Ge Nanoparticles Research Articles

Alleviated volume changes of germanium anode via facile chemical confinement strategy

Germanium (Ge) anode shows great promise in overcoming unsatisfied capacity and dendrite formation concerns facing conventional graphite anodes in next generation lithium ion batteries. However, volume changes during repeated alloying and de-alloying cycles seriously impair structural stability and cycle lifespan. In this work, a facile chemical confinement strategy has been firstly proposed to alleviate volume changes of Ge anode. Benefited from strong binding interaction between Ge and ZnS, discrete Ge nanoparticle can be successfully encapsulated within thin protective ZnS shell and N-doped carbon layer (Ge-ZnS@N-C) after two-step carbonization and sulfurization of polydopamine-coating Zn2GeO4 nanorod precursors. In contrast, bulk Ge aggregates and hollow N-doped carbon nanotubes can be formed without chemical confinement of ZnS. The as-prepared Ge-ZnS@N-C sample displays multifold structural merits, including nanosized Ge particles with highly electrochemical activity, sufficient pores and functional groups that facilitate ion diffusion. Besides, protective ZnS shell and N-doped carbon layer can suppress volume changes of Ge nanoparticles and guarantee high electrode reversibility, demonstrated by a series of in-situ and ex-situ experiments. The as-synthesized Ge-ZnS@N-C anodes exhibit stable long-cycle performance (1389.7 mAh/g after 450 cycles at a current density of 0.5 A/g) and excellent rate performance (548.5 and 397.8 mAh/g at 5.0 and 8.0 A/g, respectively).

(Invited) Microwave-Assisted Synthesis and Characterization of Doped Ge Nanocrystals

Ge is one of the quintessential semiconductors being considered in nanoform for optoelectronic applications. As a group 14 semiconductor, bulk Ge has a small bandgap and a large Bohr exciton radius, making it an attractive semiconductor for various applications, including solar cell technology, photodetectors, and integrated flash memory devices. I will present our work on doped and alloyed Ge nanoparticles via microwave-assisted synthesis and galvanic replacement. I will present new insights from this chemical route that may impact the nanoparticle synthesis of other covalently bonding semiconductors.

Accurate and efficient prediction of optical gaps in silicon and germanium nanoparticles using a high-local-exchange density functional

We investigated the HOMO-LUMO gaps and the optical gaps of Si and Ge nanoparticles (NPs) with various terminations and sizes using different functionals (HLE16, B3LYP, HSE-HJS) and basis sets (CRENBL, def2-SVP, def2-TZVP). The high-local-exchange functional HLE16, without Hartree–Fock exchange, effectively reproduces optical gaps using HOMO−LUMO gaps, offering a cost-effective alternative to hybrid functionals and TDDFT in nanoscale systems. Size (quantum confinement effects) and termination ligands (surface effects) significantly impact energy gaps: nonpolar CH3 had minimal effects, while polar ligands reduced gaps notably. Finally, ECP basis sets like CRENBL are better suited for NP electronic structures than all-electron basis sets.

Clean water harvesting and power generation by solar-absorbing Germanium@k-carrageenan evaporator demonstrating superior energy conversion

The deterioration of climate exacerbates the freshwater crisis. Solar-thermal interfacial evaporation, using sunlight as a driving energy source, is a promising approach to provide an effective solution to freshwater shortages. However, the low energy conversion efficiency and expensive evaporator manufacturing are still to be resolved. Herein, a strategy of clean water harvesting by solar-absorbing germanium@k-carrageenan (Ge@CA) evaporator demonstrating superior energy conversion is proposed. The Ge nanoparticles exhibit a significant solar absorption of 92.33% to achieve efficient solar-thermal conversion. The CA hydrogel provides three-dimensional water transmission channels to the evaporating surface. Meanwhile, the Ge nanoparticles can be fabricated by a facile ball-milling method. The CA as a cheap biomass can be easily interacted with KCl to obtain the porous hydrogel. Taking the advantages of Ge nanoparticles and CA hydrogel, the Janus-type Ge@CA hydrogel evaporator can achieve an evaporation rate of 2.88 kg m−2·h−1 and a solar-vapor conversion efficiency of 82.65% under 1 sun irradiation. Furthermore, the evaporator can produce thermoelectricity with the output voltage of 140.95 mV and the short-circuit current of 13.32 mA, yielding a power of 1.17 W m−2. This reported solar device has huge potential for cutting-edge solar harvesting and usage.

