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PubMed2000

Energy linearity of high-purity germanium detectors in the region of the Ge K-absorption edge: experimental results

Non-linearities in the energy response of gas detectors in the regions of the absorption edges of the detection medium are well documented. Monte Carlo calculations show that the non-linearity results from differences in efficiencies for converting absorbed radiation into ionisation for different atomic sub-shells. Energy non-linearity in germanium-based solid-state detectors in the region of the germanium 11.104-keV K-edge is not well documented, although a 1% non-linearity has been previously reported in a Ge(Li) detector. This relatively high value is of practical concern since high-purity germanium (HPGe) is often the detector of choice for alpha- and X-ray spectrometry down to a few keV. In this paper, we present the experimental results for the energy response of a HPGe detector in the 8-15-keV energy region of the germanium K-edge. Within the accuracy of our measurements, we conclude that there is no measurable non-linearity effect in germanium at the K-edge.

Journal Article↗
PubMed2006

Synthesis, characterization, and growth rates of germanium silicalite-1 grown from clear solutions.

The synthesis, characterization, and growth of Ge-silicalite-1 from optically clear solutions are reported. Ge-silicalite-1 is readily formed from optically clear solutions of TEOS, TPAOH, water, and a germanium source at 368 K. X-ray fluorescence (XRF) is used to determine the Si/Ge ratio and indicates that germanium inclusion is typically 30-50% of that in the actual mixture. Adsorption, power X-ray diffraction (PXRD), and 29Si NMR indicate the materials are crystalline and microporous. In situ small-angle X-ray scattering (SAXS) is applied to investigate the influences of germanium source (GeO2 and Ge(OC2H5)4) and content (Si/Ge 100:5) on the growth of Ge-silicalite-1 from clear solutions at 368 K. The in situ SAXS investigations show that for solutions with Si/Ge ratios of 100, 50, and 25 using Ge(OC2H5)4 the induction periods are approximately 6 h and the particle growth rates are 1.82 +/- 0.04, 2.52 +/- 0.13, and 2.85 +/- 0.08 nm/h, respectively, at 368 K, compared to those of pure silicalite-1 (6 h induction period, 1.93 +/- 0.1 nm/h growth rate). Further increasing the Si/Ge ratio to 15 and 5 shortens the induction period to approximately 4.5 h, and the growth rates are 3.07 +/- 0.16 and 2.05 +/- 0.10 nm/h, respectively, indicating the Si/Ge ratio that maximizes Ge-silicalite-1 growth is between 25 and 15. Similar trends are obtained with germanium oxide; however, the growth rates are all consistently larger than those for syntheses with Ge(OC2H5)4. The results indicate that Ge-silicalite-1 growth rates in the presence of germanium are increased as compared to those of pure-silica syntheses.

Journal Article↗
PubMed2006

Reactivity of the germanium surface: Chemical passivation and functionalization.

With the rapidly changing materials needs of modern microelectronics, germanium provides an opportunity for future-generation devices. Controlling germanium interfaces will be essential for this purpose. We review germanium surface reactivity, beginning with a description of the most commonly used surfaces, Ge(100) and Ge(111). An analysis of oxide formation shows why the poor oxide properties have hindered practical use of germanium to date. This is followed by an examination of alternate means of surface passivation, with particular attention given to sulfide, chloride, and hydride termination. Specific tailoring of the interface properties is possible through organic functionalization. The few solution functionalization methods that have been studied are reviewed. Vacuum functionalization has been studied to a much greater extent, with dative bonding and cycloaddition reactions emerging as principle reaction mechanisms. These are reviewed through molecular reaction studies that demonstrate the versatility of the germanium surface.

Journal Article↗
PubMed1987

Preventive effect of zinc for toxic actions of germanium and selenium on bone metabolism in weanling rats.

