Exploring Two-dimensional Nanomaterials for Future Applications

We introduce a new interlayer potential (ILP) for simulating the adsorption and diffusion properties of planar organic molecules with partially charged heteroatoms on hexagonal boron nitride (hBN). Unlike previous models, this ILP incorporates all-atom electrostatic interactions alongside short-range repulsion and long-range attraction, enabling the accurate treatment of polar molecules. Parametrized against density functional theory data for pentacene and PTCDI, the ILP demonstrates transferability to related systems such as terrylene and PTCDA. Comparative studies of nonpolar pentacene and polar PTCDA reveal distinct behaviors in single-molecule diffusion, cluster formation, and monolayer growth. PTCDA exhibits stronger binding due to electrostatic contributions, limiting diffusion to short-ranged hops, while pentacene undergoes long-range translocations facilitated by out-of-plane motions. At low coverage, PTCDA molecules lock into place via carbonyl-mediated hydrogen bonds, enabling only collective motion, whereas pentacene remains mobile. Monolayer simulations reproduce experimentally observed epitaxial morphologies: PTCDA forms a dense square lattice, while pentacene aligns parallel along its long axis. This ILP offers a computationally efficient and accurate alternative to ab initio and machine-learning methods, opening avenues for modeling polar organic molecules on hBN. Its utility extends to understanding layer formation and structural properties in hBN-encapsulated or -supported organic systems.

Cadmium free and lead free quantum dots are attracting increasing attention as environmentally safer luminescent materials for photovoltaic spectral management. In this work, ZnInSe quantum dots were synthesized and investigated as a potential down converting material for crystalline silicon solar cells. ZnInSe is particularly attractive because it avoids the toxicity concerns, while offering composition dependent optical tunability. The synthesized ZnInSe quantum dots were evaluated through optical and structural characterization to understand their suitability for luminescent down shifting applications. UV-visible absorption analysis was used to examine the light harvesting region, while photoluminescence spectroscopy was employed to assess the emission behavior and spectral overlap with silicon solar cell response. The ZnInSe quantum dots exhibited visible photoluminescence, indicating their potential to act as photon converting centers. The are sustainable for photovoltaic integration, particularly for polymer embedded coatings designed for outdoor operation. This study demonstrates the feasibility of using ZnInSe quantum dots as an emerging down converting material for photovoltaic applications. The work provides a foundation for further optimization of ZnInSe quantum dot composition, surface passivation, shell growth, polymer compatibility, and device level validation. Overall, ZnInSe quantum dots represent a promising route toward environmentally compatible spectral conversion coatings for next generation photovoltaic modules. Keywords: ZnInSe quantum dots, down conversion, luminescent down shifting, crystalline silicon solar cells, cadmium free quantum dots, photovoltaic spectral management.

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic organofluorines widely used in industrial and consumer applications due to their thermal stability, chemical resistance, and surfactant properties. The same properties cause environmental persistence and create compliance risks with the EU Drinking Water Directive limits that became mandatory since 2026 (0.1 µg/L sum of 20 PFAS or 0.5 µg/L PFAS total) [1]. While anionic PFAS such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are widely studied, zwitterionic precursors such as 6:2 fluorotelomer sulfonamidopropyl betaine (6:2 FTAB), a major component in modern firefighting foams such as Capstone®/Forafac® 1157 (Product B), pose a unique threat. These compounds act as persistent precursor reservoirs being transformed into regulated PFAS in the environment and have recently been detected in drinking water sources in Europe, Canada, and the UK [2]. The state-of-the-art technology relies on adsorption by activated carbon (AC) in fixed-bed columns; however, AC production has a high carbon footprint (8.6–18.3 kg CO₂-eq/kg AC) and lacks efficient on-site regeneration options. Electrosorption, the field-driven and reversible uptake of ions at polarized electrodes, has been applied for conventional anionic PFAS such as PFOA and PFOS, but its application to zwitterionic PFAS remains unclear due to their dual ionic character [3]. In this study, electrosorption of 6:2 FTAB using Ti₃C₂Tₓ MXenes was investigated. MXenes are attractive for environmental applications due to their conductivity, tunable chemistry, and their layered structure. Two stable and homogeneous MXene electrodes were developed, including a binder-free electrode and one using a non-fluorinated polymer binder. Electrochemical characterization showed a specific capacitance of ~90 F/g in 1 M Na2SO4 at 3 mV/s. Electrosorption of 6:2 FTAB (C0=100 µg/L) was strongly potential dependent, with adsorption enhanced at negative potentials due to favorable electrostatic attraction with the positively charged tertiary amine group. Distribution coefficients (Kd) of up to 105 L/kg were achieved at -800 mV vs Ag/AgCl, which is two orders of magnitude higher than the Kd obtained at positive potential of +800 mV in 10 mM Na2SO4. The approach was further validated using real firefighting-foam samples containing 6:2 FTAB and co-occurring organic PFAS and the performance was maintained, achieving selective electrosorption of 6:2 FTAB with Kd of 1.3 × 105 L/kg. Characterization analyses confirmed adsorption mechanisms and electrode stability across the applied potential range. [1] “https://environment.ec.europa.eu/topics/water/drinking-water_en.” [2] T. Teymoorian, G. Munoz, and S. Sauvé, “PFAS contamination in tap water: Target and suspect screening of zwitterionic, cationic, and anionic species across Canada and beyond,” Environ. Int., vol. 195, Jan. 2025, doi: 10.1016/j.envint.2025.109250. [3] N. Saeidi, F. Harnisch, V. Presser, F. D. Kopinke, and A. Georgi, “Electrosorption of organic compounds: State of the art, challenges, performance, and perspectives,” Sep. 01, 2023, Elsevier B.V. doi: 10.1016/j.cej.2023.144354.

