The growing demand for autonomous, wearable technologies calls for energy solutions that are not only efficient but also environmentally responsible. Graphene and related two-dimensional (2D) materials stand at the forefront of this transformation, offering a unique combination of flexibility, sensitivity, and energy utilization performance that is redefining the future of self-powered wearable electronics. This presentation explores sustainable and scalable approaches to the synthesis and integration of 2D materials, particularly graphene-based systems, for triboelectric nanogenerator (TENG)-driven wearable sensors. These self-powered devices convert energy from human motion, physiological signals, and ambient vibrations into electricity, providing an eco-friendly alternative to conventional battery-powered electronics, suitable for wearable healthcare and environmental monitoring. Emphasizing green synthesis routes and conscious fabrications, we explore strategies to maintain high material quality while minimizing ecological impact. The talk will highlight advances in device architecture, including textile integration and flexible platforms, and demonstrate how graphene and 2D materials heterostructures can be scaled toward real-world applications. Addressing both the scientific challenges and manufacturing pathways, this work supports the sustainable development of next-generation self-powered wearable systems that meet the growing demands for energy autonomy and environmental responsibility.

Engineering electrochemical sensors often relies on biological components such as enzymes and aptamers, which provide exceptional specificity but suffer from limited conductivity and poor long-term stability. In contrast, inorganic and composite materials are being developed to overcome these limitations, offering enhanced sensitivity, and stability, while their specificity can be tuned through surface functionalization or selective catalytic activity. Among those materials, transition metal dichalcogenides (TMDs) stand out thanks to their 2D structure that offers a large surface area in combination with abundant active metal sites that promote electrocatalytic reactions.[1]

Within this class of materials, selenides are of great interest for electrochemical applications, as selenium offers higher conductivity than sulfur due to the more delocalized electron cloud that allows electron mobility [2]. Each metallic center facilitates distinct catalytic reactions, which then drives the sensor’s response toward particular analytes, allowing their electrochemical determination.

The electrocatalytic properties of VSe₂ towards nitrobenzene reduction enable the development of a sensitive sensor for this nitroaromatic compound [3]. Additionally, WSe₂ coupled with a Ti₃C₂Cl₂ MXene is used for the determination of hydrogen peroxide, with WSe₂ offering the electrocatalytic properties and MXene enhancing the conductivity facilitating the electron transfer process, and thus, the sensor performance [4]. Materials have been characterized for their morphological and structural characteristics and their ethanolic suspension was applied on a glassy carbon electrode. The electrochemical sensing performance of the modified electrodes was optimized, and the capabilities was assessed through calibration features.

References

[1] Sajjad, M., Amin, M., Javed, M. S., Imran, M., Hu, W., Mao, Z., & Lu, W. (2021). Recent trends in transition metal diselenides (XSe2: X = Ni, Mn, Co) and their composites for high energy faradic supercapacitors. Journal of Energy Storage, 43, 103176.

[2] Papavasileiou, A.V., Antonatos, N., Luxa, J., Dekanovsky, L., Ashtiani, S., Lontio Fomekong, R., Sofer, Z., Two-dimensional VSe2 nanoflakes as a promising sensing electrocatalyst for nitrobenzene determination in water samples, Electrochimica Acta, 475, 2024, 143653

[3] Kagkoura, A., Papavasileiou, A. V., Wei, S., Oliveira, F. M., Šturala, J., Sofer, Z., WSe2 nanoflowers grown on Ti3C2Cl2 MXene for energy applications and sensing, npj 2D materials and applications, 9, 2025, 73

Advanced Metal-Oxide and Molybdenum-Based Nanostructures for Wearable Breath Monitoring and Selective Gas Sensing

The development of highly responsive, low-power, and real-time sensors is essential for both environmental safety and non-invasive healthcare diagnostics. In this cumulative work, SnO₂-decorated WO₃ composites were first engineered to extend sensing capabilities toward breath-based monitoring. These wearable humidity sensors exhibit ultrafast 0.6 s response/recovery, high sensitivity, and excellent mechanical stability, enabling reliable wireless tracking of breathing patterns, including apnea and hypopnea events. Their performance demonstrates strong potential for continuous respiratory-health applications.

