Due to their high surface-to-volume ratio and native band gaps, two-dimensional (2D) materials are widely used as supports for metal nanoparticle (NP) catalysts. Various synthesis methods exist to prepare such materials, but controlling the amount, size, and distribution of the deposited NPs remains a challenge. Here, we investigate the use of electron beam lithography (EBL) for this purpose. A dual-beam focused ion beam-scanning electron microscope (FIB-SEM) was used to direct the deposition of platinum NPs (Pt NPs) onto 2D graphene oxide, functionalized with epoxy and hydroxyl (HUGO) or carboxyl (TOGO) groups, and black phosphorus (BP) sheets. According to NP size, the deposition was conducted for various exposure times and several types of particle distribution. EDS confirmed the required chemical composition of all of the prepared materials. SEM showed the amount and distribution of the supported NPs, and TEM confirmed their size. Raman spectroscopy revealed a strong bonding between the NPs and the support sheets according to the type of 2D support. These results suggest that EBL is a promising method for the target-controlled deposition of metal NPs of targeted amount, size, and spatial distribution onto 2D materials, which enables evaluating the specific influence of the NP-support interaction on enhanced catalytic activity.

Two-dimensional (2D) layered thiophosphates have garnered attention for advanced battery technology due to their open ionic diffusion channels, high capacity, and unique catalytic properties. However, their potential in energy storage applications remains largely unexplored. In this study, we report a 2D transition metal thiophosphate (Nb4P2S21) with high sulfur content, synthesized via chemical vapor transport (CVT). The bulk material, exhibiting a layered quasi-one-dimensional (quasi-1D) structure, can be exfoliated into high-quality nanoplates using glue-assisted grinding. Density functional theory (DFT) calculations reveal a direct bandgap of 1.64 eV (HSE06 method) for Nb4P2S21, aligning with its near-infrared (NIR) photoluminescence at 755 nm. Despite an initial discharge capacity of 1500 mA h g-1, the material shows low reversible capacity and rapid capacity decay at 0-2.6 V. In situ Raman confirms the formation of polysulfides during cycling. Given its high sulfur content, the material was evaluated at 0.5-2.6 V, 1.0-2.6 V, and 1.5-2.6 V to assess its sulfur-equivalent cathode performance. In carbonate-based electrolytes, electrochemical performance is hindered by polysulfide formation and side reactions, but switching to ether-based electrolytes improves initial reversible capacity and coulombic efficiency due to additional LixS conversion above 2.2 V. EDS and TOF-SIMS analyses of cycled electrodes show a significant sulfur loss, worsening the polysulfide shuttle effect and leading to battery failure. Adapting strategies from lithium-sulfur batteries, such as polar host catalysts, could enhance the material's performance.

The adjustable structures and remarkable physicochemical properties of 2D monoelemental materials, such as silicene and germanene, have attracted significant attention in recent years. They can be transformed into silicane (SiH) and germanane (GeH) through covalent functionalization via hydrogen atom termination. However, synthesizing these materials with a scalable and low-cost fabrication process to achieve high-quality 2D SiH and GeH poses challenges. Herein, groundbreaking 2D SiH and GeH materials with varying compositions, specifically Si0.25Ge0.75H, Si0.50Ge0.50H, and Si0.75Ge0.25H, are prepared through a simple and efficient chemical exfoliation of their Zintl phases. These 2D materials offer significant advantages, including their large surface area, high mechanical flexibility, rapid electron mobility, and defect-rich loose-layered structures. Among these compositions, the Si0.50Ge0.50H electrode demonstrates the highest discharge capacity, reaching up to 1059 mAh g-1 after 60 cycles at a current density of 75 mA g-1. A comprehensive ex-situ electrochemical analysis is conducted to investigate the reaction mechanisms of lithiation/delithiation in Si0.50Ge0.50H. Subsequently, an initial assessment of the c-Li15(SixGe1- x)4 phase after lithiation and the a-Si0.50Ge0.50 phase after delithiation is presented. Hence, this study contributes crucial insights into the (de)lithiation reaction mechanisms within germanane-silicane alloys. Such understanding is pivotal for mastering promising materials that amalgamate the finest properties of silicon and germanium.

