Publications

Memristive devices based on layered materials have the potential to enable low power electronics with ultra-fast operations toward the development of next generation memory and computing technologies. Memristor performance and switching behavior crucially depend on the switching matrix and on the type of electrodes used. In this work, we investigate the effect of different electrodes in 1D MoO2–MoS2 core shell nanowire memristors by highlighting their role in achieving distinct switching behavior. Analog and digital resistive switching are realized with carbon based passive (multi-layer graphene and multiwall carbon nanotube) and 3D active metal (silver and nickel) electrodes, respectively. Temperature dependent electrical transport studies of the conducting filament down to cryogenic temperatures reveal its semiconducting and metallic nature for passive and active top electrodes, respectively. These investigations shed light on the physics of the filament formation and provide a knob to design and develop the memristors with specific switching characteristics for desired end uses.

Abstract Selective anion transport is essential for energy conversion, water purification, and electrochemical systems, yet achieving precise ion selectivity in membranes remains a challenge. Here, we present an amino-functionalized graphene oxide (am-GO) membrane that enables tunable anion transport through nanochannels. Using a combined experimental and computational approach, we consider the three stages of ionic transport—absorption, diffusion, and desorption—to reveal that Cl− selectively diffuses through nanochannels, while NO3 −, SO4 2−, and PO4 3− are excluded. In ionic mixtures, the chemical transistor effect emerges, where Cl− pulls water from NO3 − hydration shell, enhancing its mobility, while SO4 2− and PO4 3− remain excluded due to size constraints. This mechanism enables precisely regulated Cl− and NO3 − transport, with ultrahigh rejection rates of 99.99% for SO4 2− and PO4 3−, even in complex ionic environments. The am-GO exhibits stability and anion-hopping mechanisms, making it a versatile platform for anion exchange membranes in electrolysis, energy storage, and environmental applications.

Gold clusters and individual atoms are seen on few-layer graphene in the scanning transmission electron microscopy high-angle annular dark-field (STEM-HAADF) image and individual atom positions are determined by the corresponding STEM bright-field image. The clusters nucleate exclusively in the hydrocarbon surface contamination. HAADF imaging is one of the most feasible methods to detect individual adatoms and impurities.

Metal–organic frameworks (MOFs), composed of metal nodes coordinated with organic ligands, have emerged as a versatile class of functional materials for next‐generation smart textile systems. Their high surface area, tunable pore chemistry, and modular structural diversity enable multifunctional textile platforms. When integrated into textile substrates, MOFs can retain the properties, breathability, and comfort of fabrics while imparting advanced functionalities significant for sensing, environmental protection, biomedical interfaces, and energy‐related applications. This review provides a comprehensive overview of recent advances in MOF‐integrated smart textiles, focusing on material design principles, integration strategies, and application‐driven performance. Key fabrication approaches including surface coating, in situ growth, post‐synthetic modification, hydrothermal assembly, and emerging printing techniques such as inkjet and electrohydrodynamic jet are critically examined with respect to scalability, durability, and textile compatibility. Representative applications spanning gas and chemical sensing, detoxification, antimicrobial and biomedical functions, energy harvesting, and flexible energy storage are systematically discussed. Finally, current challenges and future opportunities are outlined, highlighting pathways toward scalable, durable, and application‐oriented MOF‐based smart textiles for real‐world applications.

No abstract is provided for this article.

Defect centers in wide-band-gap crystals attracted considerable attention due to the realisations of qubits, sensors, or single photon emitters at room temperature. The family of these centers is constantly growing, including well-known examples such as nitrogen-vacancy centers in diamond, silicon-vacancy in silicon carbide, chromium substitutions in aluminium oxide, and many others. Unfortunately, such defect centers embedded in highly insulating crystals have been notoriously difficult to excite electrically. Herewith, we present a realisation of insulating light-emitting diodes based on carbon centers in hexagonal boron nitride. The rational design of the vertical tunnelling devices via van der Waals technology enabled us to control the charge dynamics related to non-radiative tunelling, defect-to-band electroluminescence, and intradefect electroluminescence. The fundamental understanding of the tunnelling events enabled us to achieve high efficiency of electrical excitation, which exceeded by a few orders of magnitude the efficiency of optical excitation in the sub-band-gap regime. A combination of a Stark effect and screening by band electrons provide a control knob for tuning the energy of emission. With this work, we solve an outstanding problem of creating electrically driven devices realised with defect centers in wide-band-gap crystals, which are relevant in the domain of optoelectronics, telecommunication, computation, or sensing.

Highlights: A new metamaterial was demonstrated to absorb microwaves with 97.2%–97.7% absorption within a wide bandwidth of 1.56 GHz-18.3 GHz. The material has achieved the highest relative bandwidth and lowest thickness in the L to S-band reported so far. The design of multiple-layer metamaterial structures was for wide bandwidth microwave absorption. A one-step laser direct writing method was demonstrated to synthesize graphene and magnetic nanoparticles simultaneously. The laser direct writing enabled the achievement of an electrical sheet resistance from 57 to 480 Ω sq −1 with a 5% deviation.