Building on this direction, a comprehensive series of molybdenum-based nanostructures was developed to address selective gas detection challenges under ambient and humid conditions. Phase-controlled MoO₃ structures (α-MoO₃ and prismatic h-MoO₃) were synthesized for enhanced ammonia detection, with h-MoO₃ delivering superior sensitivity due to its abundant edge-reactive sites. Multiphase MoS₂ containing coexisting 1T and 2H phases enabled room-temperature detection of nonpolar biomarkers such as n-dodecane, supported by DFT insights confirming stronger adsorption on metallic domains. Furthermore, MoS₂–MoO₂ achieved dual-selective sensing of NH₃ and NOₓ even under high humidity, addressing critical requirements for breath and environmental monitoring.

Together, Mo-based sensing systems establish a unified materials framework for next-generation wearable breath sensors and selective environmental gas detection.

Triboelectric nanogenerators (TENGs) can harvest low-frequency mechanical energy from the human body—such as motion and physiological activity—to power self-sustained electronic devices. However, their use in this context is often limited by the lack of soft, biocompatible, and liquid-tolerant triboelectric materials. Here, we address this challenge by integrating graphene-based 2D materials into a poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel, a soft polymer widely used in biomedical applications, to create tunable triboelectric interfaces tailored for body-related energy harvesting.

Graphene oxide (GO) and reduced graphene oxide (rGO) are incorporated into pHEMA via a water-based route, yielding robust, processable composite films. In contact–separation operation against reference dielectrics, low graphene loadings enhance surface roughness and effective contact area, leading to increased triboelectric output, whereas higher loadings increase internal resistance and promote charge trapping, reducing the signal. This response is systematically correlated with graphene phase and oxygen content, as well as controlled changes in surface morphology.

We further evaluate pHEMA/graphene composites under alternative triboelectric operating modes relevant for interaction with aqueous environments. Variations in graphene phase, surface morphology and electrode design are correlated with the electrical response, underscoring the role of interfacial engineering and operating conditions. Overall, this work establishes graphene-modified pHEMA hydrogels as a versatile integration platform for 2D materials, enabling controlled tailoring of triboelectric performance and opening pathways toward future self-powered, body-interfaced sensing and energy-harvesting devices.

Efforts in nanoscience have long sought scalable methods for producing van der Waals materials, following the landmark discovery of graphene via mechanical exfoliation. While this technique offers unmatched material quality, its scalability is limited by poor control over thickness, lateral size, and yield. In this talk, I will present a roll-to-roll platform that enables massively parallel mechanical exfoliation of layered crystals, producing films densely populated with nanosheets across large areas. The method achieves a unique compromise between lateral size, scalability, and cost-efficiency, while avoiding harsh treatments and remaining compatible with air-sensitive materials. Beyond individual flakes, we demonstrate the formation of continuous wafer-scale films and, for anisotropic compounds, the production of aligned nanosheet assemblies. These materials serve as the building blocks for large batches of field-effect transistors, flexible photodetectors, and wafer-scale electronic circuits, confirming both practicality and versatility. This scalable strategy presented here paves the way for low-cost, high-performance 2D materials integration in next-generation optoelectronic and flexible device technologies.

High Mobility Low Temperature Processed Inkjet Printed Flexible MoS₂ Transistors on Sustainable Flexible Substrate

The exponential growth of modern electronic devices including smartphones, wearables, and flexible displays has resulted in a global surge of electronic waste, projected to reach 74.7 million tons by 2030. This growing crisis not only strains natural resources but also poses serious risks to the environment, human health, and data security. Hence, the development of eco-friendly, transient electronic devices capable of controlled degradation is of growing importance. Herein, we demonstrate a sustainable approach to fabricate the field-effect transistor (FET) by integrating green materials into key device components. Polyvinyl alcohol (PVA), a biodegradable synthetic polymer with excellent film-forming properties, has been employed as the substrate, while molybdenum disulfide (MoS₂), a biocompatible two-dimensional semiconductor, served as the active layer. A solvent engineering strategy is introduced to overcome the challenge of surfactant and solvent residues that typically hinder charge mobility in solution-processed MoS₂ films. The use of green solvents enabled effective removal of PVP residues, leading to high performance transistors with a maximum mobility of 74.9 cm² V⁻¹ s⁻¹, an on-current of 1.01 mA, and an on/off ratio of 1.96 × 10⁶ at 150 °C on flexible polyimide substrates. Importantly, it has helped in fabricating devices at a very low processing temperature of 75 °C with excellent mobilities up to 1.99 cm² V⁻¹ s⁻¹ and on/off ratios of 1.15 × 10⁵. Such a low processing temperature allowed the device fabrication on a biodegradable PVA substrate demonstrating reasonable device characteristics (mobility of 0.093 cm² V⁻¹ s⁻¹ and on/off ratios of 1.15 × 10⁵). Additionally, these devices have been subjected to biodegradability study with different buffer solutions which exhibits good degradation in basic solution < 90 day when compared to the acidic solution. Furthermore, the fabricated transistors have been integrated into basic logic circuits, including depletion mode inverters and NAND, NOR, AND, and OR gates, all operating reliably at 1 kHz. These findings establish a viable route toward green, low-cost, and energy-efficient MoS₂-based electronics, contributing to sustainable device technologies that minimize e-waste and environmental impact.

