Gate-Tunable Electronic Structure of Black Phosphorus/HfS₂ P–N van der Waals Heterostructure with Uniformly Anisotropic Band Dispersion

Black phosphorus (BP)-based heterostructure with tunable band offset has been proven to be promising for rectifier diode and photoelectronic devices. However, it is usually not easy to find a suitable material to construct the heterojunction because the necessary type-II band structure and the strong unintentional p-type doping of BP should be both considered. Therefore, most of studies mainly focused on certain 2D materials, like MoS₂ and WSe₂. However, the low mobility of these materials greatly hinders the further promotion of device performance. For the first time, we demonstrate that HfS₂, which has been proven to possess a much higher mobility of electrons and has been experimentally synthesized recently, fully satisfies conditions of heterostructure with BP. The heterojunction could be used as a tunable optoelectronic device and rectifier diode. With external normal electric field, the efficiency of photon-generated charge separation and rectification ratio could be manipulated. In addition, what is interesting is that the nanostructure presents an unexpected highly anisotropic band dispersion along orthogonal directions, which suggests a superior transport performance with both high mobility and carrier density

Gate-Tunable Electronic Structure of Black Phosphorus/HfS₂ P–N van der Waals Heterostructure with Uniformly Anisotropic Band Dispersion

Black phosphorus (BP)-based heterostructure with tunable band offset has been proven to be promising for rectifier diode and photoelectronic devices. However, it is usually not easy to find a suitable material to construct the heterojunction because the necessary type-II band structure and the strong unintentional p-type doping of BP should be both considered. Therefore, most of studies mainly focused on certain 2D materials, like MoS₂ and WSe₂. However, the low mobility of these materials greatly hinders the further promotion of device performance. For the first time, we demonstrate that HfS₂, which has been proven to possess a much higher mobility of electrons and has been experimentally synthesized recently, fully satisfies conditions of heterostructure with BP. The heterojunction could be used as a tunable optoelectronic device and rectifier diode. With external normal electric field, the efficiency of photon-generated charge separation and rectification ratio could be manipulated. In addition, what is interesting is that the nanostructure presents an unexpected highly anisotropic band dispersion along orthogonal directions, which suggests a superior transport performance with both high mobility and carrier density

Quantitative Determination of Bulk Molecular Concentrations of β‑Agonists in Pork Tissue Samples by Direct Internal Extractive Electrospray Ionization-Mass Spectrometry

Rapid quantitative determination of bulk molecular concentration in solid samples without sample pretreatment is demonstrated using the internal extractive electrospray ionization-mass spectrometry (iEESI-MS) analysis of six β-agonists, including salbutamol (Sal), clenbuterol (Cle), ractopamine (Rac), terbutaline (Ter), tulobuterol (Tul), brombuterol (Bro), in pork tissue samples. Single sample analysis only required 1 min. The linear range of detection was about 0.01–1000 μg/kg (<i>R</i>² > 0.9994). The limit-of-detection (LOD) varied from 0.002 μg/kg for Sal to 0.006 μg/kg for Tul. Relative standard deviation (RSD) of quantitation was in the range 6.5–11.3%. The analytical results were validated by gas chromatography–mass spectrometry (GC–MS) and high-performance liquid chromatography–mass spectrometry (LC–MS), showing the accuracy rates of 92–105%. The current study extends the power of ambient MS as a method for the quantification of molecules at the surface of solid samples (e.g., in μg/cm² units) toward the quantification of molecules in bulk sample volume (i.e., in μg/kg units), which is commonly required in food safety control, biomedical analysis, public security, and many other disciplines

Yellow Luminescence of Polar and Nonpolar GaN Nanowires on <i>r</i>‑Plane Sapphire by Metal Organic Chemical Vapor Deposition

We have grown horizontal oriented, high growth rate, well-aligned polar (0001) single crystalline GaN nanowires and high-density and highly aligned GaN nonpolar (11–20) nanowires on <i>r</i>-plane substrates by metal organic chemical vapor deposition. It can be found that the polar nanowires showed a strong yellow luminescence (YL) intensity compared with the nonpolar nanowires. The different trends of the incorporation of carbon in the polar, nonpolar, and semipolar GaN associated with the atom bonding structure were discussed and proved by energy-dispersive X-ray spectroscopy, suggesting that C-involved defects are the origin responsible for the YL in GaN nanowires