The preventive effect of zinc for the toxic actions of germanium and selenium on bone metabolism was investigated in the femoral diaphysis of weanling rats. Germanium tetrachloride (1.53-30.60 mumol Ge/100 g b.w.) and selenium tetrachloride (1.53-7.65 mumol Se/100 g) was administered orally for 3 days. The doses of 1.53 and 7.65 mumol Ge/100 g caused a significant increase in DNA content although alkaline phosphatase activity was not altered significantly. By the dose of 30.60 mumol Ge/100 g, both alkaline phosphatase activity and DNA content were decreased significantly. Administration of selenium (1.53 and 7.65 mumol/100 g) produced significantly decreases in alkaline phosphatase activity and DNA content. The decreases of the enzyme activity and DNA content caused by administration of germanium (30.60 mumol/100 g) and selenium (7.65 mumol/100 g) were prevented completely by simultaneous injection of zinc sulfate (7.65 mumol Zn/100 g) for 3 days. Administration of zinc also produced appreciable increase in alkaline phosphatase activity and DNA content. The present study indicates that germanium and selenium disturbs bone metabolism in weanling rats, and that this disturbance is reversed by zinc.

Alkaline Phosphatase↗
PubMed1991

Nephrotoxicity and neurotoxicity in humans from organogermanium compounds and germanium dioxide.

There is no known biological requirement for germanium (Ge), germanates, or any organogermanium compound. Ge deficiency has not been demonstrated in any animal. The estimated average dietary intake of Ge in humans is 1.5 mg/d. Ge is widely distributed in edible foods, all of which, with few exceptions, contain less than 5 ppm Ge, since higher levels are toxic to most plants. Ingestion of Ge compounds has been shown to produce toxic effects in experimental animals. In recent years inorganic germanium salts and novel organogermanium compounds, such as carboxyethyl germanium sesquioxide (Ge-132) and lactate-citrate-germanate (Ge lactate citrate) have been sold as "nutritional supplements" in some countries for their purported immunomodulatory effects or as health-producing elixirs, resulting in intakes of Ge significantly exceeding the estimated average dietary intake. Since 1982, there have been 18 reported cases of acute renal dysfunction or failure, including two deaths, linked to oral intake of Ge elixirs containing germanium dioxide (GeO2) or Ge-132. In these cases, biopsies show vacuolar degeneration in renal tubular epithelial cells, without proteinuria or hematuria, in the absence of glomerular changes. Serum creatinine levels have been well above 400 mumol/L in such patients. In 17 of 18 cases, accumulated elemental Ge intakes reportedly ranged between 16 to 328 g over a 4-36 mo period, or between 100 to 2000 times the average estimated dietary intake for human. In surviving patients, renal function improved after discontinuation of Ge supplementation. However, in no case was recovery complete. One organogermanium compound, an azaspiran organogermanium compound, 2-aza-8-germanspiro[4,5] decane-2-propamine-8,8-diethyl-N,N-dimethyl dichloride (spirogermanium), has been found to cause both neurotoxicity and pulmonary toxicity in phase I and II studies examining its chemotherapeutic potential as an antitumor drug in the treatment of various malignancies. In cancer patients given the drug spirogermanium, 40% experienced marked, yet transient neurotoxicity. Two patients suffered from pulmonary toxicity. Results of phases I and II human cancer trials for spirogermanium have not been favorable, with the exception of moderate benefits for three types of malignancies. It is recommended that patients exposed to long-term (greater than 3 mo) Ge supplementation at levels well above the estimated daily intake be medically supervised and monitored for potential renal-, pulmonary- or neurotoxicity. Further study regarding the mechanism of Ge-induced nephrotoxicity in human is warranted.

Animals↗
PubMed1988

Therapeutic effects of organic germanium.

Germanium is present in all living plant and animal matter in micro-trace quantities. Its therapeutic attributes include immuno-enhancement, oxygen enrichment, free radical scavenging, analgesia and heavy metal detoxification. Toxicological studies document Germanium's rapid absorption and elimination from the body, and its safety. Clinical trials and use in private practices for more than a decade have demonstrated Germanium's efficacy in treating a wide range of serious afflictions, including cancer, arthritis and senile osteoporosis. Germanium's anti-viral and immunological properties, including the induction of interferon, macrophages, T-suppressor cells and augmentation of natural killer cell activity, suggest its possible efficacy in treating and/or preventing AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Does germanium interact with radular morphogenesis and biomineralization in the limpet Lottia gigantea?

