Exploring Adsorption and Reactivity of NH₃ on Reduced Graphene Oxide

Sensors based on graphene and functionalized graphene are emerging as the state of the art for detecting extremely small quantities of target molecules under realistic working conditions with high selectivity. Although some theoretical work has emerged to understand such adsorption processes (Tang and Cao J. Phys. Chem. C 2012, 116, 8778; Leenaerts et al. Phys. Rev. B 2008, 77, 125416; Tang and CaoJ. Chem. Phys. 2011, 134, 044710), little experimental evidence detailing the dynamics of the adsorption and resulting surface species has been reported. Here, we study the adsorption of NH₃ on reduced graphene oxide (RGO) using in situ infrared (IR) microspectroscopy performed under realistic working conditions (i.e., ambient pressure), along with density functional theory (DFT) calculations to support experimental observations. Conclusions drawn from experiment and theory reveal the presence of various surface species that impact the conductivity of the substrate at varying rates. The species arising from adsorption and interactions between NH₃ and RGO include molecularly physisorbed NH₃, as well as chemisorbed fragments such as NH₂, OH, and CH due to dissociation of NH₃ at defects and epoxide groups

Additional file 1: of Enzyme intermediates captured “on the fly” by mix-and-inject serial crystallography

Figure S1. Schematics of the short-time-point mixing injector. Figure S2. Selected views of the CEF binding site in the BlaC shard crystals including simulated annealing omit maps. Figure S3. Structural details, and simulated annealing omit maps, shard crystal form, subunit B (stereo representation, from 30 ms to 2 s). Figure S4. Structural details and simulated annealing omit maps, shard crystal form, subunit D (stereo representation, from 30 ms to 2 s). Figure S5. Structural details, and simulated annealing omit maps, needle crystal form (stereo representation, from 30 ms to 2 s). Figure S6. Backside view of the catalytic cleft of BlaC in the shard crystal form, structural details and simulated annealing omit maps (stereo representation, selected time points). Figure S7. 2mFo-DFc electron density in the catalytic clefts of BlaC in the shard crystal form (stereo representation, from 30 ms to 2 s). Figure S8. 2mFo-DFc electron density and structural details in the catalytic clefts of BlaC in the needle crystal form (stereo representation from 30 ms to 2 s). Figure S9. Details in the catalytic cleft of subunit B in the shard crystal form at 500 ms including the stacked CEF, 2FoFc maps, and simulated annealing omit maps (stereo representation). Figure S10. The catalytic cleft of BlaC, further details, including a difference map between the 500 ms and 100 ms time points. Figure S11. Crystal packing in shards and needles. Figure S12. Dynamic light scattering results. Table S1. B-factors for CEF species observed in the shard crystals at different time delays. (PDF 1646 kb