Germanene Nanosheets Research Articles

Density functional theory study of gas molecules inactivation pathway on pristine germanene nanosheet

By utilizing density functional theory, we investigated the adsorption of gas molecules (NO2 and SO2) on Germanene nanosheets (GeNS). Our findings reveal that GeNS displays notably high reactivity toward these gas molecules, with adsorption energies exceeding 1.00[Formula: see text]eV. The stability of GeNS at elevated temperatures and the thermodynamics of the adsorption process have been thoroughly investigated. These findings point toward promising applications for GeNS in the development of metal-free catalysts. Furthermore, the comprehensive examination of gas molecules inactivation pathways on GeNS enhances the understanding of its properties and opens avenues for exploring its potential as both catalysts and gas sensors.

Investigation on the characteristics of Q‐switched pulses in an EDFL based on the saturable absorption effect of germanene

AbstractIn this paper, an all‐fiber passively Q‐switched (QS) Er‐doped fiber laser (EDFL) was designed and successfully demonstrated by innovatively employing germanene as saturable absorber (SA). Due to its low‐warp honeycomb structure and remarkable zero bandgap property, germanene exhibits excellent potential for highly stable broadband pulse modulation. Based on the saturable absorption effect of germanene, a stable passive QS laser output was successfully achieved at 1530 nm under a threshold pump power of 63.7 mW. With the pump power increasing from 63.7 to 403.5 mW, the pulse repetition rate increases from 48.5 to 121.2 kHz accordingly. Meanwhile, we observe that the pulse width was shortened from 3.54 μs to 890 ns. The experimental results prove that germanene nanosheets have a promising future as a Q‐switcher in fiber lasers.

P-block germanenes as a promising electrocatalysts for the oxygen reduction reaction.

The oxygen reduction reaction (ORR), a pivotal process in hydrogen fuel cells crucial for enhancing fuel cell performance through suitable catalysts, remains a challenging aspect of development. This study explores the catalytic potential of germanene on Al (111), taking advantage of the successful preparation of stable reconstructed germanene layers on Al (111) and the excellent catalytic performance exhibited by germanium-based nanomaterials. Through first-principles calculations, we demonstrate that the O2molecule can be effectively activated on both freestanding and supported germanene nanosheets, featuring kinetic barriers of 0.40 and 0.04eV, respectively. The presence of the Al substrate not only significantly enhances the stability of the reconstructed germanene but also preserves its exceptional ORR catalytic performance. These theoretical findings offer crucial insights into the substrate-mediated modulation of germanene stability and catalytic efficiency, paving the way for the design of stable and efficient ORR catalysts for future applications.

Germanene Nanosheets as Saturable Absorbers for Soliton Rains and Large-Energy Pulse Generation in Passively Mode-Locked Fiber Lasers

Germanene Nanosheets as Saturable Absorbers for Soliton Rains and Large-Energy Pulse Generation in Passively Mode-Locked Fiber Lasers

Mechanical characteristics and thermal conductivity of defect single-layer buckled honeycomb germanene

This study uses molecular dynamics (MD) simulation to investigate the defect rate, defect morphology, and different temperature effects on the mechanical properties, deformation behavior, and thermal conductivities of a single layer of germanene nanosheets via a tensile process. Samples are squeezed in the middle, leading to filling in minor defects. Young’s modulus and yield strength decrease with increasing temperature and defect rates. Young’s modulus in the armchair direction is larger than that in the zigzag direction, with the samples with a random porosity of 0%and 2% and smaller than the model with a random porosity of 4% to 10%. Young’s modulus in the armchair direction is larger than in the zigzag order with all the different pore shapes. The yield strength in the armchair direction is smaller than that in the zigzag at all temperatures, all different pore shapes, and all defect rates except for the sample with a random porosity of 2%. The thermal conductivity depends on the sample direction, the defect morphologies due to the shrinkage of membranes are complicated, and all are smaller than the thermal conductivity of a perfect sample. The thermal conductivity of the perfect sample is highest at 300 K.

