Longer-Lasting Electron-Based Microscopy of Single Molecules in Aqueous Medium

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1 Supporting Information Longer-Lasting Electron-Based Microscopy of Single Molecules in Aqueous Medium Huan Wang, K. Hima Nagamanasa, Ye-Jin Kim, Oh-Hoon Kwon, and Steve Granick* Figure S Liquid Pocket with D 2 O 400 Background Graphene e - X e - X ev ev Figure S1. EELS measurements allow estimation of the liquid thickness by the method described in the accompanying text. Electron counts are plotted against electron energy loss. Specifically, following others, 1 Beer s Law was used to estimate water thickness, twater. Here, I zlp is defined as area under the zero loss peak; I total is the total area under the spectrum; l water and l gr is the mean free path of electron in H 2 O and graphene at 120 kev. Though l H2 O = 230 nm, 2 there appears to be no reported value of this quantity for D 2 O, so we used this same value for both H 2 O and D 2 O. In the equation, t gr, background graphene thickness can first be obtained using the same equation, with l gr = 0.7 nm, 3 from a background EELS spectrum acquired on background graphene only. Our 5 measurements gave an average water layer thickness 100 ± 20 nm. ln (I total I zlp ) t water l water + 2 t gr /l gr page S1

2 Figure S2. Figure S2. Average width and distribution of liquid pockets made with D 2 O (78 pockets; red) and H 2 O with 3% glycerol (54 pockets; blue). Inset show the full distribution. These data show no statistical difference. page S2

3 Figure S3. Figure S3. Comparison of averaged bubble growth rate in liquid pockets made with D 2 O (red) and H 2 O (blue) with 3% glycerol. The data for D 2 O pockets involves harshest radiation, 120 kev, 22 e Å -2 s -1 ). Averaged bubble growth rate was calculated by dividing total area of the pocket divided by the time it takes bubble from first appearance to fill up the pocket. page S3

4 Figure. S4. Figure. S4. Polystyrenesulfonate dissolved in D 2 O liquid pockets probed by electronenergy-loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS). These assays confirm the presence of sulphur from 1 wt% polystyrenesulfonate polymer in D 2 O. page S4

5 Figure S5. Figure. S5. Concentration of H 2 and D 2 estimated using kinetic rate equations of water hydrolysis. A) Concentration of H 2 as a function of time for 120 kev and 22 e Å -2 s -1 (black), 120 kev and e Å -2 s -1 (red), 80 kev and e Å -2 s -1 (blue). B) Time-dependent concentration of H 2 (black) and D 2 (red) for γ-radiation. The argument is as follows. Bubbles in liquid-cell TEM experiments are believed to be composed primarily of H 2 (D 2 ) gas. 4-5 Using the kinetic rate equations 5 and open-source Matlab codes introduced by Elliot and McCracken, 6 we estimated the time evolution of H 2 (D 2 ) gas concentration, considering (as the entire channel is exposed to the electron beam) their homogeneous case in which diffusion need not be considered. These models are based on an inventory of radiolytic cascade reactions and each one s rate constant. Equally important is the volumetric production of each species from incident radiation, these numbers being obtained from the respective G-values. First we performed these calculations for plain H 2 O water using the same set of reactions and G-values used in refs. 5-6 As shown in Figure S5A, the concentration of H 2 gas increases with increasing dose rate, which is expected physically and consistent with our observation of page S5

6 shorter lifetime at higher dose rates. For D 2 O, G-values for high-energy electron beams are not known. Therefore, instead, we performed simulations using these numbers for low-energy γ- radiation (dose rate 0.25 Gy/s, the same as ref 5 ) as the yields 7-9 and reaction rates 7-8 of D 2 O under these conditions are known. The findings are consistent with what is expected in refs References 1. Chee, S. W.; Baraissov, Z.; Loh, N. D.; Matsudaira, P. T.; Mirsaidov, U., Desorption- Mediated Motion of Nanoparticles at the Liquid Solid Interface. J. Phys. Chem. C 2016, 120, Feja, B.; Aebi, U., Determination of the Inelastic Mean Free Path of Electrons in Vitrified Ice Layers for On-Line Thickness Measurements by Zero-Loss Imaging. J. Microsc 1999, 193, Joshua, D. S.; Andrei, K., Electron Transparent Graphene Windows for Environmental Scanning Electron Microscopy in Liquids and Dense Gases. Nanotechnology 2012, 23, Grogan, J. M.; Schneider, N. M.; Ross, F. M.; Bau, H. H., Bubble and Pattern Formation in Liquid Induced by An Electron Beam. Nano Lett. 2014, 14, Schneider, N. M.; Norton, M. M.; Mendel, B. J.; Grogan, J. M.; Ross, F. M.; Bau, H. H., Electron Water Interactions and Implications for Liquid Cell Electron Microscopy. J. Phys. Chem. C 2014, 118, Elliot, A. J.; McCracken, D. R., Computer Modelling of the Radiolysis in An Aqueous Lithium Salt Blanket: Suppression of Radiolysis by Addition of Hydrogen. Fusion Eng. Des. 1990, 13, Elliot, A.; Ouellette, D.; Stuart, C. The Temperature Dependence of the Rate Constants and Yields for the Simulation of the Radiolysis of Heavy Water; Atomic Energy of Canada Ltd.: Draganic, Z. D.; Micic, O. I.; Nenadovic, M., Radiolysis of Some Heavy Water Solutions at pd J. Phys. Chem. 1968, 72, Hart, E. J.; Fielden, E. M., Reaction of the Deuterated Electron, ed-, with ed-, D, OD, and D2O. J. Phys. Chem. 1968, 72, Hayon, E., Radiolysis of Heavy Water in the pd range J. Phys. Chem. 1965, 69, Elliot, A. J.; Chenier, M. P.; Ouellette, D. C., Temperature Dependence of G Values for H2O and D2O Irradiated with Low Linear Energy Transfer Radiation. J. Chem. Soc., Faraday Trans. 1993, 89, page S6