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Infrared radiation detection is significantly important in communication, imaging, and sensing fields. Here, we present the integration of germanium selenide (GeSe) with a metal-oxide heterojunction to achieve efficient near-infrared (850 nm) photodetection under zero bias conditions. Nickel oxide (NiO) and silicon (Si) formed a favorable energy band alignment for the efficient separation of photogenerated charge carriers, resulting in a high figure of merits. The additional incorporation of a germanium selenide (GeSe) interlayer between the nickel oxide (NiO) and silicon (Si) heterojunction improved the external responsivity (from 0.22 to 3300 mA W -1 ), detectivity (from 1.24 × 10 7 to 20 × 10 9 Jones), normalized photocurrent to dark current ratio (from 4 × 10 3 to 3 × 10 5 W -1 ), noise equivalent power (from nW to pW), and rise/fall time (from 34/34.5 ms to 14/13 ms). The interlayer introduction of a semiconductor in various heterojunctions can facilitate self-biased and broadband photodetection for widely used optoelectronic applications.

Solution-processable 2D materials are promising candidates for a range of printed electronics applications. Yet maximizing their potential requires solution-phase processing of nanosheets into high-quality networks with carrier mobility (μ Net ) as close as possible to that of individual nanosheets (μ NS ). In practice, the presence of internanosheet junctions generally limits electronic conduction, such that the ratio of junction resistance ( R J ) to nanosheet resistance ( R NS ), determines the network mobility via μ NS /μ Net ≈ R J / R NS + 1. Hence, achieving R J / R NS < 1 is a crucial step for implementation of 2D materials in printed electronics applications. In this work, we utilize an advanced liquid-interface deposition process to maximize nanosheet alignment and network uniformity, thus reducing R J . We demonstrate the approach using graphene and MoS 2 as model materials, achieving low R J / R NS values of 0.5 and 0.2, respectively. The resultant graphene networks show a high conductivity of σ Net = 5 × 10 4 S/m while our semiconducting MoS 2 networks demonstrate record mobility of μ Net = 30 cm 2 /(V s), both at extremely low network thickness ( t Net < 10 nm). Finally, we show that the deposition process is compatible with nonlayered quasi-2D materials such as silver nanosheets (AgNS), achieving network conductivity close to bulk silver for networks <100 nm-thick.

The ongoing energy crisis has made it imperative to develop low-cost, easily fabricated, yet efficient materials. It is highly desirable for these nanomaterials to function effectively in multiple applications. Among transition metal dichalcogenides, tungsten diselenide (WSe 2 ) shows great promise but remains understudied. In this work, we doped WSe 2 with Mn using a simple hydrothermal method. The resulting material exhibited excellent electrocatalytic activity for the hydrogen evolution reaction, achieving a low overpotential of -0.28 V vs. RHE at -10 mA cm -2 , enhanced conductivity, and high stability and durability. Moreover, as an anode material in lithium-ion batteries, the Mn-doped WSe 2 outperformed pristine WSe 2 , reaching initial discharge capacities of 1223 and 922 mA h g -1 , respectively. Additionally, the Mn-doped material maintained a significantly higher discharge capacity of 201 mA h g -1 compared to intact WSe 2 , which had 68 mA h g -1 after 150 cycles. This work offers novel insights into designing efficient bifunctional nanomaterials using transition metal dichalcogenides.

van der Waals MnPS 3 compound belonging to the class of Néel-type antiferromagnets (AFM) has recently emerged as a promising two-dimensional material for spintronic applications. In this study, we report on the electron spin resonance (ESR) study of an MnPS 3 single crystal across the Néel transition temperature ( T N = 78 K) for the magnetic field applied in the directions parallel and perpendicular to the crystallographic c axis. Furthermore, the ESR angular dependence at a temperature near T N has been investigated. We observed multiple resonance modes with antiferromagnetic, ferromagnetic, and paramagnetic characters. In addition, we revealed the occurrence of complex spin-spin correlations and a magnetic-topological Berezinskii-Kosterlitz-Thouless (BKT) phase transition (i.e., bound vortex-antivortex pairs) at T BKT with T BKT / T N typically found in two-dimensional magnets., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

The concept of self-powered photodetectors has attracted significant attention due to their versatile applications in areas such as intelligent systems and hazardous substance detection. Among these, p-n junction and Schottky junction photodetectors are the most widely studied types; however, their fabrication processes are often complex and costly. To overcome these challenges, we focused on the emerging self-powered, ultrasensitive photodetector platform based on photoelectrochemical (PEC) principles. This platform leverages the unique properties of the emerging material bismuth oxide selenide (Bi 2 O 2 Se), which features a wide bandgap (∼2 eV) and a high absorption coefficient. We utilized chemical exfoliation to obtain thin layers of Bi 2 O 2 Se, enabling highly efficient photodetection. The device characterization demonstrated impressive performance metrics, including a responsivity of 97.1 μA W -1 and a specific detectivity of 2 × 10 8 cm Hz 1/2 W -1 . The PEC photodetector also exhibits broad-spectrum sensitivity, from blue to infrared wavelengths, and features an ultrafast response time of ∼82 ms and a recovery time of ∼86 ms, highlighting its practical potential. Moreover, these self-powered photodetectors show excellent stability in electrochemical environments, positioning them promising candidates for integration into future high-efficiency devices., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Graphite is one of only a few layered materials that can be exfoliated into nanosheets with semimetallic properties, which limits the applications of nanosheet-based electrodes to material combinations compatible with the work function of graphene. It is therefore important to identify additional metallic or semimetallic two-dimensional (2D) nanomaterials that can be processed in solution for scalable fabrication of printed electronic devices. Metal diborides represent a family of layered non-van der Waals crystals with semimetallic properties for all nanosheet thicknesses. While previous reports show that the exfoliated nanomaterial is prone to oxidation, we demonstrate a readily accessible inert exfoliation process to produce quasi-2D nanoplatelets with intrinsic material properties. For this purpose, we demonstrate the exfoliation of three representative metal diborides (MgB 2 , CrB 2 , and ZrB 2 ) under inert conditions. Nanomaterial is characterized using a combination of transmission electron microscopy, scanning electron microscopy, atomic force microscopy, IR, and UV-vis measurements, with only minimal oxidation indicated postprocessing. By depositing the pristine metal diboride nanoplatelets as thin films using a Langmuir-type deposition technique, the ohmic behavior of the networks is validated. Furthermore, the material decomposition is studied by using a combination of electrical and optical measurements after controlled exposure to ambient conditions. Finally, we report an efficient, low-cost approach for sample encapsulation to protect the nanomaterials from oxidation. This is used to demonstrate low-gauge factor strain sensors, confirming metal diboride nanosheets as a suitable alternative to graphene for electrode materials in printed electronics.

