Supporting Information

Transcription

1 Supporting Information Visualizing the Effect of Partial Oxide Formation on Single Silver Nanoparticle Electrodissolution Vignesh Sundaresan, Joseph W. Monaghan, and Katherine A. Willets* Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States Corresponding Author Katherine A. Willets, S1

2 Table of Contents 1. Statistics for three different oxidation behavior at various potentials... S3 2. Diverse slow oxidation behaviors... S Dimensional super-localization imaging... S5 4. Super-localization imaging of Ag NP under no potential.... S6 5. Super- localization imaging at 1.2 V.... S7 6. Center positions of two Ag NPs showing no oxidation at 1.2 V... S8 7. Histogams of d at various potentials.... S9 8. Calculating the ratio of the extracted center positions.... S10 9. Polar plot of calculated r at two different potentials, color coded by t 50%.... S Oxidation of Ag NPs at ph S Movie S1 Electrodeposition of Ag particles.... S13 S2

3 1. Statistics for three different oxidation behavior at various potentials Figure S1. Comparison of the three sub-types of silver oxidation (slow, fast and no oxidation) observed at varying potentials as labelled. For each potential, 250 particles were analyzed and separated into the respective sub-type of oxidation behavior. S3

4 2. Diverse slow oxidation behaviors Figure S2. Four different individual Ag NP showing diverse slow oxidation (t>0.5 s to oxidize) behaviors. S4

5 3. 2-Dimensional super-localization imaging Figure S3. Schematic depicting the process of super-localization imaging to extract the center positions of a single Ag NP. (A) Diffraction limited dark-field optical image (bottom) of a Ag NP and a three dimensional representation of the optical image (top) with the pixel coordinates in x & y and the intensity in the z coordinates. (B) After fitting the image in panel A to a 2- dimensional (2-D) Gaussian equation, the center position of the particle is extracted which shown as a red X mark in the optical image. S5

6 4. Super-localization imaging of Ag NP under no potential Figure S4. Scatter plots showing center positions of 4 different Ag NPs under no electrochemical potential for 1500 frames with the acquisition time of 0.1 s/frame. The deviation in the localization is due to the precision while fitting to the 2-D Gaussian function. S6

7 5. Super-localization imaging at 1.2 V Figure S5. More examples of Ag NPs undergoing oxidation with three distinct behaviors: (A) Symmetric oxidation (B) Asymmetric oxidation and (C) Jump followed by either symmetric or asymmetric oxidation. Black dots correspond to the center positions when the electrode was held at 0 V (1-10 s) and orange to red points corresponds to the center positions when the electrode was held at 1.2 V. The corresponding d and ratio values of these examples are shown in Table S1. Table - S1: d (nm) Ratio A A A B B B C C C S7

8 6. Center positions of two Ag NPs showing no oxidation at 1.2 V Figure S6. Scatter plot showing the center positions of two different Ag NP (A and B) undergoing no oxidation at 1.2 V were stationary and showing a symmetric behavior. (C) The intensity-time traces of the two particles shown in panel A and B which are color coded respectively. S8

9 7. Histograms of d at various potentials Figure S7. Histograms of particle movement, d (nm), upon switching the potential from 0 V to the different oxidation potential (0.3,0.6, and 0.9V) as labelled. S9

10 8. Calculating the ratio of the extracted center positions Figure S8. (A) Scatter plot showing the center positions of a Ag NP during oxidation (1-10s 0 V, s 1.2 V). The points within the red border represents the center positions starting from 10.1 s to the time taken to for the particle to show 90 % drop in scattering intensity. (B) Zoomed in portion of the center positions within the red border from panel A. The average of all included center positions was calculated and arbitrarily set as a point of origin (0,0) as indicated by the blue dashed line. A linear fit of all points is shown as the red solid line. Angle (θ o ) was calculated using the slope of this line. (C) Center points in panel B before rotation (black dots) and after rotating by -θ o (red dots). After the rotation, the ratio of the average distance in x and y of all center position is calculated. S10

11 9. Polar plot of calculated r at two different potentials, color coded by t 50%. Figure S9. Polar plots showing calculated r and the orientation of 15 different particles undergoing electrodissolution at 1.0 (left) and 1.2 V (right). The average center position of the Ag NP between 10.1 and 20 s (1.2 V) was set as an origin for the polar plot. The color of each trajectory represents the time taken for the particle to show 50% drop in the intensity based on the respective color bars. S11

12 10. Oxidation of Ag NPs at ph = 9 Figure S10. (A) Dark-field optical images of Ag NP imaged through the birefringent crystal at ph 9 at 0 V (0.1 s) and 1.2 V (12 s and 130 s) as labelled. Scale bars = 3 µm. (B) Intensity time traces of two different particles from panel A indicated by two arrows as color coded. S12

13 11. Movie S1 Electrodeposition of Ag particles (AVI) Electrodeposition of Ag particles on bare ITO was achieved by applying -0.2 V with 1 µm AgNO 3 as an electrolyte solution, the two diffraction limited spots for each individual particle in the optical image is due to the birefringent crystal in the detection path. Movie playing with the speed of 10 frames/second. S13