Preparation and evaluation of germanium concentrate by ultrasonic purification of tannin germanium residue.

Germanium (Ge) is a dispersed metal primarily recovered from secondary Ge-containing resources. The traditional treatment method is hindered by incomplete impurity removal, resulting in a low grade of tannin germanium residue (TGR) and Ge concentrate, high production costs, and significant hazardous waste. This study proposes a new technology involving ultrasonic pre-purification of TGR to enhance the quality of Ge concentrate prepared by roasting. Under optimal conditions (ultrasonic power 225 W, liquid-solid ratio 7:1, H2SO4 concentration 20 g/L, reaction time 30 min, and reaction temperature 40 °C), the removal efficiencies of impurities Zn, Mg, Fe, As, and S from purified tannin germanium residue (PTGR) increased by 4.2%, 4.2%, 17.4%, 8.7%, and 2.9% respectively. Moreover, the Ge content in PTGR increased from 2.9% to 4.1%. The mechanism of ultrasonic action indicated the ultrasonic energy reduced the particle size of the reactants from 67.698 µm to 31.768 µm, thereby accelerating impurity removal. Roasting ultrasonic-purified tannin germanium residue (U-PTGR) at 650 °C with 40 L/h air flow for 120 min produced Ge concentrate with a Ge grade of 33.26%, which is 6.11% higher than the regular method. Analysis using XRD and HRTEM, combined with crystallite size calculation, revealed that the Ge concentrate prepared by U-PTGR exhibited low sintering degree, good crystal properties, and high crystallinity. Implementing this technology could save enterprises approximately $57,412 annually in production costs. Additionally, it holds significant practical importance in reducing hazardous waste emissions and promoting the high-quality development of the Ge industry.

Single-step fabrication of hybrid germanium-gold/silver nanoentities by femtosecond laser ablation and applications in SERS-based sensing.

We present a simple, fast, and single-step approach for fabricating hybrid semiconductor-metal nanoentities through liquid-assisted ultrafast (∼50 fs, 1 kHz, 800 nm) laser ablation. Femtosecond (fs) ablation of Germanium (Ge) substrate was executed in (i) distilled water (ii) silver nitrate (AgNO3-3, 5, 10 mM) (iii) Chloroauric acid (HAuCl4-3, 5, 10 mM), yielding the formation of pure Ge, hybrid Ge-silver (Ag), Ge-gold (Au) nanostructures (NSs) and nanoparticles (NPs). The morphological features and corresponding elemental compositions of Ge, Ge-Ag, and Ge-Au NSs/NPs have been conscientiously studied using different characterization techniques. Most importantly, the deposition of Ag/Au NPs on the Ge substrate and their size variation were thoroughly investigated by changing the precursor concentration. By increasing the precursor concentration (from 3 mM to 10 mM), the deposited Au NPs and Ag NPs' size on the Ge nanostructured surface was increased from ∼46 nm to ∼100 nm and from ∼43 nm to ∼70 nm, respectively. Subsequently, the as-fabricated hybrid (Ge-Au/Ge-Ag) NSs were effectively utilized to detect diverse hazardous molecules (e.g. picric acid and thiram) via the technique of surface-enhanced Raman scattering (SERS). Our findings revealed that the hybrid SERS substrates achieved at 5 mM precursor concentration of Ag (denoted as Ge-5Ag) and Au (denoted as Ge-5Au) had demonstrated superior sensitivity with the enhancement factors of ∼2.5 × 104, 1.38 × 104(for PA), and ∼9.7 × 105and 9.2 × 104(for thiram), respectively. Interestingly, the Ge-5Ag substrate has exhibited ∼10.5 times higher SERS signals than the Ge-5Au substrate.

The Limits of Electromechanical Coupling in Highly-Tensile Strained Germanium.

Speculations regarding electronic and photonic properties of strained germanium (Ge) have perpetually put it into contention for next-generation devices since the start of the information age. Here, the electromechanical coupling of <111> Ge nanowires (NWs) is reported from unstrained conditions to the ultimate tensile strength. Under tensile strain, the conductivity of the NW is enhanced exponentially, reaching an enhancement factor of ∼130 at ∼3.5% of strain. Under strains larger than ∼2.5%, the electrical properties of Ge also exhibit a dependence on the electric field. The conductivity can be further enhanced by ∼2.2× with a high bias condition at ∼3.5% of strain. Cyclic loading tests confirm that the observed electromechanical responses are repeatable, reversible, and related to the changing electronic band structure. These tests reveal the excellent prospects for utilizing strained Ge NWs in photodetector or piezoelectronic transistor applications, but significant challenges remain to realize strict direct band gap devices.

Activation with Li enables facile sodium storage in germanium.