Contamination is a major concern in surface and interface technologies. Given that graphene is a 2D monolayer material with an extremely large surface area, surface contamination may seriously degrade its intrinsic properties and strongly hinder its applicability in surface and interfacial regions. However, large-scale and facile treatment methods for producing clean graphene films that preserve its excellent properties have not yet been achieved. Herein, an efficient postgrowth treatment method for selectively removing surface contamination to achieve a large-area superclean graphene surface is reported. The as-obtained superclean graphene, with surface cleanness exceeding 99%, can be transferred to dielectric substrates with significantly reduced polymer residues, yielding ultrahigh carrier mobility of 500 000 cm2 V-1 s-1 and low contact resistance of 118 Ω µm. The successful removal of contamination is enabled by the strong adhesive force of the activated-carbon-based lint roller on graphene contaminants.

No abstract is provided for this article.

Bottom-up electrochemical synthesis of atomically thin materials is desirable yet challenging, especially for non-van der Waals (vdW) materials. Thicknesses below few nm have not been reported yet, posing the question how thin can non-vdW materials be electrochemically synthesized? This is important as materials with (sub-) unit cell thickness often show remarkably different properties compared to their bulk form or thin films of several nm thickness. Here, we introduce a straightforward electrochemical method utilizing the angstrom-confinement of laminar reduced graphene oxide (rGO) nanochannels to obtain a centimeter-scale network of atomically thin (< 0.43nm) 2D-transition metal oxides (2D-TMO). The angstrom-confinement provides a thickness limitation, forcing sub-unit cell growth of 2D-TMO with oxygen and metal vacancies. We showcase that Cr2O3, a material without significant catalytic activity for OER in bulk form, can be activated as a high-performing catalyst if synthesized in the 2D sub-unit cell form. Our method displays the high activity of sub-unit cell form while retaining the stability of bulk form, promising to yield unexplored fundamental science and applications. We show that while retaining the advantages of bottom-up electrochemical synthesis like simplicity, high yield, and mild conditions, the thickness of TMO can be limited to sub-unit cell dimensions.

We use graphene bubbles to study the Raman spectrum of graphene under biaxial (e.g., isotropic) strain. Our Gruneisen parameters are in excellent agreement with the theoretical values. Discrepancy in the previously reported values is attributed to the interaction of graphene with the substrate. Bilayer balloons (intentionally pressurized membranes) have been used to avoid the effect of the substrate and to study the dependence of strain on the interlayer interactions.

No abstract is provided for this article.

Tunneling conductance between two bilayer graphene (BLG) sheets separated by 2 nm-thick insulating barrier was measured in two devices with the twist angles between BLGs less than 1°. At small bias voltages, tunneling occurs with conservation of energy and momentum at the points of intersection between two relatively shifted Fermi circles. Here, we experimentally found and theoretically described signatures of electron–hole asymmetric band structure of BLG: since holes are heavier, the tunneling conductance is enhanced at the hole doping due to the higher density of states. Another key feature of BLG that we explore is gap opening in a vertical electric field with a strong polarization of electron wave function at van Hove singularities near the gap edges. This polarization, by shifting electron wave function in one BLG closer to or father from the other BLG, gives rise to asymmetric tunneling resonances in the conductance around charge neutrality points, which result in strong sensitivity of the tunneling current to minor changes of the gate voltages. The observed phenomena are reproduced by our theoretical model taking into account electrostatics of the dual-gated structure, quantum capacitance effects, and self-consistent gap openings in both BLGs.

There are few phenomena in condensed matter physics that are defined only by the fundamental constants and do not depend on material parameters. Examples are the resistivity quantum, h/e2 (h is Planck's constant and e the electron charge), that appears in a variety of transport experiments and the magnetic flux quantum, h/e, playing an important role in the physics of superconductivity. By and large, sophisticated facilities and special measurement conditions are required to observe any of these phenomena. We show that the opacity of suspended graphene is defined solely by the fine structure constant, a = e2/hc � 1/137 (where c is the speed of light), the parameter that describes coupling between light and relativistic electrons and that is traditionally associated with quantum electrodynamics rather than materials science. Despite being only one atom thick, graphene is found to absorb a significant (pa = 2.3%) fraction of incident white light, a consequence of graphene's unique electronic structure.

Hexagonal boron nitride is the only substrate that has so far allowed graphene devices exhibiting micron-scale ballistic transport. Can other atomically flat crystals be used as substrates for making quality graphene heterostructures? Here we report on our search for alternative substrates. The devices fabricated by encapsulating graphene with molybdenum or tungsten disulphides and hBN are found to exhibit consistently high carrier mobilities of about 60,000 cm$^{2}$V$^{-1}$s$^{-1}$. In contrast, encapsulation with atomically flat layered oxides such as mica, bismuth strontium calcium copper oxide and vanadium pentoxide results in exceptionally low quality of graphene devices with mobilities of ~ 1,000 cm$^{2}$ V$^{-1}$s$^{-1}$. We attribute the difference mainly to self-cleansing that takes place at interfaces between graphene, hBN and transition metal dichalcogenides. Surface contamination assembles into large pockets allowing the rest of the interface to become atomically clean. The cleansing process does not occur for graphene on atomically flat oxide substrates.

Herein, we address the conflicting behaviour of different pristine graphene dispersions through their careful preparation and characterization in aqueous media.