Optical imaging and spectroscopy of atomically precise armchair graphene nanoribbons
S. Zhao, G. Borin Barin, T. Cao, J. Overbeck, R. Darawish, T. Lyu, S. Grant Drapcho, S. Wang, T. Dumslaff, A. Narita, M. Calame, K. Müllen, S. G. Louie, P. Ruffieux, R. Fasel, and F. Wang
Nano Letters (2020)
We report the optical imaging and absorption spectroscopy on atomically precise armchair graphene nanoribbons (GNRs) on insulating fused silica substrates. This is achieved by controlling light polarization on macroscopically aligned GNRs, which greatly enhances the sub-monolayer GNR optical contrast on the insulating substrates. We measured the linear absorption spectra of 7-armchair and 9-armchair GNRs in this study, and the experimental data agree qualitatively with ab inito calculation results. The polarization spectroscopy technique enables an unambiguous optical identification of GNR samples and provides a rapid tool to characterize the transferred film over large area.
Influence of helium ion irradiation on the structure and strength of diamond
Chen M, Best JP, Shorubalko I, Michler J, Spolenak R & Wheeler JM
Stable ultra-concentrated and ultra-dilute colloids of CsPbX3 (X=Cl, Br) nanocrystals using natural lecithin as a capping ligand
Krieg F, Ong QK, Burian M, Rainò G, Naumenko D, Amenitsch H, Süess A, Grotevent MJ, Krumeich F, Bodnarchuk MI, Shorubalko I, Stellacci F & Kovalenko MV
Journal of the American Chemical Society, 141(50), 19839-19849.
Attaining thermodynamic stability of colloids in a broad range of concentrations had long been a major thrust in the field of colloidal ligand-capped semiconductor nanocrystals (NCs). This challenge is particularly pressing for the novel NCs of cesium lead halide perovskites (CsPbX3; X=Cl, Br) owing to their highly dynamic and labile surfaces. Herein we demonstrate that soy-lecithin, a mass-produced natural phospholipid, serves as a tightly-binding surface capping ligand, suited for a high-reaction yield synthesis of CsPbX3 NCs (6-10 nm) and allowing for the long-term retention of colloidal and structural integrity of CsPbX3 NCs in a broad range of concentrations – from a few ng/mL to >400 mg/mL (inorganic core mass). The high colloidal stability achieved with this long-chain zwitterionic ligand can be rationalized with the Alexander-De Gennes model that considers the increased particle-particle repulsion due to branched chains and ligand polydispersity. The versatility and immense practical utility of such colloids is showcased by the single NC spectroscopy on ultra-dilute samples and, conversely, by obtaining micron-thick, optically homogeneous dense NC films in a single spin-coating step from ultra-concentrated colloids.