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 K{sub 4}Nb{sub 6}O{sub 17}.3H{sub 2}O with a H{sub 2}S/N{sub 2} gas mixture. It was confirmed that heating the starting layered oxide at 750 deg. C for 10 h under the gas flow yielded a highly crystalline, single-phase K{sub 0.34}(H{sub 2}O){sub 0.7}NbS{sub 2}. The layered sulfide slabs had a large plate-like shape. Potassium ions in the interlayer of K{sub 0.34}(H{sub 2}O){sub 0.7}NbS{sub 2} could be exchanged with protons by stirring in 2 M H{sub 2}SO{sub 4}. 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 NbS{sub 2} nanosheets by ultrasonication in water. According to the atomic force microscopy (AFM) images, NbS{sub 2} nanosheets had a thickness of around 4 A, which roughly corresponded to the thickness of a single NbS{sub 2} host layer. NbS{sub 2} nanosheets could be restacked with the intercalation of Eu{sup 3+} or tetrabutylammonium ions by an electrostatic self-assembly deposition (ESD) technique. - Graphical abstract: Potassium-intercalated layered niobium sulfide has been synthesized by heating a corresponding layered niobate in a H{sub 2}S/N{sub 2} mixture gas. Proton-exchanged layeredmore » niobium sulfide has been exfoliated into NbS{sub 2} mono-nanosheet. The NbS{sub 2} mono-nanosheet was restacked with cationic species by an electrostatic self-assembly deposition.« less