Two-dimensional transition metal dichalcogenides have attracted significant attention due to their tunable electronic structure and potential for energy conversion applications. In this work, we investigate the thermoelectric transport properties of layered WTe₂ and Mo-alloyed WTe₂ (MoWTe₂) single crystals. Structural characterization using X-ray diffraction confirms the orthorhombic phase, while Raman spectroscopy reveals characteristic vibrational modes of the layered structure. Temperature-dependent electrical conductivity and Seebeck coefficient measurements were performed to understand charge transport behavior. The results show that alloying with Mo enhances the Seebeck response at low temperatures, which can be attributed to enhanced carrier scattering and possible energy filtering effects. However, the electrical conductivity is reduced compared to pristine WTe₂, leading to a lower power factor in the alloyed compound. These findings highlight the influence of compositional tuning on thermoelectric performance in layered materials and provide insights into optimizing transport properties in two-dimensional systems for energy harvesting applications.

Quantum dots offer a flexible platform for studying quantum coherence and transport phenomena at the nanoscale. The closed-loop shape of toroidal quantum dots, in particular, enables quantum interference of electron wave functions, hence facilitating the study of persistent currents. Persistent currents are sensitive to confinement geometry, magnetic flux quantization, and external perturbations, making them valuable probes of mesoscopic physics. The general problem addressed here is how magnetic and intense laser fields jointly influence the magnitude and profile of persistent currents in toroidal quantum dots. Here, we show that the persistent current is strongly modified by the presence and configuration of laser fields, with Gaussian and Bessel profiles producing distinct resonant features, while shifting the Bessel field results in a nearly linear current response. Machine learning techniques were employed in the calculations to optimize efficiency and minimize computational costs. The results reveal that the profile and spatial positioning of optical fields can be used to tailor current behavior. It is shown how optical variations affect current profiles through confinement modification and symmetry breaking, providing new insights into the control of quantum transport. In a broader context, the study emphasizes how geometry, magnetic flux, and optical fields interact in nanoscale structures, offering new opportunities for the accurate engineering of quantum states and currents. Quantum devices that depend on coherence, topological states, or laser-induced transport in nanostructures may be affected by this kind of control.

Hybrid materials of two-dimensional transition metal dichalcogenides (2D TMDCs) and organic molecules offer a versatile platform for engineering optoelectronic properties [1]. Such properties can be tuned by selecting the molecular component to control charge transfer and doping. We investigate a model of such systems using phthalocyanine (Pc) molecules on 2D $MoS_2$ and, in addition, we employ fluorinated Pc molecules with modified electronic properties [2], which can affect the charge transfer interaction with 2D $MoS_2$. We prepare Pc particles in suspension and then dropcast onto monolayer $MoS_2$ films supported on sapphire. The samples are then heated on a hotplate to evaporate the dispersion medium. We use Raman and photoluminescence (PL) spectroscopies to characterize the samples, probing the interactions at the interface of the molecules with 2D $MoS_2$. Using Raman measurements, we probe doping induced changes in the 2D $MoS_2$ modes and signal enhancement of the Pc molecular modes. With PL measurements, we explore the excitonic response, particularly the exciton/trion ratio, which relates to charge transfer. Preliminary results suggest that fluorinated CuPc on 2D $MoS_2$ exhibits a behaviour very distinct from that of CuPc on 2D $MoS_2$. References [1] Ghimire, G.; Adhikari, S.; Jo, S. G.; Kim, H.; Jiang, J.; Joo, J.; Kim, J. Local Enhancement of Exciton Emission of Monolayer $MoS_2$ by Copper Phthalocyanine Nanoparticles. J. Phys. Chem. C 2018, 122 (12), 6794–6800. https://doi.org/10.1021/acs.jpcc.8b00092. [2] (1) Zahn, D. R. T.; Gavrila, G. N.; Gorgoi, M. The Transport Gap of Organic Semiconductors Studied Using the Combination of Direct and Inverse Photoemission. Chemical Physics 2006, 325 (1), 99–112. https://doi.org/10.1016/j.chemphys.2006.02.003.