The solvothermal functionalization of graphite and thermally reduced graphene oxide (TRGO) using a bis-hydrazone copper(I) complex is demonstrated. This treatment resulted in a remarkable 328% increase in the BET specific surface area of graphite, reaching 374 m 2 g -1 , while the surface area of TRGO remained unchanged. The hybrid composites show promise as potential components for gas sensors.

MAX phases represent a crucial building block for the synthesis of MXenes, which constitute an intriguing class of materials with significant application potential. This study investigates the catalytic properties of the Mo 2 TiAlC 2 MAX phase and the corresponding Mo 2 TiC 2 T x MXene for the hydrogen evolution reaction (HER). Characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) revealed that despite the presence of secondary phases, the HER catalytic activity is primarily influenced by the MAX phase and its derived MXene. Interestingly, the catalytic activity of the MXene improves over time, attributed to the formation of MoO 2 as identified by XPS. This work enhances the understanding of MXene-based materials for electrochemical applications, highlighting crucial structural and chemical transformations that optimize their performance in energy conversion technologies., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

This research examines vanadium-deficient V 2 C MXene, a two-dimensional (2D) vanadium carbide with exceptional electrochemical properties for rechargeable zinc-ion batteries. Through a meticulous etching process, a V-deficient, porous architecture with an expansive surface area is achieved, fostering three-dimensional (3D) diffusion channels and boosting zinc ion storage. Analytical techniques like scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller, and X-ray diffraction confirm the formation of V 2 C MXene and its defective porous structure. X-ray photoelectron spectroscopy further verifies its transformation from the MAX phase to MXene, noting an increase in V 3+ and V 4+ states with etching. Cyclic voltammetry reveals superior de-zincation kinetics, evidenced by consistent V 3+ /V 4+ oxidation peaks at varied scanning rates. Overall, this V-deficient MXene outperforms raw MXenes in capacity and rate, although its capacity diminishes over extended cycling due to structural flaws. Theoretical analyses suggest conductivity rises with vacancies, enhancing 3D ionic diffusion as vacancy size grows. This work sheds light on enhancing V-based MXene structures for optimized zinc-ion storage., (© 2024 The Authors. Small Methods published by Wiley‐VCH GmbH.)

This study employs the molten-salt-shielded method to dope the Ti 3 AlC 2 MAX phase with Nb and Mo, aiming to expand the intrinsic potential of the material. X-ray diffraction confirms the preservation of the hexagonal lattice structure of Ti 3 AlC 2 , while Raman and X-ray photoelectron spectroscopic analyses reveal the successful incorporation of dopants with subtle yet significant alterations in the vibrational modes and chemical environment. Scanning electron microscopy with energy-dispersive X-ray spectroscopy characterizations illustrate the characteristic layered morphology and uniform dopant distribution. Density functional theory simulations provide insights into the modified electronic structure, displaying changes in carrier transport mechanisms and potential increases in metallic conductivity, particularly when doping occurs at both the M and A sites. The computational findings are corroborated by the experimental results, suggesting that the enhanced material may possess improved properties for electronic applications. This comprehensive approach not only expands the MAX phase family but also tailors its functionality, which could allow for the production of hybrid materials with novel functionalities not present in the pristine form.

The oxygen evolution reaction (OER) is a key reaction in the production of green hydrogen by water electrolysis. In alkaline media, the current state of the art catalysts used for the OER are based on non-noble metal oxides. However, despite their huge potential as OER catalysts, these materials exhibit various disadvantages including lack of stability and conductivity that hinder the wide-spread utilization of these materials in alkaline electrolyzer devices. This study highlights the innovative chemical functionalization of a mixed copper cobalt hydroxide with the V 2 CT x MXene to enhance the OER efficiency, addressing the need for effective electrocatalytic interfaces for sustainable hydrogen production. The herein synthesized CuCo@V 2 CT x electrocatalysts demonstrate remarkable activity, outperforming the pure CuCo catalysts for the OER and moreover show increased efficiency after 12 hours of continuous operation. This strategic integration improved the water oxidation performance of the pure oxide material by improving the composite's hydrophilicity, charge transfer properties and ability to hinder Cu leaching. The materials were characterized using an array of materials characterization techniques to help decipher both structure of the composite materials after synthesis and to elucidate the reasoning for the OER enhancement for the composites. This work demonstrates the significant potential of TMO-based nanomaterials combined with V 2 CT x for advanced innovative electrocatalytic interfaces in energy conversion applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Chiral superconductors, a unique class of unconventional superconductors in which the complex superconducting order parameter winds clockwise or anticlockwise in the momentum space 1 , represent a topologically non-trivial system with intrinsic time-reversal symmetry breaking (TRSB) and direct implications for topological quantum computing 2,3 . Intrinsic chiral superconductors are extremely rare, with only a few arguable examples, including UTe 2 , UPt 3 and Sr 2 RuO 4 (refs.  4-7 ). It has been suggested that chiral superconductivity may exist in non-centrosymmetric superconductors 8,9 , although such non-centrosymmetry is uncommon in typical solid-state superconductors. Alternatively, chiral molecules with neither mirror nor inversion symmetry have been widely investigated. We suggest that an incorporation of chiral molecules into conventional superconductor lattices could introduce non-centrosymmetry and help realize chiral superconductivity 10 . Here we explore unconventional superconductivity in chiral molecule intercalated TaS 2 hybrid superlattices. Our studies reveal an exceptionally large in-plane upper critical field B c2,|| well beyond the Pauli paramagnetic limit, a robust π-phase shift in Little-Parks measurements and a field-free superconducting diode effect (SDE). These experimental signatures of unconventional superconductivity suggest that the intriguing interplay between crystalline atomic layers and the self-assembled chiral molecular layers may lead to exotic topological materials. Our study highlights that the hybrid superlattices could lay a versatile path to artificial quantum materials by combining a vast library of layered crystals of rich physical properties with the nearly infinite variations of molecules of designable structural motifs and functional groups 11 ., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