A theoretical investigation on MgB11N12, GeB11N12, GaB11N12, SiB11N12, AlB11N12, and pristine B12N12 clusters for sensing Memantine and its drug delivery for Alzheimer’s disease

As an important problem, Alzheimer disease has resulted in thousands of deaths in the human society. Thus, researches around drug design and drug delivery methods for treating this illness is crucial. The MgB11N12, GeB11N12, GaB11N12, SiB11N12, AlB11N12 and pristine B12N12 clusters were designed to investigate effective modes of transporting memantine (MMT) nanoparticles as anti-Alzheimer agents.The results showed that among all considered heteroatoms, the Germanium, and Gallium atoms have the highest effect on decreasing the Eg of the system albeit by making the B12N12 clusters, a semiconductor-like nanoparticle. Due to these results, GeB11N12 derivate with the Eg of 2.76182 eV, is a suitable semiconductor cluster. Also, after adsorption of MMT, the Ge nanoparticles enhances Eg to 3.32533 eV, resulting in a strong signal. Thus, between all studied clusters, the GeB11N12, is the best choice to be used as a sensor for detection of MMT residues. Additionally, the energy surface data indicated that the SiB11N12 is a suitable nanoparticle for delivering memantine, better than the pristine B12N12 cluster. We hope this work will be useful for future experimental studies about the adsorption and sensing of MMT drug residues.

Triblock Polymer/Acetylene Black Dual‐Assisted Preparation of Ge/C Nanocomposites with Superior Lithium Storage Performance

AbstractAnode materials based on IV main group elements like Si, Ge, and Sn show great potential for lithium‐ion batteries (LIBs) due to their high specific capacity and low working potential. However, issues such as volume expansion and lattice pulverization hinder their practical usage. To address these issues for Ge, a novel F127 triblock polymer/acetylene black dual‐assisted strategy is proposed to achieve uniform dispersion of polycrystalline Ge, enabling the preparation of Ge@C nanocomposites via hydrogen reduction. The introduced F127 triblock polymer and acetylene black serves a dual purpose to enhance electrical conductivity and prevent Ge nanoparticles from agglomeration. When tested as anode material for LIBs, the Ge@C nanocomposites exhibit exceptional electrochemical performances, demonstrating a sustained specific discharge capacity of 780 mA h g−1 at 0.2 A g−1 after 100 cycles. Moreover, the capacity remains at 767 mA h g−1 even after 300 cycles at a higher current density of 0.5 A g−1. These enhanced lithium storage performances are attributed to the combined effects of well‐dispersed tiny Ge nanoparticles, uniform carbon coating, and an abundance of defects. These factors effectively mitigate the volume expansion and lattice pulverization of Ge nanoparticles and concurrently enhance their conductivity, leading to improved overall performance in LIBs.

Complementary absorption effect to improve the optical efficiency of dual-absorption-layered PSCs

By taking advantage of the complementary absorption effect of germanium (Ge) and perovskite, a novel perovskite solar cell (PSC) was proposed by stacking Ge and perovskite thin films to serve as the dual absorption layer. Its absorption spectra and photocurrent were calculated and optimized as a function of the thickness of Ge film by finite element method (FEM). Then, the optical efficiency was further boosted by embedding an array of Ge semi-ellipsoidal nanoparticles within the perovskite film. The predicted maximum photocurrent is revealed to reach 45.72 mA/cm2, which is 2.55 times larger than that of planar referenced PSC. Besides the complementary absorption effect, the localized surface plasmon resonance (LSPR) of Ge nanoparticles and the grating effects of Ge nanoparticle array are revealed to contribute to the obtained Jsc improvement. The present work is insightful for future design and applications of PSCs by introducing Ge thin film and Ge nanoparticles.

