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A liquid gallium–polydopamine composite was synthesised and utilised as a soft biocompatible electrode for cell culture by electro-stimulation increasing the proliferation rate of model animal fibroblasts. more...

Liquid metals can be surface activated to generate a controlled galvanic potential by immersing them in aqueous solutions. This creates energized liquid-liquid interfaces that can promote interfacial chemical reactions. Here we utilize this interfacial phenomenon of liquid metals to deposit thin films of tin-doped tellurium onto rigid and flexible substrates. This is accomplished by exposing liquid metals to a precursor solution of Sn more...

Insights into metal-matrix interactions in atomically dispersed catalytic systems are necessary to exploit the true catalytic activity of isolated metal atoms. Distinct from catalytic atoms spatially separated but immobile in a solid matrix, here we demonstrate that a trace amount of platinum naturally dissolved in liquid gallium can drive a range of catalytic reactions with enhanced kinetics at low temperature (318 to 343 K). Molecular simulations provide evidence that the platinum atoms remain in a liquid state in the gallium matrix without atomic segregation and activate the surrounding gallium atoms for catalysis. When used for electrochemical methanol oxidation, the surface platinum atoms in the gallium-platinum system exhibit an activity of [Formula: see text] three orders of magnitude higher than existing solid platinum catalysts. Such a liquid catalyst system, with a dynamic interface, sets a foundation for future exploration of high-throughput catalysis. more...

Post-transition metal-based liquid alloys are emerging as media for undertaking chemical reactions.

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 Ga3+ from the EGaIn nanoalloys when the synthesis proceeds, leading to a Ga3+-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 Ga3+-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. more...

Liquid metals and alloys with high-aspect-ratio nanodimensional features are highly sought-after for emerging electronic applications. However, high surface tension, water-like fluidity, and the existence of self-limiting oxides confer specific peculiarities to their characteristics. Here, we introduce a high accuracy nanometric three-dimensional pulling and stretching method to fabricate liquid-metal-based nanotips from room- or near-room-temperature gallium-based alloys. The pulling rate and step size were controlled with a resolution of up to 10 nm and yielded different nanotip morphologies and lengths as a function of the base liquid metal alloy composition and the pulling parameters. The obtained nanotips presented high aspect ratios over lengths of a few microns and apexes between 10 and 100 nm. The liquid metal alloys were found confined within nanotips with about 10 nm apexes when vertically pulled at 100 nm/s. An amorphous gallium oxide skin was shown to cover the surface of the nanotips, while the liquid core was composed of the initial liquid metal alloys. The electrical contact established at the nanotips was characterized under dynamic conditions. The liquid metal nanotips showed an Ohmic resistance when a continuous liquid metal channel was formed, and a controllable semiconductor state corresponding to a heterojunction formed at the junction between the liquid metal phase and the gallium oxide semiconductor skin. The variable threshold voltages of the heterojunction were controlled via stretching of the nanotips with a 10 nm step resolution. The liquid metal nanotips were also used for establishing soft electronic junctions. This novel method of liquid metal nanotip fabrication with Ohmic and semiconducting behaviors will lead to exciting avenues for developing electronic and sensing devices. more...

Phonon-polaritons (PhPs) arise from the strong coupling of photons to optical phonons. They offer light confinement and harnessing below the diffraction limit for applications including sensing, imaging, superlensing, and photonics-based communications. However, structures consisting of both suspended and supported hyperbolic materials on periodic dielectric substrates are yet to be explored. Here we investigate phonon-polaritonic crystals (PPCs) that incorporate hyperbolic hexagonal boron nitride (hBN) to a silicon-based photonic crystal. By using the near-field excitation in scattering-type scanning near-field optical microscopy (s-SNOM), we resolved two types of repetitive local field distribution patterns resembling the Archimedean-like tiling on hBN-based PPCs, i.e., dipolar-like field distributions and highly dispersive PhP interference patterns. We demonstrate the tunability of PPC band structures by varying the thickness of hyperbolic materials, supported by numerical simulations. Lastly, we conducted scattering-type nanoIR spectroscopy to confirm the interaction of hBN with photonic crystals. The introduced PPCs will provide the base for fabricating essential subdiffraction components of advanced optical systems in the mid-IR range. more...

