Layered black phosphorus has been attracting great attention due to its interesting material properties which lead to a plethora of proposed applications. Several approaches are demonstrated here for covalent chemical modifications of layered black phosphorus in order to form P-C and P-O-C bonds. Nucleophilic reagents are highly effective for chemical modification of black phosphorus. Further derivatization approaches investigated were based on radical reactions. These reagents are not as effective as nucleophilic reagents for the surface covalent modification of black phosphorus. The influence of covalent modification on the electronic structure of black phosphorus was investigated using ab initio calculations. Covalent modification exerts a strong effect on the electronic structure including the change of band-gap width and spin polarization.

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 H 2 SO 4 (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.

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 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.

Thin films of noble-metal-based transition metal dichalcogenides, such as PtSe2, 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 PtSe2 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 PtSe2, as well as thin films produced by a range of bottom up techniques. We demonstrate that the Eg 1 peak position and the intensity ratio of the Eg 1/A1g 1 peaks can serve as a robust metric for layer number across all sample types.This will be of importance in future benchmarking of PtSe2 films.