Lithium enrichment of the magmatic-hydrothermal fluid in albite-spodumene pegmatite from Lijiagou, Eastern Tibetan Plateau: Evidence from fluid inclusions

Albite-spodumene pegmatites, which are remarkable resources of Li worldwide, may experience both magmatic-hydrothermal transition and sub-solidus hydrothermal alteration during their formation and evolution. However, fluids involved in the different stages of the evolution of a spodumene-bearing pegmatitic systems are not well defined, especially at the magmatic-hydrothermal transition stage. In the Lijiagou deposit, western Sichuan Province, fluid inclusions of a typical albite-spodumene pegmatite were studied to determine the degree of magmatic-hydrothermal fluid Li enrichment and the potential for lithium mineral crystallization at the magmatic-hydrothermal transition stage. Micro-petrographic analyses identified different types of fluid inclusions of either primary, pseudo-secondary or secondary origin and inclusions containing devitrified silicate glass. The presence of these inclusions suggests that the pegmatite underwent both the magmatic-hydrothermal transition stage and a post-crystallization hydrothermal process over its evolution. The results of fluid inclusion LA-ICP-MS analyses show that the aqueous ± carbonic fluids represented by the pseudo-secondary type 1a and 1b inclusions carry significant amount of Li, with Na and Li predominating the cation budget of these pegmatitic fluids. The aqueous ± carbonic fluids exhibit typical magmatic-hydrothermal fluid compositional characteristics and exhibit high abundance of Li in this pegmatitic system at the magmatic-hydrothermal transition stage. The relative abundance of Li to Na and K lies within the uppermost range of those reported from lithium-cesium-tantalum pegmatite systems. This is consistent with the elevated incorporation of Li in pegmatitic quartz from the albite-spodumene pegmatite. The compositional characteristics of the fluids at the magmatic-hydrothermal transition stage may be used to imply the Li mineralization potential of the pegmatitic system

Thermodynamic Origins of Structural Metastability in Two-Dimensional Black Arsenic

Two-dimensional (2D) materials have aroused considerable research interests owing to their potential applications in nanoelectronics and optoelectronics. Thermodynamic stability of 2D structures inevitably affects the performance and power consumption of the fabricated nanodevices. Black arsenic (b-As), as a cousin of black phosphorus, has presented the extremely high anisotropy in physical properties. However, the systematic research on structural stability of b-As is still lack. Herein, we demonstrated the detailed analysis on structural metastability of the natural b-As, and determined its existence conditions in terms of two essential thermodynamic variables as hydrostatic pressure and temperature. Our results confirmed that b-As can only survive below 0.7 GPa, and then irreversibly transform to gray arsenic, in consistent with our theoretical calculations. Furthermore, thermal annealing strategy was developed to precisely control the thickness of b-As flake, and it sublimates at 300 oC. These results could pave the way for 2D b-As in many promising applications.Comment: 28 pages, 4 figure

Pressurizing Field-Effect Transistors of Few-Layer MoS2 in a Diamond Anvil Cell

Hydrostatic pressure applied using diamond anvil cells (DAC) has been widely explored to modulate physical properties of materials by tuning their lattice degree of freedom. Independently, electrical field is able to tune the electronic degree of freedom of functional materials via, for example, the field-effect transistor (FET) configuration. Combining these two orthogonal approaches would allow discovery of new physical properties and phases going beyond the known phase space. Such experiments are, however, technically challenging and have not been demonstrated. Herein, we report a feasible strategy to prepare and measure FETs in a DAC by lithographically patterning the nanodevices onto the diamond culet. Multiple-terminal FETs were fabricated in the DAC using few-layer MoS2 and BN as the channel semiconductor and dielectric layer, respectively. It is found that the mobility, conductance, carrier concentration, and contact conductance of MoS2 can all be significantly enhanced with pressure. We expect that the approach could enable unprecedented ways to explore new phases and properties of materials under coupled mechano-electrostatic modulation.Comment: 15 pages, 5 figure

Experimental observation of highly anisotropic elastic properties of two-dimensional black arsenic

Anisotropic two-dimensional layered materials with low-symmetric lattices have attracted increasing attention due to their unique orientation-dependent mechanical properties. Black arsenic (b-As), with the puckered structure, exhibits extreme in-plane anisotropy in optical, electrical and thermal properties. However, experimental research on mechanical properties of b-As is very rare, although theoretical calculations predicted the exotic elastic properties of b-As, such as anisotropic Young's modulus and negative Poisson's ratio. Herein, experimental observations on highly anisotropic elastic properties of b-As were demonstrated using our developed in situ tensile straining setup based on the effective microelectromechanical system. The cyclic and repeatable load-displacement curves proved that Young's modulus along zigzag direction was ~1.6 times greater than that along armchair direction, while the anisotropic ratio of ultimate strain reached ~2.5, attributed to hinge structure in armchair direction. This study could provide significant insights to design novel anisotropic materials and explore their potential applications in nanomechanics and nanodevices.Comment: 19 pages, 5 figure

