Gel synthesis and crystallization of lithium-germanate glass powders

Lithium germanate gels, whose compositions are expressed by the general formula Li₂O·xGeO₂ with x=3; 4; 7, were synthesized by hydrolytic polycondensation of germanium ethoxide with lithium methoxide (x=3 and 7) or lithium hydroxide monohydrate (x=4) in alcoholic medium. The values of glass transition temperature of the gels exhibit a maximum at x=4. Crystallization behaviour of the gels, examined by differential thermal analysis and X-ray diffraction, is reported and discussed. The terms x=4 and 7 crystallize in two steps. Microcrystallites of the same composition of the gel are initially formed in an amorphous matrix and are then converted at higher temperatures into well shaped crystals. In term x=3, Li₂GeO₃ and Li₂Ge₄O₉ crystals are directly formed. The values of activation energy for each crystallization step are consistent with the crystallization mechanisms and comparable with those reported with conventional melt glasses from oxides.     

Formation of GeO2 under Graphene on Ge(001)/Si(001) Substrates Using Water Vapor

The problem of graphene protection of Ge surfaces against oxidation is investigated. Raman, X-Ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements of graphene epitaxially grown on Ge(001)/Si(001) substrates are presented. It is shown that the penetration of water vapor through graphene defects on Gr/Ge(001)/Si(001) samples leads to the oxidation of germanium, forming GeO₂. The presence of trigonal GeO₂ under graphene was identified by Raman and XRD measurements. The oxidation of Ge leads to the formation of blisters under the graphene layer. It is suggested that oxidation of Ge is connected with the dissociation of water molecules and penetration of OH molecules or O to the Ge surface. It has also been found that the formation of blisters of GeO₂ leads to a dramatic increase in the intensity of the graphene Raman spectrum. The increase in the Raman signal intensity is most likely due to the screening of graphene by GeO₂ from the Ge(001) surface.     

Micropattern of GeO2/GeC lines prepared by UV irradiation and heat treatment of polygermane copolymers of methylphenylgermylene/phenylgermyne units

Upon ultraviolet irradiation of polygermane copolymers of methylphenylgermylene/phenylgermyne units (PhMeGe)_n(PhGe)_m in air, the germanium–germanium bond in the copolymer film changed into a digermoxane chain. Laser flash photolysis of the copolymer film showed the intermediacy of polygermyl radicals generated by Ge–Ge bond homolysis. The XPS showed the formation of germanium carbide (GeC) and germanium dioxide (GeO₂) upon heating the unirradiated and irradiated copolymer (PhMeGe)_n(PhGe)_m films, respectively. A relatively high-resolution micro- pattern of GeC/GeO₂ was obtained by combining the photochemical and thermal properties of the copolymers of methylphenylgermylene/phenylgermyne units. © 1997 John Wiley & Sons, Ltd.     

Synthesis and Characterization of the Germanium Sulfonate Ge(CH3SO3)2 – a 3D Coordination Network Solid

The reaction of germanium(II)‐bis(2‐methoxyphenyl)methoxide with methanesulfonic acid provides the germanium(II) sulfonate Ge(CH₃SO₃)₂ ( 1 ), which was characterized by X‐ray diffraction, elemental analysis, NMR spectroscopy, and IR spectroscopy. The decomposition process of 1 was investigated by thermal gravimetric analysis (TGA) and temperature‐dependent X‐ray powder diffraction (PXRD) and both are consistent with the formation of GeO₂ as major final product. Single crystal X‐ray diffraction at 110 K revealed the chiral tetragonal space group P4₁2₁2 and formation of a three‐dimensional (3D) coordination network solid. The 3D network is composed of interconnected twenty four‐membered rings comprising bridging methanesulfonate groups, which link the germanium atoms.     

Effect of dicitrato- and dimalatogermanic acids on polycondensation of maleic anhydride with ethylene glycol

The catalytic activity of citric (H₄Citr) and malic (H₃Mal) acids, their coordination compounds with germanium(IV) H₂[Ge(HCit)₂] and H₂[Ge(Mal)₂], and germanium dioxide GeO₂ in polycondensation of maleic anhydride and ethylene glycol at various temperatures was studied (catalyst: ethylene glycol molar ratio 0.01: 1). The process kinetics was evaluated and the time of its completion was determined. The copolymerization kinetics of some of the prepared oligoesters with triethylene glycol dimethacrylate was studied, and the copolymer properties were determined.     

