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.
Eutectic gallium‐indium (EGaIn) liquid metal droplets have been considered as a suitable platform for producing customized 3D composites with functional nanomaterials owing to their soft and highly ...reductive surface. Herein, the synthesis of a 3D plasmonic oxide framework (POF) is reported by incorporating the ultra‐thin angstrom‐scale‐porous hexagonal molybdenum oxide (h‐MoO3) onto the spherical EGaIn nanodroplets through ultrasonication. Simultaneously, a large number of oxygen vacancies form in h‐MoO3, boosting its free charge carrier concentration and therefore generating a broad surface plasmon resonance across the whole visible light spectrum. The plasmonic chemical sensing properties of the POF is investigated by the surface‐enhanced Raman scattering detection of rhodamine 6G (R6G) at 532 nm, in which the minimum detectable concentration is 10−8 m and the enhancement factor reached up to 6.14 × 106. The extended optical absorption of the POF also allowed the efficient degradation of the R6G dye under the excitation of ultraviolet‐filtered simulated solar light. Furthermore, the POF exhibits remarkable photocurrent responses towards the entire visible light region with the maximum response of ≈1588 A W−1 at 455 nm. This work demonstrates the great potential of the liquid metal‐based POFs for high‐performance sensing, catalytic, and optoelectronic devices.
A liquid metal‐based 3D plasmonic oxide framework (POF) is developed, which consists of eutectic EGaIn nanodroplets coated with sub‐stoichiometric ultra‐thin hexagonal MoO3–x. The POF shows a broadband surface plasmon resonance across the visible and near‐infrared region. Together with the ultra‐high surface active area, the 3D POF demonstrates excellent performances in chemical sensing, photocatalytic, and optoelectronic applications.
Atomically thin 2D materials are highly sought for high‐performance electronic and optoelectronic devices. Despite being a widely recognized functional material for a plethora of applications, ...ultra‐thin nanosheets of zinc oxide (ZnO) at a millimeter‐scale for developing high‐performance electronic/optoelectronic devices have not been reported. This has prevented the exploration of electronic and optical properties of ZnO when it is only a few atoms thick. Here, a liquid metal exfoliation technique is used that takes advantage of the van der Waals forces between the interfacial oxide and the chosen substrate to obtain ZnO nanosheets with lateral dimensions in the millimeter scale and thickness down to 5 nm. Their suitability for applications is shown by demonstrating a visible‐blind photodetector with high figures of merit as compared to other ZnO morphologies. At extremely low operating bias of 50 mV and low optical intensity of 0.5 mW cm−2, the ZnO photodetector demonstrates an external quantum efficiency (EQE), responsivity (R), and detectivity (D*) of 4.3 × 103%, 12.64 A W−1, and 5.81 × 1015 Jones at a wavelength of 365 nm. The trap‐mediated photoresponse in the ZnO nanosheets is further utilized to demonstrate optoelectronic synapses. Versatile synaptic functions of the nervous systems are optically emulated with the ultra‐thin ZnO nanosheets.
Liquid metal exfoliated ZnO nanosheets provide a simple yet effective platform to demonstrate two key optoelectronic applications in a two‐terminal configuration—one as a miniaturized UV photodetector and the other as an artificial optoelectronic synapse. By exploiting the trap mediated states in the material, many key cognitive functionalities are emulated solely through optical stimuli.
Sulfur-rich molybdenum sulfides are an emerging class of inorganic coordination polymers that are predominantly utilized for their superior catalytic properties. Here we investigate surface water ...dependent properties of sulfur-rich MoS x (x = 32/3) and its interaction with water vapor. We report that MoS x is a highly hygroscopic semiconductor, which can reversibly bind up to 0.9 H2O molecule per Mo. The presence of surface water is found to have a profound influence on the semiconductor’s properties, modulating the material’s photoluminescence by over 1 order of magnitude, in transition from dry to moist ambient. Furthermore, the conductivity of a MoS x -based moisture sensor is modulated in excess of 2 orders of magnitude for 30% increase in humidity. As the core application, we utilize the discovered properties of MoS x to develop an electrolyteless water splitting photocatalyst that relies entirely on the hygroscopic nature of MoS x as the water source. The catalyst is formulated as an ink that can be coated onto insulating substrates, such as glass, leading to efficient hydrogen and oxygen evolution from water vapor. The concept has the potential to be widely adopted for future solar fuel production.
