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With growing research interest in liquid metals, such as Ga and Ga-based alloys, understanding their behaviours at reduced dimensions is becoming of more fundamental significance, especially for exploiting their properties in a variety of applications. Mechanical sonication is a common technique used for micronising bulk liquid metals into smaller sized particles. One distinct characteristic of Ga and Ga-based liquid metal alloy particles, micronised via sonication, is the formation of native oxygen species such as GaOOH and Ga2O3. However, the nitridation of these particles has not been reported. In this work, we demonstrate a room temperature nitridation process during the micronisation of eutectic Ga–In alloy (EGaIn). Characterisations reveal that the sonication in the N-containing precursors of PVP and N2 results in the formation of GaN within the GaOOH crystallites that separate themselves from the bulk of EGaIn during sonication. As a model example of the applicability of such particles, low-detection-limit biosensing by photoluminescence of the obtained particles is demonstrated. The work shows a room temperature pathway for the creation of GaN that can be further investigated, expanded upon, and implemented for different future applications.

One of the major challenges in the development of soft electronics is to devise scalable and automated strategies for the microfabrication of deformable and flexible electronic components and sensors. Liquid metals have demonstrated unique characteristics suitable for such applications. To date, conductive patterning using liquid metals has mainly focused on writing or injection of liquid metals into prefabricated channels, requiring multiple complicated procedures and reliance on specific inks formulae. Here a new strategy has been introduced for direct patterning of liquid metal particles onto substrates via UV photolithography. A variety of different tracks, patterns and sensors, on both rigid and flexible substrates, are demonstrated using a dispersion of eutectic alloy of gallium and indium in photoresist, to present the extent of capability of the introduced method. The method provides simple, effective, high-resolution and precision patterning of liquid metals for the emerging fields of soft electronics and sensors.

Cellulose-based supercapacitors display important advantages in comparison with devices fabricated with other materials, regarding environmental friendliness, flexibility, cost and versatility. Recent progress in the field has been mainly focused on the utilization of cellulose fibres as: structural mechanical reinforcement of electrodes; precursors of electrically active carbon-based materials; or primary electrolytes that act as reservoirs of secondary electrolytes. In this work, a flexible, lightweight, robust, portable and manageable all-carboxymethyl cellulose symmetric supercapacitor has been obtained by assembling two electrodes based on carboxymethyl cellulose hydrogels to a solid electrolytic medium formulated with the same material. Hydrogels, which were made by cross-linking carboxymethyl cellulose paste with citric acid in water, rendered not only effective solid electrolytic media by simply loading NaCl but also electroactive electrodes. For the latter, conducting polymer microparticles, which were loaded into the hydrogel network during the physical cross-linking step, were appropriately connected through the in situ anodic polymerization of a similar conducting polymer in aqueous medium, thus creating conduction paths. The performance of the assembled supercapacitors has been proved by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. This design opens a new window for the green and mass production of flexible cellulose-based supercapacitors

We report the reduction of poly(3,4-ethylenedioxythiophene) (PEDOT) films with a cationic 1,4-diazabicyclo[2.2.2]octane-based ionene bearing N,N0-(meta-phenylene)dibenzamide linkages (mPI). Our main goal is to obtain n-doped PEDOT using a polymeric dopant agent rather than small conventional tetramethylammonium (TMA), as is usual. This has been achieved using a three-step process, which has been individually optimized: (1) preparation of p-doped (oxidized) PEDOT at a constant potential of +1.40 V in acetonitrile with LiClO4 as the electrolyte; (2) dedoping of oxidized PEDOT using a fixed potential of 1.30 V in water; and (3) redoping of dedoped PEDOT applying a reduction potential of 1.10 V in water with mPI. The resulting films display the globular appearance typically observed for PEDOT, with mPI being structured in separated phases forming nanospheres or ultrathin sheets. This organization, which has been supported by atomistic molecular dynamics simulations, resembles the nanosegregated phase distribution observed for PEDOT p-doped with poly(styrenesulfonate). Furthermore, the doping level achieved using mPI as the doping agent is comparable to that achieved using TMA, even though ionene provides distinctive properties to the conducting polymer. For example, films redoped with mPI exhibit much more hydrophilicity than the oxidized ones, whereas films redoped with TMA are hydrophobic. Similarly, films redoped with mPI exhibit the highest thermal stability, while those redoped with TMA show thermal stability that is intermediate between those of the latter and the dedoped PEDOT. Overall, the incorporation of an mPI polycation as the n-dopant into PEDOT has important advantages for modulating the properties of this emblematic conducting polymer.

A green carbon capture and conversion technology offering scalability and economic viability for mitigating CO2 emissions is reported. The technology uses suspensions of gallium liquid metal to reduce CO2 into carbonaceous solid products and O2 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 CO2 ) for the capture and conversion of a tonne of CO2 . This green technology presents an economical solution for CO2 emissions.

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.