Liquid metal (LM) catalysts have been demonstrated to accelerate chemical reactions, providing an intriguing route to fine chemical synthesis with immense technological implications. Herein, we exp... more...

It is well-understood that during the liquid-to-solid phase transition of alloys, elements segregate in the bulk phase with the formation of microstructures. In contrast, we show here that in a Bi–Ga alloy system, highly ordered nanopatterns emerge preferentially at the alloy surfaces during solidification. We observed a variety of transition, hybrid and crystal-defect-like patterns, in addition to lamellar and rod-like structures. Combining experiments and molecular dynamics simulations, we investigated the influence of the superficial Bi and Ga2O3 layers during surface solidification and elucidated the pattern-formation mechanisms, which involve surface-catalysed heterogeneous nucleation. We further demonstrated the dynamic nature and robustness of the phenomenon under different solidification conditions and for various alloy systems. The surface patterns we observed enable high-spatial-resolution nanoscale-infrared and surface-enhanced Raman mapping, which reveal promising potential for surface- and nanoscale-based applications. During a liquid-to-solid phase transition, a Bi–Ga alloy forms ordered nanostructured patterns on its surface. more...

The separation and sensing of alkali metal ions from aqueous lithium resources is of great importance for building future renewable and lithium-based energy storage technologies. As such, interest arises for the development of functional composites selective to ionic lithium (Li+) over sodium (Na+) and potassium (K+) that allows for a range of low carbon-footprint sensing and recovery processes. Here, selective separation of Li+ from aqueous mixtures of Na+ and K+ ions using polyvinyl alcohol/maleic acid composites was enhanced by the inclusion as nano-additives of post-transition metals gallium (Ga) and indium (In), together with their alloys and oxidized species, in the composite casting process. The co-addition of Ga and In resulted in the spontaneous formation of Ga oxides and hydroxides while In remained in the metallic state. This Ga–In composite was stable in aqueous solutions containing a high concentration (0.1 M) of mixed alkali metal ions over 5 days and achieved exceptionally high selectivities of Li+ over Na+ (3.8 ± 0.1) and K+ (7.1 ± 0.1). Results from an electrochemical sensing platform technique revealed that Li+ selectivity was in the same order as the diffusion rates. This work demonstrated that the low-melting-point post-transition metal alloy enables a one-step low energy fabrication of selective polymeric composites with diverse applications for energy, sensing and separation industries. The work has implications for the efficient manufacture of renewable and lithium-based energy storage technologies. more...

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. more...

Summary To keep up with the fast-paced transitioning of the global energy sector, which is constantly thriving to enable reliable, economic, and sustainable energy production, catalysis research has been required to continuously evolve in response. The challenges in the existing systems are predominantly due to dependencies on heterogeneous solid catalysts that are susceptible to coking. In this respect, liquid-metal (LM) catalysts have been demonstrated to have a critical advantage over conventional catalysts. Recently, LMs acquired a place in catalysis, with a reputation often synonymous with interesting properties and a remarkable ability to break trade-offs between homogeneous and heterogeneous catalysis. This review bridges the fundamental principles of LM research and the recent advances in LM-based thermal and electrochemical catalysis for energy applications. Moreover, emerging approaches for the improved utilization of LMs are outlined, and the concepts requiring greater research attention that could enable the development of exciting energy solutions are highlighted. more...

Liquid metals can play an essential role in the generation of electrically conductive composites for electronic devices and environmental sensing and remediation applications. Here, a method for gr... more...

Liquid metals are fast becoming a new class of universal and frictionless additives for the development of multifunctional soft and flexible materials. Herein, nanodroplets of eutectic gallium-indium alloy, which is liquid at room temperature, were used as a platform for the formulation of electrically conductive and magnetically responsive gels with the incorporation of Fe3O4 nanoparticles. The nanoadditives were prepared in situ within a water-based solution of polyvinyl alcohol. A borax cross-linking reaction was then performed to yield multifunctional flexible and self-healing gels. The physicochemical properties and changes in the nanoadditives at each step of the gel preparation method were characterized. Oxidation and complexation reactions between the liquid metal and iron oxide nanoadditives were observed. A mixture of nanosized functional magnetic Fe3O4/Fe2O3 and In-Fe oxide complexes was found to enable the magnetic susceptibility of the gels. The mechanical and self-healing properties of the gels were assessed, and finally, this flexible and multifunctional material was used as an electronic switch via remote magnetic actuation. The developed conductive and magnetic gels demonstrate great potential for the design of soft electronic systems. more...

