A Straightforward approach to multifunctional graphene

Graphene has been covalently functionalized through a one‐pot reductive pathway using graphite intercalation compounds (GICs), in particular KC8, with three different orthogonally protected derivatives of 4‐aminobenzylamine. This novel multifunctional platform exhibits excellent bulk functionalization homogeneity (Hbulk) and degree of addition while preserving the chemical functionalities of the organic addends through different protecting groups, namely: tert‐butyloxycarbonyl (Boc), benzyloxycarbonyl (Cbz) and phthalimide (Pht). We have employed (temperature‐dependent) statistical Raman spectroscopy (SRS), X‐ray photoelectron spectroscopy (XPS), magic angle spinning solid state 13C NMR (MAS‐NMR), and a characterization tool consisting of thermogravimetric analysis coupled with gas chromatography and mass spectrometry (TG‐GC‐MS) to unambiguously demonstrate the covalent binding and the chemical nature of the different molecular linkers. This work paves the way for the development of smart graphene‐based materials of great interest in biomedicine or electronics, to name a few, and will serve as a guide in the design of new 2D multifunctional materials

HAT-P-11: Discovery of a Second Planet and a Clue to Understanding Exoplanet Obliquities

HAT-P-11 is a mid-K dwarf that hosts one of the first Neptune-sized planets found outside the solar system. The orbit of HAT-P-11b is misaligned with the star's spin --- one of the few known cases of a misaligned planet orbiting a star less massive than the Sun. We find an additional planet in the system based on a decade of precision radial velocity (RV) measurements from Keck/HIRES. HAT-P-11c is similar to Jupiter in its mass ($M_P \sin{i} = 1.6\pm0.1$ $M_J$) and orbital period ($P = 9.3^{+1.0}_{-0.5}$ year), but has a much more eccentric orbit ($e=0.60\pm0.03$). In our joint modeling of RV and stellar activity, we found an activity-induced RV signal of $\sim$7 m s$^{-1}$, consistent with other active K dwarfs, but significantly smaller than the 31 m s$^{-1}$ reflex motion due to HAT-P-11c. We investigated the dynamical coupling between HAT-P-11b and c as a possible explanation for HAT-P-11b's misaligned orbit, finding that planet-planet Kozai interactions cannot tilt planet b's orbit due to general relativistic precession; however, nodal precession operating on million year timescales is a viable mechanism to explain HAT-P-11b's high obliquity. This leaves open the question of why HAT-P-11c may have such a tilted orbit. At a distance of 38 pc, the HAT-P-11 system offers rich opportunities for further exoplanet characterization through astrometry and direct imaging.Comment: 16 pages, 11 figures, 4 tables. Accepted to A

Carbon Nanodot:Supramolecular electron donor-acceptor hybrids featuring Perylenediimides

We describe the formation of charge-transfer complexes that feature electron-donating carbon nanodots (CND) and electron-accepting perylenediimides (PDI). The functionalities of PDIs have been selected to complement those of CNDs in terms of electrostatic and \u3c0-stacking interactions based on oppositely charged ionic head groups and extended \u3c0-systems, respectively. Importantly, the contributions from electrostatic interactions were confirmed in reference experiments, in which stronger interactions were found for PDIs that feature positively rather than negatively charged head groups. The electronic interactions between the components in the ground and excited state were characterized in complementary absorption and fluorescence titration assays that suggest charge-transfer interactions in both states with binding constants on the order of 8 7104\u2009M 121 (25\u2005L\u2009g 121). Selective excitation of the two components in ultrafast pump probe experiments gave a 210\u2005ps lived charge-separated state

Precise determination of graphene functionalization by in situ Raman spectroscopy

The verification of a successful covalent functionalization of graphene and related carbon allotropes can easily be carried out by Raman spectroscopy. Nevertheless, the unequivocal assignment and resolution of individual lattice modes associated with the covalent binding of addends was elusive up to now. Here we present an in situ Raman study of a controlled functionalization of potassium intercalated graphite, revealing several new bands appearing in the D-region of the spectrum. The evolution of these bands with increasing degree of functionalization from low to moderate levels provides a basis for the deconvolution of the different components towards quantifying the extent of functionalization. By complementary DFT calculations we were able to identify the vibrational changes in the close proximity of the addend bearing lattice carbon atoms and to assign them to specific Raman modes. The experimental in situ observation of the developing functionalization along with the reoxidation of the intercalated graphite represents an important step towards an improved understanding of the chemistry of graphene

Exposing the Oxygen-Centered Radical Character of the Tetraoxido Ruthenium(VIII) Cation [RuO4]+

The tetraoxido ruthenium(VIII) radical cation, [RuO4]+, should be a strong oxidizing agent, but has been difficult to produce and investigate so far. In our X-ray absorption spectroscopy study, in combination with quantum-chemical calculations, we show that [RuO4]+, produced via oxidation of ruthenium cations by ozone in the gas phase, forms the oxygen-centered radical ground state. The oxygen-centered radical character of [RuO4]+ is identified by the chemical shift at the ruthenium M3 edge, indicative of ruthenium(VIII), and by the presence of a characteristic low-energy transition at the oxygen K edge, involving an oxygen-centered singly-occupied molecular orbital, which is suppressed when the oxygen-centered radical is quenched by hydrogenation of [RuO4]+ to the closed-shell [RuO4H]+ ion. Hydrogen-atom abstraction from methane is calculated to be only slightly less exothermic for [RuO4]+ than for [OsO4]+

The Highest Oxidation State of Rhodium: Rhodium(VII) in [RhO3]+

Although the highest possible oxidation states of all transition elements are rare, they are not only of fundamental interest but also relevant as potentially strong oxidizing agents. In general, the highest oxidation states are found in the electron‐rich late transition elements of groups 7–9 of the periodic table. Rhodium is the first element of the 4d transition metal series for which the highest known oxidation state does not equal its group number of 9, but reaches only a significantly lower value of +6 in exceptional cases. Higher oxidation states of rhodium have remained elusive so far. In a combined mass spectrometry, X‐ray absorption spectroscopy, and quantum‐chemical study of gas‐phaseRhOn+ (n=1–4), we identify RhO3+ as the 1A1' trioxidorhodium(VII) cation, the first chemical species to contain rhodium in the +7 oxidation state, which is the third‐highest oxidation state experimentally verified among all elements in the periodic table