Recently, a novel material class has been described by Biesterfeld et al., the PbSe flat quantum dot (fQD). These highly confined nanocrystals exhibit tunable near infrared photoluminescence (0.83−1.43 eV) with high quantum yields up to 61 %. With efficient telecommunication band emission in combination with high exciton binding energies of up to 600 meV, PbSe fQDs present themselves as an interesting material class for optical fiber information processing. To enhance the (photo)stability and simultaneously suppress non-radiative relaxation, introduction of a second semiconductor material, such as CdSe, may yield heterostructures with these improved qualities. To gain insight into the influence of different morphologies, PbSe/CdSe core-shell and core-crown heterostructures were synthesized and their optical properties investigated.

Recently, a layered conjugated organic polymer, graphitic carbon nitride (g-C3N4), with a bandgap of ~2.7 eV, has gained significant attention due to its effective photocatalytic activity, low cost, ease of production, and its unique layered structure. In the present work, the First-principles Density Functional Theory (DFT) calculations were performed using QuantumATK software for the structural geometry optimization and evaluation of electronic and optical properties of g-C3N4. The calculations employed the Hybrid Generalized Gradient Approximation (HGGA) and the Perdew–Burke–Ernzerhof (PBE) functional, implemented through the Linear Combination of Atomic Orbitals (LCAO) method. These results confirmed strong visible-light absorption, suggesting potential applications in pollutant degradation, water splitting, and solar energy conversion. Further, g C3N4 was synthesized via thermal polycondensation of melamine and characterized using XRD, UV-Vis absorption spectroscopy, FTIR spectroscopy, TGA/DTA, Raman scattering, SEM, Photoluminescence, and photocatalytic performance. The experimental results closely matched the theoretical predictions in terms of structural integrity and band gap values. Its photocatalytic activity was evaluated for the degradation of various dyes and expired pharmaceutical drugs upon visible-light exposure.The results demonstrate that g-C3N4, a 2D nanomaterial, is a promising candidate for sustainable environmental remediation.

The emergence of two-dimensional (2D) materials has fundamentally transformed science and technology, highlighting the need for scalable production strategies to fully exploit their unique thickness-dependent physicochemical properties. In this context, transition metal dichalcogenides (TMDs), particularly molybdenum disulfide (MoS$_₂$), have emerged as promising semiconductors for electronic and optoelectronic applications. Such nanosheets can be efficiently produced via electrochemical exfoliation and subsequently processed as stable dispersions (“inks”). A commonly used gold standard for dispersion is a DMF/PVP system; however, this approach suffers from significant toxicity and the presence of the difficult-to-remove polymer (PVP), which compromises material purity. Therefore, the aim of this work is to identify an additive-free solvent that enables efficient dispersion of MoS$_₂$ and ideally meets the criteria of a “green” solvent. Following electrochemical exfoliation, MoS$_₂$ was dispersed in more than 100 pure solvents and solvent mixtures and systematically evaluated. Five additive-free systems exhibited outstanding performance: N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), 1,2-difluorobenzene (DFB), and the green solvent γ-valerolactone (GVL). A solvent-specific optimized centrifugation process enables the effective removal of residual electrolyte, decomposition byproducts, agglomerates, and non-exfoliated material. Purity was analyzed using DRIFT spectroscopy (diffuse reflectance infrared Fourier transform spectroscopy), while UV/Vis spectroscopy and AFM measurements confirm exfoliation efficiency and layer thickness. Our results demonstrate that GVL represents an additive-free, environmentally friendly alternative to conventional solvent systems without compromising dispersion or material quality. This establishes a scalable and more sustainable route for the production of high-purity MoS₂ dispersions and opens new perspectives for the industrial processing of TMD-based materials.

Rapidly polluting surface water bodies pose an unprecedented challenge to society. These waters are the primary drinking water sources not only for humans but also for wildlife. Ecotoxicity results indicated that pollution in wastewater treatment plants (WWTPs) led to a critical situation in Czechia and nearby regions, where the current technologies were unable to effectively treat the incoming wastewater. Advanced oxidation via Photocatalysis is emerging as a promising alternative technology in the realm of water purification. Bismuth oxy-iodides (BiOI), which are a type of V-VI-VII ternary semiconductor material, have drawn much more interest due to their outstanding visible light absorption and electron-hole pair separation in addition to chemical inertness, non-toxicity, and low cost. Despite the promising results, it still has key drawbacks, such as low quantum efficiency and poor recoverability. A practical approach is to build heterostructured photocatalysts by combining narrow and wide bandgap semiconductors. In this study, photocatalytic NPs, including BiOI, ZnO, and BiOI-ZnO, were synthesized and embedded into PES flat-sheet membranes fabricated by the non-solvent-induced phase separation (NIPS) technique to enhance their functional surface properties, attain antifouling characteristics, and enable the simultaneous light-driven degradation of CECs along with physical separation. Surface characterization, morphological analysis, and photocatalytic performance confirmed the successful synthesis and high activity of the NPs, achieving more than 90 % BPA degradation in the suspension. When embedded into the membrane matrix, the photocatalytic NPs carried dual functionality, while maintaining 50% degradation efficiency after five reuse cycles under LED illumination. Antimicrobial testing under both visible light and dark conditions revealed additional anti-(bio)fouling properties, broadening the application potential of the modified membranes. Furthermore, using a transparent membrane module with low-energy visible LEDs or natural sunlight supports sustainable operation with minimal energy input, making this approach suitable for scalable and decentralized water treatment solutions.