Specimens of Lottia gigantea were incubated in germanium enriched seawater [( Ge]/[Si] = 0.2-783) for 1-8 days. The siliceous radulae were examined histologically. No visible changes, degenerations or deformations were found in all 62 experimental radulae, although germanium is known to be a competitive inhibitor of silicon. In high concentrations, germanium was toxic to the limpets and killed them. Germanium was incorporated into the radular teeth in a distribution similar to silicon. Two suggestions are discussed for the apparent noninhibitory result.

Animals↗
PubMed2000

High-speed recovery of germanium in a convection-aided mode using functional porous hollow-fiber membranes.

A porous hollow-fiber membrane capable of recovery of germanium from a liquid stream was prepared by radiation-induced graft polymerization of an epoxy-group-containing vinyl monomer, glycidyl methacrylate, and subsequent functionalization with 2,2'-iminodiethanol, di-2-propanolamine, N-methylglucamine, and 3-amino-1,2-propanediol. The functional group density was as high as 1.4 mol per kg of the resultant hollow fiber. The polymer chains containing functional groups surrounding the pores enabled a high-speed recovery of germanium during permeation of a germanium oxide (GeO2) solution through the pores of the hollow fiber. Because of a negligible diffusional mass-transfer resistance, germanium concentration changes with the effluent volume, i.e., breakthrough curves, overlapped irrespective of the residence time of the solution, which ranged from 0.37 to 3.7 s across the hollow fiber. After repeated use of adsorption and elution, the adsorption capacity did not deteriorate.

Chromatography↗
PubMed2000

Chest wall thickness measurements of the LLNL phantom for small area germanium detector counting.

The Lawrence Livermore National Laboratory (LLNL) phantom was developed to calibrate lung counting systems that are used to estimate plutonium and other low energy photon emitting radionuclides deposited in the lung. Originally, low energy photon counting systems consisted of sodium iodide or phoswich detectors, but they have been largely replaced by smaller germanium detector arrays. The average chest wall thicknesses of the LLNL phantom's torso plate and its overlay plates provided by the manufacturer refer to the regions covered by phoswich detectors; however, germanium detectors are of a different size and are placed in different locations on the phantom's torso plate. Previous work has shown that the manufacturer's data were not applicable for large area germanium detectors. The lung counting system at the Korea Atomic Energy Institute (KAERI) is a small area germanium detector array. Although the detectors are placed within the phoswich circles, only about 25% of the area is covered by the detectors. The LLNL phantom at KAERI has been examined to determine if the manufacturer's data are valid or if new chest wall thickness values must be determined. This paper presents chest wall thickness data for the LLNL phantom with and without its B-series overlay plates at 17 keV, 60 keV, 200 keV, and 1,500 keV and shows that these values are different from the manufacturer's values.

Calibration↗
PubMed2003

Formation and size dependence of germanium nanoparticles at different helium pressures.

We report the formation of germanium nanoparticles and threadlike nanostructures by the process of thermal vapor deposition. Germanium was thermally evaporated and condensed on graphite substrates under varied ambient helium pressures of 100, 200, 300, and 400 torr. The deposited films were characterized through transmission electron microscopy. These investigations revealed the occurrence of germanium particles. The size of these particles varied inversely with ambient pressure. Whereas for an ambient pressure of 100 torr the average particle size was approximately 0.3-0.5 micron, for 400 torr the average size was approximately 30-60 nm. At high He pressure (e.g., approximately 400 torr), the nanoparticles that formed when annealed for 30 min at 200 degrees C in vacuum adopted threadlike nanostructures. A qualitative explanation has been put forward for the formation of germanium particles and variation of size of these particles with helium pressure in terms of condensation, collision, and coalescence.

Chemical Precipitation↗
PubMed1992

[A patient with liver cirrhosis manifesting various symptoms including cerebellar ataxia due to germanium intoxication].