Tuning thermal stability and electronic properties of germanium oxide on Ge(001) surface with the incorporation of nitrogen

The application of germanium as a channel material of transistors in near future requires an improved understanding of the interface between germanium and its potential passivation layer. In this study, we study effects of nitrogen incorporation on the thermal stability and electronic properties of GeO_xN_y/Ge interface by using high‐resolution X‐ray photoemission spectroscopy. We find that with the increasing nitrogen concentration in the GeO_xN_y films, the thermal stability can be increased, while the valence band offset with the Ge(001)substrate is decreased. First‐principles calculations further suggest that the unpaired p orbitals of nitrogen atoms induce electronic states near valence band edge, contributing to the reduction of the valence band offset. Our results provide a possibility to tune electronic and thermal properties of GeO_xN_y/Ge interface by controlling nitrogen concentrations during the growth.     

Ab initio study of the high‐temperature phase transition in crystalline GeO2

Germanium dioxide (GeO₂) takes two forms at ambient pressure: a thermodynamically stable rutile‐type structure and a high‐temperature quartz‐type polymorph. Here, we investigate the phase stability at finite temperatures by ab initio phonon and thermochemical computations. We use gradient‐corrected density‐functional theory (PBE‐GGA) and pay particular attention to the modeling of the “semicore” germanium 3d orbitals (ascribing them either to the core or to the valence region). The phase transition is predicted correctly in both cases, and computed heat capacities and entropies are in excellent agreement with thermochemical database values. Nonetheless, the computed formation energies of α‐quartz‐type GeO₂ (and, consequently, the predicted transition temperatures) differ significantly depending on theoretical method. Remarkably, the simpler and cheaper computational approach produces seemingly better results, not worse. In our opinion, GeO₂ is a nice test case that illustrates both possibilities and limitations of modern ab initio thermochemistry. © 2013 Wiley Periodicals, Inc.     

First-principles study of structural,elastic, electronic and optical properties of rutile GeO2 and α-quartz GeO2

Structural parameters, elastic, electronic, bonding and optical properties of rutile GeO₂ and α-quartz GeO₂ have been investigated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density functional theory (DFT). The ground-state properties obtained by minimizing the total energy are in favorable agreement with the previous work. Two phases of GeO₂ are found to be elastically stable and we have derived the bulk, shear and Young’s modulus, Poisson coefficient for rutile GeO₂ and α-quartz GeO₂. We estimated the Debye temperature of rutile GeO₂ and α-quartz GeO₂ from the acoustic velocity. Electronic and chemical bonding properties have been studied from the calculation of band structure, density of states and charge densities. Furthermore, in order to clarify the mechanism of optical transitions for rutile GeO₂ and α-quartz GeO₂, the complex dielectric function, refractive index, extinction coefficient, optical reflectivity, absorption coefficient, energy-loss spectrum and the complex conductivity function are calculated, which show the significant optical anisotropy in the components of polarization directions (100) and (001) for rutile GeO₂ and α-quartz GeO₂.     

碱熔融-电感耦合等离子体原子发射光谱法测定氧化铟锡烧结混合粉中5种杂质元素

采用氢氧化钠熔融样品,热水浸取后盐酸酸化,建立了碱熔融-电感耦合等离子体原子发射光谱(ICP-AES)法测定氧化铟锡烧结混合粉中Fe、Ca、Mg、Al和Si等元素的分析方法.试验结果表明:称取0.500 0 g试样,加入0.80 g氢氧化钠,在灰化炉中熔融120 min,可将样品完全溶解.基体铟和锡的干扰采用基体匹配法消除,被测元素之间没有光谱干扰.钠盐对硅的测定有一定影响,可在标准溶液中加入一定量氢氧化钠予以消除.对方法进行精密度和加标回收试验,测得结果的相对标准偏差均小于5%,方法加标回收率在90%~105%之间.     

