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Gallium‐based liquid metal alloys exhibit unconventional and intriguing properties as metallic solvents, demonstrating an exceptional potential to dissolve and reconfigure a vast array of elements within the liquid metal matrix. Leveraging on these distinctive characteristics of gallium‐based alloys, the synthesis of high‐entropy liquid metal alloys (HELMAs) in low dimensions is reported. The nanoscale HELMAs offer advantages including the solvation of multiple metallic elements at room temperature, while promoting their atomic dispersion at elevated concentrations. Entropy estimations for HELMAs surpass those of high‐temperature molten metals, leading to the realization of high‐entropy liquid metal systems at room temperature. Through a proof‐of‐concept hydrogen evolution reaction comparison, the potential of these HELMAs in enhancing the activities of nanocatalysts is demonstrated. In this case, atomic dispersion of Pt is shown in senary GaIn‐AuCuPtPd HELMA, contrasting with lower entropy systems in which Pt forms discernible clusters. These presented features can lead to catalytic systems with enhanced and tailored activities.

Abstract Tuning electrical properties of 2D materials through mechanical strain has predominantly focused on n‐type 2D materials like MoS2 and WS2, while p‐type 2D materials such as WSe2 remain relatively unexplored. Here, the impact of controlled mechanical strain on the electron transport characteristics of both mono and bi‐layer WSe2 is studied. Through coupling atomic force microscopy (AFM) nanoindentation techniques and conductive AFM, the ability to finely tune the electronic band structure of WSe2 is demonstrated. The research offers valuable mechanistic insights into understanding how WSe2's electronic properties respond to mechanical strain, a critical prerequisite for the development of flexible photoelectronic devices. It is also observed that under high pressure, the AFM tip/monolayer WSe2/metal substrate junction transitions from Schottky to Ohmic contact, attributed to significant charge injection from the substrate to the WSe2. These findings are significant for designing efficient metal/semiconductor contact in thin and flexible PMOS (p‐type Metal–Oxide–Semiconductor) devices.

The synthesis of nanometer‐thick (≈3 nm) gallium oxynitride (GaOxNy) layers with a variable stoichiometry is reported. The approach primarily exploits the liquid metal chemistry (LMC) technique and promises easier integration of 2D materials onto photonic devices compared to traditional top‐down and bottom‐up methods. The fabrication follows a two‐step process, involving first liquid metal‐based printing of a nanometer‐thick layer of gallium oxide (Ga2O3), followed a plasma‐enhanced nitridation reaction. Control over nitridation parameters (plasma power, exposure time) allows adjustment of the GaOxNy layer's composition, granting access to compounds with distinct optical properties (e.g., a 20% index variation), as demonstrated by ellipsometry and density functional theory (DFT) simulations. DFT provides a microscopic understanding of the effect of the bond polarization and crystallinity on the optical properties of GaOxNy compounds. These findings expand the knowledge of ultrathin GaOxNy alloys, which are poorly studied with respect to their gallium nitride (GaN) and Ga2O3 counterparts. They also represent an essential step toward integrating such 2D materials into photonic chips and offer new opportunities to improve the performance of hybrid optoelectronic devices.

While obtaining H2 from water splitting offers a promising strategy for renewable fuel production, current technologies rely on liquid freshwater. Here, authors use a hygroscopic electrolyte to achieve electrocatalytic water vapor splitting driven by renewable resources without liquid water.

Abstract Catalytic solvent regeneration has attracted broad interest owing to its potential to reduce energy consumption in CO2 separation, enabling industry to achieve emission reduction targets of the Paris Climate Accord. Despite recent advances, the development of engineered acidic nanocatalysts with unique characteristics remains a challenge. Herein, we establish a strategy to tailor the physicochemical properties of metal-organic frameworks (MOFs) for the synthesis of water-dispersible core-shell nanocatalysts with ease of use. We demonstrate that functionalized nanoclusters (Fe3O4-COOH) effectively induce missing-linker deficiencies and fabricate mesoporosity during the self-assembly of MOFs. Superacid sites are created by introducing chelating sulfates on the uncoordinated metal clusters, providing high proton donation capability. The obtained nanomaterials drastically reduce the energy consumption of CO2 capture by 44.7% using only 0.1 wt.% nanocatalyst, which is a ∽10-fold improvement in efficiency compared to heterogeneous catalysts. This research represents a new avenue for the next generation of advanced nanomaterials in catalytic solvent regeneration.