Two types of ultrafast mode-locking operations from an Er-doped fiber laser based on germanene nanosheets

As a member of Xenes family, germanene has excellent nonlinear saturable absorption characteristics. In this work, we prepared germanene nanosheets by liquid phase exfoliation and measured their saturation intensity as 0.6 GW/cm2 with a modulation depth of 8%. Then, conventional solitons with a pulse width of 946 fs and high-energy noise-like pulses with a pulse width of 784 fs were obtained by using germanene nanosheet as a saturable absorber for a mode-locked Erbium-doped fiber laser. The characteristics of the two types of pulses were investigated experimentally. The results reveal that germanene has great potential for modulation devices in ultrafast lasers and can be used as a material for creation of excellent nonlinear optical devices to explore richer applications in ultrafast photonics.Graphical

Investigation on the saturable absorption characteristics of GeNS and its application to harmonic mode‐locked modulation

AbstractThe high‐quality germanene nanosheets (GeNS) were fabricated by a liquid‐phase exfoliated technique and used as the saturable absorber (SA) to generate the harmonic mode‐locked (HML) pulses in an Er‐doped fiber laser. The investigation on the nonlinear absorption effect of the GeNS was carried out systemically in this work. On the basis of the GeNS SA, the third‐ and fourth‐order HML pulses with repetition rates of 5.275 and 7.031 MHz were achieved, corresponding to the minimum pulse width of 3.04 and 3.21 ps, respectively. The research reveals that the GeNS has great capability for ultrafast pulses modulation and can be used as an outstanding nonlinear optical device to expand its applications in nonlinear optics.

Inside Back Cover: Bandgap‐Engineered Germanene Nanosheets as an Efficient Photodynamic Agent for Cancer Therapy (Angew. Chem. Int. Ed. 12/2023)

Preparation of two-dimensional nanosheets with suitable band gap has been a challenge for their photodynamic applications. In their Research Article (DOI: 10.1002/anie.202215795), Min Ge, Jianlin Shi et al. report a cutting-edge regulatory approach to create H-terminated germanene with a bio-medically favorable direct band gap by a simple surface chemical modulation for bio-application in cancer photodynamic therapy.

Innenrücktitelbild: Bandgap‐Engineered Germanene Nanosheets as an Efficient Photodynamic Agent for Cancer Therapy (Angew. Chem. 12/2023)

The preparation of 2D nanosheets with suitable bandgaps for photodynamic applications has been a challenge. In their Research Article (e202215795), Han Lin, Jianlin Shi, and co-workers report a cutting-edge regulatory approach to create H-terminated germanene with a biomedically favorable direct bandgap by simple surface chemical modulation for application in cancer photodynamic therapy.

Bandgap‐Engineered Germanene Nanosheets as an Efficient Photodynamic Agent for Cancer Therapy

AbstractTwo‐dimensional (2D) monoelemental materials (Xenes) show considerable potential in bioapplications owing to their unique 2D physicochemical features and the favored biosafety resulting from their monoelemental composition. However, the narrow band gaps of Xenes prevent their broad applications in biosensors, bioimaging and phototherapeutics. In this study, it is demonstrated that 2D germanene terminated with −H via surface chemical engineering, shows a much broadened direct band gap of 1.65 eV, which enables the material to be used as a novel inorganic photosensitizer for the photodynamic therapy of singlet oxygen. Through theoretical analysis and in vitro studies, H‐germanene nanosheets demonstrate a substantially enlarged band gap and favorable biodegradability, demonstrating a substantial cancer treatment capacity. This study demonstrates the feasibility of constructing novel therapeutic photodynamic agents by surface covalent engineering for catalytic tumor therapy.

Bandgap-Engineered Germanene Nanosheets as an Efficient Photodynamic Agent for Cancer Therapy.

Two-dimensional (2D) monoelemental materials (Xenes) show considerable potential in bioapplications owing to their unique 2D physicochemical features and the favored biosafety resulting from their monoelemental composition. However, the narrow band gaps of Xenes prevent their broad applications in biosensors, bioimaging and phototherapeutics. In this study, it is demonstrated that 2D germanene terminated with -H via surface chemical engineering, shows a much broadened direct band gap of 1.65 eV, which enables the material to be used as a novel inorganic photosensitizer for the photodynamic therapy of singlet oxygen. Through theoretical analysis and in vitro studies, H-germanene nanosheets demonstrate a substantially enlarged band gap and favorable biodegradability, demonstrating a substantial cancer treatment capacity. This study demonstrates the feasibility of constructing novel therapeutic photodynamic agents by surface covalent engineering for catalytic tumor therapy.