Isolation of graphene was a milestone in condensed matter physics paving the way to a new and unprecedentedly rich fashion of two-dimensional (2D) materials. While many of them are derived through exfoliation methods, an urgent need remains as to how they can be produced through scalable synthesis schemes and manipulated in diverse functional configurations by design. Here we will report on bottom-up approaches to the synthesis 2D Xenes, their engineering in new materials configuration or hybrids, and their integration into nanotechnology device applications. Xenes, i.e. single-element 2D crystals, are a representative case in this respect [1]. With silicene stannene, and tellurene as examples, we will describe how the Xenes can be synthesized by interface engineering up to developing new Xene hybrids and heterostructures [2]. As results, we will show how to stabilized silicene membranes for transfer to a target substrate aiming at electronic device applications like silicene transistors on solid-state platforms and silicene piezoresistors on bendable substrates [3,4]. Alternately, silicene will be reconfigured in a hybrid configuration along with other 2D materials like MoS2 or a stand-along flakes aiming at making electronic heterojunctions/layers by design. On the same line, we will also focus on the tellurium chemistry to show how to grow 2D materials with unprecedented properties. Tellurium vapours transported by an inert carrier gas in a chemical vapour deposition reactor are exploited to produce topological ditellurides by tellurization of a pre-desposited metal film or tellurium nanosheets down to the 2D level (tellurene). In the former case, we will report on the growth of PtTe2 Dirac semimetals aiming at the fabrication of THz plasmonic gratings [5]. In the latter case, tellurium nanosheets on Au-based substrates are designed for diode cells with memristive behavior [6]. The reported cases are examples of how to engineer and configure Xene towards prototypical device structures targeting flexible electronics, nanophotonics, and nanoelectronics.

Contactless electroreflectance (CER) is a very powerful absorption like technique to investigate semiconductor materials and heterostructures [1] including hybrid heterostructures containing van der Waals (vdW) crystals. Due to the Franz-Keldysh effect, this method can be used to study the built-in electric field in semiconductor heterostructures as well as the Fermi level position on semiconductor interfaces such as vdW/GaN interfaces [2, 3]. Engineering the Fermi level position on AlGaN surface is very important for fabrication of electrical contacts to AlGaN with desired characteristics, i.e. ohmic or Schottky contact. In this paper we will present how to determine the Fermi level position at the vdW/III-N interface, and then focus on our recent progress in the engineering the Fermi level position in hybrid vdW/III-N heterostructures including photovoltaic detectors based on the vdW-stack/AlGaN junction with vdW-stacks composed of graphene, h-BN, MoS₂, WS₂, MXene, and other two-dimensional crystals.

Flux-assisted synthesis provides powerful opportunities for expanding the structural and chemical diversity of layered carbides and borides relevant to the 2D materials community. By optimising metal-flux compositions, the crystallite size of MAX and MAB phases can be increased dramatically—from sub-micron grains in conventional solid-state routes to well-faceted millimetre-scale crystals suitable for high-quality exfoliation. Beyond classical metallic fluxes, we demonstrate that transition-metal sulfide flux environments enable the direct formation of S-containing MAX phases, offering new pathways to engineer layered precursors for sulfur-rich MXenes.

Morphology control is further achieved through the use of structured carbon precursors, which direct the growth of MAX phases into anisotropic architectures such as hollow or tubular crystals. These unconventional morphologies can be subsequently exfoliated to yield MXene nanotubes, expanding the accessible geometries of 2D materials beyond the planar limit and enabling curvature-dependent surface and electronic effects.

Post-synthetic reactivity of both MAX phases and exfoliated MXenes with halogens, chalcogens, and other small atoms provides an effective route to tailor surface terminations, interlayer chemistry, and electronic structure. Such controlled functionalisation is critical for optimizing MXene performance in electrocatalytic applications, including the hydrogen and oxygen evolution reactions.

Together, these approaches establish a versatile synthetic toolbox for producing high-quality, structurally engineered precursors and MXenes with advanced properties for next-generation 2D material technologies.

