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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]

The argument of phase coexistence in the lead-free piezoelectric perovskite K0.5Na0.5NbO3 (KNN) has led to significant discrepancies in the interpretation of its exact crystalline structure in the literature. In this work, the structural details of hydrothermally prepared KNN nanofibres and microcubes were investigated by a combination of high resolution transmission electron microscopy (TEM), solid-state 23Na and 93Nb nuclear magnetic resonance (NMR) spectroscopy and two-dimensional 23Na 3QMAS NMR. Although powder X-ray diffraction yielded an average orthorhombic structure for both morphologies, high resolution TEM revealed mixed phases of orthorhombic (O) and monoclinic (M) symmetry with a growth direction of [001] and [110], respectively, in individual KNN nanofibres. Consistent with the TEM analysis, solid-state 23Na NMR indicated a distribution of multiple Na sites in the KNN nanofibers, which were not observed in the KNN microcubes. This study provided microscopic evidence of phase coexistence in KNN nanofibers and suggested that a two-phase concomitant state might be highly dependent on the size and morphologies of the KNN nanostructures. [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]

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]

Transforming natural resources to energy sources, such as converting CH 4 to H 2 and carbon, at high efficiency and low cost is crucial for many industries and environmental sustainability. The high temperature requirement of CH 4 conversion regarding many of the current methods remains a critical bottleneck for their practical uptake. Here we report an approach based on gallium (Ga) liquid metal droplets, Ni(OH) 2 cocatalysts, and mechanical energy input that offers low-temperature and scalable CH 4 conversion into H 2 and carbon. Mainly driven by the triboelectric voltage, originating from the joint contributions of the cocatalysts during agitation, CH 4 is converted at the Ga and Ni(OH) 2 interface through nanotribo-electrochemical reaction pathways. The efficiency of the system is enhanced when the reaction is performed at an increased pressure. The dehydrogenation of other nongaseous hydrocarbons using this approach is also demonstrated. This technology presents a possible low energy route for CH 4 conversion without involving high temperature and harsh operating conditions.

Amine-functionalized polymers (AFPs) are able to react with carbon dioxide (CO 2 ) and are therefore useful in CO 2 capture and sensing. To develop AFP-based CO 2 sensors, it is critical to examine their electrical responses to CO 2 over long periods of time, so that the device can be used consistently for measuring CO 2 concentration. To this end, we synthesized poly( N -[3-(dimethylamino)propyl] methacrylamide) (pDMAPMAm) by free radical polymerization and tested its ability to behave as a CO 2 -responsive polymer in a transducer. The electrical response of this polymer to CO 2 upon long exposure times was measured in both the aqueous and solid phases. Direct current resistance measurement tests on pDMAPMAm films printed along with the silver electrodes in the presence of CO 2 at various concentrations reveal a two-region electrical response. Upon continuous exposure to different CO 2 flow rates (at a constant pressure of 0.2 MPa), the resistance first decreased over time, reaching a minimum, followed by a gradual increase with further exposure to CO 2 . A similar trend is observed when CO 2 is introduced to an aqueous solution of pDMAPMAm. The in situ monitoring of pH suggests that the change in resistance of pDMAPMAm can be attributed to the protonation of tertiary amine groups in the presence of CO 2 . This two-region response of pDMAPMAm is based on a proton-hopping mechanism and a change in the number of free amines when pDMAPMAm is exposed to various levels of CO 2 ., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

A green carbon capture and conversion technology offering scalability and economic viability for mitigating CO 2 emissions is reported. The technology uses suspensions of gallium liquid metal to reduce CO 2 into carbonaceous solid products and O 2 at near room temperature. The nonpolar nature of the liquid gallium interface allows the solid products to instantaneously exfoliate, hence keeping active sites accessible. The solid co-contributor of silver-gallium rods ensures a cyclic sustainable process. The overall process relies on mechanical energy as the input, which drives nano-dimensional triboelectrochemical reactions. When a gallium/silver fluoride mix at 7:1 mass ratio is employed to create the reaction material, 92% efficiency is obtained at a remarkably low input energy of 230 kWh (excluding the energy used for dissolving CO 2 ) for the capture and conversion of a tonne of CO 2 . This green technology presents an economical solution for CO 2 emissions., (© 2021 Wiley-VCH GmbH.)

Low melting point eutectic systems, such as the eutectic gallium-indium (EGaIn) alloy, offer great potential in the domain of nanometallurgy; however, many of their interfacial behaviors remain to be explored. Here, a compositional change of EGaIn nanoalloys triggered by polydopamine (PDA) coating is demonstrated. Incorporating PDA on the surface of EGaIn nanoalloys renders core-shell nanostructures that accompany Ga-In phase separation within the nanoalloys. The PDA shell keeps depleting the Ga 3+ from the EGaIn nanoalloys when the synthesis proceeds, leading to a Ga 3+ -coordinated PDA coating and a smaller nanoalloy. During this process, the eutectic nanoalloys turn into non-eutectic systems that ultimately result in the solidification of In when Ga is fully depleted. The reaction of Ga 3+ -coordinated PDA-coated nanoalloys with nitrogen dioxide gas is presented as an example for demonstrating the functionality of such hybrid composites. The concept of phase-separating systems, with polymeric reservoirs, may lead to tailored materials and can be explored on a variety of post-transition metals.