Molybdenum disulfide (Mo$S_2$) is among the most widely studied two-dimensional transition metal dichalcogenides, yet a systematic, layer-resolved understanding of its mechanical and thermoelectric properties, spanning monolayer to the few-to-multilayer regime remains incomplete. Here, we present a comprehensive study linking controlled Chemical Vapor Deposition (CVD) synthesis to the quantitative characterization of elastic and thermoelectric properties across Mo$S_2$ films ranging from 1 to 20 layers. High-quality Mo$S_2$ films were grown using gas-phase CVD with metal-organic precursors under precisely controlled low-pressure conditions. Layer number was confirmed by Raman spectroscopy and atomic force microscopy (AFM) thickness profiling. Elastic properties were then investigated non-destructively using Atomic Force Acoustic Microscopy (AFAM), which probes the contact resonance frequency of the cantilever as a function of local surface stiffness. From the AFAM frequency response data, we derived the Young's modulus as a function of layer number through established contact mechanics frameworks, and further extracted the shear modulus, buckling length, critical strain, and interfacial strain using classical thin plate and beam mechanics models. The results reveal a clear and systematic layer-dependence: the Young's modulus decreases from the monolayer limit and converges toward bulk-like values with increasing layer number, consistent with the transition from a freely suspended 2D membrane to a constrained multilayer stack governed by interlayer interactions. The contribution of surface modulus to the effective elastic response is analysed and discussed. Beyond mechanical characterisation, we exploit the AFAM frequency transfer function as a pathway to probe thermoelectric behaviour across the same layer range. Variations in the contact resonance response across thermally biased samples are correlated with layer-dependent phonon transport and thermal boundary resistance, providing a non-contact, substrate-compatible approach to estimating thermoelectric conductivity trends as a function of thickness. This approach offers a practical route to thermoelectric screening of 2D materials without complex device fabrication. Taken together, this work establishes a growth-to-property pipeline for Mo$S_2$ that is directly relevant to flexible electronics, nanomechanical sensing, and thermoelectric device design, and provides a methodological framework transferable to other layered 2D systems including W$S_2$ and beyond.

Title: Thermophysical Properties and Heat Transfer Performance of g-C₃N₄ Nanofluids in Distilled Water–Ethylene Glycol Mixtures Abstract In this study, graphitic carbon nitride (g-C3N4) nanofluids were systematically prepared and evaluated using distilled water (DW) and ethylene glycol (EG) as base fluids in varying volume ratios of 100:0, 0:100, 30:70, 70:30, and 50:50 (DW:EG). A two-step dispersion method was employed, where pre-synthesized g-C3N4 nanoparticles were incorporated into the base fluids at different weight concentrations of 0.01, 0.03, and 0.05 wt%, followed by magnetic stirring and ultrasonication to achieve stable suspensions. The stability of the prepared nanofluids was assessed using zeta potential analysis and sedimentation observation, confirming good dispersion behavior across selected compositions. The influence of nanoparticle concentration, base fluid ratio, and temperature on thermophysical properties was systematically investigated. Viscosity measurements revealed a moderate increase with nanoparticle loading, while maintaining acceptable flow characteristics, particularly in DW-rich mixtures. Thermal conductivity showed a significant enhancement with increasing g-C3N4 concentration and temperature, with hybrid base fluids (DW–EG mixtures) demonstrating optimized performance due to synergistic effects. Furthermore, heat transfer capability was evaluated under varying thermal conditions, indicating that nanofluids with balanced DW:EG ratios (e.g., 50:50 and 70:30) exhibited superior performance compared to pure base fluids. The enhancement is attributed to improved particle dispersion, Brownian motion, and interfacial heat transport mechanisms. Overall, g-C3N4 nanofluids prepared in DW–EG mixtures show strong potential for advanced thermal management applications such as heat exchangers and cooling systems. Keywords: g-C3N4 nanofluids, water–ethylene glycol mixture, thermal conductivity, viscosity, heat transfer, stability

Among the candidate materials for photocatalysts to perform water splitting, a standout choice are 2D materials (with one of their dimensions in the nanometric scale), due to their high relative surface to volume ratio, higher mobilities and tunable bandgaps. Transition Metal Dichalcogenides (TMD) are a family of 2D materials with promising properties in photocatalysis. Here we propose, for the first time to our knowledge, the generation of a protein/2D-nanosheet bio-hybrid system with the objective of enhancing the photocatalytic properties of TMD 2D materials. The functionalization of the TMD nanosheets with a protein-chromophore complex is expected to perform an expansion of the absorption wavelength range of the system thanks to the contribution form the chromophore, and improve charge carrier separation within the system, as well as an anti-aggregant function for the nanosheets. The combination of the TMD nanosheets and prototype Alpha4 protein has shown novel features in the steady-state absorption spectrum. Femtosecond transient absorption spectroscopy experiments show a slight red-shifting (around 20 meV) of WS2 excitonic spectral fingerprints when functionalized with proteins. Changes in the relative intensity of excited state absorption signals points towards an increase in the WS2 doping.