As electronic devices based on two-dimensional (2D) materials continue to advance in complexity and miniaturization, local probing techniques are becoming essential for investigating material behavior at the nanoscale, particularly when devices are integrated with electrodes and operated under external electric fields. Understanding their electronic structure under realistic working conditions is increasingly critical. Here, we discuss how to access the local energy landscape and electric-field distribution in 2D-material-based devices using operando scanning X-ray photoemission spectromicroscopy (SPEM), focusing on 2D field-effect transistors and van der Waals heterojunctions. By exploiting the high spatial resolution of SPEM [1], we achieve detailed mapping of the local energy landscape while devices are biased in situ. This technique provides direct access to both the out-of-plane gate field and the in-plane vectorial electric-field distribution with sub-micrometer resolution [2]. Our results demonstrate that this method serves as a sensitive local probe of device design, flake geometry, thickness, and morphology, factors that strongly influence nanoscale current flow within the device channel [2]. The approach highlights finite-size effects and the spatial distribution of electric fields at flake interfaces [3]. Ultimately, it enables a correlative description connecting the bias-modified local energy landscape to the macroscopic electrical response, offering a pathway toward systematic and rational optimization of nanoelectronic devices, including—but not limited to—those based on 2D materials.

2D-AlN is a thermodynamically stable compound that has been predicted by density functional theory (DFT) calculations. It has attracted considerable attention due to its ultrawide band gap (> 2.8 eV) and its strong adsorption of CO₂ (0.91 eV) molecules on its surface. This represents a breakthrough for CO₂ capture technologies because the adsorption of gases directly on the 2D-AlN nanosheets is a simple and sustainable alternative for replacing the current strategy of decorating carbon nanostructure with metal nanoparticles for gas storage and CO₂ capture. In addition, the high adsorption CO₂ selectivity in comparison with other gases such as CO, H₂, N₂, O₂, and NO (<0.5 eV) opens other potential applications like gas separation membranes and gas sensors, among others. The DFT calculations have put 2D-AlN in the spotlight, but so far, the synthesis of free-standing 2D-AlN layers have not yet been achieved.

In this work I will present a new strategy to synthesize 2D-AlN nanoflakes for the first time. First, I will introduce the precursor materials including their characterization and properties. Then, I will continue with the different approaches for the synthesis of the 2D nanoflakes and their main characteristics. Afterwards, I will present the preliminary characterization of these new 2D materials as well as their main applications.

Ti3AlC2, a typical MAX phase compound, serves as the parent structure of Ti3C2Tx MXenes, the most extensively studied member of the MXene family for diverse applications. Despite the growing interest, most experimental studies on Ti3AlC2 rely on polycrystalline samples, limiting the accurate determination of its intrinsic physical properties. The synthesis of large, high-quality single crystals remains a significant challenge, yet it is essential for probing fundamental electronic, optical, and transport behaviours. In this work, we report the first successful growth of high-quality large Ti3AlC2 single crystals via a TiAl3 flux-assisted approach. The crystals exhibit excellent structural quality, with individual flakes exceeding 1 cm in length and basal-plane surface areas reaching up to ~36 mm2. Hall measurements on individual flakes reveal a high carrier density of ~1021 cm-3, while polarisation-resolved Raman spectra show a nearly circular intensity pattern, indicating optical isotropy within the basal plane. To investigate surface characteristics, scanning tunnelling microscopy was performed on freshly cleaved crystals, revealing non-flat surface topography influenced by cleavage termination. First-principles calculations indicate that cleavage predominantly occurs between Ti–Al layers and reveal distinct surface-dependent band structures and Fermi surfaces. A nearly regular hexagonal Fermi contour corresponds to the Al-terminated surface, while a star-like sixfold modulated contour is associated with the Ti-terminated surface. Chemical etching of these MAX phase crystals yields millimetre-scale Ti3C2Tx flakes, which can be mechanically exfoliated onto chips. Raman spectra exhibit a strong G-band peak at ~1550 cm-1, with no discernible D-band, indicating ultralow-defect sp2-like carbon structures. Two-terminal devices fabricated from these flakes display symmetric I–V characteristics and negligible gate modulation across 2.5 μm channels, confirming metallic behaviour and good electrical contact. This work establishes a scalable route to large Ti3AlC2 single crystals, offering new insights into their intrinsic properties, laying a solid foundation for future MXene-based device technologies.