Laser-Synthesized Germanium Nanoparticles as Biodegradable Material for Near-Infrared Photoacoustic Imaging and Cancer Phototherapy.

Biodegradable nanomaterials can significantly improve the safety profile of nanomedicine. Germanium nanoparticles (Ge NPs) with a safe biodegradation pathway are developed as efficient photothermal converters for biomedical applications. Ge NPs synthesized by femtosecond-laser ablation in liquids rapidly dissolve in physiological-like environment through the oxidation mechanism. The biodegradation of Ge nanoparticles is preserved in tumor cells in vitro and in normal tissues in mice with a half-life as short as 3.5 days. Biocompatibility of Ge NPs is confirmed in vivo by hematological, biochemical, and histological analyses. Strong optical absorption of Ge in the near-infrared spectral range enables photothermal treatment of engrafted tumors in vivo, following intravenous injection of Ge NPs. The photothermal therapy results in a 3.9-fold reduction of the EMT6/P adenocarcinoma tumor growth with significant prolongation of the mice survival. Excellent mass-extinction of Ge NPs (7.9 L g-1 cm-1 at 808nm) enables photoacoustic imaging of bones and tumors, following intravenous and intratumoral administrations of the nanomaterial. As such, strongly absorbing near-infrared-light biodegradable Ge nanomaterial holds promise for advanced theranostics.

F127 assisted fabrication of Ge/rGO/CNTs nanocomposites with three-dimensional network structure for efficient lithium storage

To solve the volume expansion and poor electrical conductivity of germanium-based anode materials, Ge/rGO/CNTs nanocomposites with three-dimensional network structure are fabricated through the dispersion of polyethylene-polypropylene glycol (F127) and reduction of hydrogen. An interesting phenomenon is discovered that F127 can break GeO2 polycrystalline microparticles into 100 nm nanoparticles by only physical interaction, which promotes the uniform dispersion of GeO2 in a carbon network structure composed of graphene (rGO) and carbon nanotubes (CNTs). As evaluated as anode material of Lithium-ion batteries, Ge/rGO/CNTs nanocomposites exhibit excellent lithium storage performance. The initial specific capacity is high to 1549.7 mAh/g at 0.2 A/g, and the reversible capacity still retains 972.4 mAh/g after 100 cycles. The improved lithium storage performance is attributed to that Ge nanoparticles can effectively slow down the volume expansion during charge and discharge processes, and three-dimensional carbon networks can improve electrical conductivity and accelerate lithium-ion transfer of anode materials.

Stabilization of Colloidal Germanium Nanoparticles: From the Study to the Prospects of the Application in Thin-Film Technology.

We present the stabilization of halide-terminated Ge nanoparticles prepared via a disproportionation reaction of metastable Ge(I)X solutions with well-defined size distribution. Further tailoring of the stability of the Ge nanoparticles was achieved using variations in the substituent. Ge nanoparticles obtained in this way are readily dispersed in organic solvents, long-term colloidally stable, and are perfect prerequisites for thin-film preparation. This gives these nanomaterials a future in surface-dependent optical applications, as shown for the halide-terminated nanoparticles.

Wide frequency phonons manipulation in Si nanowire by introducing nanopillars and nanoparticles

Abstract The combination of different nanostructures can hinder phonons transmission in a wide frequency range and further reduce the thermal conductivity (TC). This will benefit the improvement and application of thermoelectric conversion, insulating materials and thermal barrier coatings, etc. In this work, the effects of nanopillars and Ge nanoparticles (GNPs) on the thermal transport of Si nanowire (SN) were investigated by nonequilibrium molecular dynamics (NEMD) simulation. By analyzing phonons transport behaviors, it is confirmed that the introduction of nanopillars leads to the occurrence of low-frequency phonons resonance, and nanoparticles enhance high-frequency phonons interface scattering and localization. The results showed that phonons transport in the whole frequency range can be strongly hindered by the simultaneously introduction of nanopillars and nanoparticles. In addition, the effects of system length, temperature, sizes and numbers of nanoparticles on the TC were investigated. Our work provides useful insights into effective regulation of the TC of nanomaterials.