In this study, the adsorption behavior of free-base porphine and selected metalloporphine molecules on a $Ti_2C$ monolayer was investigated in two different configurations using first-principles DFT calculations. All adsorption processes were found to be exothermic, with metal doping enhancing the adsorption energies. A magnetic phase shift from a semiconducting antiferromagnetic (AFM) state to a metallic ferromagnetic (FM) state was observed upon adsorption. The molecules acted as charge acceptors in all cases, which decreased the work function even though metal doping decreased the total magnetic moment. Electron localization function (ELF) maps were examined in order to obtain a better understanding of the charge redistribution. Overall, the findings show that these hybrid systems have strong potential for applications in electronic and spintronic devices in the future.

Two-dimensional Tungsten Disulfide (WS2) possesses distinctive optoelectronic properties such as high photoluminescence yield, a tunable band gap, large exciton binding, quantum confinement, strong-light matter interaction. The combination with low dimensionality makes them a favorable candidate for a variety of lightweight and flexible optoelectronic devices such as photodetectors, solar cells and LEDs. However, large-scale industrial implementation of optoelectronic 2D materials is often impeded by their high spatial heterogeneity, caused by nanoscale variations in layer thickness, substrates interactions and local strain. Thus, standard optical characterization methods like Photoluminescence (PL) and Raman spectroscopy, which commonly provide such information, can lack the spatial resolution to resolve these variations. Here, electrical atomic force microscopy (AFM) methods with in-situ illumination at different wavelengths deliver nanoscale information on the impact of layer thickness, changes in substrates interactions and local strain onto the material’s optoelectronic response. In our study, we demonstrate the capability of photo-Kelvin probe force microscopy (pKPFM) to capture local photo-potential in mono- and few-layer WS2 and correlate PL spectroscopy. Furthermore, we investigate the impact of substrates on the local charge carriers.

In optoelectronic applications, metal halide perovskites (MHPs) are compelling materials due to their highly tunable and highly competitive optical properties. Colloidal synthesis enables the controlled formation of various morphologies of MHP nanocrystals, each with distinct carrier properties and, hence, different optical and carrier-transport behaviors. We characterized different morphologies of methylammonium lead tribromide perovskite (MAPbBr3) synthesized by hot-injection protocols with slightly different parameters. A double-path fluorescence imaging microscope (FLIM) for time- and space-resolved measurements of carrier migration was employed to quantify the carrier migration process upon photoexcitation and to reveal waveguiding characteristics within individual nanosheets. Waveguiding, combined with reabsorption, enables the determination of the intrinsic absorption coefficient.

Quasi-2D CuInSe₂ nanosheets were synthesized via a cation-exchange strategy using CuSe templates, enabling preservation of sheet-like morphology while achieving controlled multinary phase formation. CuInSe₂ is a RoHS-compliant (Cd- and Pb-free) chalcogenide semiconductor with a direct band gap of ~1.1 eV, ideally suited for photovoltaic applications and optoelectronics due to its high absorption coefficient arising from p–d hybridization. TEM, XRD, and optical absorption spectroscopy confirm morphology retention, EDS confirms their chemical composition, formation of the chalcopyrite CuInSe₂ phase, and a clear transition from metallic CuSe to semiconducting optical behavior, demonstrating the effectiveness of cation exchange in overcoming precursor reactivity and polymorphism challenges in multinary systems.

Two-dimensional nanoplatelets (NPLs) are promising materials for optical technologies like LEDs and lasers [1], owing to their high photoluminescence quantum yields, large absorption [2] and gain cross-sections [3] as well as inherently suppressed nonradiative Auger recombination [4]. In practice, achieving gain with colloidal NPLs usually requires high concentrations, which promotes densely stacked solid thin films. Yet such a configuration can introduce additional loss channels, like scattering or Förster resonance energy transfer followed by charge-carrier trapping [5]. In contrast, keeping NPLs dispersed in a liquid environment mitigates these losses but is often constrained by limited NPL solubility and challenges in efficient integration into optical devices. To address both, the solubility and integration of NPLs, we report the incorporation of bright CdSe/CdS core/crown NPLs into liquid-core optical fibers as a scalable platform for stimulated emission [6]. We show that the fiber’s low-loss waveguiding enables efficient stimulated emission from dilute NPL solutions, while also achieving low gain thresholds. The use of colloidal solutions further demonstrates a possibility for exchange of nanomaterials to access a broad spectral emission range in the future. Overall, liquid-core fibers provide a scalable, chemically inert, and environmentally robust platform for photonic integration of NPLs. Literature: [1] Q. Zhang et al. ACS Photonics 2023, 10, 5, 1397 [2] A. W. Achtstein et al. J. Phys. Chem. C 2015 119, 20156 [3] B. Guzelturk et al. ACS Nano 2014 8, 6599 [4] A. Polovitsyn et al. Chem. Mater. 2017, 29, 13, 5671 [5] F. Li et al. Langmuir 2022 38, 11149 [6] V. Adolfs*, D.A. Rudoph* et al. Nano Lett. 2026, accepted