The topic of inorganic nanotube synthesis and some selected applications will be elucidated in the series of research projects. The main emphasis will be on understanding the procedures connected to the high-temperature conversion of tungsten suboxide nanowhiskers to the WS₂ multiwall nanotubes. The process was followed via in-situ and ex-situ scanning and transmission electron microscopies, respectively.¹ The exact reaction mechanism was then revealed on the atomic and layer-by-layer scale. In a follow-up study, the synthetic nuances were exploited to reach the ultralong WS₂ nanotubes with lengths reaching over half millimeters and on. Such unique materials promise opening new application playgrounds as demonstrated by assembling “WS₂ inorganic bucky paper” – felt-like materials capable of ultrafiltration of gold nanoparticles.²  

Another new application of WS₂ nanotubes is the entrapment and encapsulation of uranium oxide within a nanotube lumen. The procedure is based on the facile melting of uranyl nitrate hydrate in the presence of WS₂ nanotube powder. Chemical changes during the encapsulation were closely followed by XPS and XRD analyses. The procedure could be eventually exploited as a storage protocol for highly active and hazardous nuclear materials, including other isotopes capable of forming low melting salts.³

The final part of the talk will be focused on the description of the synthesis of advanced inorganic nanotubes, WTe2, MoTe2, ReSe2, and ReS2, utilizing Van der Waals epitaxy. The developed synthetic protocol exploits WS₂ nanotubes as a useful substrate for the deposition of additional layers. New compounds deposited on the top of the nanotube copy the curvature of WS₂ nanotubes, ultimately forming core-shell WS₂ – MX₂ nanotubular structures. This methodology allows the formation of unprecedented nanotubular structures, challenging for synthesis in the classical manner.^4,5

(1)          Kundrát, V.; Novák, L.; Bukvišová, K.; Zálešák, J.; Kolíbalová, E.; Rosentsveig, R.; Sreedhara, M. B.; Shalom, H.; Yadgarov, L.; Zak, A.; Kolíbal, M.; Tenne, R. Mechanism of WS ₂ Nanotube Formation Revealed by in Situ / Ex Situ Imaging. ACS Nano 2024, 18 (19), 12284–12294. https://doi.org/10.1021/acsnano.4c01150.

(2)          Kundrát, V.; Rosentsveig, R.; Bukvišová, K.; Citterberg, D.; Kolíbal, M.; Keren, S.; Pinkas, I.; Yaffe, O.; Zak, A.; Tenne, R. Submillimeter-Long WS ₂ Nanotubes: The Pathway to Inorganic Buckypaper. Nano Lett. 2023, 23 (22), 10259–10266. https://doi.org/10.1021/acs.nanolett.3c02783.

(3)          Kundrat, V.; Cohen, H.; Kossoy, A.; Bonani, W.; Houben, L.; Zalesak, J.; Wu, B.; Sofer, Z.; Popa, K.; Tenne, R. Encapsulation of Uranium Oxide in Multiwall WS ₂ Nanotubes. Small 2023, 2307684. https://doi.org/10.1002/smll.202307684.

(4)          Kundrat, V.; Houben, L.; Zalesak, J.; Pinkas, I.; Rosentsveig, R.; Tenne, R. Core-Shell Nanotubes from Tungsten/Molybdenum Ditelluride-Tungsten Disulfide via Van Der Waals Epitaxy. American Chemical Society (ACS) September 9, 2024. https://doi.org/10.26434/chemrxiv-2024-8zm9v.

(5)          Koma, A. Van Der Waals Epitaxy—a New Epitaxial Growth Method for a Highly Lattice-Mismatched System. Thin Solid Films 1992, 216 (1), 72–76. https://doi.org/10.1016/0040-6090(92)90872-9.

Metal halide perovskites (MHPs) have attracted significant interest from the scientific community due to their exceptional optoelectronic properties, making them promising candidates for various applications. Initially recognized for their potential in solar cells, these materials have since demonstrated their versatility, emerging as key components in a range of optoelectronic devices, including photodetectors and light emitters. As research progresses, tin-based MHPs continue to gain attention as a lead-free eco-friendly alternative with the potential to revolutionize multiple fields of optoelectronics.

In this work, the optical properties of the 2D A₂SnI₄ (A = 4-fluorophenethylammonium (4-FPEA)) perovskite— the first reported ambient-stable tin iodide microcrystals—are investigated. This material was successfully applied in orange-emitting LEDs with improved performance [1]. A detailed optical investigation, including temperature-dependent photoluminescence (PL) and reflectance (R) studies coupled with DFT calculations, enabled us to assign the features observed in the PL and R spectra to specific optical transitions within the band structure. This study presents the first comprehensive resolution of the band structure proposed for this perovskite.