F127/PDA dual-assisted fabricating high dispersed Ge nanoparticles /N-doped porous carbon composites with efficient lithium storage

Nanocrystallization and carbon composite are effective methods to solve the mechanical instability and low conductivity of Ge-based anode materials. In this work, a meaningful phenomenon is discovered that F127 can effectively disperse GeO2 polycrystalline particles, which facilitates the formation of Ge nanoparticles embedded in N-doped carbon (Ge/N-C) composites. Polydopamine (PDA) has cross-linking effect, effectively alleviating the reaggregation of GeO2 nanoparticles, and its derived N-doped carbon ensures the uniform dispersion and independent structure of Ge nanoparticles. When assessed as anode material for lithium-ion batteries (LIBs), Ge/N-C composites exhibit a high discharge capacity of 1323 mA h g−1 in the second cycle at 0.2 A g−1 and 981 mA h g−1 after 100 cycles, with a capacity retention rate of 74%. Additionally, the composites show high-rate capability of 959 mA h g−1 at 2 A g−1. The excellent lithium storage performance is attributed to that the synergistic effect between three-dimensional carbon network structure and Ge nanoparticles, which provides stable mechanical structure and abundant redox sites, suppressing volume expansion and accelerating the electrochemical reaction kinetics.

In situ magnesiothermic reduction synthesis of a Ge@C composite for high-performance lithium-ion batterie anodes.

Metallothermic, especially magnesiothermic, solid-state reactions have been widely applied to synthesize various materials. However, further investigations regarding the use of this method for composite syntheses are needed because of the high reactivity of magnesium. Herein, we report an in situ magnesiothermic reduction to synthesize a composite of Ge@C as an anode material for lithium-ion batteries. The obtained electrode delivered a specific capacity of 454.2 mAh·g-1 after 200 cycles at a specific current of 1000 mA·g-1. The stable electrochemical performance and good rate performance of the electrode (432.3 mAh·g-1 at a specific current of 5000 mA·g-1) are attributed to the enhancement in distribution and chemical contact between Ge nanoparticles and the biomass-based carbon matrix. A comparison with other synthesis routes has been conducted to demonstrate the effectiveness of contact formation during in situ synthesis.

Solid-state processed novel germanium/reduced graphene oxide composite: Its detailed characterization, formation mechanism and excellent Li storage ability

By using a simple solid-state reduction process, germanium oxide (GeO2) and graphene oxide (GO) are reduced to germanium (Ge) and reduced graphene oxide (rGO), respectively, to form Ge/rGO composite. Transmission electron microscopy showed that clusters of Ge nanoparticles are decorated on the graphene layers of rGO. Detailed x-ray diffraction, Raman scattering, and x-ray photoelectron spectroscopic analyses confirmed Ge/rGO composite formation. The thermal stability of Ge/rGO composite and the reduction mechanism through which the composite is formed are experimentally elucidated. Further, Brunauer–Emmett–Teller (BET) specific surface area, average pore volume, and average pore size of Ge/rGO composite are measured to be ∼115 m2/g, ∼0.4 cm3/g, and ∼14 nm, respectively. The thermal analysis quantified the amount of rGO in the Ge/rGO composite to be ∼66%. As-synthesized Ge/rGO composite is tested as anode material in Li-ion batteries. When cycled at 160 mA/g current density and in the 0.005–3.0 V voltage range, the composite showed an excellent reversible capacity of ∼539 mAh/g that corresponds to 98% capacity retention at the end of the 100th cycle. The Ge/rGO composite also showed high reversible capacity retention, good rate capability, and excellent cycle life when tested at 80 and 320 mA/g in the same voltage range. The redox peaks in the cyclic voltammetry (CV) curves revealed that alloying-dealloying and electrochemical adsorption-desorption mechanisms are the primary reasons for the lithium-ions storage by Ge and rGO, respectively. A constant area under the CV curves throughout the test indicated the stable capacity. Also, the CV results align with the galvanostatic cycling results.