Abstract Thin film transistors (TFTs) are key components for the fabrication of electronic and optoelectronic devices, resulting in a push for the wider exploration of semiconducting materials and cost‐effective synthesis processes. In this report, a simple approach is proposed to achieve 2‐nm‐thick indium oxide nanosheets from liquid metal surfaces by employing a squeeze printing technique and thermal annealing at 250 °C in air. The resulting materials exhibit a high degree of transparency (>99 %) and an excellent electron mobility of ≈96 cm2 V−1 s−1, surpassing that of pristine printed 2D In2O3 and many other reported 2D semiconductors. UV‐detectors based on annealed 2D In2O3 also benefit from this process step, with the photoresponsivity reaching 5.2 × 104 and 9.4 × 103 A W−1 at the wavelengths of 285 and 365 nm, respectively. These values are an order of magnitude higher than for as‐synthesized 2D In2O3. Utilizing transmission electron microscopy with in situ annealing, it is demonstrated that the improvement in device performances is due to nanostructural changes within the oxide layers during annealing process. This work highlights a facile and ambient air compatible method for fabricating high‐quality semiconducting oxides, which will find application in emerging transparent electronics and optoelectronics.

Abstract The need for effective and adaptive technologies for carbon dioxide (CO2) mitigation targeting global net‐zero carbon emissions is critically growing. Hence, innovative technologies for CO2 reduction have attracted worldwide interest from scientific research communities. The use of liquid metals for the conversion of CO2 into carbon or solid carbonaceous products has gained increasing attention in recent years due to their high activity and resistance to coking. Here, a facile approach for the reduction of CO2 to solid carbon using liquid Mg at and near room temperature, and atmospheric pressure is presented. In this process, magnesium (Mg) plays a major role in driving the dissociation of CO2 to its elemental constituents, carbon and oxygen. During the reaction process, Mg ions dissolve in gallium (Ga) liquid metal alloy, diffuse to the gas–liquid interface, and reduce CO2 to carbon while undergoing an oxidation reaction. The electrochemical method ensures a sustainable cyclic process by reducing Mg and Ga ions back to their metallic counterpart. The use of liquid metal alloys for CO2 reduction reactions can enable to achieve CO2 capture and storage at room temperature, setting a new foundation for the future exploration of efficient CO2 mitigation issues.

The presence of strong inter-layer interactions has hindered the synthesis efforts towards large-area and highly crystalline monolayer SnS. Here, the authors report synthesis of large-area monolayer SnS using a liquid metal-based technique, and fabricate piezoelectric nano-generators with average peak output voltage of 150 mV at 0.7% strain.

Abstract Large-area and high-quality two-dimensional crystals are the basis for the development of the next-generation electronic and optical devices. The synthesis of two-dimensional materials in wafer scales is the first critical step for future technology uptake by the industries; however, currently presented as a significant challenge. Substantial efforts have been devoted to producing atomically thin two-dimensional materials with large lateral dimensions, controllable and uniform thicknesses, large crystal domains and minimum defects. In this review, recent advances in synthetic routes to obtain high-quality two-dimensional crystals with lateral sizes exceeding a hundred micrometres are outlined. Applications of the achieved large-area two-dimensional crystals in electronics and optoelectronics are summarised, and advantages and disadvantages of each approach considering ease of the synthesis, defects, grain sizes and uniformity are discussed.

The combination of metallurgy concepts and nanotechnology with liquid metal processing has been largely unexplored. Here the authors use liquid-phase ultrasonication to produce a model system of catalytically active nano-alloys, demonstrating electrocatalysis and photocatalysis.

While CO2 reduction proves an appealing means to convert greenhouse emissions to high-value products, there are few materials capable of such a conversion. Here, the authors demonstrate a liquid-metal electrocatalyst to convert CO2 directly into solid carbon that can be used as capacitor electrodes.

