Surface water dependent properties of sulphur-rich molybdenum sulfides: electrolyteless gas phase water splitting

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 MoSx (x = 32/3) and its interaction with water vapor. We report that MoSx 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 MoSx-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 MoSx to develop an electrolyteless water splitting photocatalyst that relies entirely on the hygroscopic nature of MoSx 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

Wafer-scale two-dimensional semiconductors from printed oxide skin of liquid metals

A variety of deposition methods for two-dimensional crystals have been demonstrated; however, their wafer-scale deposition remains a challenge. Here we introduce a technique for depositing and patterning of wafer-scale two-dimensional metal chalcogenide compounds by transforming the native interfacial metal oxide layer of low melting point metal precursors (group III and IV) in liquid form. In an oxygen-containing atmosphere, these metals establish an atomically thin oxide layer in a self-limiting reaction. The layer increases the wettability of the liquid metal placed on oxygen-terminated substrates, leaving the thin oxide layer behind. In the case of liquid gallium, the oxide skin attaches exclusively to a substrate and is then sulfurized via a relatively low temperature process. By controlling the surface chemistry of the substrate, we produce large area two-dimensional semiconducting GaS of unit cell thickness (∼1.5 nm). The presented deposition and patterning method offers great commercial potential for wafer-scale processes

Liquid-Metal Synthesized Ultrathin SnS Layers for High-Performance Broadband Photodetectors

Atomically thin materials face an ongoing challenge of scalability, hampering practical deployment despite their fascinating properties. Tin monosulfide (SnS), a low-cost, naturally abundant layered material with a tunable bandgap, displays properties of superior carrier mobility and large absorption coefficient at atomic thicknesses, making it attractive for electronics and optoelectronics. However, the lack of successful synthesis techniques to prepare large-area and stoichiometric atomically thin SnS layers (mainly due to the strong interlayer interactions) has prevented exploration of these properties for versatile applications. Here, SnS layers are printed with thicknesses varying from a single unit cell (0.8 nm) to multiple stacked unit cells (approximate to 1.8 nm) synthesized from metallic liquid tin, with lateral dimensions on the millimeter scale. It is reveal that these large-area SnS layers exhibit a broadband spectral response ranging from deep-ultraviolet (UV) to near-infrared (NIR) wavelengths (i.e., 280-850 nm) with fast photodetection capabilities. For single-unit-cell-thick layered SnS, the photodetectors show upto three orders of magnitude higher responsivity (927 A W-1) than commercial photodetectors at a room-temperature operating wavelength of 660 nm. This study opens a new pathway to synthesize reproduceable nanosheets of large lateral sizes for broadband, high-performance photodetectors. It also provides important technological implications for scalable applications in integrated optoelectronic circuits, sensing, and biomedical imaging

Chemical analysis of acoustically levitated drops by Raman spectroscopy

An experimental apparatus combining Raman spectroscopy with acoustic levitation, Raman acoustic levitation spectroscopy (RALS), is investigated in the field of physical and chemical analytics. Whereas acoustic levitation enables the contactless handling of microsized samples, Raman spectroscopy offers the advantage of a noninvasive method without complex sample preparation. After carrying out some systematic tests to probe the sensitivity of the technique to drop size, shape, and position, RALS has been successfully applied in monitoring sample dilution and preconcentration, evaporation, crystallization, an acid–base reaction, and analytes in a surface-enhanced Raman spectroscopy colloidal suspension

A gallium-based magnetocaloric liquid metal ferrofluid

We demonstrate a magnetocaloric ferrofluid based on a gadolinium saturated liquid metal matrix, using a gallium-based liquid metal alloy as the solvent and suspension medium. The material is liquid at room temperature, while exhibiting spontaneous magnetization and a large magnetocaloric effect. The magnetic properties were attributed to the formation of gadolinium nanoparticles suspended within the liquid gallium alloy, which acts as a reaction solvent during the nanoparticle synthesis. High nanoparticle weight fractions exceeding 2% could be suspended within the liquid metal matrix. The liquid metal ferrofluid shows promise for magnetocaloric cooling due to its high thermal conductivity and its liquid nature. Magnetic and thermoanalytic characterizations reveal that the developed material remains liquid within the temperature window required for domestic refrigeration purposes, which enables future fluidic magnetocaloric devices. Additionally, the observed formation of nanometer-sized metallic particles within the supersaturated liquid metal solution has general implications for chemical synthesis and provides a new synthetic pathway toward metallic nanoparticles based on highly reactive rare earth metals