Two-dimensional layered perovskites (2DLPs) are non-conventional semiconductors that combine strong excitonic effects, intrinsic quantum confinement, and compositional tunability, making them promising materials for integrated photonics [1,2]. A key challenge for their implementation into photonic architectures is the fabrication of single microcrystal-based structures with controlled geometry and homogeneous quality, which are required for nanoscale patterning.

In response to this challenge, we developed a fast and reproducible recrystallization strategy to grow single crystalline 2DLP microcrystals with well-defined rectangular geometry, atomically flat surfaces, and controllable lateral sizes ranging from a few to several hundred micrometers. These microcrystals exhibit spatially homogeneous emission and act as open cavities that support confined photonic modes, fundamental for strong light-matter interaction [3]. Their high optical quality makes these microcrystals ideal platforms for deterministic nanofabrication, allowing the introduction of controlled features or defects to tailor light–matter interactions at the microscale and paving the way for potential monolithic integration into photonic circuits.

To achieve precise structuring, we optimized focused ion beam (FIB) milling as a nanofabrication technique for these soft materials. By systematically evaluating how ion dose and gallium implantation affect their optical properties, we defined a processing window that preserves emission while enabling accurate geometry control. Within this regime, individual microcrystals can be patterned into photonic-crystal or grating architectures, offering new routes to control light propagation directly within the crystal.

Enabling on-chip integration further requires electrical contacting of individual microcrystals. To this end, we adapted electron beam lithography by tuning the developer chemistry to prevent microcrystal dissolution, achieving reliable fabrication of metal electrodes directly on their surfaces.

By combining reproducible recrystallization, controlled ion-beam processing, and on-crystal lithography, we establish a robust toolbox for deterministic microstructure design and integration, allowing both active and passive photonic components to be integrated within a single perovskite-based photonic circuit

A large number of promising two-dimensional (2D) semiconductor materials, represented by black phosphorus (0.3 eV), transition metal dichalcogenide (TMDCs) (<2 eV), and hexagonal boron nitride (6 eV), have been extensively studied in optoelectronic devices. However, the spectrum of large-band gap materials remains very narrow, limiting the application for broadband optoelectronic devices. The broad family of III–VI monochalcogenides are a relatively unexplored part of the layered semiconductor family with the intralayer structure X–M–M–X, where M is a group III element (Ga, In) and X is a chalcogen (S, Se, Te). We present the synthesis and fabrication of high-performance broadband photodetector based on a few layers of GaTe with different dopants (Zn, Cd, Sb). The polarity of dopants was characterized by Hall measurements. Also, we have fabricated heterojunctions with Zn-doped GaTe (p-type) and As-doped GaSe (n-type). Fabricated devices were irradiated with different wavelengths (300-1100 nm) of light, showing outstanding responsivity with low dark current and a high on/off ratio. Time-resolved photocurrent measurements were also performed, which exhibit a fast response time. We have calculated the electronic band structure and density of states of the samples. We also have designed photodetectors using multiscale modeling to explore the device's performance. By using a semiconductor module for theoretically modeled devices, the terminal current across the device with respective wavelength was calculated and compared with the experimental results.

The capacity to capture and convert solar energy into efficient, environmentally friendly, and renewable power sources has wide-ranging implications globally, spanning scientific and technological domains. Halide perovskites (HPs) exhibit remarkable performance in optoelectronics and photovoltaic devices, making them promising materials for various applications. Nonetheless, their widespread adoption faces obstacles due to their intrinsic instability and toxicity, resulting in detrimental phase changes and decomposition when exposed to environmental factors. A practical approach to overcome these challenges entails developing a protective shell surrounding the core perovskite. This shell acts as a physical barrier, providing stability to the perovskite and augmenting the optical characteristics of the core material. Herein, we developed a new synthetic strategy for stabilizing HPs and boosting their optoelectronic properties by sheeting the NCs with MoS2. We investigate the synthesis mechanism by analyzing each step using a gamut of analytical methods. Namely, we study the mechanism of MoS2 shell formation around the CsPbBr3 NCs by examining the impact of the reaction temperature and the concentration of the precursors. Moreover, the analysis of the optical properties of the core-shell nanostructures indicates a charge transfer from the conduction band (CB) of the CsPbBr3 NCs to the CB of MoS2. This study's insights can guide the design and optimization of stable photonic and optoelectronic HPs-based devices. Moreover, it can address the urgent need to develop sustainable and efficient energy technologies and pave the way toward a more sustainable future.