By using transient-adsorption spectroscopic techniques, we discovered extraordinarily long-lived hot electrons in degenerately doped molybdenum oxides with surface plasmon resonance in the visible ...and near-infrared region. This finding provides new insights for the development of the new plasmonic photo-catalysts.
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Plasmon-induced hot electrons offer unique advantages in solar-light-driven chemical reactions. Noble metal nanostructures have been the most studied plasmonic materials, but the hot electron lifetime is extremely short. Here, we have discovered extraordinarily long-lived hot electrons in degenerately doped molybdenum oxides with surface plasmon resonance in the visible and near-infrared region. Their lifetime is nanosecond-scale, which is enhanced by 4 orders of magnitude compared to their noble metal counterparts. Such a property is ascribed to the quasi-metallic feature of molybdenum oxides driven by hydrogen dopant-induced bandgap trap states, in which the electron–phonon scattering is dominant over the ultrafast electron–electron scattering in the decay dynamics of hot electrons. The plasmonic dye oxidation and hydrogen evolution are explored without the coupling of semiconductors, providing a viable way towards expanding the candidates for direct plasmonic photocatalysis.
•Particle size <120 µ enables above 95% hemicellulose recovery.•Lower substrate concentration gives higher xylooligosaccharides yield.•Produced XOS comparable to commercial XOS in terms of gas and ...acid levels.•Short chain oligosaccharides produce higher level of acetate.
Almond shell, a by-product obtained from the nut industry, was valorised into low degree of polymerisation xylooligosaccharides using alkaline pretreatment and enzymatic hydrolysis. The effect of particle size on hemicellulose recovery upon pretreatment was studied using 1 and 2 M NaOH. It was observed that particle size significantly influences hemicellulose recovery, as particles below 120 µm resulted in near complete recovery at 2 M NaOH. Enzymatic hydrolysis of hemicellulose was optimised using response surface methodology, to obtain efficient xylooligosaccharides production at low enzyme dose and high substrate concentration. For higher XOS yield, an enzyme dose of 10 U and substrate concentration <2% was optimal. The in-vitro human faecal fermentation study revealed no significant difference in gas and short chain fatty acid level among substrates evaluated. It was observed that short chain oligosaccharides produce higher level of acetate than medium chain oligosaccharides.
Intriguing physical and chemical properties of atomically thin semiconductors provide avenues for the development of the next-generation electronics, optoelectronics, and sensing applications. ...However, many materials are intrinsically nonlayered and therefore difficult to obtain in two dimensions (2D) due to the presence of strong in-plane bonds. Here, we adopted liquid metal synthetic strategies to produce 2D gallium sulfide (Ga2S3), which is an intrinsically nonlayered material. The obtained monoclinic α-Ga2S3 has a relatively high field-effect mobility of 3.5 cm2 V–1 s–1 and features a p-type material with a bandgap of 2.1 eV. Photodetectors that are made based on these synthesized 2D Ga2S3 exhibit relatively strong photodetectivity of 1010 jones and photoresponsivity of 240 A W–1 in visible wavelengths. The 2D Ga2S3 is also found to be suitable for sensing of nitrogen dioxide (NO2) gas at low evaluated temperatures. Excellent electronic, optical, and gas sensing performance demonstrated in this work offers great promises for synthesizing high quality 2D materials based on the liquid metal framework.
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.
Abstract
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‐In
2
O
3
with ease. The heterostructure exhibits both outstanding photodetectivity of 5 × 10
9
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/In
2
O
3
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.
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