Fabrication of newly developed pectin –GeO2 nanocomposite using extreme biomimetics route and its antibacterial activities

The combination of pectins and germanium dioxide may generate novel materials with excellent and unique properties combining the advantages of macromolecules, derived from renewable resources and metal oxide nanoparticles. Pectin–GeO₂ nanocomposite was prepared by hydrothermal method at room temperature. Structural morphology and chemical interactions between GeO₂ and pectin were analyzed using Fourier Transform Infrared Spectroscopy Equipped with Attenuated Total Reflectance (FTIR-ATR), AC impedance spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray Spectrophotometer (SEM-EDS) Thermo gravimetric analysis (TG) and Differential Scanning Calorimetry (DSC). According to the TEM observation, the average composite granules size was about 70 nm and the embedded GeO₂ nanoparticles were uniform with an average diameter of 20 nm. The pectin-germanium dioxide degradation was observed in one single DSC endoderm peak at 100°C (Area swept 276.4 mJ and enthalpy change 48.1 J/g) and three DTG peaks in the temperature range between 165 and 570°C. All the results suggest the pectin–GeO₂ nanocomposite as a promising candidate for biomedical and environmental applications.     

Time‐dependent density functional theory studies of the electronic absorption spectra of metallophthalocyanines of group IVA

Time‐dependent density functional theory (TD‐DFT) calculations were carried out in a comparative study of the electronic absorption spectra of lead(II) phthalocyaninate (PbPc), tin(II) phthalocyaninate (SnPc), tin(IV) dichlorophalocyaninate (PcSnCl₂), germanium(II) phthalocyaninate (GePc), and germanium (IV) dichlorophalocyaninate (PcGeCl₂) with the B3LYP method and LANL2DZ basis set. Our calculated bands correspond well with the experimental results. The electronic natures of all the bands in the absorption spectra are assigned and analyzed comparatively according to the calculated electronic transition contributions. With the increase of the dielectric constant from CHCl₃ to DMSO, all the electronic absorption bands are somewhat red shift, consistent with the shift rules measured experimentally. The radius of the central metals has great influence to the absorption spectra, especially for the B bands. The influence of the radius of the central metals to the absorption spectra of PcSnCl₂ and PcGeCl₂ is smaller than to the spectra of the nonplanar MPcs (M = Pb, Sn, and Ge). Axial ligands also greatly changed the electronic absorption spectra due to the change of the orbital energy level and the molecular symmetry. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Crystal growth,structures, magnetic and photoluminescent properties of NaLnGeO4 (Ln = Sm,Eu, Gd,Tb)

Single crystals of NaLnGeO₄ (Ln = Sm, Eu, Gd) were grown out of a molten sodium hydroxide flux, and their crystal structures were determined by single crystal X-ray diffraction. The lanthanide containing germanates crystallize in the orthorhombic space group of Pnma, and exhibit a complex three-dimensional structure consisting of corner- or edge-shared LnO₆, GeO₄, and NaO₆ polyhedra. UV–vis diffuse reflectance spectra indicated that the reported oxides are insulating materials with wide band gaps. The magnetic susceptibility data shows paramagnetic behavior. For the NaEuGeO₄ and NaTbGeO₄ compositions intense room temperature photoluminescence was observed.     

Ge4Cl4[MCp(CO)3]4 (M = Cr,Mo, W): A Series of Transition Metal Substituted Four-membered Cyclogermanes

The reaction of GeCl₂ · dioxane with the sodium salts NaMCp(CO)₃ (M = Cr, Mo, W) leads to new four-membered ring compounds Ge₄Cl₄[MCp(CO)₃]₄, where the remaining chlorine atom cannot be substituted by another MCp(CO)₃ substituent. A large excess of the sodium salts only leads to some minor side-reactions. All Ge₄-compounds exhibit a non-planar four-membered Ge₄ ring, which can be traced back to electrostatic effects as shown by quantum chemical calculations. Furthermore, cluster build-up reactions might be possible due to the halide substituents in the new ring compounds of germanium, showing that GeCl₂ · dioxane is an excellent starting material for the synthesis of cluster compounds of germanium.     