Liquid metals (LMs) are electronic liquid with enigmatic interfacial chemistry and physics. These features make them promising materials for driving chemical reactions on their surfaces for designing nanoarchitectonic systems. Herein, we showed the interfacial interaction between eutectic gallium-indium (EGaIn) liquid metal and graphene oxide (GO) for the reduction of both substrate-based and free-standing GO. NanoIR surface mapping indicated the successful removal of carbonyl groups. Based on the gained knowledge, a composite consisting of assembled reduced GO sheets on LM microdroplets (LM-rGO) was developed. The LM enforced Ga3+ coordination within the rGO assembly found to modify the electrochemical interface for selective dopamine sensing by separating the peaks of interfering biologicals. Subsequently, paper-based electrodes were developed and modified with the LM-rGO that presented the compatibility of the assembly with low-cost commercial technologies. The observed interfacial interaction, imparted by LM's interfaces, and electrochemical performance observed for LM-rGO will lead to effective functional materials and electrode modifiers. more...

Molybdenum dioxide (MoO2), considering its near-metallic conductivity and surface plasmonic properties, is a great material for electronics, energy storage devices and biosensing. Yet to this day, room-temperature synthesis of large area MoO2, which allows deposition on arbitrary substrates, has remained a challenge. Due to their reactive interfaces and specific solubility conditions, gallium-based liquid metal alloys offer unique opportunities for synthesizing materials that can meet these challenges. Herein, a substrate-independent liquid metal-based method for the room temperature deposition and patterning of MoO2 is presented. By introducing a molybdate precursor to the surrounding of a eutectic gallium-indium alloy droplet, a uniform layer of hydrated molybdenum oxide (H2MoO3) is formed at the interface. This layer is then exfoliated and transferred onto a desired substrate. Utilizing the transferred H2MoO3 layer, a laser-writing technique is developed which selectively transforms this H2MoO3 into crystalline MoO2 and produces electrically conductive MoO2 patterns at room temperature. The electrical conductivity and plasmonic properties of the MoO2 are analyzed and demonstrated. The presented metal oxide room-temperature deposition and patterning method can find many applications in optoelectronics, sensing, and energy industries. more...

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 more...

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. more...

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. more...

Liquid metal interfaces with their unique chemistry can provide an extraordinary tool to synthesise materials with controlled characteristics at room temperature. Here, the templated synthesis of cupric oxide (CuO) onto a gallium based liquid metal (galinstan) surface is explored. The interaction between galinstan and copper sulphate solution yields initial interfacial CuO sheets and then secondary dendritic nanostructures are grown from the sheets. It is shown that the pH of the aqueous environment plays a critical role in tuning the synthesis of substoichiometric CuxO to CuO. For enhancing the interfacial area and establishing heterojunctions, the liquid metal is processed into a suspension of micro and nano droplets by sonication and the example of using the synthesised nano structures for enhanced photocatalysis is demonstrated for the catalysis of a model dye. This study presents a facile approach for synthesising highly functional systems based on liquid metals, and it can be extended to explore other metal oxide–liquid metal composites. more...

Phonon-polaritons (PhPs) in layered crystals, including hexagonal boron nitride (hBN), have been investigated by combined scattering-type scanning near-field optical microscopy (s-SNOM) and Fourier transform infrared (FTIR) spectroscopy. Nevertheless, many of such s-SNOM-based FTIR spectra features remain unexplored, especially those originated from the impact of boundaries. Here we observe real-space PhP propagations in thin-layer hBN sheets either supported or suspended by s-SNOM imaging. Then with a high-power broadband IR laser source, we identify two major peaks and multiple auxiliary peaks in the near-field amplitude spectra, obtained using scattering-type near-field FTIR spectroscopy, from both supported and suspended hBN. The major PhP propagation interference peak moves toward the major in-plane phonon peak when the IR illumination moves away from the hBN edge. Specific differences between the auxiliary peaks in the near-field amplitude spectra from supported and suspended hBN sheets are investigated regarding different boundary conditions, associated with edges and substrate interfaces. The outcomes may be explored in heterostructures for advanced nanophotonic applications. more...