Synthesis of Nano-Structured Ge as Transmissive or Reflective Saturable Absorber for Mode-Locked Fiber Laser.

Amorphous-Ge (α-Ge) or free-standing nanoparticles (NPs) synthesized via hydrogen-free plasma-enhanced chemical vapor deposition (PECVD) were applied as transmissive or reflective saturable absorbers, respectively, for starting up passively mode-locked erbium-doped fiber lasers (EDFLs). Under a threshold pumping power of 41 mW for mode-locking the EDFL, the transmissive α-Ge film could serve as a saturable absorber with a modulation depth of 52-58%, self-starting EDFL pulsation with a pulsewidth of approximately 700 fs. Under a high power of 155 mW, the pulsewidth of the EDFL mode-locked by the 15 s-grown α-Ge was suppressed to 290 fs, with a corresponding spectral linewidth of 8.95 nm due to the soliton compression induced by intra-cavity self-phase modulation. The Ge-NP-on-Au (Ge-NP/Au) films could also serve as a reflective-type saturable absorber to passively mode-lock the EDFL with a broadened pulsewidth of 3.7-3.9 ps under a high-gain operation with 250 mW pumping power. The reflection-type Ge-NP/Au film was an imperfect mode-locker, owing to their strong surface-scattered deflection in the near-infrared wavelength region. From the abovementioned results, both ultra-thin α-Ge film and free-standing Ge NP exhibit potential as transmissive and reflective saturable absorbers, respectively, for ultrafast fiber lasers.

Atomic-scale in situ observation of electron beam and heat induced crystallization of Ge nanoparticles and transformation of Ag@Ge core-shell nanocrystals.

Crystallization of amorphous materials by thermal annealing has been investigated for numerous applications in the fields of nanotechnology, such as thin-film transistors and thermoelectric devices. The phase transition and shape evolution of amorphous germanium (Ge) and Ag@Ge core-shell nanoparticles with average diameters of 10 and 12nm, respectively, were investigated by high-energy electron beam irradiation and in situ heating within a transmission electron microscope. The transition of a single Ge amorphous nanoparticle to the crystalline diamond cubic structure at the atomic scale was clearly demonstrated. Depending on the heating temperature, a hollow Ge structure can be maintained or transformed into a solid Ge nanocrystal through a diffusive process during the amorphous to crystalline phase transition. Selected area diffraction patterns were obtained to confirm the crystallization process. In addition, the thermal stability of Ag@Ge core-shell nanoparticles with an average core of 7.4 and a 2.1nm Ge shell was studied by applying the same beam conditions and temperatures. The results show that at a moderate temperature (e.g., 385°C), the amorphous Ge shell can completely crystallize while maintaining the well-defined core-shell structure, while at a high temperature (e.g., 545°C), the high thermal energy enables a freely diffusive process of both Ag and Ge atoms on the carbon support film and leads to transformation into a phase segregated Ag-Ge Janus nanoparticle with a clear interface between the Ag and Ge domains. This study provides a protocol as well as insight into the thermal stability and strain relief mechanism of complex nanostructures at the single nanoparticle level with atomic resolution.

Spinodal Decomposition Method for Structuring Germanium–Carbon Li-Ion Battery Anodes

To increase the energy density of lithium-ion batteries (LIBs), high-capacity anodes which alloy with Li ions at a low voltage against Li/Li+ have been actively pursued. So far, Si has been studied the most extensively because of its high specific capacity and cost efficiency; however, Ge is an interesting alternative. While the theoretical specific capacity of Ge (1600 mAh g-1) is only half that of Si, its density is more than twice as high (Ge, 5.3 g cm-3; Si, 2.33 g cm-3), and therefore the charge stored per volume is better than that of Si. In addition, Ge has a 400 times higher ionic diffusivity and 4 orders of magnitude higher electronic conductivity compared to Si. However, similarly to Si, Ge needs to be structured in order to manage stresses induced during lithiation and many reports have achieved sufficient areal loadings to be commercially viable. In this work, spinodal decomposition is used to make secondary particles of about 2 μm in diameter that consist of a mixture of ∼30 nm Ge nanoparticles embedded in a carbon matrix. The secondary structure of these germanium-carbon particles allows for specific capacities of over 1100 mAh g-1 and a capacity retention of 91.8% after 100 cycles. Finally, high packing densities of ∼1.67 g cm-3 are achieved in blended electrodes by creating a bimodal size distribution with natural graphite.

