Intercalation of organic molecules into SnS2 single crystals

SnS2 is a layered semiconductor with a van der Waals gap separating the covalently bonded layers. In this study, post-synthesis intercalation of donor organic amine molecules, such as ethylenediamine (en), into tin disulfide and secondary intercalation of p-phenylenediamine (PPD) and 1, 5-naphthalenediamine (NDA) into SnS2_en have been verified with X-ray diffraction. PPD and NDA did not intercalate directly even during prolonged annealing but replaced en readily if en was already present in the van der Waals gap. The c-lattice dilation is proportional to the intercalant size. Unit cell lattices of intercalated products were determined from the positions of the X-ray diffraction peaks. Optical images taken during the intercalation showed that intercalation progressed from the periphery towards the interior of the crystal. TEM diffraction patterns in the [0 0 1] direction of SnS2 after intercalation revealed defects and stacking mismatches among the SnS2 layers caused by the intercalation. UV–Vis absorption studies showed a red shift in the band edge of the SnS2 material after intercalation. The band edge was 2.2 eV for pristine SnS2; after intercalation with en or PPD, the absorbance spectra band edges shifted to approximately 0.7 eV or 0.5 eV, respectively.

Graphical AbstractSnS2 single crystals were intercalated with organic amine molecules such as ethylenediamine, phenylenediamine and naphthalenediamine. Absorption studies showed red shift of band edge after intercalation, which was consistent with optical observations. X-ray diffraction indicated lattice dilation in the c-lattice of SnS2 after intercalation.Figure optionsDownload as PowerPoint slideHighlights
► Organic molecules intercalated inhomogenously between covalently bonded SnS2 layers.
► Ethylenediamine (en) intercalate directly into SnS2.
► Phenylenediamine (PPD) and naphthalenediamine (NDA) can be intercalated into SnS2 secondary.
► In a secondary intercalation the bonds between layers are weakened by direct intercalation of (en).
► The optical band gap of SnS2 is reduced due to intercalation.