The characteristics of widely explored two-dimensional (2D) layered materials make them promising objects for structural functionalization to adjust their physical and chemical properties. The chemical functionalization of graphene family members has been reported to be useful in catalysis, although the efficiency of organic substitution of germanene, the newborn in the graphene family, remains limited and fairly attracts significant scientific attention. In this study, we explore the photoelectrochemical (PEC) activity of hydroxyalkyl germananes Gen-(CH2)n-OH (n = 2, 6, 10) through PEC-type photodetector experiments, employing excitation wavelengths ranging from 360 to 720 nm. Our findings reveal that organic substitution induces the opening of the germanane band gap, leading to a significant widening up to 2.38 eV and enhanced charge transfer kinetics under visible light irradiation.

Long-term stable gas sensors by tiled networks from LPE-PtSe2.

2D materials are being widely investigated for their potential application in light‐detecting devices. Very recently, a spin‐coated flexible 2D germanium‐based photodetector with great photocurrent density and responsivity as well as short rise and decay time is presented by Liu et. al. In this paper, the solid‐state single flake photodetector base on either pure germanane or (3‐hydroxypropyl)germanane is reported. Both prepared photodetectors while irradiated with different wavelengths of light exhibit outstanding responsivity of 1157 mA W −1 for GeH and 362 mA W −1 for (3‐hydroxypropyl)germanane, which exceeds Liu's flexible reported GeH photodetector (22 µA W −1 ) by more than five orders of magnitude. These constructed photodetectors also exhibit rise and fall times lower than 20 ms, which is also significantly faster than the GeH photodetector reported by Liu with rise and decay times 240 and 740 ms, respectively.

2D monoelemental materials, particularly germanene and silicene (the single layer of germanium and silicon), which are the base materials for modern electronic devices demonstrated tremendous attraction for their 2D layer structure along with the tuneable electronics and optical band gap. The major shortcoming of synthesized thermodynamically very unstable layered germanene and silicene with their inclination toward oxidation was overcome by topochemical deintercalation of a Zintl phase (CaGe2, CaGe1.5Si0.5, and CaGeSi) in a protic environment. The exfoliated Ge-H, Ge0.75Si0.25H, and Ge0.5Si0.5H were successfully synthesized and employed as the active layer for photoelectrochemical photodetectors, which showed broad response (420-940 nm), unprecedented responsivity, and detectivity on the order of 168 μA W-1 and 3.45 × 108 cm Hz1/2 W-1, respectively. The sensing capability of exfoliated germanane and silicane composites was explored using electrochemical impedance spectroscopy with ultrafast response and recovery time of less than 1 s. These positive findings serve as the application of exfoliated germanene and silicene composites and can pave a new path to practical applications in efficient future devices.

Successful postmodification of germanene-based materials opens new applications in the chemistry of monoelemental two-dimensional materials. Here, we demonstrate the successful synthesis of germanane bearing benzyl group and its coordination with carbonyl metal complexes from the group 6. The photochemical reaction was used for in situ formation of reactive intermediates based on chromium, molybdenum and tungsten carbonyls and led to the attachment of the metal-carbonyl group to the benzyl group on the germanane surface. Successful functionalization was proven by various spectroscopic methods including FTIR, Raman and x-ray photoelectron spectroscopy as well as TG-MS measurements showing the evolution of carbon monoxide at elevated temperature. The homogeneous distribution of metals and morphology was also approved by microscopy method SEM/ EDS and AFM. This work shows new possibilities in the chemistry of two-dimensional monoelemental materials like germanane giving the opportunity to homogenously distribute metal atoms over the sheet surface by coordination to the benzyl group.

