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PubMed2006

Interaction of diatomic germanium with lithium atoms: electronic structure and stability.

Quantum chemical calculations were applied to investigate the electronic structure of mono-, di-, and trilithiated digermanium (Ge2Lin) and their cations (n=0-3). Computations using a multiconfigurational quasidegenerate perturbation approach based on complete active space self-consistent-field wave functions, and density functional theory reveal that Ge2Li has a 2B1 ground state with a doublet-quartet energy gap of 33 kcal/mol. Ge2Li2 has a singlet ground state with a 3Au-1A1 gap of 29 kcal/mol, and Ge2Li3 a doublet ground state with a 4B2-2A2 separation of 22 kcal/mol. The cation Ge2Li+ has a 3B1 ground state, being 13 kcal/mol below the open-shell 1B1 state. The computed electron affinities for diatomic germanium are EA(1)=1.9 eV, EA(2)=-2.5 eV, and EA(3)=-6.0 eV, for Ge2-, Ge2 (2-), and Ge2 (3-), respectively, indicating that only the monoanion is stable with respect to electron detachment, in such a way that Ge2Li is composed by Ge2-Li+ ions. An "atoms-in-molecules" analysis shows the absence of a ring critical point in Ge(2)Li. An electron localization function analysis on Ge2Li supports the view that the Ge-Li bond is predominantly ionic; however, a small covalent character could be anticipated from the analysis of the Laplacian at the Ge-Li bond critical point. The ionic picture of the Ge-Li bond is further supported by a natural-bond-order analysis and the Laplacian of the electron density. The calculated Li affinity value for Ge2 is 2.08 eV, while the Li+ cation affinity value for Ge2- is 5.7 eV. The larger Li+ cation affinity value of Ge2- suggests a Ge2-Li+ interaction and thus supports the ionic nature of Ge-Li bond. In GeLi4 and Ge2Li, the presence of trisynaptic basins indicates a three-center bond connecting the germanium and lithium atoms.

Journal Article↗
PubMed2000

Anharmonic lattice dynamics in germanium measured with ultrafast x-ray diffraction.

Damping of impulsively generated coherent acoustic oscillations in a femtosecond laser-heated thin germanium film is measured as a function of fluence by means of ultrafast x-ray diffraction. By simultaneously measuring picosecond strain dynamics in the film and in the unexcited silicon substrate, we separate anharmonic damping from acoustic transmission through the buried interface. The measured damping rate and its dependence on the calculated temperature of the thermal bath is consistent with estimated four-body, elastic dephasing times (T2) for 7-GHz longitudinal acoustic phonons in germanium.

Journal Article↗
PubMed2003

Two isomorphous complexes: dichloro[phthalocyaninato(2-)]tin(IV) and dichloro[phthalocyaninato(2-)]germanium(IV).

Isomorphous triclinic forms of dichloro[phthalocyaninato(2-)]tin(IV), [Sn(C(32)H(16)N(8))Cl(2)], and dichloro[phthalocyaninato(2-)]germanium(IV), [Sn(C(32)H(16)N(8))Cl(2)], and a monoclinic form of the latter have been obtained from the reaction of pure tin and germanium powder, respectively, with phthalonitrile under a stream of ICl vapour. All three crystal structures consist of centrosymmetric [SnPcCl(2)] and [GePcCl(2)] [Pc is phthalocyaninate(2-)] molecules, which are separated but interacting. In the triclinic forms (Sn and Ge), the Pc macrocycles are not staggered but slipped, and in the monoclinic form (Ge), the molecules are additionally inclined. In both cases, the central Sn or Ge atom is six-coordinated by the four isoindole N atoms of the Pc macrocyclic ligand and by two Cl atoms (located trans) into a tetragonal-bipyramidal structure. The arrangement of [SnPcCl(2)] and [GePcCl(2)] molecules in the crystal structure is determined mainly by intermolecular C-H.Cl, pi-pi and van der Waals interactions.

Journal Article↗
PubMed2006

Hexagonal mesoporous germanium.

