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Exploring and controlling surface tension‐driven phenomena in liquid metals may lead to unprecedented possibilities for next‐generation microfluidics, electronics, catalysis, and materials synthesis. In pursuit of these goals, the impact of minor constituents within liquid alloys is largely overlooked. Herein, it is showed that the presence of a fraction of solute metals such as tin, bismuth, and zinc in liquid gallium can significantly influence their electrocapillarity and electrochemistry. The instability‐driven fractal formation of liquid alloy droplets is investigated with different solutes and reveals the formation of distinctive non‐branched droplets, unstable fractals, and stable fractal modes under controlled voltage and alkaline solution conditions. In their individually unique fractal morphology diagrams, different liquid alloys demonstrate significantly shifted voltage thresholds in transition between the three fractal modes, depending on the choice of the solute metal. Surface tension measurements, cycle voltammetry and surface compositional characterizations provide strong evidence that the minor alloy components drastically alter the surface tension, surface electrochemical oxidation, and oxide dissolution processes that govern the droplet deformation and instability dynamics. The findings that minor components are able to regulate liquid alloys' surface tensions, surface element distributions and electrochemical activities offer great promises for harnessing the tunability and functionality of liquid metals. [ABSTRACT FROM AUTHOR]

Atomically thin, mechanically flexible, memory‐functional, and power‐generating crystals play a crucial role in the technological advancement of portable devices. However, the adoption of these crystals in such technologies is sometimes impeded by expensive and laborious synthesis methods, as well as the need for large‐scale, mechanically stable, and air‐stable materials. Here, an instant‐in‐air liquid metal printing process utilizing liquid bismuth (Bi) is presented, forming naturally occurring, air‐stable, atomically thin, mechanically flexible nanogenerators and ferroelectric oxides. Despite the centrosymmetric nature of the monoclinic P21/c system of achieved α‐Bi2O3‐δ the high kinetics of liquid metal synthesis leads to the formation of vacancies that disrupt the symmetry which is confirmed by density functional theory (DFT) calculations. The polarization switching is measured and utilized for ferroelectric nanopatterning. The exceptional attributes of these atomically thin multifunctional stable oxides, including piezoelectricity, mechanical flexibility, and polarizability, present significant opportunities for developing nano‐components that can be seamlessly integrated into a wide range of devices. [ABSTRACT FROM AUTHOR]

Liquid metals provide new dimensions for controlling and governing of reactions. The concept of freely moving metal solutes in liquid metals can be potentially used for enhancing and tuning interfacial reactions. In this work, zinc (Zn), as the solute metal is shown that, can move to the interface, enriching the interfacial area for the efficient synthesis of highly crystalline and porous zeolitic imidazolate framework‐8 (ZIF‐8). The highest rate of reaction is illustrated, and the best quality ZIF‐8, are obtained when a eutectic liquid metal system of Zn with gallium (Ga), containing 3.6 wt.% of Zn, is implemented. It is computationally shown that a combination of Ga activation and freely moving Zn leads to the highest reaction rate and better coordination with organic linkers. The comparisons with solid samples and non‐eutectic systems of Ga liquid demonstrate the advantages of eutectic mix. The work can be expanded to a variety of future interfacial reactions of zeolite imidazole frameworks for commercial scale up. [ABSTRACT FROM AUTHOR]

The nascent field of liquid metals, metals, and alloys of low melting points has provided opportunities for synthesizing low-dimensional materials. Located between transition- and non-metals in the periodic table, post-transition elements exhibit unique properties in particular low melting points. Taking on a liquid form at low temperature, post-transition liquid metals can be used as solvents for metallic solutes. The enigmatic surface of liquid metals is also ultra-active and smooth, offering opportunities for fabricating and templating two-dimensional (2D) films. So far, various 2D materials have been harvested from the surface of liquid metals including 2D metal compounds and nonmetallic materials. Utilizing different extraction and transfer techniques, the produced 2D films can be uniformly deposited on desired substrates at large lateral dimensions. Here, we present a comprehensive overview of the fundamentals underlying post-transition-elements-based liquid metals and alloys and explain the effect of atomic level electron configurations on their characteristics. We discuss the key physical properties of liquid metals including the origin of their low melting points and their high thermal and electrical conductivities. We illustrate their boundary-induced layering and oxidation as essential traits for creating 2D films. Afterward, the interfacial synthesis of 2D materials is depicted with the discussion of surface oxidation, reduction and exfoliation. We present different types of devices using liquid metal-induced 2D synthesis processes, including field-effect transistors, optoelectronic devices, systems that use 2D dielectric and conductive layers, and piezoelectric devices. Eventually, we discuss future prospects and outline how liquid metals can contribute to exciting future applications. [ABSTRACT FROM AUTHOR]