Highly Anisotropic Elastic Properties of Suspended Black Arsenic Nanoribbons

Anisotropy, as an exotic degree of freedom, enables us to discover the emergent two-dimensional (2D) layered nanomaterials with low in-plane symmetry and to explore their outstanding properties and promising applications. 2D black arsenic (b-As) with puckered structure has garnered increasing attention these years owing to its extreme anisotropy with respect to the electrical, thermal, and optical properties. However, the investigation on mechanical properties of 2D b-As is still lacking, despite much effort on theoretical simulations. Herein, we report the highly anisotropic elastic properties of suspended b-As nanoribbons via atomic force microscope-based nanoindentation. It was found that the extracted Young's modulus of b-As nanoribbons exhibits remarkable anisotropy, which approximates to 72.2 +- 5.4 and 44.3 +- 1.4 GPa along zigzag and armchair directions, respectively. The anisotropic ratio reaches up to ~ 1.6. We expect that these results could lay a solid foundation for the potential applications of 2D anisotropic nanomaterials in the next-generation nanomechanics and optoelectronics.Comment: 17 pages, 5 figure

Quantitative urinalysis using aggregation-induced emission bioprobes for monitoring chronic kidney disease

Open Access Article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Early detection and appropriate management of chronic kidney disease can reduce the progression of kidney failure and cardiovascular disease. The urine albumin to creatinine ratio (UACR) test is a standard urine test for identifying individuals at high risk of developing progressive kidney disease. In this study, IDATPE, a novel fluorescent probe with aggregation-induced emission (AIE) features, is successfully developed for creatinine detection and quantitation. An excellent correlation between fluorescent light intensity and creatinine concentration is achieved. In addition, BSPOTPE, a reported excellent AIE bioprobe for human serum albumin (HSA) quantitation, is used together with IDATPE in artificial urine for UACR testing. The mutual interference of HSA and creatinine when the bioprobes are used for quantitation is characterised, with promising results. Further improvements and potential applications in CKD quantitation are highlighted

Phase-Modulated Elastic Properties of Two-Dimensional Magnetic FeTe: Hexagonal and Tetragonal Polymorphs

Two-dimensional (2D) layered magnets, such as iron chalcogenides, have emerged these years as a new family of unconventional superconductor and provided the key insights to understand the phonon-electron interaction and pairing mechanism. Their mechanical properties are of strategic importance for the potential applications in spintronics and optoelectronics. However, there is still lack of efficient approach to tune the elastic modulus despite the extensive studies. Herein, we report the modulated elastic modulus of 2D magnetic FeTe and its thickness-dependence via phase engineering. The grown 2D FeTe by chemical vapor deposition can present various polymorphs, i.e. tetragonal FeTe (t-FeTe, antiferromagnetic) and hexagonal FeTe (h-FeTe, ferromagnetic). The measured Young's modulus of t-FeTe by nanoindentation method showed an obvious thickness-dependence, from 290.9+-9.2 to 113.0+-8.7 GPa when the thicknesses increased from 13.2 to 42.5 nm, respectively. In comparison, the elastic modulus of h-FeTe remains unchanged. Our results could shed light on the efficient modulation of mechanical properties of 2D magnetic materials and pave the avenues for their practical applications in nanodevices.Comment: 19 pages, 4 figure

Pressure-Temperature Phase Diagram of Vanadium Dioxide

The complexity of strongly correlated electron physics in vanadium dioxide is exemplified as its rich phase diagrams of all kinds, which in turn shed light on the mechanisms behind its various phase transitions. In this work, we map out the hydrostatic pressure - temperature phase diagram of vanadium dioxide nanobeams by independently varying pressure and temperature with a diamond anvil cell. In addition to the well-known insulating M1 (monoclinic) and metallic R (tetragonal) phases, the diagram identifies the existence at high pressures of the insulating M1' (monoclinic, more conductive than M1) phase, and two metallic phases of X (monoclinic) and O (orthorhombic, at high temperature only). Systematic optical and electrical measurements combined with density functional calculations allow us to delineate their phase boundaries as well as reveal some basic features of the transitions.Comment: 9 pages, 4 figure