Germanium is a promising sodium ion battery (NIB, NAB, SIB) anode material that is held back by its extremely sluggish kinetics and poor cyclability. We are the first to demonstrate that activation by a single lithiation-delithiation cycle leads to a dramatic improvement in the practically achievable capacity, in rate capability, and in cycling stability of Ge nanowires (GeNWs) and Ge thin film (GeTF). TEM and TOF-SIMS analysis shows that without activation, the initially single crystal GeNWs are effectively Na inactive, while the 100 nm amorphous GeTF sodiates only partially and inhomogeneously. Activation with Li induces amorphization in GeNWs reducing the barrier for nucleation of the NaxGe phase(s) and accelerates solid-state diffusion that aids the performance of both GeNWs and GeTF. Low rate (0.1C) Li activation also introduces a dense distribution of nanopores that lead to further improvements in the rate capability, which is ascribed to the lowered solid-state diffusion distances caused by the effective thinning of the Ge walls and by an additional Na diffusion path via the pore surfaces. The resultant kinetics are promising. Tested at 0.15C (1C = 369 mA/g, i.e. Na/Ge 1:1) for 50 cycles the GeNWs and GeTF maintain a reversible (desodiation) capacity of 346 and 418 mAh/g, respectively. They also demonstrate a capacity of 355 and 360 mAh/g at 1C and 284 and 310 mAh/g at 4C. Even at a very high rate of 10C the GeTF delivers 169 mAh/g. Preliminary results demonstrate that Li activation is also effective in promoting cycling stability of Sb blanket films.

[Characteristics and Causes of Ge Enrichment in Vegetable Growing Areas of Beixintun Town, Zhangjiakou City].

The vegetable planting base in the Beixintun area of Zhangjiakou City was selected as the study area, divided into the focus area and regional range as well as the upstream area. A total of 132 surface soil samples, 16 vertical soil profiles, 3 groups of surface profiles, and 4 samples each of colored pepper fruit, purple kale fruit, and corn fruit were collected. From the soil, rock, and crop sample Sc, Cr, Mo, Cd, V, Zn, Sr, Pb, Co Ni, Cu, Ge, and REE on the basis of the referenced germanium (Ge) enrichment standards and enrichment factor levels, it was found that the regional Ge enrichment rate was not high (19.7%), whereas the key area had a high Ge enrichment rate (52%). The spatial distribution of Ge and rare earth elements in the soils of the regional scope and the focal area showed a more obvious consistency, and further comparison of the correlation characteristics of Ge and rare earth elements in soil and crops showed that the ranking of rare earth content was purple kale>colored pepper>maize, whereas the ranking of the Ge element uptake intensity was maize (weak uptake)>purple kale (very weak uptake)>colored pepper (very weak uptake), and there was no obvious synergy between the uptake of Ge and rare earth elements by crops. The PMF and RDA analysis of 28 elements and indicators of soil in the study area showed that the source of regional Ge was dominated by natural geological background factors (66.3%), supplemented by anthropogenic activity-influenced factors (27%) and river deposition factors (6.7%). The source of Ge in the focal area was dominated by natural geological background factors (33.8%) and anthropogenic activity-influenced factors (27.2%), with river sedimentation factors (18.5%) and atmospheric dry and wet deposition factors Ge (20.5%) being supplemented. Soil Ge was positively correlated with rare earth elements and trace elements such as Cd, Zn, Mn, Ni, V, Co, and Cr and negatively correlated with the main elements CNa2[KG-*2/5]O, SiO2, and K2[KG-*2/5]O and pH. Finally, by combining the analysis of soil lateral profiles with vertical profiles, it was found that the Ge migrating from the source area to the area was primarily in the main river pathway, supplemented by the secondary river and flood flow pathways.

[Distribution Characteristics and Influencing Factors of Germanium in Soil in the Eastern Mountainous Area of the Nanyang Basin].

Based on the land quality geochemical survey results in the southwest cultivated area of Nanyang Basin, the content, spatial distribution, and enrichment characteristics of Ge in surface soil (0-20 cm) and deep soil (150-200 cm) in the eastern mountainous area of Nanyang Basin were studied, and the influencing factors of Ge in the surface soil were analyzed. The results showed that the average ω(Ge) in the surface soil and deep soil were 1.39 mg·kg-1 and 1.45 mg·kg-1, respectively. In the study area, 32.22% of surface soil and 12.77% of surface soil was rich in Ge, and the rich areas of the surface soil Ge were mainly distributed in the metamorphic rock and granite-dominant development areas. The optimal theoretical model of surface soil Ge variogram in the study area was a spherical model, and the nugget effect value was 0.434, indicating that surface soil Ge had moderate spatial correlation due to the joint influence of random factors and structural factors. The enrichment factor showed that 93.61% of Ge sites in the topsoil were mainly affected by natural factors, whereas 6.39% of Ge sites were significantly affected by human factors. The source of Ge in soil in the study area was mainly affected by the parent materials of soil formation, but the enrichment of Ge in surface soil was mainly affected by the Fe, Mn oxides, quartz, and pH in the soil.