Massive and massless plasmons in germanene nanosheets

Atomically thin crystals may exhibit peculiar dispersive electronic states equivalent to free charged particles of ultralight to ultraheavy masses. A rare coexistence of linear and parabolic dispersions yields correlated charge density modes exploitable for nanometric light confinement. Here, we use a time-dependent density-functional approach, under several levels of increasing accuracy, from the random-phase approximation to the Bethe-Salpeter equation formalism, to assess the role of different synthesized germanene samples as platforms for these plasmon excitations. In particular, we establish that both freestanding and some supported germenene monolayers can sustain infrared massless modes, resolved into an out-of-phase (optical) and an in-phase (acoustic) component. We further indicate precise experimental geometries that naturally host infrared massive modes, involving two different families of parabolic charge carriers. We thus show that the interplay of the massless and massive plasmons can be finetuned by applied extrinsic conditions or geometry deformations, which constitutes the core mechanism of germanene-based optoelectronic and plasmonic applications.

Hydrogenated Germanene Nanosheets as an Antioxidative Defense Agent for Acute Kidney Injury Treatment.

Acute kidney injury (AKI) is a sudden kidney dysfunction caused by aberrant reactive oxygen species (ROS) metabolism that results in high clinical mortality. The rapid development of ROS scavengers provides new opportunities for AKI treatment. Herein, the use of hydrogen-terminated germanene (H-germanene) nanosheets is reported as an antioxidative defense nanoplatform against AKI in mice. The simulation results show that 2D H-germanene can effectively scavenge ROS through free radical adsorption and subsequent redox reactions. In particular, the H-germanene exhibits high accumulation in injured kidneys, thereby offering a favorable opportunity for treating renal diseases. In the glycerol-induced murine AKI model, H-germanene delivers robust antioxidative protection against ROS attack to maintain normal kidney function indicators without negative influence in vivo. This positive in vivo antioxidative defense in living animals demonstrates that the present H-germanene nanoplatform is a powerful antioxidant against AKI and various anti-inflammatory diseases.

Watt-level high-stability all-solid-state passively Q-switched laser based on germanene nanosheets

Excellent Q-switching operations modulated by new two-dimensional (2D) saturable absorber (SA) materials with stable performance is a hot topic in all-solid-state pulsed laser research. In this work, the watt-level high-stability passive Q-switching operation in a solid-state Nd:YVO4 laser utilizing the 2D germanene nanosheets as SA was first realized. The nonlinear optical properties of the germanene nanosheets (Ge-Ns) were characterized by experimental means. The stable Q-switched pulse sequence was acquired with a 60.6 ns narrowest pulse width and a 528.6 kHz maximal repetition rate. The average output power of 0.965 W and the corresponding pulse peak power of 30.12 W are obtained under the pump power of 7 W. The findings of the experiments demonstrate that germanene material has remarkable nonlinear optical properties and can be used as an excellent saturable absorber in the field of optical pulse modulation.

Germanene nanosheets for mode-locked pulse generation in fiber lasers

Based on an as-prepared high-quality germanene-polyvinyl alcohol (germanenen-PVA) film, the mode-locked operation and 2th, 4th, 5th and 6th order harmonic mode-locked operations with high stability were generated in an erbium-doped (Er-doped) fiber laser for the first time. The mode-locked pulse with a fundamental of 3.9 MHz and a pulse energy of 2.47 nJ was obtained, corresponding to the signal-to-noise ratio (SNR) of about 90 dB. In addition, the characteristics of four kinds of harmonics with frequencies of 7.8 MHz, 15.7 MHz, 19.6 MHz and 23.5 MHz were also systemically investigated. The results proved that the germanene can be used as an excellent nonlinear photonic device for pulse lasers.

