Mesoporous GeOx/Ge/C as a Highly Reversible Anode Material with High Specific Capacity for Lithium-Ion Batteries.

Nanostructured Ge is considered a highly promising material for Li-ion battery applications as Ge offers high specific capacity and Li-ion diffusivity, while inherent mesoporous nanostructures can contribute resistance against capacity fading as typically induced by high volume expansion in bulk Ge films. Mesoporous GeOx/Ge/C films are synthesized using K4Ge9 Zintl clusters as a Ge precursor and the amphiphilic diblock copolymer polystyrene-block-polyethylene oxide as a templating tool. As compared to a reference sample without post-treatment, enhanced surface-to-volume ratios are achieved through post-treatment with a poor-good azeotrope solvent mixture. High capacities of over 2000 mA h g-1 are obtained with good stability over 300 cycles. Information from morphological and compositional characterization for both reference and post-treated sample suggests that the good electrochemical performance originates from reversible GeO2 conversion reactions.

Amphiphilic diblock copolymer-mediated structure control in nanoporous germanium-based thin films.

Fabrication of porous, foam-like germanium-based (Ge-based) nanostructures is achieved with the use of the amphiphilic diblock copolymer polystyrene-b-polyethylene oxide as structure directing agent. Basic concepts of block copolymer assisted sol-gel synthesis are successfully realized based on the [Ge9]4- Zintl clusters as a precursor for Ge-based thin films. Material/elemental composition and crystalline Ge-based phases are investigated via X-ray photoelectron spectroscopy and X-ray diffraction measurements, respectively. Poor-good solvent pair induced phase separation leads to pore sizes in the Ge-based films up to 40 nm, which can be tuned through a change of the molar mixing ratio between polymer template and precursor as proven by grazing incidence small angle X-ray scattering and scanning electron microscopy.

N-Heterocyclic Carbene Coinage Metal Complexes of the Germanium-Rich Metalloid Clusters [Ge9R3]- and [Ge9RI2]²- with R = Si(iPr)3 and RI = Si(TMS)3.

We report on the synthesis of novel coinage metal NHC (N-heterocyclic carbene) compounds of the germanium-rich metalloid clusters [Ge9R3]- and [Ge9RI2]²- with R = Si(iPr)3 and RI = Si(TMS)3. NHCDippCu{η³Ge9R3} with R = Si(iPr)3 (1) represents a less bulky silyl group-substituted derivative of the known analogous compounds with R = Si(iBu)3 or Si(TMS)3. The coordination of the [NHCDippCu]⁺ moiety to the cluster unit occurs via one triangular face of the tri-capped trigonal prismatic [Ge9] cluster. Furthermore, a series of novel Zintl cluster coinage metal NHC compounds of the type (NHCM)2{η³Ge9RI2} (RI = Si(TMS)3 M = Cu, Ag and Au; NHC = NHCDipp or NHCMes) is presented. These novel compounds represent a new class of neutral dinuclear Zintl cluster coinage metal NHC compounds, which are obtained either by the stepwise reaction of a suspension of K12Ge17 with Si(TMS)3Cl and the coinage metal carbene complexes NHCMCl (M = Cu, Ag, Au), or via a homogenous reaction using the preformed bis-silylated cluster K2[Ge9(Si(TMS)3)2] and the corresponding NHCMCl (M = Cu, Ag, Au) complex. The molecular structures of NHCDippCu{η³Ge9(Si(iPr)3)3} (1) and (NHCDippCu)2{η³-Ge9(Si(TMS)3)2} (2) were determined by single crystal X-ray diffraction methods. In 2, the coordination of the [NHCDippCu]⁺ moieties to the cluster unit takes place via both open triangular faces of the [Ge9] entity. Furthermore, all compounds were characterized by means of NMR spectroscopy (¹H, 13C, 29Si) and ESI-MS.