Two-dimensional (2D) oxides have a wide variety of applications in electronics and other technologies. However, many oxides are not easy to synthesize as 2D materials through conventional methods. We ...used nontoxic eutectic gallium-based alloys as a reaction solvent and co-alloyed desired metals into the melt. On the basis of thermodynamic considerations, we predicted the composition of the self-limiting interfacial oxide. We isolated the surface oxide as a 2D layer, either on substrates or in suspension. This enabled us to produce extremely thin subnanometer layers of HfO₂, Al₂O₃, and Gd₂O₃. The liquid metal–based reaction route can be used to create 2D materials that were previously inaccessible with preexisting methods. The work introduces room-temperature liquid metals as a reaction environment for the synthesis of oxide nanomaterials with low dimensionality.
Antibiotic resistance has made the treatment of biofilm-related infections challenging. As such, the quest for next-generation antimicrobial technologies must focus on targeted therapies to which ...pathogenic bacteria cannot develop resistance. Stimuli-responsive therapies represent an alternative technological focus due to their capability of delivering targeted treatment. This study provides a proof-of-concept investigation into the use of magneto-responsive gallium-based liquid metal (LM) droplets as antibacterial materials, which can physically damage, disintegrate, and kill pathogens within a mature biofilm. Once exposed to a low-intensity rotating magnetic field, the LM droplets become physically actuated and transform their shape, developing sharp edges. When placed in contact with a bacterial biofilm, the movement of the particles resulting from the magnetic field, coupled with the presence of nanosharp edges, physically ruptures the bacterial cells and the dense biofilm matrix is broken down. The antibacterial efficacy of the magnetically activated LM particles was assessed against both Gram-positive and Gram-negative bacterial biofilms. After 90 min over 99% of both bacterial species became nonviable, and the destruction of the biofilms was observed. These results will impact the design of next-generation, LM-based biofilm treatments.
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.
A “liquid metal”–“liquid solution” reaction to grow Cabrera–Mott like monolayers of hydrated MnO2 is introduced. These self‐limiting monolayers are formed on the surface of the eutectic EGaIn. A unique phenomenon of metal dealloying is observed as a result of mechanical agitation, leading to an extraordinary gallium migration out into oxidative dissolution, leaving an indium solid core behind, within a porous shell.
Plasmonic biosensors based on noble metals generally suffer from low sensitivities if the perturbation of refractive‐index in the ambient is not significant. By contrast, the features of degenerately ...doped semiconductors offer new dimensions for plasmonic biosensing, by allowing charge‐based detection. Here, this concept is demonstrated in plasmonic hydrogen doped molybdenum oxides (HxMoO3), with the morphology of 2D nanodisks, using a representative enzymatic glucose sensing model. Based on the ultrahigh capacity of the molybdenum oxide nanodisks for accommodating H+, the plasmon resonance wavelengths of HxMoO3 are shifted into visible‐near‐infrared wavelengths. These plasmonic features alter significantly as a function of the intercalated H+ concentration. The facile H+ deintercalation out of HxMoO3 provides an exceptional sensitivity and fast kinetics to charge perturbations during enzymatic oxidation. The optimum sensing response is found at H1.55MoO3, achieving a detection limit of 2 × 10−9m at 410 nm, even when the biosensing platform is adapted into a light‐emitting diode‐photodetector setup. The performance is superior in comparison to all previously reported plasmonic enzymatic glucose sensors, providing a great opportunity in developing high performance biosensors.
HxMoO3 plasmonic disks are synthesized. H+ and concurrently electrons can be extracted from the host structure during a designed biochemical event. This alteration in charge rapidly changes the plasmon resonance features, hence creating an ultrasensitive platform.
Atomically thin transition metal dichalcogenide crystals (TMDCs) have extraordinary optical properties that make them attractive for future optoelectronic applications. Integration of TMDCs into ...practical all‐dielectric heterostructures hinges on the ability to passivate and protect them against necessary fabrication steps on large scales. Despite its limited scalability, encapsulation of TMDCs in hexagonal boron nitride (hBN) currently has no viable alternative for achieving high performance of the final device. Here, it is shown that the novel, ultrathin Ga2O3 glass is an ideal centimeter‐scale coating material that enhances optical performance of the monolayers and protects them against further material deposition. In particular, Ga2O3 capping of monolayer WS2 outperforms commercial‐grade hBN in both scalability and optical performance at room temperature. These properties make Ga2O3 highly suitable for large‐scale passivation and protection of monolayer TMDCs in functional heterostructures.
2D transition metal dichalcogenides have promising properties for future semiconductor technologies. Their integration into functional devices requires cost‐efficient and large‐scale passivation and protection against material deposition. This work introduces ultrathin Ga2O3 glass as a new, scalable capping material for monolayer WS2. It exhibits a novel passivation mechanism and offers extraordinary protection against deposition of dielectric materials, for example, for top‐gating.
Two-dimensional piezotronics will benefit from the emergence of new crystals featuring high piezoelectric coefficients. Gallium phosphate (GaPO
) is an archetypal piezoelectric material, which does ...not naturally crystallise in a stratified structure and hence cannot be exfoliated using conventional methods. Here, we report a low-temperature liquid metal-based two-dimensional printing and synthesis strategy to achieve this goal. We exfoliate and surface print the interfacial oxide layer of liquid gallium, followed by a vapour phase reaction. The method offers access to large-area, wide bandgap two-dimensional (2D) GaPO
nanosheets of unit cell thickness, while featuring lateral dimensions reaching centimetres. The unit cell thick nanosheets present a large effective out-of-plane piezoelectric coefficient of 7.5 ± 0.8 pm V
. The developed printing process is also suitable for the synthesis of free standing GaPO
nanosheets. The low temperature synthesis method is compatible with a variety of electronic device fabrication procedures, providing a route for the development of future 2D piezoelectric materials.
