title: Spatially Resolved in Situ Reaction Dynamics of Graphene via Optical Microscopy.
abstract: The potential of rising two-dimensional materials, such as graphene, can be substantially expanded through chemistry. However, it has been a challenge to study how chemical reactions of two-dimensional materials progress. Existing techniques offer limited signal contrast and/or spatial-temporal resolution and are difficult to apply to in situ studies. Here we employ an optical approach, namely interference reflection microscopy, to quantitatively monitor the redox reaction dynamics of graphene and graphene oxide (GO) in situ with diffraction-limited (∼300 nm) spatial resolution and video-rate time resolution. Remarkably, we found that the oxidation kinetics of graphene is characterized by a seeded, autocatalytic process that gives rise to unique, wave-like propagation of reaction in two dimensions. The reaction is initially slow and confined to highly localized, nanoscale hot spots associated with structural defects, but then self-accelerates while propagating outward, hence flower-like, micrometer-sized reaction patterns over the entire sample. In contrast, the reduction of GO is spatially homogeneous and temporally pseudo-first-order, and through in situ data, we further identify pH as a key reaction parameter.
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.
authors.forename: Michal
authors.identifier: 0000-0002-0053-1018
authors.initials: M
authors.lastname: Wojcik
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.|Department of Chemistry, Tsinghua University , Beijing 100084, China.
authors.forename: Yunqi
authors.identifier: 0000-0001-8794-9910
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.
authors.forename: Wan
authors.identifier: 0000-0001-5751-3550
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.|Division of Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Ke
authors.identifier: 0000-0002-2788-194X
authors.initials: K
authors.lastname: Xu