A new high‐pressure strontium germanate,SrGe2O5

The Sr–Ge–O system has an earth‐scientific importance as a potentially good low‐pressure analog of the Ca–Si–O system, one of the major components in the constituent minerals of the Earth's crust and mantle. However, it is one of the germanate systems that has not yet been fully examined in the phase relations and structural properties. The recent findings that the SrGeO₃ high‐pressure perovskite phase is the first Ge‐based transparent electronic conductor make the Sr–Ge–O system interesting in the field of materials science. In the present study, we have revealed the existence of a new high‐pressure strontium germanate, SrGe₂O₅. Single crystals of this compound crystallized as a co‐existent phase with SrGeO₃ perovskite single crystals in the sample recovered in the compression experiment of SrGeO₃ pseudowollastonite conducted at 6 GPa and 1223 K. The crystal structure consists of germanium–oxygen framework layers stacked along [001], with Sr atoms located at the 12‐coordinated cuboctahedral site; the layers are formed by the corner linkages between GeO₆ octahedra and between GeO₆ octahedra and GeO₄ tetrahedra. The present SrGe₂O₅ is thus isostructural with the high‐pressure phases of SrSi₂O₅ and BaGe₂O₅. Comparison of these three compounds leads to the conclusion that the structural responses of the GeO₆ and GeO₄ polyhedra to cation substitution at the Sr site are much less than that of the SrO₁₂ cuboctahedron to cation substitution at the Ge sites. Such a difference in the structural response is closely related to the bonding nature.     

Extraction—spectrophotometric determination of traces of cadmium with 4-(2-pyridylazo)resorcinol and a long-chain quaternary ammonium salt

A simple and highly sensitive extraction—spectrophotometric determination of cadmium is described. The ion-associate formed between the cadmium-PAR anionic chelate and cetyldimethylbenzylammonium chloride (CDBA) is extracted with chloroform at pH 10. The absorption maximum of the extracted species occurs at 505 nm, the molar absorptivity being (9.82 ± 0.30) × 10⁴ l mol^-1 cm^-1. The optimal concentration range for measurements is 0.2–1.0 μg Cd ml^-1; Beer's law is obeyed. The composition of the ion-associate is estimated to be CdPAR₂-2CDBA. The conditional extraction constant is log K'_ex ≈ 8. The stability constant of the cadmium—PAR chelate in aqueous solution is log β₂ = 17.5 ± 0.3. Extraction with N-benzoyl-N-phenylhydroxylamine is used to avoid several interferences. Moderate amounts of zinc are masked with sodium hydroxide.     

Chromium ion incorporation in the crystal structure of BGO

Comprehensive investigations have been performed by EPR and optical spectroscopy for Bi₃GeO₄ crystals doped with chromium ions. It is demonstrated that the known optical absorption spectrum for chromium ions, specifically, the triplet in the region 600–900 nm has an analog in the EPR spectra — the center with electron spin S = 1. The spectrum is described by the spin-Hamiltonian with the parameters D = 550 G, E = 10 G, g _xx = g _yy = 1.915, g _zz = 1.932. The EPR spectrum is dictated by Cr⁴⁺ incorporation at the germanium sites. Luminescence observed in the region 1.2–1.7 μm is also caused by transitions of Cr⁴⁺ with tetrahedral surroundings to germanium sites. Original Russian Text Copyright ? 2005 N. V. Chernei, V. A. Nadolinnyi, N. V. Ivannikova, V. A. Gusev, I. N. Kupriyanov, V. N. Shlegel, and Ya. V. Vasiliev __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 3, pp. 444–450, May–June, 2005.     