Germanium Metasurfaces with Lattice Kerker Effect in Near-Infrared Photodetectors.

In O-and C-band optical communications, Ge is a promising material for detecting optical signals that are encoded into electrical signals. Herein, we study 2D periodic Ge metasurfaces that support optically induced electric dipole and magnetic dipole lattice resonances. By overlapping Mie resonances and electric dipole lattice resonances, we realize the resonant lattice Kerker effect and achieve narrowband absorption. This effect was applied to the photodetector demonstrated in this study. The absorptance of the Ge nanoantenna arrays increased 6-fold compared to that of the unpatterned Ge films. In addition, the photocurrent in such Ge metasurface photodetectors increases by approximately 5 times compared with that in plane Ge film photodetectors by the interaction of these strong near-fields with semiconductors and the further transformation of the optical energy into electricity.

Germanium Nanoparticles Prepared by Laser Ablation in Low Pressure Helium and Nitrogen Atmosphere for Biophotonic Applications.

Due to particular physico-chemical characteristics and prominent optical properties, nanostructured germanium (Ge) appears as a promising material for biomedical applications, but its use in biological systems has been limited so far due to the difficulty of preparation of Ge nanostructures in a pure, uncontaminated state. Here, we explored the fabrication of Ge nanoparticles (NPs) using methods of pulsed laser ablation in ambient gas (He or He-N2 mixtures) maintained at low residual pressures (1-5 Torr). We show that the ablated material can be deposited on a substrate (silicon wafer in our case) to form a nanostructured thin film, which can then be ground in ethanol by ultrasound to form a stable suspension of Ge NPs. It was found that these formed NPs have a wide size dispersion, with sizes between a few nm and hundreds of nm, while a subsequent centrifugation step renders possible the selection of one or another NP size fraction. Structural characterization of NPs showed that they are composed of aggregations of Ge crystals, covered by an oxide shell. Solutions of the prepared NPs exhibited largely dominating photoluminescence (PL) around 450 nm, attributed to defects in the germanium oxide shell, while a separated fraction of relatively small (5-10 nm) NPs exhibited a red-shifted PL band around 725 nm under 633 nm excitation, which could be attributed to quantum confinement effects. It was also found that the formed NPs exhibit high absorption in the visible and near-IR spectral ranges and can be strongly heated under photoexcitation in the region of relative tissue transparency, which opens access to phototherapy functionality. Combining imaging and therapy functionalities in the biological transparency window, laser-synthesized Ge NPs present a novel promising object for cancer theranostics.

Opto-Electrical Properties of Group IV Alloys: The Inherent Challenges of Processing Hydrogenated Germanium.

In this paper the opto-electrical nature of hydrogenated group IV alloys with optical bandgap energies ranging from 1.0 eV up to 2.3 eV are studied. The fundamental physical principles that determine the relation between the bandgap and the structural characteristics such as material density, elemental composition, void fraction and crystalline phase fraction are revealed. Next, the fundamental physical principles that determine the relation between the bandgap and electrical properties such as the dark conductivity, activation energy, and photoresponse are discussed. The unique wide range of IV valence alloys helps to understand the nature of amorphous (a-) and nanocrystalline (nc-) hydrogenated (:H) germanium films with respect to the intrinsicity, chemical stability, and photoresponse. These insights resulted in the discovery of i) a processing window that results in chemically stable Ge:H films with the lowest reported dark conductivity values down to 4.6·10-4 (Ω ·cm)-1 for chemical vapor deposited Ge:H films, and ii) O, C and Sn alloying approaches to improve the photoresponse and chemical stability of the a/nc-Ge:H alloys.

Macroscopic Versus Microscopic Schottky Barrier Determination at (Au/Pt)/Ge(100): Interfacial Local Modulation.

Macroscopic current-voltage measurements and nanoscopic ballistic electron emission spectroscopy (BEES) have been used to probe the Schottky barrier height (SBH) at metal/Ge(100) junctions for two metal electrodes (Au and Pt) and different metallization methods, specifically, thermal-vapor and laser-vapor deposition. Analysis of macroscopic current-voltage characteristics indicates that a SBH of 0.61-0.63 eV controls rectification at room temperature. On the other hand, BEES measured at 80 K reveals the coexistence of two distinct barriers at the nanoscale, taking values in the ranges 0.61-0.64 and 0.70-0.74 eV for the cases studied. For each metal-semiconductor junction, the macroscopic measurement agrees well with the lower barrier found with BEES. Ab initio modeling of BEES spectra ascribes the two barriers to two different atomic registries between the metals and the Ge(100) surface, a significant relevant insight for next-generation highly miniaturized Ge-based devices.