Lara Schäfers, Claudia Backes University of Kassel, Heinrich-Plett-Straße 40, 34132 Kassel, Germany Transition metal dichalcogenides (TMD) have many interesting properties in electronic or photonic applications e.g. as dielectric layers for insulators[1; 2], light emitting diodes (LEDs)[3] or raindrop triboelectric nanogenerators (RD-TENGs)[4]. Starting from a model system of WS$_2$ in a water-surfactant solution a promising in-situ approach of a non-covalent coating with a hydrophobic polymer can help to solve some issues with these applications. For the RD-TENGs a problem is the hydrophobicity, which could be tuned through different polymers used as a coating. Another challenge which can potentially be addressed it to block charge leaking, which can be reduced with a polymeric coating. Widening the chemical and material space could also help in other application areas where well-defined interfaces are requires such as LEDs or polymer composited. To achieve in-situ coating the polymer, which in this model system is polyvinylcarbazole (PVK), is added directly at the beginning of the liquid phase exfoliation (LPE)[5] of WS$_2$ with a tip sonicator in a sodium cholate solution in water. Due to the hydrophobic nature of the polymer, it has a tendency to adsorb between the surfactant and the nanosheet to avoid interaction with water. After exfoliation the 2D-nanosheets are size selected by the means of a liquid cascade centrifugation (LCC).[6] First tests through a UV/Vis measurement showed a changing amount of PVK with a changing size of the nanosheets. For applications the nanosheets are deposited on a substrate as a thin film with the help of the liquid-liquid interface deposition (LLID) method[7] with the densely packed polymer physisorbed. [1] R. Mupparapu, T. Bucher und I. Staude, Advances in Physics: X, 5, 1734083, DOI: 10.1080/23746149.2020.1734083. [2] R. Verre, D. G. Baranov, B. Munkhbat, J. Cuadra, M. Käll und T. Shegai, Nature nanotechnology, 14, 679–683, DOI: 10.1038/s41565-019-0442-x. [3] C. Wang, F. Yang und Y. Gao, Nanoscale advances, 2, 4323–4340, DOI: 10.1039/d0na00501k. [4] T. Cheng, J. Shao und Z. L. Wang, Nat Rev Methods Primers, 3, DOI: 10.1038/s43586-023-00220-3. [5] A. Amiri, M. Naraghi, G. Ahmadi, M. Soleymaniha und M. Shanbedi, FlatChem, 8, 40–71, DOI: 10.1016/j.flatc.2018.03.004. [6] C. Backes, B. M. Szydłowska, A. Harvey, S. Yuan, V. Vega-Mayoral, B. R. Davies, P.-L. Zhao, D. Hanlon, E. J. G. Santos, M. I. Katsnelson, W. J. Blau, C. Gadermaier und J. N. Coleman, ACS nano, 10, 1589–1601, DOI: 10.1021/acsnano.5b07228. [7] J. Neilson, E. Caffrey, O. Cassidy, C. Gabbett, K. Synnatschke, E. Schneider, J. M. Munuera, T. Carey, M. Rimmer, Z. Sofer, J. Maultzsch, S. J. Haigh und J. N. Coleman, ACS nano 2024, 18, 32589–32601, DOI: 10.1021/acsnano.4c09745.

We report on the room-temperature ultrasonication-assisted synthesis of two-dimensional cesium lead halide perovskites, with halide compositions spanning chloride, bromide, and iodide. By varying the ligand-to-precursor ratio and ultrasonication time, we systematically controlled dimensions and thickness of the 2D nanostructures. The photoluminescence quantum yield was also evaluated, revealing how synthetic conditions influence optical efficiency. This study provides insights into the tailored dimension and optical performance of cesium lead halide perovskite nanosheets.

Low-dimensional materials have attracted significant research interest owing to their unusual physical properties that are not observed in bulk counterparts. Recently, chalcogenide-based heteromorphic superlattices were demonstrated via atomic layer deposition (ALD) of pc-PbS and a-SnS$_2$. As suggested by Tsu in 1989, such combination shows clear advantages that emerge for investigating quantum effects, such as quantum confinement, with broader material selectivity. In addition, phonon reshaping was observed, as evidenced by Brillouin zone-folded modes in Raman spectroscopy that evolved with the superlattice period. With well-defined control of sublayer thickness, the bandgap was successfully tuned from 1.5 eV to 2.5 eV. Furthermore, we demonstrate the potential of this material system as a platform for transformation into a one-dimensional (1D) ternary phase via post-treatment. By adjusting the sublayer thickness through precise control of ALD cycle numbers, the elemental ratio between PbS and SnS$_2$ can be finely tuned, resulting in single-phase PbSnS$_3$. In situ investigations using temperature-dependent XRD and TEM provide deep insights into achieving highly anisotropic 1D crystal structures with ultra-low thermal conductivity.