Since the first synthesis of germanane (GeH) reported in 2013, two-dimensional germanium-based materials have been intensively studied. Over the past decade, several methodologies for the functionalization of germanane have been introduced. The first approach utilized exfoliation of Zintl phase CaGe2 with alkyl halides. Liu's solvothermal method was used for the synthesis of methyl germanane. Another methodology utilized Ge-H activation with sodium naphthalenide and its subsequent alkylation. All of these methods provide functionalized germananes; thus, a comparison of these methods is needed. In this paper, such a comparison of current synthetic approaches towards alkyl germananes is reported, and additionally, a new method for Ge-H activation utilizing a NaK equimolar alloy is presented as a fourth approach. For this purpose, eight alkyl reagents were chosen representing reactive benzyl bromides as well as linear esters and nitriles because they contain easily trackable functional groups. The materials were characterized using Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis, and the data were compared. The comparison of all methods revealed not only some drawbacks for each method but also their advantages. The method utilizing sodium naphthalenide provided the lowest degree of surface coverage, whereas the solvothermal method seemed to provide materials with the highest degree of functionalization; unfortunately, the functionalization was also accompanied by a high degree of surface oxidation, i.e., (Ge-OH/Ge═O) formation. The highest degree of surface coverage accompanied by the lowest degree of surface oxidation was achieved employing Goldberger's phase transfer direct exfoliation of CaGe2 as well as Ge-H activation using the NaK alloy with subsequent alkylation.

Integration of 2D layered materials into micromotors is of great interest for scientists since 2D materials can endow micromotors with new characteristics or enhance their intrinsic properties. In this work, we develop the BiOI-based self-propelled micromotors (i.e., rGO/ZnO/BiOI/Co-Pi/Pt micromotors) with tubular and arc geometric shapes via template-assisted electrochemical deposition method. BiOI, constructed by nanosheets, is a visible-light-excited photocatalyst. The elaborately designed heterostructure is able to promote the charge separation and transport capacity of BiOI. Each micromotor can not only exhibit vigorous stirring-like movement for self-propulsion but also lead to enhanced photocatalytic dynamics for dye degradation. Using Rhodamine 6G as the dye pollutant model, BiOI-based micromotors can degrade 94% of dye molecules within 30 min under visible light illumination while their degradation efficiency is only 5.2% when in dark. The dye degradation mechanism is mainly based on the generation of reactive oxygen species during the photocatalysis process. The synergistic effect among i) "on-the-fly" chemistry, ii) the collective behavior of micromotors and iii) the visible-light-excited BiOI photocatalyst with synthetic nanoflake morphology and well-designed heterojunction make an efficient and active photocatalytic platform for water purification.

Germanium, with a high theoretical capacity based on alloyed lithium and germanium (1384 mA h g-1 Li15Ge4), has stimulated tremendous research as a promising candidate anode material for lithium-ion batteries (LIBs). However, due to the alloying reaction of Li/Ge, the problems of inferior cycle life and massive volume expansion of germanium are equally obvious. Among all Ge-based materials, the unique layered 2D germanane (GeH and GeCH3) with a graphene-like structure, obtained by a chemical etching process from the Zintl phase CaGe2, could enable storage of large quantities of lithium between their interlayers. Besides, the layered structure has the merit of buffering the volume expansion due to the tunable interlayer spacing. In this work, the beyond theoretical capacities of 1637 mA h g-1 for GeH and 2048 mA h g-1 for GeCH3 were achieved in the initial lithiation reaction. Unfortunately, the dreadful capacity fading and electrode fracture happened during the subsequent electrochemical process. A solution, i.e. introducing single-wall carbon nanotubes (SWCNTs) into the structure of the electrodes, was found and further confirmed to improve their electrochemical performance. More noteworthy is the GeH/SWCNT flexible electrode, which exhibits a capacity of 1032.0 mA h g-1 at a high current density of 2000 mA g-1 and a remaining capacity of 653.6 mA h g-1 after 100 cycles at 500 mA g-1. After 100 cycles, the hybrid germanane/SWCNT electrodes maintained good integrity without visible fractures. These results indicate that introducing SWCNTs into germanane effectively improves the electrochemical performance and maintains the integrity of the electrodes for LIBs.

The Cover Feature shows the photocatalytic oxidative cycloelimination of a coumarin dimer by a flavinium salt inspired by the light-induced photolyase DNA repair reaction in nature. Light absorption and subsequent intersystem crossing (isc) enable diffusion-controlled electron transfer (eT) from the coumarin dimer to the excited triplet flavinium salt. The oxidized coumarin dimer dissociates and back electron transfer (beT) completes the photocatalytic cycle. More information can be found in the Full Paper by R. Cibulka, R. Kutta, and co-workers.