A patient with hepatitis B virus-associated cirrhosis manifested various symptoms such as anemia, renal damage and neurological signs including cerebellar ataxia due to long-term administration of germanium-containing food. The patient was a 40-year-old male who had taken germanium containing mineral cheese for 26 months after he was diagnosed as having cirrhosis. Twenty four months after beginning to take the mineral cheese, he began manifesting paresthesia of the extremities, dysarthria and gait ataxia. Laboratory findings revealed anemia and renal damage. Biopsy of the peripheral nerve revealed loss of the large sheathed nerve, a characteristic feature of germanium intoxication. A high concentration of germanium (GeO2) was detected in patient's hair and urine. Cerebellar ataxia was characteristic in this patient, which was not reported in the previous papers.

Adult↗
PubMedDate not supplied

[Absolute and relative bioavailability of germanium in the rabbit].

The debated consumption of germanium suggested the authors to compare biopharmaceutical parameters of germanium oxide and germanium sesquioxide. A first evaluation, in rabbit, has been based on Germanium blood levels determined by atomic absorption spectrometry, after cross administration of both products by the I.V. and oral routes. When given orally, the apparent oxide bioavailability is very low (about 10%) but better than that of the sesquioxide. That difference could result from differences of disposition parameters of both products, which have to be studied late.

Animals↗
PubMed1998

An Activated Germanium Metal-Promoted, Highly Diastereoselective Reformatsky Reaction.

Activated germanium metal, prepared by the reduction of germanium(II) iodide with potassium metal, was found to promote the Reformatsky reaction effectively under mild conditions. In the presence of activated germanium metal, the reactions of alpha-bromo ketones 2a and 2b and alpha-bromo imides 2e and 2f with benzaldehyde (1a) proceeded smoothly to give the corresponding beta-hydroxy carbonyl compounds 3a, 3b, 3e and 3f, respectively, in good yields and with good syn diastereoselectivity. The activated germanium metal-promoted, asymmetric Reformatsky reaction of enantiomerically pure-oxazolidinone derivatives 2g-j with various aldehydes 1a-d was also examined; the highest diastereoselectivity was achieved when (1S,2R)-2-amino-1,2-diphenylethanol-derived 2j was used as the Reformatsky donor. The excellent diastereoselectivity could be explained in terms of the formation of a chairlike, six-membered transition state between the aldehyde and enolate as in the Zimmerman-Traxler model. A single recrystallization of the Reformatsky adducts, followed by hydrolysis and subsequent esterification, led to enantiomerically pure methyl 3-hydroxy-2-methylalkanoates 10j-m, with almost quantitative recovery of the enantiomerically pure 2-oxazolidinone 14.

Journal Article↗
PubMed2006

A theoretical study on growth patterns of Ni-doped germanium clusters.

Ni-doped germanium clusters have been systematically investigated by using the density functional approach. The growth-pattern behaviors, stabilities, charge transfer, and polarities of these clusters are discussed in detail. Obviously different growth patterns appear between small-sized Ni-doped germanium clusters and middle- or larger-sized Ni-doped germanium clusters. The Ni-convex or substituted Ge(n) frames for small-sized clusters as well as Ni-concaved or encapsulated Ge(n) frames for middle- or large-sized clusters are dominant growth patterns. The calculated fragmentation energies manifest that the magic numbers of stabilities are 5, 8, 10, and 13 for Ni-doped germanium clusters; the obtained relative stabilities exhibit that the Ni-encapsulated Ge(10) cluster is the most stable species of all different-sized clusters, which is in good agreement with available experimental observations of CoGe(10)(-). Natural population analysis shows that different charge-transfer phenomena depend on the sizes of the Ni-doped Ge(n) clusters. Additionally, the properties of frontier orbitals and the polarities of Ni-doped Ge(n) clusters are also discussed.

Journal Article↗
PubMed2005

Strong quantum-confined Stark effect in germanium quantum-well structures on silicon.