Synthesis and Properties of Triphenylgermanium Heteroaromatic Carboxylates and Crystal Structure of Triphenylgermanium 2‐Furoate

Ten triphenylgermanium heteroaromatic carboxylates Ph₃GeO₂CR (where R=2‐furanyl, 2‐furanvinyl, 2‐(5‐tertbutyl) furanyl, 2‐thiophenyl, 2‐pyridinyl, 3‐pyridinyl, 4‐pyridinyl, 3‐indolyl, 3‐indolylmethyl, 3‐indolylpropyl) were synthesized by the reaction of sodium heteroaromatic carboxylates with the triphenylgermanium chloride. All compounds were characterized by elemental analysis, ¹H NMR and MS spectra. The compounds were tested against two human tumour cell lines: MCF‐7 and WiDr. The results showed that they had high activities. The crystal structure of triphenylgermanium 2‐furoate was determined by X‐ray single crystal diffraction. The crystal belongs to monoclinic with space group P2₁/c, a = 1.1545(4), b=0.9934(3), c = 1.6284(5) nm, β= 91.59(5), Z = 4. In this crystal, the structure consists of discrete molecule containing four‐coordinate germanium atom in a distored tetrahedron.     

Préparation et structure des germanates métalliques. I

Résumé L'auteur reprend et complète la méthode de dosage microgravimétrique du germanium à l'état de germanimolybdate de tétraphénylarsonium (F _Ge=0,02137). Dans une deuxième partie, il décrit une méthode de préparation des heptagermanates alcalins et de métagermanates de métaux bivalents à partir des solutions d'oxyde GeO₂ et d'acétates métalliques. Les courbes de thermolyse et les spectres d'absorption infrarouge sont présentés. Aucun orthogermanate ne précipite des solutions aqueuses.

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Summary The author resumes and completes the method for the microgravimetric determination of germanium as the germanium molybdate of tetraphenylarsonium (F _Ge=0.02137). In a second part he describes a method for preparing some heptagermanates of divalent metals from solutions of the oxide GeO₂ and metal acetates. The thermolysis curves and the infrared absorption curves are given. No orthogermanate precipitates from aqueous solutions.

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Zusammenfassung Der Verfasser berichtet über die mikrogravimetrische Bestimmung des Germaniums als Tetraphenylarsonium-Germanium-Molybdat (F _Ge=0,02137). Im zweiten Teil der Arbeit wird die Herstellung von Alkaliheptagermanat sowie von Metagermanaten bivalenter Metalle aus Germaniumoxidlösungen und Metallacetaten beschrieben. Die Thermolysekurven und IR-Absorptionsspektren werden vorgelegt. Aus wäßrigen Lösungen fällt kein Orthogermanat aus.

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Mémoire en l'honneur du professeurA. A. Benedetti-Pichler.     

Zur chalkogenolyse von monoorganyl-germanium-trichloriden I. Halogenhaltige verbindungen

New organylgermanium sesquichlorochalcogenides (RGe)_2nY_3n−1Cl₂ (n = 3, R = t-Bu, Y=O; n = 2, R = t-Bu, Y = S; n = 2, R = t-Bu, Y=Se; n = 1, R = Mes, Y = S; n = 1, R = t-Bu, Y = Se) have been prepared by reaction of t-butyl or mesityl germanium trichloride with sodium hydroxide or sodium chalcogenides. In contrast to the sesquichalcogenides in these compounds one chalcogen atom is formally replaced by two chlorine atoms. X-ray analysis confirms that these sesquichlorochalcogenides cannot be converted into the corresponding sesquichalcogenides by replacement of the chlorine atoms owing to steric factors.     

Effects of ammonia/ammonium thiocyanate on cotton fabric

The effect of ammonia/ammonium thiocyanate (NH₃/NH₄SCN) treatment of the swelling behavior, structural changes, and physical properties of cotton sheeting was compared with that of sodium hydroxide and liquid ammonia mercerization. Increased percent shrinkage, accessibility to a large dye molecule, dyestuff absorption, swelling with water, and water imbibition showed that NH₃/NH₄SCN had improved the accessibility of the cotton fabric. X-ray diffractograms showed the characteristic Cellulose I crystal lattice. X-ray diffraction and infrared absorption spectroscopy indicated that the crystallite size was unchanged and the swelling from the NH₃/NH₄SCN treatment occurred in the amorphous regions of the cellulose since the observed crystal structure was unchanged. Moisture regain determinations and barium hydroxide absorption suggested that some recrystallization of the cellulose may have occurred from the NH₃/NH₄SCN treatment. Fibers treated with NH₃/NH₄SCN showed a cross sectional shape similar to that of the origianl fibers but with reduced lumen area.