Flavinium salts are frequently used in organocatalysis but their application in photoredox catalysis has not been systematically investigated to date. We synthesized a series of 5-ethyl-1,3-dimethylalloxazinium salts with different substituents in the positions 7 and 8 and investigated their application in light-dependent oxidative cycloelimination of cyclobutanes. Detailed mechanistic investigations with a coumarin dimer as a model substrate reveal that the reaction preferentially occurs via the triplet-born radical pair after electron transfer from the substrate to the triplet state of an alloxazinium salt. The very photostable 7,8-dimethoxy derivative is a superior catalyst with a sufficiently high oxidation power (E*=2.26 V) allowing the conversion of various cyclobutanes (with E-ox up to 2.05 V) in high yields. Even compounds such as all-trans dimethyl 3,4-bis(4-methoxyphenyl)cyclobutane-1,2-dicarboxylate can be converted, whose opening requires a high activation energy due to a missing pre-activation caused by bulky adjacent substituents in cis-position.

Photoelectrochemical (PEC) systems represent powerful tools to convert electromagnetic radiation into chemical fuels and electricity. In this context, two-dimensional (2D) materials are attracting enormous interest as potential advanced photo(electro)catalysts and, recently, 2D group-IVA metal monochalcogenides have been theoretically predicted to be water splitting photocatalysts. In this work, we use density functional theory calculations to theoretically investigate the photocatalytic activity of single-/few-layer GeSe nanoflakes for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in pH conditions ranging from 0 to 14. Our simulations show that GeSe nanoflakes with different thickness can be mixed in the form of nanoporous films to act as nanoscale tandem systems, in which the flakes, depending on their thickness, can operate as HER- and/or OER photocatalysts. On the basis of theoretical predictions, we report the first experimental characterization of the photo(electro)catalytic activity of single-/few-layer GeSe flakes in different aqueous media, ranging from acidic to alkaline solutions: 0.5 M H2SO4 (pH 0.3), 1 M KCl (pH 6.5), and 1 M KOH (pH 14). The films of the GeSe nanoflakes are fabricated by spray coating GeSe nanoflakes dispersion in 2-propanol obtained through liquid-phase exfoliation of synthesized orthorhombic (Pnma) GeSe bulk crystals. The PEC properties of the GeSe nanoflakes are used to design PEC-type photodetectors, reaching a responsivity of up to 0.32 AW-1 (external quantum efficiency of 86.3%) under 455 nm excitation wavelength in acidic electrolyte. The obtained performances are superior to those of several self-powered and low-voltage solution-processed photodetectors, approaching that of self-powered commercial UV-Vis photodetectors. The obtained results inspire the use of 2D GeSe in proof-of-concept water photoelectrolysis cells.

Thin films of noble-metal-based transition metal dichalcogenides, such as PtSe 2 , have attracted increasing attention due to their interesting layer-number dependent properties and application potential. While it is difficult to cleave bulk crystals down to mono- and few-layers, a range of growth techniques have been established producing material of varying quality and layer number. However, to date, no reliable high-throughput characterization to assess layer number exists. Here, we use top-down liquid phase exfoliation (LPE) coupled with centrifugation to produce PtSe 2 nanosheets of varying sizes and thicknesses with a low degree of basal plane defectiveness. Measurement of the dimensions by statistical atomic force microscopy allows us to quantitatively link information contained in optical spectra to the dimensions. For LPE nanosheets we establish metrics for lateral size and layer number based on extinction spectroscopy. Further, we compare the Raman spectroscopic response of LPE nanosheets with micromechanically exfoliated PtSe 2 , as well as thin films produced by a range of bottom up techniques. We demonstrate that the E g 1 peak position and the intensity ratio of the E g 1 /A 1g 1 peaks can serve as a robust metric for layer number across all sample types.This will be of importance in future benchmarking of PtSe 2 films.

