Edge-Hydrogenated Germanene by Electrochemical Decalcification-Exfoliation of CaGe₂: Germanene-Enabled Vapor Sensor

Abstract

Two-dimensional germanene has been recently explored for applications in sensing, catalysis, and energy storage. The potential of this van der Waals material lies in its optoelectronic and chemical properties. However, pure free-standing germanene cannot be found in nature, and the synthesis methods are hindering the potentially fascinating properties of germanene. Herein, we report a single-step synthesis of few-layer germanene by electrochemical exfoliation in a nonaqueous environment. As a result of simultaneous decalcification and intercalation of the electrolyte’s active ions, we achieved low-level hydrogenation of germanene that occurs at the edges of the material. The obtained edge-hydrogenated germanene flakes have a lateral size of several micrometers and possess a cubic structure. We have pioneered the potential application of edge-hydrogenated germanene for vapor sensing and demonstrated its specific sensitivity to methanol and ethanol. Furthermore, we have shown a selective behavior of the germanene-based sensor that appears to increase the electrical resistance in the vapors where methanol prevails. We anticipate that these results can provide an approach for emerging layered materials with the potential utility in advanced gas sensing.

Electrochemical exfoliation of two-dimensional siligene SixGey; material characterization and perspectives for lithium-ion storage

“…The structure of the exfoliated siligene and its intrinsic crystal CaSiGe were analysed by XRD (Figure 6a). The XRD pattern possesses relative similarity to hexagonal R3̅ m symmetry when compared with the CaSi2 and CaGe2, [1,9] and aligns with the SAED patterns (Figure 4b).…”

“…[16] This is consistent with the results obtained by Raman, FTIR and XPS as well as our previous study on edge-hydrogenated germanene. [9] Chemical analysis of electrochemically exfoliated SiGe and its bulk precursor CaSiGe was performed by XPS (Figure 7). The elemental composition of samples shown in wide-scan survey spectra (Figure 7a, 7d) demonstrates the presence of Si, Ge, C, O, Ca and Au.…”

“…The results demonstrate the material's tendency to oxidation and surface termination with low-level hydrogenation, accordingly. [9]…”

Germanium‐based monoelemental and binary two‐dimensional materials: Theoretical and experimental investigations and promising applications

“…556 The results showed that germanane nanosheets are highly sensitive to volatile organic compounds (VOCs), the biomarker, indicating that germanane nanosheets can be used as molecular devices for detecting liver cirrhosis VOCs (Figure 25E). The most recent work by Kovalska et al 573 demonstrated the edge hydrogenation of germanene by electrochemical decalcification-exfoliation of CaGe 2 , enabling germanene specific sensitivity to organic vapors, showing selectivity to methanol over ethanol as a sensor. This result confirms the potential of Ge-based 2D materials as gas sensors.…”

Layered selenophosphate HgPSe3 single crystals: a new candidate for X-ray to visible light photodetectors

“…1,2 By contrast, transition metal dichalcogenide (TMD) materials show outstanding quantum confinement effects and strong light-matter interactions, but limited optical wavelength regimes due to the large bandgap. [3][4][5] Besides, various attempts intend to go beyond the aforementioned limited bandgap towards ultra-broadband photodetection by integrating 2D materials with mixeddimensional materials (0D, 1D, and 3D) or introducing midgap defect states. [6][7][8][9][10][11] But these heterostructures formed by structural engineering cannot change the intrinsic feature of a material for ionizing radiation detection.…”