Fig. 2 3-pyridyloxy-phthalocyanine
on Cl-precovered Cu(111) [1] on iodide precovered Cu(100) [2].