Layer-by-Layer Sorting of Rhenium Disulfide via High-Density Isopycnic Density Gradient Ultracentrifugation

Joohoon Kang, Vinod K. Sangwan, Joshua D. Wood, Xiaolong Liu, Itamar Balla, David Lam, Mark C. Hersam*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


Isopycnic density gradient ultracentrifugation (iDGU) has been widely applied to sort nanomaterials by their physical and electronic structure. However, the commonly used density-gradient medium iodixanol has a finite maximum buoyant density that prevents the use of iDGU for high-density nanomaterials. Here, we overcome this limit by adding cesium chloride (CsCl) to iodixanol, thus increasing its maximum buoyant density to the point where the high-density two-dimensional nanomaterial rhenium disulfide (ReS2) can be sorted in a layer-by-layer manner with iDGU. The resulting aqueous ReS2 dispersions show photoluminescence at ∼1.5 eV, which is consistent with its direct bandgap semiconductor electronic structure. Furthermore, photocurrent measurements on thin films formed from solution-processed ReS2 show a spectral response that is consistent with optical absorbance and photoluminescence data. In addition to providing a pathway for effective solution processing of ReS2, this work establishes a general methodology for sorting high-density nanomaterials via iDGU.

Original languageEnglish (US)
Pages (from-to)7216-7223
Number of pages8
JournalNano letters
Issue number11
StatePublished - Nov 9 2016


  • Two-dimensional nanomaterials
  • cesium chloride
  • iodixanol
  • liquid-phase exfoliation
  • photocurrent
  • photoluminescence

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering


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