The blending of mesoporosity with the properties of semiconductors promises new types of multifunctional nanomaterials. It would be particularly interesting to combine the shape selectivity of a mesoporous oxide with the electronic and photonic characteristics of a useful semiconductor. We demonstrated the synthesis of a mesoporous germanium semiconductor using liquid-crystals-templated chemistry. The template removal was achieved by a two-step ion-exchange thermal procedure. This semiconductive mesoporous form of germanium possesses hexagonal pore ordering with very high surface area and exhibits strongly size-dependent optical properties as well as photoluminescence.

Journal Article↗
PubMed2006

Modal cutoff properties in germanium-doped photonic crystal fiber.

The germanium-doped photonic crystal fiber (PCF) has some characteristics that differentiate it from pure-silica PCF for a germanium element being doped in the core, such as the intensified nonlinearity, the enhanced photosensitivity, and so on. To pave the way for the application of the Ge-doped PCF successfully, it is necessary to study its properties. We investigated the modal cutoff properties of Ge-doped PCF quantitatively by using the beam propagation method. The numerical results show that the effective refractive indices and the normalized frequency V of Ge-doped PCF not only depend on the normalized pitch delta/lambda but also depend on the normalized hole size d/delta, the modal cutoff boundary for the single mode-multimode of the Ge-doped PCF shift to the low d/delta side in contrast to the pure-silica PCF.

Journal Article↗
PubMed2005

Superbroadband 1310 nm emission from bismuth and tantalum codoped germanium oxide glasses.

Near-infrared broadband emission from bismuth-tantalum-codoped germanium oxide glasses was observed at room temperature when the glasses were pumped by an 808 nm laser diode. The emission band covered the O, E, S, C, and L bands (1260-1625 nm), with a maximum peak at approximately 1310 nm, a FWHM broader than 400 nm, and a lifetime longer than 200 micros. The observed broadband luminescence was attributed to bismuth clusters in the glasses. Bismuth-tantalum-codoped germanium oxide glass might be promising as amplification media for broadly tunable lasers and wideband amplifiers in optical communications.

Journal Article↗
PubMed1998

Vacuum ultraviolet single photon versus femtosecond multiphoton ionization of sputtered germanium clusters.

Neutral atoms and clusters desorbed from a solid germanium surface by ion bombardment are detected by laser postionization and time-of-flight mass spectrometry. Two different photoionization schemes are compared which are generally believed to be candidates for the 'soft' ionization of polyatomic species without significant photon induced fragmentation. First, a single photon ionization process is employed using an F2 laser as an intense VUV source with a photon energy in excess of all relevant ionization potentials. It is shown that the available laser pulse energy is sufficient to saturate the ionization of Ge atoms and all detected Ge(n) clusters. The resulting mass spectra are compared to those obtained with a non-resonant multiphoton ionization process using a high intensity laser delivering pulses of 250 femtoseconds duration at a wavelength of 267 nm. Also in this case, the ionization process can apparently be driven into saturation. The mass spectra measured under these conditions are found to be almost identical to those obtained using single photon ionization. We take this as an indication that the results obtained with both postionization techniques closely reflect the true cluster sputtering yields and, in particular, are not dominated by photon induced fragmentation.

Absorptiometry, Photon↗
PubMed1998

Effects of germanium oxide and other chemical compounds on phenylmercury acetate-induced genotoxicity in cultured human lymphocytes.

Phenylmercury acetate (PMA), which not only causes an elevation of sister chromatid exchanges (SCEs) but also induces high frequency of endoreduplication in human lymphocytes, may be genotoxic to humans. The major aim of our study was to investigate the effects of germanium oxide (GeO2), D-penicillamine (D-PA), dimercaprol (BAL), and diltiazem (DTM) on PMA-induced genotoxicity as quantified by SCEs. All concentrations of the four chemical compounds tested alone did not induce genotoxicity in cultured human lymphocytes. However, GeO2 significantly inhibited PMA-induced genotoxicity in a concentration-dependent manner. Similarly, D-PA at concentrations of 3 microM and 10 microM, and BAL at a concentration of 30 microM produced the antigenotoxic effects. In addition, GeO2 (1.5 microM) significantly reversed an increase of endoreduplication frequency caused by PMA. In a cell cycle kinetic study, GeO2 (0.5-5.0 microM) reversed the inhibition of PMA on the proliferating rate index (PRI) of lymphocytes. On the contrary, both D-PA and DTM at concentrations of 30-300 microM markedly potentiated PMA-induced inhibition of PRI. These findings show that GeO2, D-PA and BAL could antagonize PMA-induced genotoxicity, and GeO2 appears to be the most effective.

