Synergistic photothermal conversion and photocatalysis in 2D/2D MXene/Bi2S3 hybrids for efficient solar-driven water purification.

Plasmonic hybrids are regarded as promising candidates for water purification due to their structure-dependent photocatalysis and photothermal performance. It remains a challenge to develop materials that possess these two characteristics for efficient water purification. Herein, plasmonic Ti3C2Tx/Bi2S3 two-dimensional (2D)/2D hybrids were prepared for efficient solar-driven water purification via the combination of photothermal conversion and photocatalysis. Benefitting from broad light absorption, large 2D/2D interfaces, and efficient charge transfer, the binary hybrids showed high-efficiency photothermal conversion and photothermal-assisted photocatalytic activity. By depositing these 2D/2D hybrids on a hydrophilic and porous cotton piece, the Ti3C2Tx/Bi2S3 membrane displayed a high water evaporation rate and solar-to-vapor efficiency under one-sun irradiation. The solar-driven evaporation of seawater, heavy metal ion solution, and dye solution jointly indicated that the plasmonic membrane shows great potential for drinkable water generation and industrial wastewater treatment. Most importantly, the synergistic effect of photothermal evaporation and photocatalysis of the Ti3C2Tx/Bi2S3 membrane on water purification was demonstrated. The polluted water can not only be treated by evaporation, but also be degraded via photocatalysis under solar light irradiation. This work provides new insight into designing functional materials for water purification based on the combination of photothermal conversion and photocatalysis.

Plasmon Coupling and Efficient Charge Transfer in Rough-Surfaced Au Nanotriangles/MXene Hybrids as an Ultrasensitive Surface-Enhanced Raman Scattering Platform.

The rational design of Raman substrate materials with prominent electromagnetic enhancement and charge transfer is quite important for surface-enhanced Raman scattering (SERS). Herein, an efficient SERS substrate based on two-dimensional ultrathin Ti3C2T x MXene and rough-surfaced Au nanotriangles (NTs) was successfully prepared for efficient detection of organic molecules due to the synthetic effect of an optimized electromagnetic field and charge transfer. Uniform Au NTs with tunable surface roughness were controllably prepared by selectively depositing of Au on the smooth Au NTs. Due to the large surface area, tunable plasmon resonance, and abundant hotspots on the planar surface, the modified Au NTs showed much better SERS performance than initial Au NTs. By combination of the rough-surfaced Au NTs with MXene, the Ti3C2T x /Au NT hybrids exhibited much better SERS performance than initial Au NTs and Au NTs with a rough surface. The detection limit is down to 10-12 M, and the analytical enhancement factors reach 3.6 × 109 (at 1174 cm-1) on detecting crystal violet excited at 785 nm. This is because the strong plasmon coupling between the in-plane resonance of Au NTs and transversal plasmon resonance of Ti3C2T x MXene around 785 nm can generate an intense interfacial electromagnetic field for amplifying SERS signals. Additionally, the efficient charge transfer between Au NTs, MXene, and molecules also plays an important role in enhancing the SERS performance. This work presents a new insight to develop high-performance SERS substrates based on plasmon.

Plasmon-Mediated 2D/2D Phase Junction for Improved Photocatalytic Hydrogen Generation Activity.

A phase junction fabricated by two crystalline phases of the same semiconductor is a promising photocatalyst with efficient charge transfer and separation. However, the weak light absorption and uncontrolled phase junction interface limit the generation and separation of photogenerated carriers. Herein, a two-dimensional (2D)/2D phase junction was prepared by growing orthorhombic WO3 ultrathin nanosheets on hexagonal WO3 nanosheets through a one-step hydrothermal method. The orthorhombic/hexagonal WO3 possesses large-area phase junction interfaces, rich reactive sites, and built-in electric field, which greatly accelerate the photogenerated charge separation and transfer. Thus, the orthorhombic/hexagonal WO3 displayed excellent photocatalytic hydrogen generation activity from water splitting under light irradiation (λ > 420 nm), which is 2.16 and 2.85 times those of orthorhombic and hexagonal WO3 phase components. Furthermore, Au nanoparticles (about 4.5 nm in diameter) were deposited on both orthorhombic and hexagonal WO3 nanosheets to form a plasmon-mediated phase junction. The hybrids exhibit prominent visible-light absorption and efficient charge transfer, leading to a further improved photocatalytic hydrogen generation activity. Further characterization studies demonstrate that superior photoactivity arises from the excellent visible-light-harvesting ability, appropriate band structure, and high-efficiency and multichannel transferring processes of photogenerated carriers.