Liquid–liquid interfaces of liquid alloys with electrolytic solutions present fertile platforms for realizing exciting interfacial phenomena that can be devised to process alloys and produce nanomaterials. Here, such an interface is established by immersing a gallium–bismuth binary liquid alloy into aqueous electrolytes. It is shown that the application of a negative voltage to this interface results in a rapid and complete liberation of bismuth nanostructures from liquid gallium. The set of conditions that govern the chemistry of the interface can be adjusted to control the oxidation state, morphology, and crystal structure of the expelled bismuth. By changing the conditions; nanotubular, atomically thin plates, and sea‐urchin‐shaped bismuth oxide morphologies are obtained. The process can also control the crystal phase of bismuth oxide as monoclinic (α), tetragonal (β), or body‐centered cubic (γ). The addition of ascorbic acid to the electrolyte is observed to prevent the oxidation of the expelled entities, resulting in bismuth metal nanoparticles. Ab initio molecular dynamics and computational fluid dynamics simulations are performed to elucidate this rapid phase separation at the interface. This knowledge will potentially lead to new pathways for using alloys as reaction media to refine metals while simultaneously producing nanomaterials for various applications. [ABSTRACT FROM AUTHOR]

Surface patterning of liquid metals (LMs) is a key processing step for LM‐based functional systems. Current patterning methods are substrate specific and largely suffer from undesired imperfections—restricting their widespread applications. Inspired by the universal catechol adhesion chemistry observed in nature, LM inks stabilized by the assembly of a naturally abundant polyphenol, tannic acid, has been developed. The intrinsic adhesive properties of tannic acid containing multiple catechol/gallol groups, allow the inks to be applied to a variety of substrates ranging from flexible to rigid, metallic to plastics and flat to curved, even using a ballpoint pen. This method can be further extended from hand‐written texts to complex conductive patterns using an automated setup. In addition, capacitive touch and hazardous heavy metal ion sensors have been patterned, leveraging from the synergistic combination of polyphenols and LMs. Overall, this strategy provides a unique platform to manipulate LMs from hand‐written pattern to complex designs onto the substrate of choice, that has remained challenging to achieve otherwise. [ABSTRACT FROM AUTHOR]

2D transition metal dichalcogenides (TMDs) play increasingly significant roles in research and future optoelectronics. However, the large‐scale deposition of 2D TMDs remains challenging due to sparse nucleation and substrate dependency. Liquid metals can offer effective solutions to meet these challenges due to their reactive, non‐polarized, and templating properties. Here, self‐deposition of 2D molybdenum sulfide is shown by introducing a molybdenum precursor onto the surface of a eutectic alloy of gallium and indium (EGaIn). EGaIn serves as an ultra‐smooth template and reducing agent for the precursor to form large‐scale planar molybdenum sulfides, which is transferrable to any substrate. The molybdenum sulfides form spontaneously on the surface of EGaIn, which has a sufficient potential to drive the cathodic reactions of the deposition process. A highly crystalline 2H‐MoS2 is obtained after a final annealing step. This work demonstrates a fundamentally new capability for the formation of large‐scale 2D TMDs. [ABSTRACT FROM AUTHOR]

Gallic acid, a natural phenolic compound, efficiently establishes surface complexes with liquid gallium leading to the formation of an aqueous gallium dispersion via sonication. The surface functionalised gallium particles thus obtained were easily impregnated into paper membranes that could be turned from insulating to conductive by pressure induced deformation of the embedded particles. [ABSTRACT FROM AUTHOR]

Gallium (Ga), a low‐melting‐point liquid metal with soft, metallic, and biocompatible properties, offers many possibilities. However, the potential of composites that integrate Ga with biomacromolecules, combining their biocompatibility, elasticity, and conductivity, has not been thoroughly explored, which is a gap for advancing these composites in various applications. In parallel and independently, protein self‐assembled l.,;3bhnanofibrils have attracted great interest as building blocks for functional biomaterials. Here, composites of Ga droplets and nanofibrils are presented, self‐assembled from plant proteins of soy protein isolate (SPI). It is evidenced that in these composites self‐assembled SPI nanofibrils can effectively reduce the oxidation of Ga droplets. It is observed that the composites of β‐sheet nanofibrils and Ga droplets offer mechanical properties similar to only fibrils‐based films. Films of 32 wt% Ga in SPI showed enhanced electrical conductivity and well‐structured nanofibrils with multifunctional potential in gas‐sensing and electronically controlled antibacterial applications. It is illustrated that the 32 wt% Ga in SPI composite offered the best sensing performance for a diatomic molecule, CO, and electro‐stimulation of this composite effectively reduced bacterial growth. The Ga in SPI composite, combining the advantages of protein nanofibrils and Ga droplets, offers great potential in future biomedical applications. [ABSTRACT FROM AUTHOR]