Two-dimensional layered metal-halide perovskites (2DLPs) are a versatile class of semiconductors with strong quantum and dielectric confinement, enabling tunable optical and electronic properties for photonics and optoelectronics. By varying the number of inorganic octahedral layers (n), the band gap and carrier confinement can be precisely controlled. However, achieving phase-pure materials with n > 1 remains challenging due to the coexistence of multiple phases, leading to broadened optical features and reduced reproducibility. In this work, we present a simple and scalable approach to obtain phase-pure Cs-based 2D bromide perovskites by controlling post-nucleation dynamics. Using an acid-based synthesis with prolonged isothermal dwell times, we show that phase purity is governed mainly by dwell time rather than cooling rate. In-situ photoluminescence reveals the transformation from mixed-phase systems to phase-pure materials with well-defined optical properties. We further demonstrate that controlled mixing of phase-pure materials enables tuning of spectral absorption and photodetection response. This approach provides an effective route for engineering band-edge properties and device performance in layered perovskites.

Single-photon emitters (SPEs) in transition metal dichalcogenide (TMDC) monolayers are a promising platform for quantum photonics, yet the fundamental mechanism of their defect-related emission remains unresolved. In this project, we combine single-emitter microscopy at the University of Amsterdam (UvA) with ultrafast spectroscopy at Technical University of Delft (TUD) to cover the complete exciton pathway—from photogeneration to single-photon emission. At TUD, we apply time-resolved terahertz (THz) conductivity and transient absorption (TA) spectroscopy to monitor charge carriers and excitons from the femtosecond to nanosecond timescale. These measurements track the formation of free carriers and their mobility, and subsequent transfer into conventional and defect-localized exciton states. Importantly, this will be the first time TA and THz are performed on exfoliated monolayers, made possible by a new large-area exfoliation and transfer method developed at UvA. By correlating ultrafast exciton dynamics with single-photon measurements at UvA, this joint effort will establish a direct link between defect states, and emission properties. In the future, we aim to incorporate these single photon emitters into photonic integrated circuits for applications in photonic quantum computing.

Bismuth oxychalcogenides are promising layered semiconductors with tunable optical and electronic properties, yet their direct low-temperature growth by atomic layer deposition (ALD) remains largely unexplored. Here, we report a supercycle ALD route to mixed BixOySez thin films by combining two new sub-processes: a Bi2O3 process based on tris(3-methylpentan-3-olato)bismuth (TMTP3Bi) and H2O2, and a Bi2Se3 process based on TMTP3Bi and bis(trimethylstannyl)selenide (TMT2Se). Alternating these sub-cycles enables direct film growth at 170 °C without post-deposition annealing. Density functional theory supports a ligand-exchange/ligand-elimination mechanism for both the oxide and supercycle steps, accounting for Bi–O and Bi–Se bond formation and the regeneration of reactive hydroxylated surface sites. Systematic variation of the Bi2O3:Bi2Se3 supercycle ratio drives a continuous evolution from β-Bi2O3-like films toward Se-rich compositions with increasing Bi2Se3-like character, while the intermediate regime remains structurally mixed rather than converging to a well-defined single-phase Bi2O2Se analogue. This structural evolution produces strong optical modulation, with the bandgap decreasing from ~2.7 eV to ~0.43 eV and the refractive index increasing toward n ~4-5 as Se incorporation increases. Despite this optical tunability, transport in the intermediate and Se-rich films is governed by high carrier concentrations and donor-dominated Bi2Se3-like behavior, and films with a cycle ratio of Bi2O3:Bi2Se3 1:1 show a p-to-n carrier-type inversion as the deposition temperature is increased from 140 ̊C to 200 ̊C.

Semiconductor nanocrystals exhibit interesting optical properties for application as classical and quantum emitters. The absorption and photoluminescence of two-dimensional (2D) lead chalcogenide nanoplatelets and flat quantum dots (PbS, PbSe, PbTe) can reach near-infrared wavelengths, including communication-related low-loss fiber optic telecommunication windows. We colloidally synthesized strongly confined (1-2 nm in thickness) 2D PbS nanoplatelets (NPLs) with lateral dimensions of 16 x 9 nm^2, which show narrow photoluminescence (PL) centered at 720 nm (1.72 eV) with a FWHM of 171 meV at room temperature. To further investigate the optical transitions in 2D PbS NPLs, we conducted single NPL PL measurements at cryogenic temperatures. We find a narrowed emission (detector limited ~1 nm FWHM) and multiple emission signals at 10 K with a main contribution at 684 nm (1.81 eV). Time-correlated single photon counting (TCSPC) measurements reveal a drastic reduction in the PL lifetimes upon cooling. At room temperature, lifetimes of up to 1 μs are measured, while at 10 K, the PL decayed within 4 ns. We provide the comparison of the single NPL PL with temperature-dependent PbS NPL PL ensemble measurements to be able to rate the suitability of PbS as quantum (single photon) emitter in future applications.