Which patients are not included in the English Cancer Waiting Times monitoring dataset, 2009-2013? Implications for use of the data in research.

BACKGROUND: Cancer waiting time targets are routinely monitored in England, but the Cancer Waiting Times monitoring dataset (CWT) does not include all eligible patients, introducing scope for bias. METHODS: Data from adults diagnosed in England (2009-2013) with colorectal, lung, or ovarian cancer were linked from CWT to cancer registry, mortality, and Hospital Episode Statistics data. We present demographic characteristics and net survival for patients who were and were not included in CWT. RESULTS: A CWT record was found for 82% of colorectal, 76% of lung, and 77% of ovarian cancer patients. Patients not recorded in CWT were more likely to be in the youngest or oldest age groups, have more comorbidities, have been diagnosed through emergency presentation, have late or missing stage, and have much poorer survival. CONCLUSIONS: Researchers and policy-makers should be aware of the limitations in the completeness and representativeness of CWT, and draw conclusions with appropriate caution

Nickel Phosphides Electrodeposited on TiO2 Nanotube Arrays as Electrocatalysts for Hydrogen Evolution

Nickel phosphide (NiPx)-based nanocomposites emerged as a new class of highly promising non-noble-metal-based electrocatalysts for hydrogen evolution reactions (HER). However, conventional synthesis for this type of nanocomposite involves using harsh organic solvents and multiple complicated procedures as well as the release of concomitant toxic gases, thus significantly restricting their practical applications. To explore a much greener and more sustainable synthesis approach, a facile one-step electrodeposition technique for nanoelectrode toward HER is developed in this research, in which amorphous NiPx is anchored onto TiO2 nanotube arrays to form a nanocomposite material. The synthesized nanocomposites have a synergistic coupling of material properties in two components of the nanocomposites, with an enhanced charge transfer and electrochemically active surface areas. Because of such unique characteristics, the system exhibits a remarkable catalytic reduction activity and superior stability in alkaline electrolytes, requiring overpotentials of 104 and 129 mV to achieve current densities of 10 and 20 mA cm-2, respectively. This method provides an effective and green approach to fabricate NiPx-based nanocomposites with enhanced HER performances

Dual selective gas sensing characteristics of 2D α-MoO3x via a facile transfer process

Metal oxide-based gas sensor technology is promising due to their practical applications in toxic and hazardous gas detection. Orthorhombic α-MoO3 is a planar metal oxide with a unique layered structure, which can be obtained in a two-dimensional (2D) form. In the 2D form, the larger surface area-to-volume ratio of the material facilitates significantly higher interaction with gas molecules while exhibiting exceptional transport properties. The presence of oxygen vacancies results in nonstoichiometric MoO3 (MoO3-x), which further enhances the charge carrier mobility. Here, we study dual gas sensing characteristics and mechanism of 2D α-MoO3-x. Herein, conductometric dual gas sensors based on chemical vapor deposited 2D α-MoO3-x are developed and demonstrated. A facile transfer process is established to integrate the material into any arbitrary substrate. The sensors show high selectivity toward NO2 and H2S gases with response and recovery rates of 295.0 and 276.0 kω/s toward NO2 and 28.5 and 48.0 kω/s toward H2S, respectively. These gas sensors also show excellent cyclic endurance with a variation in δR ∼112 ± 1.64 and 19.5 ± 1.13 Mω for NO2 and H2S, respectively. As such, this work presents the viability of planar 2D α-MoO3-x as a dual selective gas sensor