The exploration of 1D magnetism, frequently portrayed as spin chains, constitutes an actively pursued research field that illuminates fundamental principles in many-body problems and applications in magnonics and spintronics. The inherent reduction in dimensionality often leads to robust spin fluctuations, impacting magnetic ordering and resulting in novel magnetic phenomena. Here, structural, magnetic, and optical properties of highly anisotropic 2D van der Waals antiferromagnets that uniquely host spin chains are explored. First-principle calculations reveal that the weakest interaction is interchain, leading to essentially 1D magnetic behavior in each layer. With the additional degree of freedom arising from its anisotropic structure, the structure is engineered by alloying, varying the 1D spin chain lengths using electron beam irradiation, or twisting for localized patterning, and spin textures are calculated, predicting robust stability of the antiferromagnetic ordering. Comparing with other spin chain magnets, these materials are anticipated to bring fresh perspectives on harvesting low-dimensional magnetism., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

Solution-processable 2D semiconductor inks based on electrochemical molecular intercalation and exfoliation of bulk layered crystals using organic cations has offered an alternative pathway to low-cost fabrication of large-area flexible and wearable electronic devices. However, the growth of large-piece bulk crystals as starting material relies on costly and prolonged high-temperature process, representing a critical roadblock towards practical and large-scale applications. Here we report a general liquid-metal-assisted approach that enables the electrochemical molecular intercalation of low-cost and readily available crystal powders. The resulted solution-processable MoS 2 nanosheets are of comparable quality to those exfoliated from bulk crystals. Furthermore, this method can create a rich library of functional 2D electronic inks ( >50 types), including 2D wide-bandgap semiconductors of low electrical conductivity. Lastly, we demonstrated the all-solution-processable integration of 2D semiconductors with 2D conductors and 2D dielectrics for the fabrication of large-area thin-film transistors and memristors at a greatly reduced cost., (© 2024. The Author(s).)

In this work, we investigate trion dynamics occurring at the heterojunction between organometallic molecules and a monolayer transition metal dichalcogenide (TMD) with transient electronic sum frequency generation (tr-ESFG) spectroscopy. By pumping at 2.4 eV with laser pulses, we have observed an ultrafast hole transfer, succeeded by the emergence of charge-transfer trions. This observation is facilitated by the cancellation of ground state bleach and stimulated emission signals due to their opposite phases, making tr-ESFG especially sensitive to the trion formation dynamics. The presence of charge-transfer trion at molecular functionalized TMD monolayers suggests the potential for engineering the local electronic structures and dynamics of specific locations on TMDs and offers a potential for transferring unique electronic attributes of TMD to the molecular layers., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Designing a multifunctional device that combines solar energy conversion and energy storage is an appealing and promising approach for the next generation of green power and sustainable society. In this work, we fabricated a single-piece device incorporating undoped WSe 2 , Re- or Nb-doped WSe 2 photocathode, and zinc foil anode system enabling a light-assisted rechargeable aqueous zinc metal cell. Comparison of structural, optical, and photoelectric characteristics of undoped and doped WSe 2 has further confirmed that ionic insertion of donor metal (rhenium and niobium) plays an important role in enhancing photoelectrochemical energy storage properties. The electrochemical energy storage cell consisting of Re-doped WSe 2 (as the photoactive cathode and zinc metal as anode) showed the best photodriven enhancement in the specific capacitance of around 45% due to efficient harvesting of visible light irradiation. The assembled device exhibited a loss of 20% of its initial specific capacitance after 1500 galvanostatic charge-discharge cycles at 50 mA g -1 . The cell also provided a specific energy density of 574.21 mWh kg 1- and a power density of 5906 mW kg 1- at 15 mA g -1 . Under otherwise similar conditions, the pristine WSe 2 and Nb-doped WSe 2 showed photoenhanced induced capacitance of 43% and 27% at 15 mA g -1 and supplied an energy density of 436.4 mWh kg 1- and 202 mWh kg 1- , respectively. As a result, a reasonable capacitance improvement obtained by the Re-WSe 2 photoenhanced zinc-ion capacitor could provide a facile and constructive way to achieve a highly efficient and low-cost solar-electrochemical capacitor system., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

This study investigates the electronic band structure of chromium sulfur bromide (CrSBr) through comprehensive photoluminescence (PL) characterization. We clearly identify low-temperature optical transitions between two closely adjacent conduction-band states and two different valence-band states. The analysis on the PL data robustly unveils energy splittings, band gaps, and excitonic transitions across different thicknesses of CrSBr, from monolayer to bulk. Temperature-dependent PL measurements elucidate the stability of the band splitting below the Néel temperature, suggesting that magnons coupled with excitons are responsible for the symmetry breaking and brightening of the transitions from the secondary conduction band minimum (CBM2) to the global valence band maximum (VBM1). Collectively, these results not only reveal splitting in both the conduction and valence bands but also highlight a significant advance in our understanding of the interplay between the optical, electronic, and magnetic properties of antiferromagnetic two-dimensional van der Waals crystals.