Reduced graphene oxides (rGOs) have attracted substantial interest as potential carbon electrode material for energy storage applications. Yet, the utility of this material for these applications is governed by its stability, composition (C, H, O), surface area and porosity. Tuning the structure and porosity of the rGO sheets is possible by varying the synthesis conditions. Herein, we report the growth of rGO sheets onto a metal substrate from a diluted GO suspension. The prepared electrode material demonstrated a stable electrochemical performance with a supercapacitance value of 195 F g−1 at 1 mV s−1 and low real impedance with good stability and integrity after 4000 cycles of continuous charge-discharge in 1 M KOH electrolyte. This performance is attributed to the unique architecture of the rGO based electrodes which are composed of nano-channels between the sheets that allow rapid diffusion of charge carriers and ions for electrochemical interactions. The observations reported in this work create a new understanding of the structure-stability-performance trade-off in rGO and layout the foundation for further investigations on their sustainable utilization in energy storage applications. more...

The heavy use of coal-derived coke (CDC) in steel industry makes it a major contributor to the greenhouse emissions. With the impact of global warming knocking our doors, the CDC has experienced supply shortages and increasing costs. Such scenario has raised the need to find a sustainable and renewable replacement to CDC. Hard-wood biomass has emerged as a promising alternative to the CDC. While such sources of virgin biomass remain at high cost, other types of agro-industrial residues constitute an opportunity for further sustainable utilization. In the current work, we have assessed the suitability of an abundant source of biomass waste, i.e., lignin-rich press mud (LPM), for steel industry. Hard carbons were obtained from LPM through a thermal treatment at a wide range of temperatures, and the chemical content (i.e., impurity) of all carbons was compatible with the steel making process. Before fitting the LPM-derived carbons (LPMCs) for such purpose, several carbon properties (e.g., chemical content and reactivity) and carbon-steel interactions (e.g., iron oxide/slag reduction, steel carburizing) were comprehensively studied and evaluated. The LPMC obtained at high temperature has particularly demonstrated an excellent reduction performance and desirable slag interactions compared to a typical metallurgical coke. The diffusion of S from LPMC into steel was an issue raised and discussed in this study. The reduction of S in LPMC was demonstrated and a subsequent enhanced C uptake in steel of 2.38% was achieved. more...

A green carbon capture and conversion technology offering scalability and economic viability for mitigating CO

The emergence of three-dimensional (3D) printing promises a disruption in the design and on-demand fabrication of smart structures in applications ranging from functional devices to human organs. However, the scale at which 3D printing excels is within macro- and microlevels and principally lacks the spatial ordering of building blocks at nanolevels, which is vital for most multifunctional devices. Herein, we employ liquid crystal (LC) inks to bridge the gap between the nano- and microscales in a single-step 3D printing. The LC ink is prepared from mixtures of LCs of nanocellulose whiskers and large sheets of graphene oxide, which offers a highly ordered laminar organization not inherently present in the source materials. LC-mediated 3D printing imparts the fine-tuning required for the design freedom of architecturally layered systems at the nanoscale with intricate patterns within the 3D-printed constructs. This approach empowered the development of a high-performance humidity sensor composed of self-assembled lamellar organization of NC whiskers. We observed that the NC whiskers that are flat and parallel to each other in the laminar organization allow facile mass transport through the structure, demonstrating a significant improvement in the sensor performance. This work exemplifies how LC ink, implemented in a 3D printing process, can unlock the potential of individual constituents to allow macroscopic printing architectures with nanoscopic arrangements. more...

We report a green carbon capture and conversion technology offering scalability and economic viability for mitigating CO2 emissions. 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. By altering the secondary solvent and changing the reactor height, the dissolution and conversion efficiency can be tuned. The optimum reactor height is only 27 cm, when gallium/silver fluoride mix at 7:1 mass ratio is employed as the reaction material. At CO2 input of ~8 sccm, 92% efficiency was obtained at the record low input energy of 228.5 kW∙h for the capture and conversion of a tonne of CO2. The potential impact of this green technology is remarkable, likely benefiting a variety of industries and offering an economical solution for CO2 capture and conversion. more...