Adult↗
PubMed1984

Difference spectrophotometric assay of 1,2-diphenolic drugs in pharmaceutical formulations II: Germanium dioxide reagent.

A rapid, difference UV spectrophotometric assay of formulated drugs containing a 1,2-diphenolic group is described. In this assay are utilized the bathochromic shift of the absorption band of 1,2-diphenolic substances from approximately 280 to approximately 287 nm and the concomitant hyperchromic effect induced by the addition of germanium dioxide to an aqueous solution of the drug buffered at pH 6. The absorbance of the solution of the complexed drug relative to that of an equimolar solution of the free drug, which is maximum at approximately 292 nm, is proportional to the concentration of the drug and is unaffected by the presence of other UV-absorbing substances in the formulations that lack the 1,2-diphenolic moiety. Applications of the assay are described for formulations containing epinephrine, isoetharine, isoproterenol, levodopa, and methyldopa.

Catechols↗
PubMed1993

Experimental germanium dioxide-induced neuropathy in rats.

We report an experimental model of germanium dioxide (GeO2)-induced neuropathy in rats. More than 6 months administration of GeO2 to young rats produced neuropathy characterized by segmental demyelination/remyelination and nerve edema. Electron microscopic studies demonstrated that changes in Schwann cells, such as an increased cytoplasmic volume or disintegration of the cytoplasm, were the earliest pathological findings. Schwann cell mitochondria contained high electron-dense materials. Subsequent removal of necrotic Schwann cell debris and myelin by invading macrophages was evident. These findings suggested that the Schwann cells themselves are the primary target of the toxin. The deposition of electron-dense granules in the intra-axonal vesicles, which was suggestive of glycogen granules in mitochondria, was observed in the advanced stage of the neuropathy. The findings of endoneurial edema with splitting of myelin lamellae were noted at the early stage of demyelination. Nerve edema may be the result of GeO2-induced endothelial cell injury.

Animals↗
PubMed1991

Experimental germanium myopathy.

The long-term administration of germanium dioxide (GeO2) to rats produced Ge myopathy characterized by the formation of ragged-red fibers. The earliest pathological changes in experimental Ge myopathy were a decrease in cytochrome c oxidase activity and accumulation of high electron-dense materials in mitochondria. These findings suggest that a mitochondrial dysfunction may be most important in the genesis of experimental Ge myopathy, which could be a useful animal model for the investigation of and therapeutic trials for human mitochondrial myopathies.

Animals↗
PubMed1988

Antitumor properties of organometallic metallocene complexes of tin and germanium.

The antitumor activity of the four metallocene compounds decaphenylstannocene [eta 5-(C6H5)5C5]2Sn(II), decabenzylstannocene [eta 5-(C6H5CH2)5C5]2Sn(II), decaphenylgermanocene [eta 5-(C6H5)5C5]2Ge(II), and decabenzylgermanocene [eta 5-(C6H5CH2)5C5]2Ge(II), containing the main group IV elements tin or germanium as the central metal atom and two pentasubstituted cyclopentadienyl ring ligands in sandwich arrangement, were tested against Ehrlich ascites tumor in female CF1 mice. The complexes caused cure rates of 40% to 90% of the animals treated over rather broad dose ranges. With both germanocene complexes, no strong dose-activity relationship was manifest. The toxicity of all four metallocenes was low, the LD10 values of both stannocenes being 460 and 500 mg/kg, and those of both germanocenes higher than 700 mg/kg. Regarding the isolated pentasubstituted cyclopentadiene ligands (C6H5)5C5H and (C6H5CH2)5C5H, these also exhibited antitumor activity which was less pronounced than that of the metal-containing sandwich complexes. Decasubstituted stannocene and germanocene compounds represent a new type of non-platinum group metal antitumor agents structurally differing from known inorganic and organometallic cytostatics.

