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Controlling the crystal phase in layered transition metal dichalcogenides (TMDs) is critical for their diverse, flexible applications. However, due to the thermodynamic stability of 2H over other polymorphs, fine synthesis control over polymorphism in TMDs is challenging, restricting the entire range of characteristics associated with other polymorphs. Herein, we present a solution-based crystal phase engineering approach for layered transition metal disulphide nanosheets by modulating the reactivity of the molecular precursors. By tuning precursor–ligand chemistry, 2H, 1T′ and polytypic MoS2 and WS2 are synthesised. The flexibility to selectively modify the reactivity of S and metal precursors allowed control over the proportion of specific phases in synthesised nanosheets. The formation of 1T′ is facilitated by the highly reactive metal and S source, whereas less reactive sources lead to the formation of thermodynamically stable 2H. The electrocatalytic properties of the synthesised TMDs were examined for the oxygen reduction reaction. The polytypic MoS2 comprising a mix of 2H–1T′ displayed the most positive potential of 0.82 V (vs. RHE). The comprehensive mechanistic interpretation of the chemical transformations provided in this study will be instrumental in designing scalable solution-based pathways for phase engineering in layered transition metal dichalcogenides. Furthermore, this synthesis approach has the potential to be extended to various TMD compositions, enabling exquisite control over polymorphism in TMDs. [ABSTRACT FROM AUTHOR]

Multifunctional multinary metal chalcogenides have long been a research hotspot in the field of materials chemistry due to their rich composition, flexible structure, excellent properties and wide range of applications. However, the exploration of complex quinary chalcogenides is still challenging. In this work, for the first time, we have developed the controlled synthesis of quinary Cu3NiInSnS6 nanocrystals, realizing the selective preparation of hexagonal wurtzite and cubic zinc blende metastable phases by simply tuning the sulfur source. The phase structure analysis reveals that both metastable phases possess a disordered structure with a random distribution of metal atoms in the unit cells. The fabricated wurtzite and zinc blende-structure Cu3NiInSnS6 nanocrystals have a direct band gap of 1.82 and 1.94 eV, respectively, and both exhibit superparamagnetic behavior at low temperatures. This work is of great significance for the development of novel multifunctional materials based on metastable multinary metal chalcogenide phases. [ABSTRACT FROM AUTHOR]

Hollow polycrystalline structures and noble-metal-coating endow ternary sulfides with promising light absorption and electrical properties for solar energy conversion applications. We developed a facile one-pot solvothermal chemical route to synthesize hollow Cu3SbS4 microspheres with an opening. Additionally, four phase-pure Cu–Sb–S high-quality nanocrystals can be produced in a selectable way by the same route. The detailed evolution process and self-driven breakage mechanism have been proposed in detail. Subsequently, in situ reduction of the Ag-ion precursor was conducted and Ag clusters were uniformly deposited in the hollow spherical architecture with a nanoparticle-textured surface and interior to mitigate the oxidization of Cu3SbS4 nanoparticles. The created hollow metal-semiconductor nanocomposite opens up a favorable new situation. The nanocomposites exhibited a remarkably enhanced absorption of over 2 × 105 cm−1, covering the UV and visible regions of the electromagnetic spectrum. The electrical resistivity decreased drastically by 90% after the coating of noble metals. A reduction in the bandgap energy after the addition of Ag to Cu3SbS4 was confirmed from extrapolated optical results and theoretical calculation validation. The synthetic effect of hollow structures and nanocomposites results in the superior performance of Cu–Sb–S compounds, thus highlighting their potential applications in light absorbers and energy conversion technologies. [ABSTRACT FROM AUTHOR]