Rapid and reliable immunosensing is undoubtedly one of the priorities in the efficient management and combat against a pandemic, as society has experienced with the SARS-CoV-2 outbreak; simple and cost-effective sensing strategies are at the forefront of these efforts. In this regard, 2D-layered MXenes hold great potential for electrochemical biosensing due to their attractive physicochemical properties. Herein, we present a V 2 CT x MXene-based sensing layer as an integral part of a label-free immunosensor for sensitive and selective detection of the SARS-CoV-2 spike protein. The sensor was fabricated on a supporting screen-printed carbon electrode using Nafion as an immobilizing agent for MXene and glutaraldehyde, the latter enabling effective binding of protein A for further site-oriented immobilization of anti-SARS-CoV-2 antibodies. A thorough structural analysis of the sensor architecture was carried out, and several key parameters affecting the fabrication and analytical performance of the immunosensor were investigated and optimized. The immunosensor showed excellent electroanalytical performance in combination with an impedimetric approach and exhibited a low detection limit of only 45 fM SARS-CoV-2 spike protein. Its practical applicability was successfully demonstrated by measuring the spike protein in a spiked artificial nasopharyngeal fluid sample.

Magnetism in two-dimensional materials reveals phenomena distinct from bulk magnetic crystals, with sensitivity to charge doping and electric fields in monolayer and bilayer van der Waals magnet CrI 3 . Within the class of layered magnets, semiconducting CrSBr stands out by featuring stability under ambient conditions, correlating excitons with magnetic order and thus providing strong magnon-exciton coupling, and exhibiting peculiar magneto-optics of exciton-polaritons. Here, we demonstrate that both exciton and magnetic transitions in bilayer and trilayer CrSBr are sensitive to voltage-controlled field-effect charging, exhibiting bound exciton-charge complexes and doping-induced metamagnetic transitions. Moreover, we demonstrate how these unique properties enable optical probes of local magnetic order, visualizing magnetic domains of competing phases across metamagnetic transitions induced by magnetic field or electrostatic doping. Our work identifies few-layer CrSBr as a rich platform for exploring collaborative effects of charge, optical excitations, and magnetism., (© 2024. The Author(s).)

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 Si 0.25 Ge 0.75 H, Si 0.50 Ge 0.50 H, and Si 0.75 Ge 0.25 H, 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 Si 0.50 Ge 0.50 H 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 Si 0.50 Ge 0.50 H. Subsequently, an initial assessment of the c-Li 15 (Si x Ge 1- x ) 4 phase after lithiation and the a-Si 0.50 Ge 0.50 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., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

van der Waals (vdW) magnetic materials, such as Cr 2 Ge 2 Te 6 (CGT), show promise for memory and logic applications. This is due to their broadly tunable magnetic properties and the presence of topological magnetic features such as skyrmionic bubbles. A systematic study of thickness and oxidation effects on magnetic domain structures is important for designing devices and vdW heterostructures for practical applications. Here, we investigate thickness effects on magnetic properties, magnetic domains, and bubbles in oxidation-controlled CGT crystals. We find that CGT exposed to ambient conditions for 5 days forms an oxide layer approximately 5 nm thick. This oxidation leads to a significant increase in the oxidation state of the Cr ions, indicating a change in local magnetic properties. This is supported by real-space magnetic texture imaging through Lorentz transmission electron microscopy. By comparing the thickness-dependent saturation field of oxidized and pristine crystals, we find that oxidation leads to a nonmagnetic surface layer that is thicker than the oxide layer alone. We also find that the stripe domain width and skyrmionic bubble size are strongly affected by the crystal thickness in pristine crystals. These findings underscore the impact of thickness and surface oxidation on the properties of CGT, such as saturation field and domain/skyrmionic bubble size, and suggest a pathway for manipulating magnetic properties through a controlled oxidation process.

Networks of nanowires, nanotubes, and nanosheets are important for many applications in printed electronics. However, the network conductivity and mobility are usually limited by the resistance between the particles, often referred to as the junction resistance. Minimising the junction resistance has proven to be challenging, partly because it is difficult to measure. Here, we develop a simple model for electrical conduction in networks of 1D or 2D nanomaterials that allows us to extract junction and nanoparticle resistances from particle-size-dependent DC network resistivity data. We find junction resistances in porous networks to scale with nanoparticle resistivity and vary from 5 Ω for silver nanosheets to 24 GΩ for WS 2 nanosheets. Moreover, our model allows junction and nanoparticle resistances to be obtained simultaneously from AC impedance spectra of semiconducting nanosheet networks. Through our model, we use the impedance data to directly link the high mobility of aligned networks of electrochemically exfoliated MoS 2 nanosheets (≈ 7 cm 2 V -1 s -1 ) to low junction resistances of ∼2.3 MΩ. Temperature-dependent impedance measurements also allow us to comprehensively investigate transport mechanisms within the network and quantitatively differentiate intra-nanosheet phonon-limited bandlike transport from inter-nanosheet hopping., (© 2024. The Author(s).)

