Complexation between molybdenum(VI) and citrate: Crystal and molecular structure of [Mo4O11(citrate)2](Me3N(CH2)6NMe3)2·12H2O

The X-ray structure of the tetrameric complex [Mo₄O₁₁(C₆H₅O₇)₂]-(Me₃N(CH₂)₆NMe₃)₂·12H₂O has been determined. Crystals are monoclinic,C2/c, witha=19.886(8),b=11.773(6),c=26.97(1) Å,=90.69(4)°,V=6313 ų,Z=4. FinalR=0.050,R _w =0.053,w=(² F)^–1 for 4451 reflections withI _rel>2I _rel. The configuration of the Mo(VI) complex is similar to that previously reported for a Mo(VI)-malate anion [Mo₄O₁₁(mal)₂]^4– but differs from that proposed previously for a Mo(VI)-citrate complex.     

Tunable n‐ and p‐type doping of single‐layer graphene by engineering its interaction with the SiO2 support

We report a technique to tune the excess charge concentration in single‐layer graphene from p‐ to n‐type up to densities of |n | ～ 1.2 × 10¹³ cm^–2, corresponding to a displacement electric field of ～2.5 V/nm. The tuning is achieved by engineering the interaction between graphene and the underlying Si/SiO₂ substrate with an amino group‐terminated self‐assembled monolayer, and subsequent rinsing in aqueous solutions at controlled pH. Raman spectroscopy and electrical measurements on treated graphene devices confirm the occurrence of doping. Interestingly, we found the field‐effect mobility not to be significantly affected by the procedure. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Experimental investigations of the nuclear level density by using heavy ion reactions

The transition of the level density parameter a _off from the low excitation energy value a _off=A/8 MeV⁻¹ to the Fermi gas value a _FG ∼ A/15 MeV⁻¹ was discovered a few years ago studying particle spectra evaporated from hot compound systems of A∼ 160. A number of experiments have been recently performed to confirm the earlier findings and extend the investigation to other mass regions and to higher excitation energies. Furthermore, precision coincidence experiments have been done in the lead region in which evaporation residues are tagged by low energy gammarays. Those experiments open the possibility of a detailed study of the level densities in nuclei where the shell effects are important.