Three-dimensional honeycomb-like porous carbon embedded with Ge nanoparticles anode composites for ultrastable lithium storage

Designing a kind of electrode material with effective morphology and structural function is always a topical issue in the field of electrochemical energy storage. Herein, we report a simple and scalable NH4Cl/KOH etching method to construct the three-dimensional honeycomb-like porous carbon material derived from biomass sweet potato starch, then load Ge nanoparticles for the use as anode material. This three-dimensional honeycomb material contains uniform cavities with size of 3–6 µm, which can provide more space for the adsorption of Ge nanoparticles because of a higher specific surface area and an increased graphitization degree. This specific structure can maintain stability and mitigate the effect of volume expansion of Ge nanoparticles, while it can effectively improve the electronic conductivity and electrochemical activity of the Ge-BSPPC composite. Therein, the honeycomb porous Ge-BSPPC composite exhibits excellent discharge capacity and ultrastable lithium storage ability: the initial discharge capacity of 1257 mAh g−1, with the initial coulombic efficiency of 85.4%; the stable capacity after 100 cycles of 1025 mAh g−1, with the coulombic efficiency of 97.8%. This method provides a simple and cost-efficient approach for converting biomass into high-performance electrode materials.

Facile synthesis of high-entropy alloy nanoparticles on germanane, Ge nanoparticles and wafers.

The unique solid-solution structure and multi-element compositions of high-entropy alloy nanoparticles (HEA NPs) have garnered substantial attention. Various methods have been developed to prepare a diverse array of HEA NPs using different substrates for support and stabilization. In this study, we present a facile surface-mediated reduction method to prepare HEA NPs (AuAgCuPdPt) decorated germanane (HEA NPs@GeNSs), and employ X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) to characterize their structure, composition, and morphology. Subsequently, we demonstrate that the HEA NPs can be liberated from the surfaces of GeNSs as freestanding systems via straightforward exposure to UV light. We also explore germanium nanoparticles (GeNPs) as an alternative substrate for HEA NP formation/production, given their similarity to germanane and their Ge-H surface. Finally, we extend our investigation to bulk Ge wafers and demonstrate successful deposition of HEA NPs.

Inoculation of soybean seeds by rhizobia with nanometal carboxylates reduces the negative effect of drought on N<sub>2</sub> and CO<sub>2</sub> assimilation

The effect of individual nanometals (Co, Fe, Cu, Ge) carboxylates (NMC) as components of the suspension for seeds inoculation with rhizobia on the nitrogen fixation rate and the parameters of CO2 and H2O gas exchange in soybean plants grown under different water conditions was investigated. The scheme of trials included the following variants: 1 – seeds + strain B1-20; 2 – seeds + (strain B1-20 + nano-cobalt carboxylate); 3 – seeds + (strain В1-20 + nano-ferrum carboxylate); 4 – seeds + (strain B1-20 + nano-cuprum carboxylate); 5 – seeds + (strain B1-20 + nano-germanium carboxylate). The results showed that during the flowering period, drought (30% field capacity) significantly reduced the rates of nitrogen fixation (Nfx), CO2 net assimilation (An), and transpiration (Tr) in soybean plants. Inoculation of seeds by rhizobia with NMC before sowing reduced the negative effect of drought on these physiological processes. Close correlations were found between the rates of Nfx and An and the stomatal conductance for CO2 and An rates. It was concluded that pre-sowing treatment of seeds by rhizobia with NMC mitigates the negative effect of drought on the main components of soybean-rhizobia symbiosis productivity formation – nitrogen fixation and CO2 assimilation, and also contributes to their recovery after the removal of the stressor. The most effective for this was the use of Ge and Fe nanoparticle carboxylates.