Transition metal thiophosphates (MPS 3 ) are of great interest due to their layered structure and magnetic properties. Although HgPS 3 may not exhibit magnetic properties, its uniqueness lies in its triclinic crystal structure and in the substantial mass of mercury, rendering it a compelling subject for exploration in terms of fundamental properties. In this work, we present comprehensive experimental and theoretical studies of the electronic band structure and optical properties for the HgPS 3 crystal and mechanically exfoliated layers from a solid crystal. Based on absorption, reflectance and photoluminescence measurements supported by theoretical calculations, it is shown that the HgPS 3 crystal has an indirect gap of 2.68 eV at room temperature. The direct gap is identified at the Γ point of the Brillouin zone (BZ) ≈ 50 meV above the indirect gap. The optical transition at the Γ point is forbidden due to selection rules, but the oscillator strength near the Γ point increases rapidly and therefore the direct optical transitions are visible in the reflectance spectra approximately at 60-120 meV above the absorption edge, across the temperature range of 40 to 300 K. The indirect nature of the bandgap and the selection rules for Γ point contribute to the absence of near-bandgap emission in HgPS 3 . Consequently, the photoluminescence spectrum is primarily governed by defect-related emission. The electronic band structure of HgPS 3 undergoes significant changes when the crystal thickness is reduced to tri- and bilayers, resulting in a direct bandgap. Interestingly, in the monolayer regime, the fundamental transition is again indirect. The layered structure of the HgPS 3 crystal was confirmed by scanning electron microscopy (SEM) and by mechanical exfoliation., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Given the challenging task of constructing an efficient nitrogen reduction reaction (NRR) electrocatalyst with enhanced ambient condition performance, properties such as high specific surface area, fast electron transfer, and design of the catalyst surface constitute a group of key factors to be taken into consideration to guarantee outstanding catalytic performance and durability. Thereof, this work investigates the contribution of the 2D/2D heterojunction interface between MoS 2 and reduced graphene oxide (rGO) on the electrocatalytic synthesis of NH 3 in an alkaline media. The results revealed remarkable NRR performance on the MoS 2 @rGO 2 D /2D hybrid electrocatalyst, characterized by a high NRR sensitivity (faradaic efficiency) of 34.7% with an NH 3 yield rate of 3.98 ± 0.19 mg h -1 cm -2 at an overpotential of -0.3 V vs RHE in 0.1 M KOH solution. The hybrid electrocatalysts also exhibited selectivity for NH 3 synthesis against the production of the hydrazine (N 2 H 4 ) byproduct, hindrance of the competitive hydrogen evolution reaction (HER), and good durability over an operation period of 8 h. In hindsight, the study presented a low-cost and highly efficient catalyst design for achieving enhanced ammonia synthesis in alkaline media via the formation of defect-rich ultrathin MoS 2 @rGO nanostructures, consisting predominantly of an HER-hindering hexagonal 2H-MoS 2 phase.

Recent studies dedicated to layered van der Waals crystals have attracted significant attention to magnetic atomically thin crystals offering unprecedented opportunities for applications in innovative magnetoelectric, magneto-optic, and spintronic devices. The active search for original platforms for the low-dimensional magnetism study has emphasized the entirely new magnetic properties of two dimensional (2D) semiconductor CrSBr. Herein, for the first time, the electrochemical exfoliation of bulk CrSBr in a non-aqueous environment is demonstrated. Notably, crystal cleavage governed by the structural anisotropy occurred along two directions forming atomically thin and few-layered nanoribbons. The exfoliated material possesses an orthorhombic crystalline structure and strong optical anisotropy, showing the polarization dependencies of Raman signals. The antiferromagnetism exhibited by multilayered CrSBr gives precedence to ferromagnetic ordering in the revealed CrSBr nanostructures. Furthermore, the potential application of CrSBr nanoribbons is pioneered for electrochemical photodetector fabrication and demonstrates its responsivity up to 30 µA cm -2 in the visible spectrum. Moreover, the CrSBr-based anode for lithium-ion batteries exhibited high performance and self-improving abilities. This anticipates that the results will pave the way toward the future study of CrSBr and practical applications in magneto- and optoelectronics., (© 2023 The Authors. Small Methods published by Wiley‐VCH GmbH.)

van der Waals heterostructures of two-dimensional materials have unveiled frontiers in condensed matter physics, unlocking unexplored possibilities in electronic and photonic device applications. However, the investigation of wide-gap, high-κ layered dielectrics for devices based on van der Waals structures has been relatively limited. In this work, we demonstrate an easily reproducible synthesis method for the rare-earth oxyhalide LaOBr, and we exfoliate it as a 2D layered material with a measured static dielectric constant of 9 and a wide bandgap of 5.3 eV. Furthermore, our research demonstrates that LaOBr can be used as a high-κ dielectric in van der Waals field-effect transistors with high performance and low interface defect concentrations. Additionally, it proves to be an attractive choice for electrical gating in excitonic devices based on 2D materials. Our work demonstrates the versatile realization and functionality of 2D systems with wide-gap and high-κ van der Waals dielectric environments.

Among atomically thin semiconductors, CrSBr stands out as both its bulk and monolayer forms host tightly bound, quasi-one-dimensional excitons in a magnetic environment. Despite its pivotal importance for solid-state research, the exciton lifetime has remained unknown. While terahertz polarization probing can directly trace all excitons, independently of interband selection rules, the corresponding large far-field foci substantially exceed the lateral sample dimensions. Here, we combine terahertz polarization spectroscopy with near-field microscopy to reveal a femtosecond decay of paramagnetic excitons in a monolayer of CrSBr, which is 30 times shorter than the bulk lifetime. We unveil low-energy fingerprints of bound and unbound electron-hole pairs in bulk CrSBr and extract the nonequilibrium dielectric function of the monolayer in a model-free manner. Our results demonstrate the first direct access to the ultrafast dielectric response of quasi-one-dimensional excitons in CrSBr, potentially advancing the development of quantum devices based on ultrathin van der Waals magnets.