Although it remains unexplored, the direct synthesis and expulsion of metals from alloys can offer many opportunities. Here, such a phenomenon is realized electrochemically by applying a polarizing voltage signal to liquid alloys. The signal induces an abrupt interfacial perturbation at the Ga-based liquid alloy surface and results in an unrestrained discharge of minority elements, such as Sn, In, and Zn, from the liquid alloy. We show that this can occur by either changing the surface tension or inducing a reversible redox reaction at the alloys' interface. The expelled metals exhibit nanosized and porous morphologies, and depending on the cell electrochemistry, these metals can be passivated with oxide layers or fully oxidized into distinct nanostructures. The proposed concept of metal expulsion from liquid alloys can be extended to a wide variety of molten metals for producing metallic and metallic compound nanostructures for advanced applications. more...

The activation of biomass using solid-phase reagents has been widely adopted to produce porous carbons. This approach, however, has remained without any improvement for decades. In the current work, we detail a simple activation and purification method where a silica-rich biomass waste (sugar press-mud, SPM) is sono-impregnated and fractionated with an alkaline solution. Upon heat-treatment, the fractionated alkali-soluble matter, which accounts for around 53 wt% of the dry SPM, results in a reasonable yield of carbon with a distinct texture of an interconnected porous structure with a high surface area of 2,066 m2·g−1 and large pore-size-distribution. The impedance spectroscopy showed that the resulting carbon has an enhanced electrochemical response and less ionic diffusion-induced ohmic losses compared to that of a typical activated carbon due to its large pore-channels and enhanced ion-in-pore admittance. The ash content (mainly silica) in the final product was found to be less than expected. By tracking silica throughout the activation process, the reduction of ash content was assigned to the silica attack reactions. In these reactions, silica is transformed into water-soluble and/or low boiling point potassium silicates which facilitates its deportment from the final product resulting in a high-porosity and purity carbon. more...

It is well-understood that during the liquid-to-solid phase transition of alloys, elements segregate in the bulk phase with the formation of microstructures. In contrast, we show here that in a Bi-Ga alloy system, highly ordered nanopatterns emerge preferentially at the alloy surfaces during solidification. We observed a variety of transition, hybrid and crystal-defect-like patterns, in addition to lamellar and rod-like structures. Combining experiments and molecular dynamics simulations, we investigated the influence of the superficial Bi and Ga more...

Metallic foams, with intrinsic catalytic properties, are critical for heterogeneous catalysis reactions and reactor designs. Market ready catalytic foams are costly and made of multimaterial coatings with large sub-millimeter open cells providing insufficient active surface area. Here we use the principle of nanometallurgy within liquid metals to prepare nanostructured catalytic metal foams using a low-cost alloy of bismuth and tin with sub-micrometer open cells. The eutectic bismuth and tin liquid metal alloy was processed into nanoparticles and blown into a tin and bismuth nanophase separated heterostructure in aqueous media at room temperature and using an indium brazing agent. The CO2 electroconversion efficiency of the catalytic foam is presented with an impressive 82% conversion efficiency toward formates at high current density of -25 mA cm-2 (-1.2 V vs RHE). Nanometallurgical process applied to liquid metals will lead to exciting possibilities for expanding industrial and research accessibility of catalytic foams. more...