1. TEM images of CsPbBr₃ NCs, (b) Schematic representation of CsPbBr₃ @MoS₂ NP, (c) TEM image of CsPbBr₃ @MoS₂ NP, (d) HR-TEM images of CsPbBr₃ with a lattice spacing of 0.419 nm (red), and MoS₂ with 0.624 nm (yellow)

Ammonia (NH₃) is a crucial component in the production of fertilisers and various chemicals, yet its traditional industrial synthesis via the Haber-Bosch process is energy-intensive and environmentally impactful [1,2]. As a result, a wide range of alternative sources, other than nitrogen gas (N₂), for the synthesis of NH₃ has been explored within the community. Electrocatalytic nitrate reduction reaction (NO₃^--to-NH₃) offers a sustainable and decentralised alternative route by utilising renewable electricity to convert abundant NO₃^- sources, such as agricultural runoff or industrial wastewater, into valuable ammonia [3,4]. However, the development of efficient, durable, and environmentally friendly catalysts for this complex multi-electron transfer process remains a significant challenge. As such, this work presents a study on the development of a flexible, high-performance electrocatalyst composed of molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) nanosheets, on a robust reduced graphene oxide (rGO) modified carbon cloth (CC) substrate [5,6]. At the low applied potential of -0.4 V (vs. RHE) and in 0.1 M KOH electrolyte containing KNO₃, MoS₂/WS₂-rGO@CC catalysts exhibited excellent nitrate reduction performance with a high Faradic Efficiency (FE) of ~30.3%, good selectivity for NO₃-reduction to N₂ (~97.9%), good hindrance to parasitic hydrogen evolution reaction (HER), along with displaying outstanding NH₃ yield rate of 50 mg.h^-1.mg_cat^-1. Upon mimicking the neutral-pH environmental conditions of real wastewater outlets, the optimised electrocatalysts were used for NO₃-RR in 0.1 M Phosphate Buffer (pH 7) electrolyte containing KNO₃, showed an enhanced and stable NH₃ yield rate of 206 μg.h^-1.mg_cat^-1 with a ~18.1% FE in a flow system. This unique design of the electrocatalyst took advantage of the high surface area and conductivity of the rGO-modified CC, combined with the enhanced catalytic activity of the MoS₂/WS₂ heterostructures. In general, this study provides a practical pathway for tailoring 2D materials for application in wastewater treatment and environmental remediation.

Germanane, an atomically thin germanium allotrope with a graphene-like buckled lattice, has emerged as a promising two-dimensional electrode material for next-generation energy-storage technologies owing to its high theoretical capacity, tuneable surface chemistry, and favourable ion-transport characteristics [1-3]. In parallel, magnesium presents an attractive charge-carrier candidate for multivalent battery systems, offering a divalent redox mechanism, high volumetric capacity, natural abundance, and improved intrinsic safety compared with conventional Li-ion systems. [4]. Building on these motivations, the present work explores the synthesis and electrochemical evaluation of germanane within a GeH-Mg-ion battery configuration.

Zintl phase precursor CaGe₂ was synthesised via solid-state reaction, in which stoichiometric Ca and Ge were sealed under inert atmosphere and annealed at 950 °C for 6 hours, yielding CaGe₂. Germanane was then obtained via exfoliation using hydrochloric acid, enabling the formation of few-layer sheets with high lateral continuity.

To evaluate their applicability in GeH-Mg-ion systems, the germanene sheets were incorporated as active electrode material in composite films with conductive carbon and a polymeric binder. Electrochemical testing was conducted in two-electrode Mg-ion cells using an active carbon-based counter electrode and a non-nucleophilic magnesium electrolyte. Preliminary electrochemical studies, including galvanostatic cycling, rate-capability measurements, and impedance analysis, are currently being carried out on germanene-based electrodes in Mg-ion coin cells to assess their Mg²⁺ insertion behaviour and overall performance.

This study highlights the viability of germanene as an electrode for emerging multivalent battery chemistries. The combination of controllable synthesis, structural stability, and promising Mg-ion electrochemical response positions germanene as a compelling platform for further optimisation.

In single-layer semiconducting transition metal dichalcogenides (TMDs), strong quantum confinement and reduced dielectric screening, due to their two-dimensional structure, leads to tightly bound excitons, trions and higher-order bound states. Understanding thetemporal evolution of such complexes after optical excitation and their response to external stimuli is essential for unlocking their potential in optoelectronic applications.