The properties of MXene flakes, a new class of two-dimensional materials, are strictly determined by their surface termination. The most common termination groups are oxygen-containing (=O or -OH) and fluorine (-F), and their relative ratio is closely related to flake stability and catalytic activity. The surface termination can vary significantly among MXene flakes depending on the preparation route and is commonly determined after flake preparation by using X-ray photoelectron spectroscopy (XPS). In this paper, as an alternative approach, we propose the combination of surface-enhanced Raman spectroscopy (SERS) and artificial neural networks (ANN) for the precise and reliable determination of MXene flakes' (Ti 3 C 2 T x ) surface chemistry. Ti 3 C 2 T x flakes were independently prepared by three scientific groups and subsequently measured using three different Raman spectrometers, employing resonant excitation wavelengths. Manual analysis of the SERS spectra did not enable accurate determination of the flake surface termination. However, the combined SERS-ANN approach allowed us to determine the surface termination with a high accuracy. The reliability of the method was verified by using a series of independently prepared samples. We also paid special attention to how the results of the SERS-ANN method are affected by the flake stability and differences in the conditions of flake preparation and Raman measurements. This way, we have developed a universal technique that is independent of the above-mentioned parameters, providing the results with accuracy similar to XPS, but enhanced in terms of analysis time and simplicity., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Uranium is a high-value energy element, yet also poses an appreciable environmental burden. The demand for a straightforward, low energy, and environmentally friendly method for encapsulating uranium species can be beneficial for long-term storage of spent uranium fuel and a host of other applications. Leveraging on the low melting point (60 °C) of uranyl nitrate hexahydrate and nanocapillary effect, a uranium compound is entrapped in the hollow core of WS 2 nanotubes. Followingly, the product is reduced at elevated temperatures in a hydrogen atmosphere. Nanocrystalline UO 2 nanoparticles anchor within the WS 2 nanotube lumen are obtained through this procedure. Such methodology can find utilization in the processing of spent nuclear fuel or other highly active radionuclides as well as a fuel for deep space missions. Moreover, the low melting temperatures of different heavy metal-nitrate hydrates, pave the way for their encapsulation within the hollow core of the WS 2 nanotubes, as demonstrated herein., (© 2023 The Authors. Small published by Wiley‐VCH GmbH.)

Apart from the extensively researched graphene under the Group 14 2D materials, monolayered germanene and its derivatives have been gaining interest lately as alternative class of 2D materials owing to their facile synthesis, and attractive electronic and optical properties. Herein, three different functionalized germanene-based nanomaterials, namely Ge-H, Ge-CH 3 and Ge-C 3 -CN were investigated on their novel incorporation in impedimetric immunosensors for the detection of gut-derived metabolites associated with neurological diseases, such as kynurenic acid (KA) and quinolinic acid (QA). The designed germanene-based immunosensor relies on an indirect competitive mechanism using disposable electrode printed chips. The competition for a fixed binding site of a primary antibody occurs between the bovine serum albumin-conjugated antigens on the electrode surface and the free antigens in the solution. Among the three materials, Ge-H displayed superior bioanalytical performance in KA and QA detection. Lower limits of detection of 5.07-11.38 ng/mL (26.79-68.11 nM) were attained for KA and QA with a faster reaction time than previously reported methods. Also, minimal cross-reactivity with interfering compounds, good reproducibility in impedimetric responses (RSD = 2.43-7.51 %) and long-term stability up to a month at 4 °C were the other attributes that the proposed Ge-H competitive impedimetric immunosensor has accomplished. The application of the developed Ge-H immunosensor to serum samples allowed an accurate KA and QA quantification at physiologically relevant levels. This work serves as a stepping-stone in the development of germanene-based nanomaterials for their implementation into cost-effective, miniaturized, portable and rapid impedimetric immunosensors, which are highly desirable for point-of-care testing in clinical settings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Green synthesis of stable metal-organic frameworks (MOFs) with permanent and highly ordered porosity at room temperature without needing toxic and harmful solvents and long-term high-temperature reactions is crucial for sustainable production. Herein, a rapid and environmentally friendly synthesis strategy is reported to synthesize the complex topological bismuth-based-MOFs (Bi-MOFs), [Bi 9 (C 9 H 3 O 6 ) 9 (H 2 O) 9 ] (denoted CAU-17), in water under ambient conditions by surfactant-mediated sonochemical approach, which could also be applicable to other MOFs. This strategy explores using cetyltrimethylammonium bromide (CTAB) amphiphilic molecules as structure-inducing agents to control the removal of non-coordinated water (dehydration) and enhance the degree of deprotonation of the ligands, thereby regulating the coordination and crystallization in aqueous solutions. In addition, another two new strategies for synthesizing CAU-17 by crystal reconstruction and one-step synthesis in binary solvents are provided, and the solvent-induced synthesis mechanism of CAU-17 is studied. The as-prepared CAU-17 presents a competitive iodine capture capability and effective delivery of the antiarrhythmic drug procainamide (PA) for enteropatia due to the broad pH tolerance and the unique phosphate-responsive destruction in the intestine. The findings will provide valuable ideas for the follow-up study of surfactant-assisted aqueous synthesis of MOFs and their potential applications., (© 2023 The Authors. Small published by Wiley‐VCH GmbH.)

