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Laser‐driven phase transition of 2D transition metal dichalcogenides has attracted much attention due to its high flexibility and rapidity. However, there are some limitations during the laser irradiation process, especially the unsatisfied surface ablation, the inability of nanoscale phase patterning, and the unexploited physical properties of new phase. In this work, the well‐controlled femtosecond (fs) laser‐driven transformation from the metallic 2M‐WS2 to the semiconducting 2H‐WS2 is reported, which is confirmed to be a single‐crystal to single‐crystal transition without layer thinning or obvious ablation. Moreover, a highly ordered 2H/2M nano‐periodic phase transition with a resolution of ≈435 nm is achieved, breaking through the existing size bottleneck of laser‐driven phase transition, which is attributed to the selective deposition of plasmon energy induced by fs laser. It is also demonstrated that the achieved 2H‐WS2 after laser irradiation contains rich sulfur vacancies, which exhibits highly competitive ammonia gas sensing performance, with a detection limit below 0.1 ppm and a fast response/recovery time of 43/67 s at room temperature. This study provides a new strategy for the preparation of the phase‐selective transition homojunction and high‐performance applications in electronics.

As a new clean energy source, the demands for and use of hydrogen fuel are rapidly increasing. Therefore, biohydrogen production technology is being developed to reduce operation costs in many countries. Improvement of biohydrogen production capacity and cost reduction are key factors to bring about industrial implementation. One of the most effective production methods is microbiological: the use of bacteria with high hydrogen-production capacity and performance. The anaerobic process of biohydrogen production was developed in the 1990s. The isolation and identification of highly efficient biohydrogen producing anaerobic bacteria is an important foundation for the fermentative production of hydrogen by anaerobic digestion of organic wastewater.

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