title: Layer-by-Layer Sorting of Rhenium Disulfide via High-Density Isopycnic Density Gradient Ultracentrifugation.
abstract: 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 ReS2dispersions 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 ReS2show 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.
authors.affiliation: Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, ∥Department of Medicine and ⊥Department of Electrical Engineering and Computer Science, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Joohoon
authors.initials: J
authors.lastname: Kang
authors.affiliation: Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, ∥Department of Medicine and ⊥Department of Electrical Engineering and Computer Science, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Vinod K
authors.initials: VK
authors.lastname: Sangwan
authors.affiliation: Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, ∥Department of Medicine and ⊥Department of Electrical Engineering and Computer Science, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Wood
authors.affiliation: Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, ∥Department of Medicine and ⊥Department of Electrical Engineering and Computer Science, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, ∥Department of Medicine and ⊥Department of Electrical Engineering and Computer Science, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Itamar
authors.initials: I
authors.lastname: Balla
authors.affiliation: Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, ∥Department of Medicine and ⊥Department of Electrical Engineering and Computer Science, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: David
authors.initials: D
authors.lastname: Lam
authors.affiliation: Department of Materials Science and Engineering, ‡Graduate Program in Applied Physics, §Department of Chemistry, ∥Department of Medicine and ⊥Department of Electrical Engineering and Computer Science, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Hersam
keywords: Two-dimensional nanomaterials; cesium chloride; iodixanol; liquid-phase exfoliation; photocurrent; photoluminescence