Phosphides of transition metals (TMPs) are a developing class of materials for hydrogen evolution reaction (HER) as an alternative to expensive noble metals to produce clean energy. Herein, the nitrogen-doped molybdenum oxide (MoOx) is developed via a facile and simple hydrothermal method, followed by annealing in the N2 atmosphere and phosphorization to form a nitrogen-doped oxygenated molybdenum phosphide (N-MoP) sphere-shaped structure. The developed N-doped phosphide structure depicts enhanced HER activity by reaching a current density of 10 mA cm−2 at a very low overpotential of only 87 mV, which is much better than annealed nitrogen-doped molybdenum oxide (A-MoOx) 138 mV in alkaline medium. N-MoP is a highly efficient electrocatalyst for HER attributed to a more exposed surface, large electrode/electrolyte interface and appropriate binding energies for reactants. This study extends the opportunity of developing nitrogen-doped TMPs, which can display exceptional properties as compared to their oxides.

Two-dimensional piezoelectric materials hold promise for nano-electromechanical technologies, yet it is challenging to prepare them in large areas with high sample homogeneity. Syed et al. surface print GaPO4 sheets with unit cell thickness over centimetres using a liquid metal-based synthesis process.

One of the key challenges 2D materials still face is their uniform wafer-scale deposition. Here, the authors present a deposition method for post-transition metal dichalcogenides, based on transformation of an ultra-thin oxide layer on the surface of liquid elemental gallium onto an oxide-coated substrate.

The control over the motion and deformation of liquid droplets is essential to many microfluidic and actuation systems. Zavabeti et al. demonstrate that applying a pH or ionic gradient across a droplet of liquid metal alloy of gallium results in its motion due to a breaking of the surface charge symmetry.

Advancements in materials science and fabrication techniques have contributed to the significant growing attention to a wide variety of sensors for digital healthcare. While the progress in this area is tremendously impressive, few wearable sensors with the capability of real-time blood pressure monitoring are approved for clinical use. One of the key obstacles in the further development of wearable sensors for medical applications is the lack of comprehensive technical evaluation of sensor materials against the expected clinical performance. Here, we present an extensive review and critical analysis of various materials applied in the design and fabrication of wearable sensors. In our unique transdisciplinary approach, we studied the fundamentals of blood pressure and examined its measuring modalities while focusing on their clinical use and sensing principles to identify material functionalities. Then, we carefully reviewed various categories of functional materials utilized in sensor building blocks allowing for comparative analysis of the performance of a wide range of materials throughout the sensor operational-life cycle. Not only this provides essential data to enhance the materials’ properties and optimize their performance, but also, it highlights new perspectives and provides suggestions to develop the next generation pressure sensors for clinical use.

The original version of this Article contained errors in the author affiliations. Affiliation 1 incorrectly read ‘School of Chemical Engineering, University of New South Wales (UNSW), Sydney, NSW 2031, Australia’ and affiliation 4 incorrectly read ‘School of Engineering, RMIT University, Melbourne, VIC 3001, Australia.’ This has now been corrected in both the PDF and HTML versions of the Article.

Ga⁻Sn⁻Zn eutectic alloy is a non-toxic liquid metal alloy which could be used in a multitude of applications, including as a heat transfer agent, in gas sensing, and in medicine. Alloys containing gallium readily oxidise in air, forming a thin oxide layer that influences the properties of liquid metals and which has not been studied. In this study, the oxide layer formed on Ga⁻Sn⁻Zn alloy was transferred at room temperature onto three substrates—quartz, glass and silicon. The contact angle between the liquid alloy and different substrates was determined. The obtained thin oxide films were characterised using atomic force microscopy, X-ray photon spectroscopy, and optical and transmission electron microscopy. The contact angle does not influence the deposition of the layers. It was determined that it is possible to obtain nanometric oxide layers of a few micrometres in size. The chemical composition was determined by XPS and EDS independently, and showed that the oxide layer contains about 90 atom % of gallium with some additions of tin and zinc. The oxides obtained from the eutectic Ga⁻Sn⁻Zn liquid alloys appear to be nanocrystalline.