Gallium is a near room temperature liquid metal with extraordinary properties that partly originate from the self‐limiting oxide layer formed on its surface. Taking advantage of the surface gallium ...oxide (Ga2O3), this work introduces a novel technique to synthesize gallium oxide nanoflakes at high yield by harvesting the self‐limiting native surface oxide of gallium. The synthesis process follows a facile two‐step method comprising liquid gallium metal sonication in DI water and subsequent annealing. In order to explore the functionalities of the product, the obtained hexagonal α‐Ga2O3 nanoflakes are used as a photocatalytic material to decompose organic model dyes. Excellent photocatalytic activity is observed under solar light irradiation. To elucidate the origin of these enhanced catalytic properties, the electronic band structure of the synthesized α‐Ga2O3 is carefully assessed. Consequently, this excellent photocatalytic performance is associated with an energy bandgap reduction, due to the presence of trap states, which are located at ≈1.65 eV under the conduction band minimum. This work presents a novel route for synthesizing oxide nanostructures that can be extended to other low melting temperature metals and their alloys, with great prospects for scaling up and high yield synthesis.
Sonication‐assisted route employed on liquid metal gallium is presented as a new route for synthesizing gallium oxide (Ga2O3) nanoflakes. The suspension of Ga2O3 is used for dye degradation, showing a remarkable efficiency, which is ascribed to the presence of trap bands.
Miniaturization and energy consumption by computational systems remain major challenges to address. Optoelectronics based synaptic and light sensing provide an exciting platform for neuromorphic ...processing and vision applications offering several advantages. It is highly desirable to achieve single‐element image sensors that allow reception of information and execution of in‐memory computing processes while maintaining memory for much longer durations without the need for frequent electrical or optical rehearsals. In this work, ultra‐thin (<3 nm) doped indium oxide (In2O3) layers are engineered to demonstrate a monolithic two‐terminal ultraviolet (UV) sensing and processing system with long optical state retention operating at 50 mV. This endows features of several conductance states within the persistent photocurrent window that are harnessed to show learning capabilities and significantly reduce the number of rehearsals. The atomically thin sheets are implemented as a focal plane array (FPA) for UV spectrum based proof‐of‐concept vision system capable of pattern recognition and memorization required for imaging and detection applications. This integrated light sensing and memory system is deployed to illustrate capabilities for real‐time, in‐sensor memorization, and recognition tasks. This study provides an important template to engineer miniaturized and low operating voltage neuromorphic platforms across the light spectrum based on application demand.
Optoelectronic vision and synaptic devices can help overcome high energy requirements of computation and enable miniaturised, precise, real‐time vision systems. Herein, atomically thin layers of Sb doped In2O3 are utilised as ultraviolet‐active optoelectronic synapses with recognition and prolonged memory capabilities. The material is devised into an imaging array of photo‐active pixels capable of pattern recognition and memorization at low power with very few training cycles.
The application of hardware‐based neural networks can be enhanced by integrating sensory neurons and synapses that enable direct input from external stimuli. This work reports direct optical control ...of an oscillatory neuron based on volatile threshold switching in V3O5. The devices exhibit electroforming‐free operation with switching parameters that can be tuned by optical illumination. Using temperature‐dependent electrical measurements, conductive atomic force microscopy (C‐AFM), in situ thermal imaging, and lumped element modelling, it is shown that the changes in switching parameters, including threshold and hold voltages, arise from overall conductivity increase of the oxide film due to the contribution of both photoconductive and bolometric characteristics of V3O5, which eventually affects the oscillation dynamics. Furthermore, V3O5 is identified as a new bolometric material with a temperature coefficient of resistance (TCR) as high as −4.6% K−1 at 423 K. The utility of these devices is illustrated by demonstrating in‐sensor reservoir computing with reduced computational effort and an optical encoding layer for spiking neural network (SNN), respectively, using a simulated array of devices.
This study reports light‐control of an oxide‐based relaxation oscillator based on the photothermal response of V3O5, a material that undergoes an insulator‐to‐metal transition at temperatures above ≈420 K. The research advances the understanding of V3O5 as a functional material, and demonstrates its potential as the basis of a solid‐state sensory neuron for neuromorphic computing.
Heterostructures assembled from atomically thin materials have led to a new paradigm in the development of the next‐generation high‐performing functional devices. However, the construction of the ...ultrathin van der Waals (vdW) heterostructures is challenging and/or limited to materials with layered crystal structures. Herein, liquid metal vdW transfer method is used to construct large area heterostructures of atomically thin metal oxides of p‐SnO/n‐In2O3 with ease. The heterostructure exhibits both outstanding photodetectivity of 5 × 109 Jones and photoresponsivity of 1047 A W−1 with fast response time of ≤1 ms under illumination of the 280 nm light. Such excellent performances are due to the formation of the narrow bandgap of the staggered gap at the p–n junction produced by the high‐quality SnO/In2O3 heterostructure. The facile production of high‐quality vdW heterostructures using the liquid metal–based method therefore provides a promising pathway for realizing future optoelectronic devices.
This work illustrates a framework for the development of van der Waals (vdW) heterostructures using atomically thin surface oxides of the low melting point liquid metals. vdW heterostructures that are made from printing surface oxides of liquid indium (In2O3) and tin (SnO) on top of each other have efficient and fast response features for photodetection.
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