Animals↗
PubMed1994

Determination of aluminum and phosphorus in biological materials by reactor activation analysis using germanium as integral flux monitor and comparator.

A method for determination of aluminum and phosphorus in biological materials, based on activation in a nuclear reactor and measurement of 28Al, produced by the 27Al(n, gamma)28Al and 31P(n, alpha)28Al reactions, is described. Irradiations in the undisturbed and epicadmium spectra provide a two-equation system in order to determine the contributions of aluminum and phosphorus to the total activities. Germanium is used as an integral flux monitor and comparator, through the reactions: 74Ge(n, gamma)75Ge, 76Ge(n, gamma)77Ge, and 72Ge(n,p)72Ga.

Activation Analysis↗
PubMed1993

Effect of organic germanium compound (Ge-132) on experimental osteoporosis in rats.

1. The therapeutic effect of organic germanium compound, 2-carboxyethylgermaniumsesquioxide (Ge-132), for experimental osteoporosis was studied using ovariectomized rats maintained on a low calcium containing diet. 2. Serum calcitonin (sCT) level was decreased and serum parathyroid hormone (sPTH) level was increased by ovariectomy and the decrement and increment rates, respectively, were reduced by administration of Ge-132. Thus, the sCT/sPTH ratio was greater in the groups given Ge-132, indicating that the resorption was somehow inhibited by Ge-132. 3. The transverse strength of femur bone was significantly enhanced by Ge-132. 4. A trend was found in the group given Ge-132 for a larger femur cortical bone index. 5. The relative femur bone wet weight was greater in the group given Ge-132. 6. These results indicate that Ge-132 prevents decreased bone strength, and affects the femur cortical bone index, and bone mineral mass caused by osteoporosis.

Animals↗
PubMed2005

Performance of a whole-body counter with five high-purity germanium detectors.

A germanium (Ge) detector system has been installed in a whole-body counting facility at NIRS (Japan). The system employs five detectors that have relative efficiencies of more than 80%. A basic performance of the Ge detectors was tested and compared with that of the former NaI(Tl) detector system. Although the Ge detector system has advantages of improved radionuclide identification capability and MDA values, it also has disadvantages of high operation costs and demanding maintenance such as supply of liquid nitrogen.

Body Burden↗
PubMed2006

Software studies for germanium detectors data analysis.

Efficiency calibrations of multiple high-purity germanium (HPGe) detectors are being maintained at the National Institute of Standards and Technology (NIST). Four generally available software packages for HPGe detector gamma-ray spectrum analysis, including the one currently used at NIST, were tested on spectra collected from two HPGe detectors at different source-to-detector distances and using point sources and ampoules as calibration geometries. The resulting efficiency curves were inter-compared.

Algorithms↗
PubMed2006

A miniaturized germanium-doped silicon dioxide-based surface plasmon resonance waveguide sensor for immunoassay detection.

A surface plasmon resonance (SPR) waveguide immunosensor fabricated by germanium-doped silicon dioxide was investigated in this study. The designed waveguide sensor consisted of a 10 microm SiO(2) substrate layer (n=1.469), a 10 microm Ge-SiO(2) channel guide (n=1.492) and a 50 nm gold film layer for immobilization of biomolecules and SPR signal detection. The resultant spectral signal was measured by a portable spectrophotometer, where the sensor was aligned by a custom-designed micro-positioner. The results of the glycerol calibration standards showed that the resonance wavelength shifted from 628 to 758 nm due to changes of refractive index from 1.36 to 1.418. Flow-through immunoassay on waveguide sensors also showed the interactions of protein A, monoclonal antibody (mAb ALV-J) and avian leucosis virus (ALVs) resulted in wavelength shifting of 4.17, 3.03 and 2.18 nm, respectively. The SPR dynamic interaction could also be demonstrated successfully in 4 min as the sensor was integrated with a lateral flow nitrocellulose strip. These results suggest that SPR detection could be carried out on designed waveguide sensor, and the integration of nitrocellulose strip for sample filtering and fluid carrier would facilitate applications in point-of-care portable system.

Biosensing Techniques↗