First, we investigate the influence of electrostatic doping via the field-eƯect on the ultrafastdynamics of trions in single-layer TMDs using broadband femtosecond pump-probemicroscopy. We study the temporal dynamics of excitons and trions as the primary photoexcited species, disentangle the formation of trions from photogenerated vs electrostatically injected charge carriers and discuss the formation of neutral and charged excitons.

As a second control parameter, we investigate the role of strain, which influences the whoseresonant energy, eƯective mass, and mobility of excitons and carriers. We report the modulation of the exciton recombination in monolayer WS2 via the application of uniaxial tensile strain. For 1 % applied strain the dominant (few-ps) recombination rate increases over the unstrained case by a factor of two. We ascribe these fast dynamics to the exciton migration towards ultrafast recombination centers and the strain-induced enhancement of this process to an increased exciton diffusion.

Coherent excitation of phonons with sufficiently short laser pulses leads to a periodic strain modulation of optical spectra. In monolayer MoTe2 we observe a dramatic rearrangement of the optical absorption induced by an out-of-plane stretching and compression of the crystal lattice, consistent with displacive excitation of an A1g -type oscillation.
 

Two-dimensional transition metal dichalcogenides (TMDs) are promising for next-generation thermal management applications due to their atomically layered structures and high thermal anisotropy.

Theoretical studies suggest that both cross-plane and in-plane thermal transport in 2D materials are highly dependent on twist angle, as it modulates interlayer phonon coupling, thereby affecting phonon transmission and scattering. These effects are particularly pronounced at small twist angles (0–5°). However, precise fabrication of high-quality, twisted bilayers with small-angles remains challenging, and experimental validation of theoretical predictions is still limited.

Here, we discuss the synthesis strategies for high-quality, large area monolayers of TMDs, such as MoS₂ and WS₂ via capping-assisted CVD method and fabrication techniques for obtaining clean, twisted bilayers. Thermal transport across the mono and bi-layers was studied using frequency-domain thermoreflectance, together with molecular dynamics (MD) simulations.  Our findings provide insights into how interlayer coupling influences phonon transport in twisted bilayers of homo- and hetero-stacking, particularly in the small-angle regime. This results are crucial for  phonon engineering strategies in 2D materials and the design of tunable thermal management systems for nanoscale devices.

Understanding the interplay between bright excitons and free carriers is fundamental for optimizing emerging optoelectronic materials, ranging from hybrid perovskites to van der Waals layered crystals. While ultrafast spectroscopy is a standard tool, high-repetition-rate measurements (MHz range) often obscure slow relaxation processes and deep trapping dynamics due to pulse pile-up and thermal accumulation.

In this contribution, we present a comprehensive study of carrier dynamics using a correlated Time-Resolved Microwave Conductivity (TRMC) and Time-Resolved Photoluminescence (TRPL) system operating in a low-repetition rate regime (100–200 kHz). This specific temporal window (>5 µs between pulses) allows for the complete relaxation of long-lived trap states, providing a pristine background for each excitation event. We demonstrate that this setup is uniquely suited for distinguishing between radiative recombination and non-radiative transport-relevant processes in materials synthesized via solution processing and chemical vapor transport.

Our results highlight that the combination of TRMC and TRPL in the sub-MHz regime offers a powerful, non-contact feedback loop for optimizing synthesis protocols, enabling the precise identification of loss mechanisms in the microsecond time domain often overlooked by standard ultrafast techniques.

Next-generation flexible electronics require a deep understanding of the mechanical limits of 2D semiconductors to ensure their effective use in strain-engineered devices. Herein, we investigate the elastic scaling behavior of gas-phase CVD-grown atomically-thin 2H-MoS₂ films  for various thickness 0.75–15 nm. Mechanical crossover at a critical thickness t_c ~3.0 nm has found, below which nanoscale elastic-size effects dominate, defining a true-2D regime, while thicker films (t > t_c) exhibit bulk-like behavior. The Young’s modulus scales with thickness as E ∝ t^−1.16, whereas the bending modulus follows D ∝ t^2.91, marking a transition from atomically-flexible to a rigid-regime for t > t_c. Monolayer MoS₂ exhibit a maximum elastic strain energy of 1.55 J/cm², arising from strong in-plane strain induced by van der Waals epitaxial coupling. These results offer essential mechanical benchmarks for guiding the design of strain-engineered, flexible MoS₂ devices.