Layered oxychalcogenides have emerged as promising materials for thermoelectric energy conversion because their mixed-anion chemistry enables simultaneous tuning of electronic structure and phonon scattering. Among these systems, Sb2Te3 is a well-known narrow-gap thermoelectric material, yet controlled oxygen incorporation remains challenging because oxygen tends to segregate at grain boundaries or form secondary oxide phases during conventional deposition processes. Here, we investigate oxygen incorporation in Sb–Te thin films using a supercycle atomic layer deposition (ALD) approach based on alternating Sb2Te3 and SbOx subcycles. Structural analyses reveal that oxygen incorporation progressively disrupts the layered growth of Sb2Te3. While pristine films grow as flat plate-like grains characteristic of quintuple-layer stacking, increasing oxygen content induces lattice strain, grain reorientation, and the formation of oxygen-rich amorphous regions coexisting with crystalline Sb2Te3 domains. These microstructural changes strongly influence the optical and electrical response of the films. Sb2Te3-rich compositions retain narrow optical band-edge transition energies of ~0.47 - 0.51 eV, whereas oxygen-rich films exhibit transitions up to ~1.8 - 4 eV due to the increasing oxide fraction up to pure SbOx. Moderate oxygen incorporation enhances the Seebeck coefficient while partially reducing electrical conductivity, leading to an optimized thermoelectric performance for the Sb2Te3:SbOx = 1:1 composition with a power factor of 422 µWm-1K-2 at 300 K and 472 µWm-1K-2 at 400 K. Overall, these results show that ALD supercycles provide a practical route to introduce oxygen into Sb–Te thin films and systematically investigate how oxygen incorporation affects microstructure and charge transport in Sb–O–Te systems.

Dumbbell-shaped quantum dots represent a unique class of nanostructures, combining the quantum confinement effects of individual quantum dots with the enhanced coherence and tunneling properties of coupled systems. In this study, we investigate the impact of an external electric field on the electronic and optical properties of dumbbell-shaped quantum dots using the finite element method to calculate the electron energy spectrum and wavefunctions. Our analysis reveals a tunable interplay between the structural geometry and external field, leading to significant changes in electron localization, symmetry-breaking distortions of wavefunctions, and coherent charge oscillations within the dumbbell-shaped quantum dot. The external field removes quasi-degeneracy in electron energy levels, drives electron migration across the structure, and alters dipole matrix elements and selection rules, resulting in the emergence of previously forbidden transitions, shifts in absorption peaks, and enhanced optical absorption in specific spectral regions. These tunable electronic and optical characteristics highlight the potential of dumbbellshaped quantum dots for advanced applications in quantum information processing, light-emitting devices, and highsensitivity optical sensors, providing a framework for designing controllable quantum systems with tailored properties.

The development of low-cost and flexible microfabrication methods is important for the rapid prototyping of electronic and optoelectronic devices based on two-dimensional materials. In this contribution, we present a maskless photolithography approach using a commercial LCD-based MSLA 3D printer as a programmable exposure system. By using the built-in LCD panel as a digital mask, photoresist-coated substrates can be patterned without conventional photomasks or mask aligners, enabling rapid design modification and accessible device fabrication. Using this approach, we fabricate Ti/Au electrode arrays on $SiO_2$/Si substrates with feature sizes approaching 20 $\mu$m. The patterned electrodes are used to integrate bilayer $MoS_2$ flakes by deterministic dry transfer and to fabricate field-effect transistors and photodetectors. The resulting devices show clear gate modulation, an ON/OFF current ratio of approximately $5 \times 10^4$, and a photoresponse associated with the excitonic features of $MoS_2$. These results demonstrate that LCD-based maskless photolithography provides a simple, flexible, and cost-effective route for integrating two-dimensional materials into functional devices, with potential applications in scalable prototyping, microelectronics, and optoelectronics.

Aqueous Zn metal batteries are attractive for large scale energy storage because they combine the intrinsic safety of aqueous electrolytes with the high capacity, low cost, and natural abundance of Zn. Their practical application, however, is still limited by the poor reversibility of the Zn metal anode. During repeated plating and stripping, Zn deposition is often spatially nonuniform, which leads to rough deposits, dendritic or porous growth, dead Zn accumulation, and severe parasitic reactions at the Zn electrolyte interface. These problems originate from localized charge transfer and uneven Zn2+ supply during cycling, indicating that stabilization of the reactive interface is essential for durable Zn metal anodes. Here, we design an Au Mesh Interphase on the Zn anode to regulate the interfacial electric field and spatial distribution of interfacial reactions. The interphase consists of a continuous two dimensional Au aerogel network with an open mesh structure. Its laterally connected conductive framework promotes electron redistribution across the Zn surface, extending charge transfer from localized regions to a broader interfacial area. At the same time, the open network preserves ion accessibility throughout the interface, enabling more uniform Zn2+ transport and alleviating concentration polarization near the electrode surface. Through this dual regulation of electron and ion pathways, the Au Mesh Interphase shifts Zn plating and stripping from a localized mode toward a more spatially distributed and controllable process. This interfacial design provides a new strategy for stabilizing Zn metal anodes by coupling electric field regulation with sustained ion access. The work also offers mechanistic insight into the role of interfacial reaction fields in governing Zn deposition behavior and suggests a broader route for interface engineering in aqueous metal batteries.