The concentrative isolation of metal traces from aqueous solutions is of vital importance for environmental and industrial processes. Developing reliable systems of nanoscale that can be fine-tuned to effectively isolate these metals remains an intriguing aim which can potentially beget economic benefits and mitigate major environmental concerns. Here we demonstrate a conceptual metal extraction system where magnetic multi-wall carbon nanotubes (M-MWCNTs) are surface-equipped with a molecular network of polyethylenimine (PEI) to serve as a reusable nano-ionic exchanger, referred to as "M-MWCNTs-PEI". The designed nano-ionic exchanger forms readily stable suspensions with the metal-bearing aqueous solutions eliminating the need for vigorous agitation. Besides, it can be magnetically manipulated and separated in/from the solution. To exemplify its potential for the isolation of metal traces, the M-MWCNTs-PEI was tested with the uranium trace ions in aqueous media. The M-MWCNTs-PEI featured distinct sorption capacity of ~488 mg/g at pH 6, with moderate, but stable, binding affinity toward uranium ions. As such, excellent isolation performance is demonstrated while bound uranium ions are effectively concentrated and recovered from the interfacial PEI molecular network. This was efficiently achieved by exposing the loaded M-MWCNTs-PEI to solutions of small volumes and specific chemistry. Such combined qualities of large capacity and reusability have not been observed with the previously reported ion exchange systems. Altogether, our observations here demonstrate how functional systems of nanoscale can be adapted for industrial applications while this concept can be extended to address other important resources such as rare-earth and lanthanide elements. more...

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. more...

In this study, a novel surface functional layer based on quaternary ammonium is synthesized in situ on the surface of silica coated magnetic nanoparticles. The composite is characterized by XRD, FTIR, SEM, VSM, TGA and zeta potential measurements. Sorption/desorption experiments were performed to evaluate its potential to remove uranium (VI) from aqueous solutions. The results indicated that the new composite has a capacity of ∼87 mg/g with 120 min equilibrium time with good recyclability and strong magnetic response. The pseudo-second order kinetic model was found to fit the experimental data fairly well, the data also suggested the presence of intra-particle diffusion. The adsorption isotherm befitted Langmuir equation. Thermodynamic analysis for the adsorption process was performed and the values of ΔG, ΔH and ΔS are reported. more...

The increases in the volumes of electronic waste have become an aggravating environmental, economic, and social health issue in recent times. This study investigates the conversion of e-waste plastics into hydrocarbon oils via noncatalytic thermal transformation followed by an in-depth characterization of these oils using diverse analytical techniques such as gas chromatography–mass spectrometry (GC–MS), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. In particular, NMR spectroscopy is a key analytical tool utilized in this study to gain a comprehensive insight into the chemical nature of the resultant oils along with a semiquantitative investigation of the changes in their composition over a temperature range of 800–1200 °C. The one-dimensional (1D) 1H and two-dimensional (2D) heteronuclear single-quantum correlation spectra were acquired for the oils, wherein the 2D NMR spectrum provided improved resolution of peaks to address the overlaps encountered in the 1D spectrum. The experimental results obtained from GC–MS, FTIR spectroscopy, and NMR spectroscopy were found to align well with each other. The oils produced in this study have a high calorific value of 38.27 MJ/kg and thus may find use in several applications. A detailed mechanism for the thermal degradation of styrene acrylonitrile plastics and the formation of major products is elucidated in this study. more...

Supercapacitors, with their high power density and quick charge/discharge capability, have gained attention as the highly desirable energy storage devices. Recent studies have shown that carbon-based materials with high surface area have huge potential for energy storage applications. It will be interesting if such carbon materials can be produced with desirable characteristics using a green approach. Herein, we report a highly reproducible sustainable approach of producing high surface area activated carbons directly from styrene acrylonitrile (SAN) plastics, obtained from the end-of-life printers. Activated carbons had high specific surface area and pore volume due to the mesopores and micropores generated in the carbon skeleton during the activation process, thus making these activated carbons a good potential candidate for supercapacitor electrode fabrication. We have studied the supercapacitance performance of these activated carbons with varied surface areas by conducting electrochemical experiments using a three-electrode system, with 2 M KOH as electrolyte, at scan rates ranging from 5 to 150 mV/s. While being used as a supercapacitor electrode without the addition of any conductive additives such as carbon black, specific gravimetric capacitance values of as high as 220 F/g were achieved. This is an outstanding supercapacitance performance of carbons produced using waste resources. more...

Recycling batteries has become essential for improving sustainability, economy and environment. Batteries recycling and recovery processes are multi steps and require purified reagents which are often very toxic. Herein, we report a feasible approach to process scrap Ni-Cd batteries into highly porous NiO nanocuboids. Cathode of Ni-Cd battery contains approximately 42% elemental Ni along with several impurities such as Mg, Co, Cd and Na. In this work, by applying few-steps of selective isolation and hydrothermal treatment, the content of Ni could be raised up to 77% and purified in the form of NiO porous nanocuboids. Morphology, crystal structure, composition, and surface area measurements of NiO nanocuboids was studied by HR-TEM, FE-SEM, XRD, XPS and BET characterization techniques, respectively. more...