Metal foams are highly sought‐after porous structures for heterogeneous catalysis, which are fabricated by templating, injecting gas, or admixing blowing agents into a metallic melt at high temperatures. They also require additional catalytic material coating. Here, a low‐melting‐point liquid metal is devised for the single‐step formation of catalytic foams in mild aqueous environments. A hybrid catalytic foam fabrication process is presented via simultaneous chemical foaming, melting, and sintering reaction of liquid metal nanoparticles. As a model, nanoparticles of tertiary low‐melting‐point eutectic alloy of indium, bismuth, and tin (Field's metal) are processed with sodium hydrogen carbonate, an environmentally benign blowing agent. The competing endothermic foaming and exothermic sintering reactions are triggered by an aqueous acidic bath. The overall foaming process occurs at a localized temperature above 200 °C, producing submicron‐ to micron‐sized open‐cell pore foams with conductive cores and semiconducting surface decorations. The catalytic properties of the metal foams are explored for a range of applications including photo‐electrocatalysis, bacteria electrofiltration, and CO2 electroconversion. In particular, the Field's metal‐based foams show exceptional CO2 electrochemical conversion performance at low applied voltages. The facile process presented here can be extended to other low‐temperature post transition and transition metal alloys. [ABSTRACT FROM AUTHOR]

The nascent field of nanotechnology-enabled metallurgy has great potential. However, the role of eutectic alloys and the nature of alloy solidification in this field are still largely unknown. To demonstrate one of the promises of liquid metals in the field, we explore a model system of catalytically active Bi-Sn nano-alloys produced using a liquid-phase ultrasonication technique and investigate their phase separation, surface oxidation, and nucleation. The Bi-Sn ratio determines the grain boundary properties and the emergence of dislocations within the nano-alloys. The eutectic system gives rise to the smallest grain dimensions among all Bi-Sn ratios along with more pronounced dislocation formation within the nano-alloys. Using electrochemical CO2 reduction and photocatalysis, we demonstrate that the structural peculiarity of the eutectic nano-alloys offers the highest catalytic activity in comparison with their non-eutectic counterparts. The fundamentals of nano-alloy formation revealed here may establish the groundwork for creating bimetallic and multimetallic nano-alloys. 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. [ABSTRACT FROM AUTHOR]

Liquid metals offer unprecedented chemistry. Here it is shown that they can facilitate self‐limiting oxidation processes on their surfaces, which enables the growth of metal oxides that are atomically thin. This claim is exemplified by creating atomically thin hydrated MnO2 using a Galvanic replacement reaction between permanganate ions and a liquid gallium–indium alloy (EGaIn). The "liquid solution"–"liquid metal" process leads to the reduction of the permanganate ions, resulting in the formation of the oxide monolayer at the interface. It is presented that under mechanical agitation liquid metal droplets are established, and simultaneously, hydrated gallium oxides and manganese oxide sheets delaminate themselves from the interfacial boundaries. The produced nanosheets encapsulate a metallic core, which is found to consist of solid indium only, with the full migration of gallium out of the droplets. This process produces core/shell structures, where the shells are made of stacked atomically thin nanosheets. The obtained core/shell structures are found to be an efficient photocatalyst for the degradation of an organic dye under simulated solar irradiation. This study presents a new research direction toward the modification and functionalization of liquid metals through spontaneous interfacial redox reactions, which has implications for many applications beyond photocatalysis. [ABSTRACT FROM AUTHOR]

Gallium and many of its alloys remain in liquid phase across impressively wide temperature ranges. Here such liquid metals are proposed as reaction media for the carbonization of low thermal stability polymeric precursors at high temperatures. Plain and cross-linked polyvinyl alcohol are chosen as representatives of such polymers. We show that due to the immiscibility of organic carbons within the liquid metal phase, these polymers that would otherwise vaporize at elevated temperatures, can function as precursors for the formation of carbonaceous films. The thin polymeric films are placed in an intimate contact with the liquid metal surface before thermal processing and show amorphous to graphitic-like characteristics after carbonization. Graphitic-like properties were obtained when a high melting point graphitization catalyst, such as copper, was co-alloyed. The proposed work can be expanded to explore other metallic elements within the bulk of gallium-based alloys for the carbonization of polymeric precursors at large-scales. Image 1 • Polymers that do not carbonize otherwise can be 'capped' by liquid metals and thereby carbonized. • Gallium-based liquid metals exhibit selective miscibility to non-metallic elements. • Gallium, gallium-indium and gallium-copper were chosen as liquid metal reactors. • Carbon films with amorphous and graphitic characteristics were formed. • Inclusion of copper in liquid metal enhanced the graphitic characteristics of the films. [ABSTRACT FROM AUTHOR]