Polarization conversion in bottom-up grown quasi-1D fibrous red phosphorus flakes.

Fibrous red phosphorus (RP) has triggered growing attention as an emerging quasi-one-dimensional (quasi-1D) van der Waals crystal recently. Unfortunately, it is difficult to achieve substrate growth of high-quality fibrous RP flakes due to their inherent quasi-1D structure, which impedes their fundamental property exploration and device integration. Herein, we demonstrate a bottom-up approach for the growth of fibrous RP flakes with (001)-preferred orientation via a chemical vapor transport (CVT) reaction in the P/Sn/I2 system. The formation of fibrous RP flakes can be attributed to the synergistic effect of Sn-mediated P4 partial pressure and the SnI2 capping layer-directed growth. Moreover, we investigate the optical anisotropy of the as-grown flakes, demonstrating their potential application as micro phase retarders in polarization conversion. Our developed bottom-up approach lays the foundation for studying the anisotropy and device integration of fibrous red phosphorus, opening up possibilities for the two-dimensional growth of quasi-1D van der Waals materials.

Unveiling the Degradation Chemistry of Fibrous Red Phosphorus under Ambient Conditions.

The practical applications of fibrous red phosphorus (FRP), an emerging quasi-one-dimensional material, might be hindered by its environmental instability. Although other phosphorus allotropes such as white phosphorus, violet phosphorus, and black phosphorus are reported unstable under ambient conditions, the chemical stability of FRP remains unexplored. Herein, we investigate the degradation chemistry of FRP by combining experimental study and density functional theory calculations. The results reveal that both oxygen and water can react with FRP, while light illumination may accelerate these reactions. Furthermore, the degradation behavior of FRP shows a pseudo-first-order reaction in oxygenated water, while it follows a pseudo-zero-order reaction in deoxygenated water. Such different reaction kinetics originates from the preferable dissociative adsorption behaviors of O2 molecular and H2O molecular on a FRP surface or at a FRP edge. A covalent modification approach using an aryl diazonium salt was adopted to passivate the surface of FRP flakes and significantly enhance their stability in air.

Uniform Tellurium Doping in Black Phosphorus Single Crystals by Chemical Vapor Transport.

Doping has been a reliable way to improve the properties of black phosphorus (BP). However, a uniform and large amount of doping in BP remains a challenge. Herein, the synthesis of tellurium-doped black phosphorus (Te-doped BP) single crystals with high crystalline quality is achieved by the chemical vapor transport reaction method. The synthetic route enables a uniform and relatively large amount (up to 0.5% atomic ratio) of Te-doping in BP single crystals. The electrocatalytic oxygen evolution reaction (OER) properties of few-layer Te-doped BP nanosheets prepared by liquid exfoliation were also investigated for the first time. Electrochemical tests demonstrated that the OER onset-potential of undoped and Te-doped BP nanosheets was 1.63 and 1.49 V, respectively. The result implies that doping provides an effective route to enhance the electrochemical OER performance of BP.