Energy harvesting and storing by dual-functional photoenhanced (photo-E) energy storage devices are being developed to battle the current energy hassles. In this research work, our investigations on the photoinduced efficiency of germanane (Ge-H) and its functionalized analogue cyanoethyl (Ge-C 2 -CN) are assessed as photocathodes in photo-E hybrid zinc-ion capacitors (ZICs). The evaluated self-powered photodetector devices made by these germanene-based samples revealed effective performances in photogenerated electrons and holes. The photo-E ZICs findings provided a photoinduced capacitance enhancement of ∼52% (for Ge-H) and ∼26% (for Ge-C 2 -CN) at a scan rate of 10 mV s -1 under 100 mW cm -2 illumination with 435 nm wavelength. Further characterizations demonstrated that the photo-E ZIC with Ge-C 2 -CN supply higher specific capacitance (∼6000 mF g -1 ), energy density (∼550 mWh kg -1 ), and power density (∼31,000 mW kg -1 ), compared to the Ge-H. In addition, capacitance retention of photo-E ZIC with Ge-C 2 -CN is ∼91% after 3000 cycles which is almost 6% greater than Ge-H. Interestingly, the photocharging voltage response in photo-E ZIC made by Ge-C 2 -CN is 1000 mV, while the photocharging voltage response with Ge-H is approximately 970 mV. The observed performances in Ge-H-based photoactive cathodes highlight the pivotal role of such two-dimensional materials to be applied as single architecture in new unconventional energy storage systems. They are particularly noteworthy when compared to the other advanced photo-E supercapacitors and could even be enhanced greatly with other suitable inorganic and organic functional precursors.

The coupling of energy harvesting and energy storage discrete modules in a single architecture as a "two-in-one" concept is significant in off-grid energy storage devices. This approach can decrease the device size and the loss of energy transmission in common integrated energy harvesting and storage systems. This work systematically investigates the photoactive characteristics of niobium carbide MXene, Nb 2 CT x , in a photoenhanced hybrid zinc-ion capacitor (P-ZIC). The unique configuration of the Nb 2 CT x photoactive cathode absorbs light to charge the capacitor and enables it to operate continuously in the light-powered mode. The Nb 2 CT x -based P-ZIC shows a photodriven capacitance enhancement of over 60% at the scan rate of 10 mV s -1 under 50 mW cm -2 illumination with 435 nm wavelength. Furthermore, a photoenhanced specific capacitance of ∼27 F g -1 , an impressive photocharging voltage response of 1.0 V, and capacitance retention of ∼85% (over 3000 cycles) are obtained., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Tungsten diselenide (WSe2) has emerged as a promising ambipolar semiconductor material for field-effect transistors (FETs) due to its unique electronic properties, including a sizeable band gap, high carrier mobility, and remarkable on-off ratio. However, engineering the contacts to WSe2 remains an issue, and high contact barriers prevent the utilization of the full performance in electronic applications. Furthermore, it could be possible to tune the contacts to WSe2 for effective electron or hole injection and consequently pin the threshold voltage to either conduction or valence band. This would be the way to achieve complementary metal-oxide-semiconductor devices without doping of the channel material.This study investigates the behaviour of two-dimensional WSe2 field-effect transistors with multi-layer palladium diselenide (PdSe2) as a contact material. We demonstrate that PdSe2 contacts favour hole injection while preserving the ambipolar nature of the channel material. This consequently yields high-performance p -type WSe2 devices with PdSe2 van der Waals contacts. Further, we explore the tunability of the contact interface by selective laser alteration of the WSe2 under the contacts, enabling pinning of the threshold voltage to the valence band of WSe2, yielding pure p -type operation of the devices.

Dual-functional photo-rechargeable (photo-R) energy storage devices, which acquire stored energy from solar energy harvesting, are being developed to battle the current energy crisis. In this study, these findings on the photo-driven characteristics of MXene-based photocathodes in photo-R zinc-ion capacitors (ZICs) are presented. Along with the pristine Ti 3 C 2 T x MXene, tellurium/Ti 3 C 2 T x (Te/Ti 3 C 2 T x ) hybrid nanostructure is synthesized via facile chemical vapor transport technique to examine them for photocathodes in ZICs. Interestingly, the evaluated self-powered photodetector devices using MXene-based samples revealed a pyro-phototronic behavior introduced into the samples, with higher desirability observed in Te/Ti 3 C 2 T x . The photo-R ZICs results exhibited a capacitance enhancement of 50.86% for Te/Ti 3 C 2 T x at two scan rates of 5 and 10 mV s -1 under illumination, compared to dark conditions. In contrast, a capacitance enhancement of 30.20% is obtained for the pristine Ti 3 C 2 T x at only a 5 mV s -1 scan rate. Furthermore, both samples achieved photo-charging voltage responses of ≈960 mV, and photoconversion efficiencies of 0.01% (for Te/ Ti 3 C 2 T x ) and 0.07% (for Ti 3 C 2 T x ). These characteristics in MXene-based single photo-R ZICs are significant and considerable with the distinguished integrated photo-R supercapacitors with solar cells, or coupled energy-harvesting and energy-storing devices reported recently in the literature., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

Advances in the hydrogen evolution reaction (HER) are intricately connected with addressing the current energy crisis and quest for sustainable energy sources. The necessity of catalysts that are efficient and inexpensive to perform the hydrogen evolution reaction is key to this. Following the ground-breaking discovery of graphene, metal thio/seleno phosphates (MPX 3 : M - transition metal, P - phosphorus and X - S/Se), two dimensional (2D) materials, exhibit excellent tunable physicochemical, electronic and optical properties, and are expected to be key to the energy industry for years to come. Taking this into account, a facile time-effective electrostatic restacking synthesis procedure has been followed to synthesize a 2D/2D heterostructure (FePS 3 @BCN) involving FePS 3 , one of the prominent MPX 3 materials, with borocarbonitride (BCN), for hydrogen evolution reaction (HER). The piled up nanosheets of FePS 3 and BCN are held together by an electrostatic force, and display extreme robustness under the harsh conditions of HER application. The amalgamated electrocatalyst achieved an overpotential of 187 mV at a current density of 10 mA cm -2 with a shallow Tafel slope of 41 mV dec -1 , following the Volmer-Heyrovsky mechanism. The resilience of the electrocatalyst has been examined through chronoamperometric testing for long term stability, and it is stable for more than 14 hours, which shows the excellent electrocatalytic activity for hydrogen evolution reaction owing to the strategic approach to the catalyst design, the use of numerous electrochemically active sites, large surface area and a barrier-free channel for quick ion transfer.

