Synthesis and properties of nanocrystalline π-SnS – a new cubic phase of tin sulphide†
We report on the synthesis of the newly discovered cubic phase of tin sulfide π-SnS and compare its properties to the well-known phase of tin sulfide, α-SnS. Shape control was achieved by the variation of synthesis parameters, resulting in cubic, rhombic dodecahedral and tetrahedral shapes of the π-SnS nanoparticles. X-ray diffraction provided authentication of the proposed model and refined determination of the lattice parameter a = 11.595 Å. Raman spectroscopy showed a substantial shift towards higher energies and peak splitting for π-SnS. Optical absorption spectroscopy indicated an indirect band gap of 1.53 eV, in good agreement with density functional theory (DFT) calculations indicating a band gap greater than that of α-SnS. DFT total energy calculations show that the π-SnS phase is energetically similar to α-SnS, and is significantly more stable than the hypothetical ideal rocksalt structure of SnS.