Silicon is the dominant semiconductor for electronics, but there is now a growing need to integrate such components with optoelectronics for telecommunications and computer interconnections. Silicon-based optical modulators have recently been successfully demonstrated; but because the light modulation mechanisms in silicon are relatively weak, long (for example, several millimetres) devices or sophisticated high-quality-factor resonators have been necessary. Thin quantum-well structures made from III-V semiconductors such as GaAs, InP and their alloys exhibit the much stronger quantum-confined Stark effect (QCSE) mechanism, which allows modulator structures with only micrometres of optical path length. Such III-V materials are unfortunately difficult to integrate with silicon electronic devices. Germanium is routinely integrated with silicon in electronics, but previous silicon-germanium structures have also not shown strong modulation effects. Here we report the discovery of the QCSE, at room temperature, in thin germanium quantum-well structures grown on silicon. The QCSE here has strengths comparable to that in III-V materials. Its clarity and strength are particularly surprising because germanium is an indirect gap semiconductor; such semiconductors often display much weaker optical effects than direct gap materials (such as the III-V materials typically used for optoelectronics). This discovery is very promising for small, high-speed, low-power optical output devices fully compatible with silicon electronics manufacture.

Journal Article↗
PubMed2006

Mesostructured germanium with cubic pore symmetry.

Regular mesoporous oxide materials have been widely studied and have a range of potential applications, such as catalysis, absorption and separation. They are not generally considered for their optical and electronic properties. Elemental semiconductors with nanopores running through them represent a different form of framework material with physical characteristics contrasting with those of the more conventional bulk, thin film and nanocrystalline forms. Here we describe cubic mesostructured germanium, MSU-Ge-1, with gyroidal channels containing surfactant molecules, separated by amorphous walls that lie on the gyroid (G) minimal surface as in the mesoporous silica MCM-48 (ref. 2). Although Ge is a high-melting, covalent semiconductor that is difficult to prepare from solution polymerization, we succeeded in assembling a continuous Ge network using a suitable precursor for Ge(4-) atoms. Our results indicate that elemental semiconductors from group 14 of the periodic table can be made to adopt mesostructured forms such as MSU-Ge-1, which features two three-dimensional labyrinthine tunnels obeying Ia3d space group symmetry and separated by a continuous germanium minimal surface that is otherwise amorphous. A consequence of this new structure for germanium, which has walls only one nanometre thick, is a wider electronic energy bandgap (1.4 eV versus 0.66 eV) than has crystalline or amorphous Ge. Controlled oxidation of MSU-Ge-1 creates a range of germanium suboxides with continuously varying Ge:O ratio and a smoothly increasing energy gap.

Letter↗
PubMed2006

A guest-free germanium clathrate.

The challenges associated with synthesizing expanded semiconductor frameworks with cage-like crystal structures continue to be of interest. Filled low-density germanium and silicon framework structures have distinct properties that address important issues in thermoelectric phonon glass-electron crystals, superconductivity and the possibility of Kondo insulators. Interest in empty framework structures of silicon and germanium is motivated by their predicted wide optical bandgaps of the same magnitude as quantum dots and porous silicon, making them and their alloys promising materials for silicon-based optoelectronic devices. Although almost-empty Na(1-x)Si136 has already been reported, the synthesis of guest-free germanium clathrate has so far been unsuccessful. Here we report the high-yield synthesis and characteristics of germanium with the empty clathrate-II structure through the oxidation of Zintl anions in ionic liquids under ambient conditions. The approach demonstrates the potential of ionic liquids as media for the reactions of polar intermetallic phases.

Journal Article↗
PubMed2004

Organotrichlorogermane synthesis by the reaction of elemental germanium, tetrachlorogermane and organic chloride via dichlorogermylene intermediate.

Organotrichlorogermanes were synthesized by the reaction of elemental germanium, tetrachlorogermane and organic chlorides, methyl, propyl, isopropyl and allyl chlorides. Dichlorogermylene formed by the reaction of elemental germanium with tetrachlorogermane was the reaction intermediate, which was inserted into the carbon-chlorine bond of the organic chloride to give organotrichlorogermane. When isopropyl or allyl chloride was used as an organic chloride, organotrichlorogermane was formed also in the absence of tetrachlorogermane. These chlorides were converted to hydrogen chloride, which subsequently reacted with elemental germanium to give the dichlorogermylene intermediate. The reaction of elemental germanium, tetrachlorogermane and organic chlorides provides a simple and easy method for synthesizing organotrichlorogermanes, and all the raw materials are easily available.

Journal Article↗