Germanene Nanosheets: Achieving Superior Sodium‐Ion Storage via Pseudointercalation Reactions

The potential of germanium‐based anodes for sodium‐ion batteries (NIBs) is seriously hindered by the high diffusion barrier of Na ions in the Ge lattice. Herein, a massive and defect‐rich 2D germanene nanosheet based anode is fabricated and exhibits enhanced Na‐storage performance for NIBs. Unlike the typical alloying/dealloying reactions of crystalline Ge, the germanene nanosheets are converted to go through a pseudointercalation mechanism during charge/discharge processes. Accordingly, the diffusion energy barriers of sodium atoms in the germanene nanosheets are significantly reduced, leading to high Na‐storage activity. Combined with its large surface area, high mechanical flexibility, fast electron mobility as well as its defect‐rich structure, the germanene anode delivers an initial capacity of 695 mAh g−1, enhanced cycling performance, and outstanding rate capacities, compared with those of GeH nanosheets and Ge particles. It is believed that the germanene anode not only extends the scope of germanene application, but also provides new insights for adjusting Na‐storage pathways toward superior battery performance.

Freestanding germanene nanosheets for rapid degradation and photothermal conversion

Germanium plays an important role in biomedical utilizations, mainly for inducing erythropoietic, antimicrobial, antiviral, antimutagenic, and immunomodulating effects. The biological applications of organic germanium have been gradually reported in recent years; however, the intrinsic poor biodegradation of most inorganic nanomaterials prevent their further in vivo applications and clinical translation in biomedicine. Herein, two-dimensional (2D) quasi-freestanding and fully biodegradable germanene nanosheets have been synthesized from Zintl-phase ladder-shaped binary germanide (CaGe2), which feature intriguing physiochemical properties for photo-triggered therapeutics and photoacoustic diagnostic imaging, as well as excellent biocompatibility, in addition to the excellent degradability compared with other typical 2D biomaterials. This work presents a novel type of 2D structured inorganic germanium biomaterial featuring attractive biomedical multifunctionalities, which is expected to benefit clinical and translational medicine.

Navigating 2D Monoelemental Materials (Xenes) for Cancer Nanomedicine

Contributing to this issue of Matter, Wei Tao, Tian Xie, and colleagues now demonstrate the killing of two birds (inhibition of tumor recurrence and wound infection) with one stone (germanene-based surgical adjuvant theranostic materials): another breakthrough of two-dimensional monoelemental materials (2D Xenes) as cancer nanomedicine.

Evaluation of the Morse potential function coefficients for germanene by the first principles approach

In this paper, first principles calculations are used to investigate atomic structure and mechanical properties of germanene nanosheet. By applying uniaxial and biaxial tensile strains as well as shear strain, the tensile and shear properties of the germanene nanosheet, including Young’s and bulk moduli, Poisson’s ratio, and shear moduli are computed. Furthermore, the parameters of the modified Morse potential function are calculated for Ge–Ge interaction in the germanene nanosheet. Also, the mechanical behavior of germanene nanosheet is studied under tensile loading at large strains extended to the plastic range. Based on the simulations, Young’s modulus of the armchair and zigzag germanene nanosheet are computed as 52.8 and 49.9N/m, respectively. Besides, the values of Poisson’s ratio of the armchair and zigzag germanene nanosheet are obtained as 0.35 and 0.29, respectively.

Account of the diversity of tunneling spectra at the germanene/Al(1 1 1) interface

Despite the wealth of tunneling spectroscopic studies performed on silicene and germanene, the observation of a well-defined Dirac cone in these materials remains elusive. Here, we study germanene grown on Al(1 1 1) at submonolayer coverages with low temperature scanning tunneling spectroscopy. We show that the tunnelling spectra of the Al(1 1 1) surface and the germanene nanosheets are identical. They exhibit a clear metallic behaviour at the beginning of the experiments, that highlights the strong electronic coupling between the adlayer and the substrate. Over the course of the experiments, the spectra deviate from this initial behaviour, although consecutive spectra measured on the Al(1 1 1) surface and germanene nanosheets are still similar. This spectral diversity is explained by modifications of the tip apex, that arise from the erratic manipulation of the germanium adlayer. The origin of the characteristic features such as a wide band gap, coherence-like peaks or zero-bias anomalies are tentatively discussed in light of the physical properties of Ge and AlGe alloy clusters, that are likely to adsorb at the tip apex.