Synthesis, structure, and gelling power of gamma-In2S3 nanoribbons with large aspect ratio

We report the synthesis of ultrathin indium sulfide In2S3 nanoribbons (NR) which display a giant aspect ratio using a simple and fast solvothermal method. We show that these NR have a thickness controlled at the atomic level below the nanometer, a width of 8.7 +/- 0.1 nm and a length which can reach several micrometers. We determined the atomic composition of the inorganic core by Rutherford backscattering spectrometry (RBS) and measured by X-ray photoelectron spectrometry (XPS) an oleylamine surface coverage of 2.3 ligands per nm2. X-ray diffraction experiments and simulations as well as high-resolution dark-field STEM point towards a P3m1trigonal crystallographic structure (gamma phase). Their lateral dimensions can be tuned by the amount of water present in the reaction medium: anhydrous synthesis conditions lead to hexagonal nanoplates whereas controlled addition of water induces a symmetry break yielding long NR with a rectangular shape. Depending on the dispersion solvent, these long ribbon-like nanoparticles can form either well-dispersed colloids or bundles in which they stack face to face. Their large aspect ratio induces the formation of gels at volume fractions as low as 1.3x10-4.