Two-dimensional materials attract enormous attention across several scientific fields. The current demands in nano- and optoelectronics, semiconductors, or in catalysis have been accelerating the research process in the field of 2D materials. Among the 14th group 2D materials besides graphene and silicene, layered germanium represents a promising candidate for another class of materials, and its functionalization represents a way to tune either its electronic or optical properties. Here, the exfoliation and functionalization of germanane surface is achieved via abstraction of hydrogen from Ge-H bond and its subsequent alkylation utilizing n-alkyl halides or trifluoromethyl (CF3) group containing benzyl halides. Composition of materials is confirmed by several methods including FT-IR, Raman, X-ray photoelectron, and energy-dispersive X-ray spectroscopy as well as X-ray powder diffraction. Scanning and transmission electron spectroscopy is used to reveal the layered morphology of functionalized germananes.

Black phosphorus (BP) in its monolayer form called phosphorene is thought of as a successor of graphene and is of great interest for (opto)electronic applications. A quantitative and scalable method for the synthesis of (mono-)few-layer phosphorene has been an outstanding challenge due to the process irreproducibility and environmental degradation capability of the BP. Here, we report a facile controlled electrochemical exfoliation method for the preparation of a few-layer phosphorene (FP) with nearly 100% yield. Our approach relies on the low-potential influence in anhydrous and oxygen-free low-boiling acetonitrile (AN) and N,N-dimethylformamide (DMF) using alkylammonium ions. Herein, intercalation of positive ions into BP interlayers occurred with a minimum potential of -2.95 V in DMF and -2.85 V in AN and the non-damaging and highly accurate electrochemical exfoliation lasted at -3.8 V. A variety of analytical methods have revealed that in particular DMF-based exfoliation results in high-quality phosphorene of 1-5 layers with good crystallinity and lateral sizes up to tens of micrometers. Moreover, assurance of the oxygen- and water-free environment allowed us to minimize the surface oxidation of BP and, consequently, exfoliated phosphorene. We pioneer an effective and reproducible printing transfer of electrochemically exfoliated phosphorene films onto various flexible and rigid substrates. The surfactant-free process of exfoliation allowed assembly and transfer of thin films based on FP. The phosphorene-based films characterized as direct gap semiconductors have a layer-number-dependent bandgap with a tuning range larger than that of other 2D materials. We show that on varying the films' thickness, it is possible to modify their optical properties, which is a significant advantage for compact and switchable optoelectronic components.

Two-dimensional materials have been extensively studied over the last two decades as they represent a class of materials with properties applicable in catalysis, sensing, optical devices, nanoelectronics, supercapacitors, and semiconductors. The properties of 2D materials can be tuned by exfoliation into mono- or few-layered systems and mainly by surface modification, which can result, for example, in altering the band gap or enhancing material stability toward degradation. This review focuses on the derivatization of group 14 layered materials beyond graphene silicene, germanene, and stanene and summarizes their preparation as well as chemical and physical properties. This review provides the current state-of-the-art in the field and provides a perspective for future development in the field of chemical derivatization of 2D materials beyond graphene.

Two-dimensional materials are at the forefront of material research in the past decade. Besides graphene, there exist large groups of its heavier analogues, silicon- and germanium-based two-dimensional materials, which are much less explored. Methods of synthesis of germanene derivatives are based on chemical exfoliation of Zintl phase precursors. Here we report a novel effective and flexible method for synthesis of alkylated derivatives of germanene by phase transfer assisted exfoliation of calcium germanide. We demonstrate the universality of the reported method and its broad application in synthesis of various germanene derivatives. The developed method allows precise control over the chemical composition and optical properties of germanene derivatives.

The rediscovery of graphene in 2004 has started an enormous chase in the research of 2D materials. A new family of layered 2D materials consisting of the 14th group elements beyond carbon has already been reported. Here, a new methodology in germanene chemistry is presented using germanane (Ge 6 H 6 ) as a stable and easily accessible starting material for effective synthesis of novel germanene derivatives. The modification procedure utilizing strong bases - alkali metal arenides - for deprotonation of germanane and its subsequent functionalization with p -nitrobenzyl bromide is described. Functionalization of germanene is confirmed by FT-IR, Raman and XPS spectroscopy as well as by X-ray diffraction analysis.