The layered, air-stable van der Waals antiferromagnetic compound CrSBr exhibits pronounced coupling among its optical, electronic, and magnetic properties. As an example, exciton dynamics can be significantly influenced by lattice vibrations through exciton-phonon coupling. Using low-temperature photoluminescence spectroscopy, we demonstrate the effective coupling between excitons and phonons in nanometer-thick CrSBr. By careful analysis, we identify that the satellite peaks predominantly arise from the interaction between the exciton and an optical phonon with a frequency of 118 cm -1 (∼14.6 meV) due to the out-of-plane vibration of Br atoms. Power-dependent and temperature-dependent photoluminescence measurements support exciton-phonon coupling and indicate a coupling between magnetic and optical properties, suggesting the possibility of carrier localization in the material. The presence of strong coupling between the exciton and the lattice may have important implications for the design of light-matter interactions in magnetic semiconductors and provide insights into the exciton dynamics in CrSBr. This highlights the potential for exploiting exciton-phonon coupling to control the optical properties of layered antiferromagnetic materials.

MXenes, a family of two-dimensional (2D) transition metal carbides, have been discovered as exciting candidates for various energy storage and conversion applications, including green hydrogen production by water splitting. Today, these materials mostly remain interesting objects for in-depth fundamental studies and scientific curiosity due to issues related to their preparation and environmental stability, limiting potential industrial applications. This work proposes a simple and inexpensive concept of composite electrodes composed of molybdenum- and titanium-containing MAX phases and MXene as functional materials. The concept is based on the modification of the initial MAX phase by the addition of metallic Ni, tuning Al- and carbon content and synthesis conditions, followed by fluoride-free etching under alkaline conditions. The proposed methodology allows producing a composite electrode with a well-developed 3D porous MAX phase-based structure acting as a support for electrocatalytic species, including MXene, and possessing good mechanical integrity. Electrochemical tests have shown a high electrochemical activity of such electrodes towards the hydrogen evolution reaction (HER), combined with a relatively high areal capacitance (up to 10 F cm -2 )., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The chalcogenides of p-block elements constitute a significant category of materials with substantial potential for advancing the field of electronic and optoelectronic devices. This is attributed to their exceptional characteristics, including elevated carrier mobility and the ability to fine-tune band gaps through solid solution formation. These compounds exhibit diverse structures, encompassing both three-dimensional and two-dimensional configurations, the latter exemplified by the compound In 2 Se 3 . Sesqui-chalcogenides were synthesized through the direct reaction of highly pure elements within a quartz ampoule. Their single-phase composition was confirmed using X-ray diffraction, and the morphology and chemical composition were characterized using scanning electron microscopy. The compositions of all six materials were also confirmed using X-ray photoelectron spectroscopy and Raman spectroscopy. This investigation delves into the thermodynamic properties of indium and gallium sesqui-chalcogenides. It involves low-temperature heat capacity measurements to evaluate standard entropies and Tian-Calvet calorimetry to elucidate the temperature dependence of heat capacity beyond the reference temperature of 298.15 K, as well as the enthalpy of formation assessed from DFT calculations.

Recent progress in polarization-resolved photodetection based on low-symmetry 2D materials has formed the basis of cutting-edge optoelectronic devices, including quantum optical communication, 3D image processing, and sensing applications. Here, we report an optical polarization-resolving photodetector (PD) fabricated from multilayer semiconducting CrSBr single crystals with high structural anisotropy. We have demonstrated self-powered photodetection due to the formation of Schottky junctions at the Au-CrSBr interfaces, which also caused the photocurrent to display a position-sensitive and binary nature. The self-biased CrSBr PD showed a photoresponsivity of ∼0.26 mA/W with a detectivity of 3.4 × 10 8 Jones at 514 nm excitation of fluency (0.42 mW/cm 2 ) under ambient conditions. The optical polarization-induced photoresponse exhibits a large dichroic ratio of 3.4, while the polarization is set along the a- and the b -axes of single-crystalline CrSBr. The PD also showed excellent stability, retaining >95% of the initial photoresponsivity in ambient conditions for more than five months without encapsulation. Thus, we demonstrate CrSBr as a fascinating material for ultralow-powered optical polarization-resolving optoelectronic devices for cutting-edge technology.

In the rapidly evolving field of thin-film electronics, the emergence of large-area flexible and wearable devices has been a significant milestone. Although organic semiconductor thin films, which can be manufactured through solution processing, have been identified, their utility is often undermined by their poor stability and low carrier mobility under ambient conditions. However, inorganic nanomaterials can be solution-processed and demonstrate outstanding intrinsic properties and structural stability. In particular, a series of two-dimensional (2D) nanosheet/nanoparticle materials have been shown to form stable colloids in their respective solvents. However, the integration of these 2D nanomaterials into continuous large-area thin with precise control of layer thickness and lattice orientation still remains a significant challenge. This review paper undertakes a detailed analysis of van der Waals thin films, derived from 2D materials, in the advancement of thin-film electronics and optoelectronic devices. The superior intrinsic properties and structural stability of inorganic nanomaterials are highlighted, which can be solution-processed and underscor the importance of solution-based processing, establishing it as a cornerstone strategy for scalable electronic and optoelectronic applications. A comprehensive exploration of the challenges and opportunities associated with the utilization of 2D materials for the next generation of thin-film electronics and optoelectronic devices is presented., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)