Auxetic and multiferroic MP5 (M = Al, Ga): a novel 2D material with negative Possion's ratio and high anisotropic carrier mobility.

In the field of materials science, the development of multifunctional 2D materials has been a long-standing research objective. In this study, we employ first-principles calculations to predict a novel 2D material named MP5 (M = Al, Ga), which exhibits ferroelasticity, ferroelectricity, negative Poisson's ratio, and high anisotropic carrier mobility. Our investigation reveals that a single layer of MP5 displays multiferroic behavior, wherein ferroelasticity and ferroelectricity are coupled. The remarkable structural anisotropy of MP5 enables easy switching between ferroelastic and ferroelectric states, rendering it suitable for nonvolatile memory applications. Simultaneously, monolayer AlP5 (GaP5) demonstrates a negative Poisson's ratio of -0.074 (-0.058) and a carrier mobility of up to 91 720 cm2 V-1 S-1 (99 690 cm2 V-1 S-1). These exceptional properties position monolayer MP5 as a highly versatile and promising 2D material for implementation in nanomechanical and microelectromechanical devices.

Two-dimensional ferroelasticity and negative Poisson's ratios in monolayer YbX (X = S, Se, Te).

Two-dimensional ferroelastic materials and two-dimensional materials with negative Poisson's ratios have attracted great interest. Here, using first-principles calculations, we reveal monolayer YbX (X = S, Se, Te) materials that harbor both ferroelasticity and negative Poisson's ratios. Indirect wide band gaps of about 3 eV have been found in these three materials. Mechanical analysis reveals that the three materials are flexible and they possess large in-plane negative Poisson's ratios from -0.114 to -0.366. Meanwhile, the ferroelasticity in the monolayer YbX shows moderate energy barriers and strong ferroelastic signals, beneficial for applications in shape memory devices. These intriguing properties make monolayer YbX promising candidate materials for applications in nanoelectronics and nanomechanics.

Trace-Level Sensing of Phosphate for Natural Soils by a Nano-Screen-Printed Electrode.

Phosphate as one of the most essential components of living systems, robust analytical techniques available for phosphate sensing in natural waters and soils are essential for monitoring and predicting water quality and agronomic evaluation of phosphate. Using cyclic voltammetry, a point-of-use electrochemical sensor zirconium dioxide/zinc oxide/multiple-wall carbon nanotubes/ammonium molybdate tetrahydrate/screen printed electrode (ZrO2/ZnO/MWCNTs/AMT/SPE) was applied to explore the electro-redox reaction of phosphomolybdate complexes on the surface of electrode, which produced a quantitative electrochemical response of phosphate anions. The modification of the electrode surface with ZrO2/ZnO/MWCNTs nanocomposites is able to generate the electroactive species via chemical reaction between molybdenum (Mo(VI)) and the targeted phosphate anions, leading to a sensitive detection technique for trace phosphate with a lower detection limit (LOD = 2.0 × 10-8 mol L-1), higher reproducibility, anti-interference, and precision in different soil sources. This system will be of great potential to advance the trace-level understanding of phosphate especially in field environmental analysis.