In this work, carbon-coated magnetic iron oxide nanoparticles (CCM) functionalized with polyethyleneimine/amide (PEIA) were successfully prepared. The prepared nanocomposite (CCMNPs-PEIA) was characterized by XRD, TEM, FT–IR, TGA and VSM techniques. The stability of CCM was tested in both acidic and basic media and they showed a high stability with good magnetic properties. CCMNPs-PEIA were used for separation of U (VI) from aqueous solutions. Several process parameters were tested to investigate the removal efficiency, adsorption capacity and reusability of the CCMNPs-PEIA including, pH, initial concentration of uranium, and desorption and activation media. The CCMNPs-PEIA nanocomposite was found to have excellent affinity toward U over a wide pH range. Surface oxidation of CCM was found to be of major effect of the adsorption capacity of CCMNPs-PEIA due it carboxylation which enhanced PEIA attachment to the carbon surface. The experimental uptake of the prepared nanocomposite was found to be 127.5 mg (U/g (nanocomposite), while the one calculated according to Langmuir model was found to be 123.45 mg/g with a correlation coefficient (R2) of 0.991. The kinetics analysis of the adsorption process suggests that the kinetics can be described well by the pseudo-second order model suggesting that the rate limiting step is chemisorption. more...

This paper details a sustainable process for synthesizing green Si₃N₄ nanowires (NWs) from high volume fractions of electronic waste (e-waste). Obsolete computers were manually dismantled, and the glass fraction of the monitors (GCM) and their plastic shells (PS) were separated and used as silica and carbon sources, respectively. E-waste is the world’s fastest growing waste stream, and although considerable research effort is currently focused on metals recovery, there are few options for the huge volumes of glass and plastic waste left behind. Using a blend of GCM and PS, we applied a novel route, thermal nanowiring at 1550 °C under nitrogen purge in atmospheric pressure. FE-SEM studies revealed the resulting Si₃N₄ NWs, with diameters of 75–250 nm, mostly appeared to turn in random directions and exhibited twisted pattern along their axes, indicating the Si₃N₄ crystalline grew through a screw-dislocation-driven mechanism. In a comparison experiment, waste toner powder with iron oxide (∼38 wt %) was added as a source of Fe to the GCM-PS blend to enable the investigation of its catalytic effect on the morphology of the Si₃N₄ synthesized. The addition of the toner powder resulted in long Si₃N₄ nanobelts (up to 40 μm) with traces of liquid droplets on their tips, indicating the Fe had promoted the formation of the long and straight nanobelts via the vapor–liquid–solid VLS mechanism. The novel route, thermal nanowiring described here, confirms a new opportunity to transform a globally significant waste burden into value-added 1D materials, thereby simultaneously delivering economic and environmental benefits. more...

The present work reports the rapid preparation of CeO2 nanorods by surfactant-free precipitation for the first time, which initiates a strategy for the quantitative elucidation of the importance of the exposed crystallographic planes and the oxygen vacancy concentrations of different morphologies of nanoceria. These relations are revealed through comparison of the relative surface areas of the exposed crystallographic planes. The precipitation temperature was critical in that nanooctahedra formed at the three lower temperatures and nanorods formed at the highest. The key feature to differentiate the photocatalytic performance was the morphology that the nanorods exhibit ∼200% superior performance compared to those of the nanooctahedra. The principal reason for this is the presence of exposed {110} planes in the nanorods, which are not present in nanoctahedra. This crystallographic dependence of the improved performance of the nanorods is attributed directly to the greater oxygen vacancy concentration for the calculated surface area of this morphology. more...

