Single-crystal SnSe 2 nanosheets with a ten atomic-layer thickness have been prepared by a facile solvothermal route reaction in benzyl alcohol in the presence of PVP. Benzyl alcohol acts as the solvent and reducing reagent to promote the formation of the hexagonal phase of SnSe 2 , and the presence of PVP provides a stable environment for the construction of the SnSe 2 nanosheets. A reasonable formation mechanism was put forward on the basis of the time-dependent experiments. The obtained SnSe 2 nanosheets displayed an enhanced photocurrent compared to the thick SnSe 2 nanoplates, which indicated potential applications in photodetectors, photovoltaic devices and so forth.

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The transformation mechanisms of thiourea in ethylene glycol solution was systematically investigated in this report, which shows the transformation process is influenced by the anion (NO 3− , Cl − , Br − ) and polyvinylpyrrolidone (PVP). Thiourea (tu) isomerizes into ammonium thiocyanate when NO 3− is present, regardless of the existence of PVP. For Cl − , thiourea coordinates with copper anion to form [Cu(tu)]Cl•1/2H 2 O complex whether PVP is present. When it comes to Br − , thiourea hydrolyzes in the cooperation of PVP or coordinates with copper anion to form [Cu(tu)Br]•1/2H 2 O complex without PVP. The different transformation routes will lead to different phase evolution of the Cu-S system. This work may provide a new understanding of the transformation of thiourea in ethylene glycol solution. The optical properties of the as-prepared copper sulfides exhibit significant stoichiometrydependent features which may have potential applications in semiconductor photovoltaic devices.

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