A 2D-0D-2D Sandwich Heterostructure toward High-Performance Room-Temperature Gas Sensing.

The construction of two-dimensional (2D) van der Waals (vdW) heterostructures over black phosphorus (BP) has been attracting significant attention to better utilize its inherent properties. The sandwich of zero-dimensional (0D) noble metals within BP-based vdW heterostructures can provide efficient catalytic channels, modulating their surface redox potentials and therefore inducing versatile functionalities. Herein, we realize a 2D WS2-Au-BP heterostructure, in which Au nanoparticles are connected between BP and WS2 via ionic bonds. The ultralow conduction band minimum position, the reduced adsorption energies of O2, and the increased dissociation barrier energy of O2- into 2O contribute greatly to improving the long-term stability of BP in the air. The formation of heterostructures can reduce the potential barrier energy in target gas molecules, thus enhancing the absorption energy and charge transfer. Taking the paramagnetic NO2 gas molecules as a representative, a stable response magnitude of 2.11 to 100 ppb NO2 is achieved for 80 days, which is far larger than the initial responses of most BP-based materials. A practical gas sensing system is also developed to demonstrate its real-world implementation. This work provides a promising demonstration of 0D noble metal within 2D BP-based vdW heterostructure for simultaneously improving the long-term stability and room-temperature reversible gas sensing.

Quasi-one-dimensional phosphorene nanoribbons grown on silicon by space-confined chemical vapor transport.

Phosphorene nanoribbons (PNRs) combine the flexibility of one-dimensional (1D) nanomaterials with the large specific surface area and the edge and electron confinement effects of two-dimensional (2D) nanomaterials. In spite of the substantial advances in bulk black phosphorus (BP) manufacturing, achieving PNRs without degradation is still a big challenge. In this work, we present a strategy for the space-confined chemical vapor transport synthesis of quasi-one-dimensional surface-passivated monocrystalline PNRs on a silicon substrate. The growth mechanism of the PNRs is proposed by combining experimental results and DFT calculations, indicating that the P4 molecules can break, restructure, and epitaxially nucleate on the surface of the Au3SnP7 catalyst, and finally prefer to grow along the zigzag (ZZ) direction to form PNRs. The low gas flow rate and an appropriate phosphorus molecule concentration allow the growth of PNRs with structural integrity, which can be regulated by the amount of red phosphorus and the confined space.

High-Quality Black Phosphorus Quantum Dots Fabricated via Microwave-Tailored Technology.

Black phosphorus quantum dots (BPQDs) have recently obtained great attention due to their high mobility and tunable bandgap features, which are beneficial for their potential application in photoelectronic devices. However, a precise synthesis of high-quality BPQDs is still a great challenge owing to the formation of an impurity phase when employing traditional methods. Herein, we demonstrate the scalable fabrication of BPQDs from mineralization-derived bulk black phosphorus (BP) single crystals by means of a microwave (MW)-assisted liquid-phase exfoliation method in ethanol. The primary results demonstrate that ethanol plays a crucial role in determining the final properties of BPQDs, such as their excellent tolerance to oxygen, good crystallinity, and uniform size. Furthermore, the mechanism behind the formation of BPQDs is proposed, revealing that a layer-by-layer disintegration process of bulk BP crystals under microwave-energy stimuli is responsible. This work may provide a novel path for the further development of BPQDs and corresponding devices.