Graphene oxide (GO)-based pervaporation membranes have great potential for desalination and lithium containing brine enrichment. However, they experienced critical challenges when used in aqueous solution and exposed to oscillating temperatures due to swelling and microdefects. In this work, the GO-based membranes were fabricated by the filtration of GO suspension with sulfonate-containing diamine molecules on porous substrates, then dip-coated with chitosan and polyvinyl alcohol (PVA). The resultant GO-based membranes demonstrated 99.99% salt rejection during pervaporation using NaCl or lithium-containing concentrated inland brine with humic acid as the feed solution under oscillating temperature. The intercalation of diamine molecules inside the GO nanochannels was able to increase water flux by 20% while the coated chitosan/PVA layer reduced structural defects and undesired scaling/fouling on the membrane surface resulting in minimal reduction of water flux (16%) over 72 h of oscillating temperature pervaporation. Moreover, the membrane exhibited good stability after chemical cleaning. The proposed GO-based membranes provided significant performance sustainability in concentrated inland brine and oscillating feed temperature condition. more...

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. more...

Macadamia nut shell, an Australian waste biomass, was pyrolyzed to produce biochars at temperatures ranging from 500 °C to 1300 °C, using lab scale horizontal tube furnace. Biochar characterization was carried out to assess their potential usefulness as a carbonaceous material in ironmaking. Thermal decomposition analysis on waste macadamia biomass was performed using thermogravimetry and kinetic studies. The changes in chemical nature and composition of produced biochars were studied using various analytical techniques. Biochar prepared at 1300 °C was found to have around 92% carbon content as well as highly ordered graphitic structure. Biochar was used as a carbon source to reduce iron oxides to metallic iron at different temperatures i.e.1000 °C, 1100 °C, 1200 °C and 1300 °C. X-ray diffraction and scanning electron microscope analysis were performed on the reduced samples to investigate the phases present in the samples and for morphology respectively. The results of the study suggest that the biochar derived from macadamia nut shell biomass waste can be used as a valuable and renewable carbon resource in sustainable and cleaner production of iron. more...

This study confirms a sustainable and clean new approach for synthesizing a mesoporous silicon carbide (SiC) nanofibre/particle composite from a binary mixture of two problematic, high volume global waste streams, e-waste glass (SiO 2 source) and waste tyre rubber (WTR) through the carbothermal reduction. The resulting composite material consisted of a mixture of nanofibres of 10–150 nm diameters and over 5 microns length, and distributed nanoparticles with particle size ranging between 30 and 40 nm with a relatively high surface area (85.1–67.3 m 2 g −1 ) and a dominant pore size smaller than 2 nm. SiC of nanomaterials is conventionally fabricated from high quality carbon and silicon sources which are expensive and may not prove cost effective from industrial perspective. E-waste glass and waste tyres are both potential sources of valuable secondary resources, but a lack of cost-effective recycling options means vast volumes are landfilled, stockpiled or diverted to unsafe processing operations in developing countries; posing serious environmental and health risks. The simultaneous conversion of two globally significant waste burdens into (SiC) nanofibre/particle composite has not previously been investigated. This novel approach highlights the opportunities for utilizing waste as an alternative resource to deliver economic and environmental benefits and also demonstrates a new low cost means of synthesizing SiC nanofibre/particle composite. more...

The chemical interaction of a typical slag of EAF with three different carbon sources, coke, rubber-derived carbon (RDC), coke-RDC blend, was studied in atmospheric pressure at 1823 K (1550 °C). Using an IR-gas analyzer, off-gases evolved from the sample were monitored. While the coke-RDC blend exhibited the best reducing performance in reaction with molten slag, the RDC sample showed poor interaction with the molten slag. The gasification of the coke, RDC, and coke-RDC blend was also carried out under oxidizing conditions using a gas mixture of CO2 (4 wt pct) and Ar (96 wt pct) and it was shown that the RDC sample had the highest rate of gasification step $$ C_{0} \mathop{\longrightarrow}\limits{{k_{3} }}{\text{CO}} + nC_{\text{f}} $$ (11.6 site/g s (×6.023 × 1023/2.24 × 104)). This may be attributed to its disordered structure confirmed by Raman spectra and its nano-particle morphology observed by FE-SEM. The high reactivity of RDC with CO2 provided evidence that the Boudouard reaction was fast during the interaction with molten slag. However, low reduction rate of iron oxide from slag with RDC can be attributed to the initial weak contact between RDC and molten slag implying that the contact between carbonaceous matter and slag plays significant roles in the reduction of iron oxide from slag. more...