A new approach for the synthesis of layered niobium sulfide and restacking route of NbS2 nanosheet

We have developed a new process for the synthesis of a layered niobium sulfide that involves heating K4Nb6O17·3H2O with a H2S/N2 gas mixture. It was confirmed that heating the starting layered oxide at 750 °C for 10 h under the gas flow yielded a highly crystalline, single-phase K0.34(H2O)0.7NbS2. The layered sulfide slabs had a large plate-like shape. Potassium ions in the interlayer of K0.34(H2O)0.7NbS2 could be exchanged with protons by stirring in 2 M H2SO4. It was found that the proton in the proton-exchanged form can be easily exchanged with other cations. The proton-exchanged form was exfoliated into NbS2 nanosheets by ultrasonication in water. According to the atomic force microscopy (AFM) images, NbS2 nanosheets had a thickness of around 4 Å, which roughly corresponded to the thickness of a single NbS2 host layer. NbS2 nanosheets could be restacked with the intercalation of Eu3+ or tetrabutylammonium ions by an electrostatic self-assembly deposition (ESD) technique.