Noncovalent Functionalization of Black Phosphorus

Black phosphorus (BP) was functionalized with organic moieties on the basis of liquid exfoliation. The treatment of BP with electron‐withdrawing 7,7,8,8‐tetracyano‐p‐quinodimethane (TCNQ) led to electron transfer from BP to the organic dopant. On the other hand, the noncovalent interaction of BP with a perylene diimide was mainly due to van der Waals interactions but also led to considerable stabilization of the BP flakes against oxygen degradation.     

The Covalent Functionalization of Layered Black Phosphorus by Nucleophilic Reagents

Layered black phosphorus has been attracting great attention due to its interesting material properties which lead to a plethora of proposed applications. Several approaches are demonstrated here for covalent chemical modifications of layered black phosphorus in order to form P−C and P‐O‐C bonds. Nucleophilic reagents are highly effective for chemical modification of black phosphorus. Further derivatization approaches investigated were based on radical reactions. These reagents are not as effective as nucleophilic reagents for the surface covalent modification of black phosphorus. The influence of covalent modification on the electronic structure of black phosphorus was investigated using ab initio calculations. Covalent modification exerts a strong effect on the electronic structure including the change of band‐gap width and spin polarization.     

Noncovalent Functionalization of Few-Layered Antimonene with Fullerene Clusters and Photoinduced Charge Separation in the Composite

Few-layered antimonene (FLSb) nanosheets were noncovalently functionalized with fullerene C₆₀ clusters by quick addition of a poor solvent (i.e., acetonitrile) into a mixed dispersion of FLSb and C₆₀ in a good solvent (i.e., toluene). In a flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurement, the FLSb-C₆₀ composite, (FLSb+C₆₀)_m, showed a rapid rise in transient conductivity, whereas no conductivity signal was observed in the single components, FLSb and C₆₀. This demonstrated the occurrence of photoinduced charge separation between FLSb and C₆₀ in (FLSb+C₆₀)_m. Furthermore, a photoelectrochemical device with an electrophoretically deposited (FLSb+C₆₀)_m film exhibited an enhanced efficiency of photocurrent generation, compared to those of the single-components, FLSb and C₆₀, due to the photoinduced charge separation between FLSb and C₆₀. This work provides a promising approach for fabrication of antimonene–organic molecule composites and paves the way for their application in optoelectronics.     

Water‐Catalyzed Oxidation of Few‐Layer Black Phosphorous in a Dark Environment

Black phosphorus (BP) shows great potential in electronic and optoelectronic devices owing to its semiconducting properties, such as thickness‐dependent direct bandgap and ambipolar transport characteristics. However, the poor stability of BP in air seriously limits its practical applications. To develop effective schemes to protect BP, it is crucial to reveal the degradation mechanism under various environments. To date, it is generally accepted that BP degrades in air via light‐induced oxidation. Herein, we report a new degradation channel via water‐catalyzed oxidation of BP in the dark. When oxygen co‐adsorbs with highly polarized water molecules on BP surface, the polarization effect of water can significantly lower the energy levels of oxygen (i.e. enhanced electron affinity), thereby facilitating the electron transfer from BP to oxygen to trigger the BP oxidation even in the dark environment. This new degradation mechanism lays important foundation for the development of proper protecting schemes in black phosphorus‐based devices.     

PbS/CdS Core–Shell Quantum Dots Suppress Charge Transfer and Enhance Triplet Transfer

A sub‐monolayer CdS shell on PbS quantum dots (QDs) enhances triplet energy transfer (TET) by suppressing competitive charge transfer from QDs to molecules. The CdS shell increases the linear photon upconversion quantum yield (QY) from 3.5 % for PbS QDs to 5.0 % for PbS/CdS QDs when functionalized with a tetracene acceptor, 5‐CT . While transient absorption spectroscopy reveals that both PbS and PbS/CdS QDs show the formation of the 5‐CT triplet (with rates of 5.91±0.60 ns⁻¹ and 1.03±0.09 ns⁻¹ respectively), ultrafast hole transfer occurs only from PbS QDs to 5‐CT . Although the CdS shell decreases the TET rate, it enhances TET efficiency from 60.3±6.1 % to 71.8±6.2 % by suppressing hole transfer. Furthermore, the CdS shell prolongs the lifetime of the 5‐CT triplet and thus enhances TET from 5‐CT to the rubrene emitter, further bolstering the upconverison QY.