Simultaneous optical and electrochemical recording of ...

Nano Res.

Electronic Supplementary Material

Simultaneous optical and electrochemical recording ofsingle nanoparticle electrochemistry

Linlin Sun, Yimin Fang, Zhimin Li, Wei Wang (), and Hongyuan Chen ()

State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University,Nanjing 210093, China

Supporting information to DOI 10.1007/s12274-017-1439-0

S1 Characterizations of nanoparticles

The nanoparticles used in the present work were characterized by transmission electron microscopy (TEM)

to access the morphology and size distribution. TEM analysis gives an average diameter of 61 ± 25 nm for

Ag nanoparticles (Fig. S1(a)) and 195 ± 30 nm for SiO2 nanoparticles (Fig. S1(b)). The UV–vis spectrum of Ag

nanoparticles shows the spherical colloids have an absorption peak at ca. 413 nm (Fig. S1(c)).

Figure S1 TEM image and size distribution (inset) of Ag nanoparticles (a) and SiO2 nanoparticles (b). (c) UV–vis absorption spectrum of Ag nanoparticles

Address correspondence to Wei Wang, [email protected]; Hongyuan Chen, [email protected]

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S2 Schematic illustration of an Au microelectrode

Figure S2 (left) Schematic illustration of an Au microelectrode. (right) Bright-field image of the microelectrode (60× objective).

S3 Distribution of collision locations

We collected collision locations of 40 Ag nanoparticles. Figure S3 shows that the distribution of collision locations

in the gold film surface is uniform.

Figure S3 Distribution of collision locations of Ag nanoparticles in the gold film surface at the potential of 300 mV in 0.1 M KNO3.

S4 Effect of the low-pass filter bandwidth of the Axon

We performed the potential step to a 10 μm Au ultramicroelectrode (UME) in 0.1 M KNO3 from 0 to 300 mV under

different electronic filters (Fig. S4). It was found that a low-pass filter significantly broaden the electrochemical

current spike.

Figure S4 (a) Transient current spike from the potential step under different electronic filters (2, 4, 10, and 20 Hz). (b) Relationship between the width of the electrochemical current spike and the low-pass filter bandwidth of the Axon.

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S5 Conversion from SPR intensity to theoretical current of single nanoparticles

The amount of charge transfer is equal to the number of dissolved (oxidized) Ag atoms from the particles, so

we have

3

A Agd( 4 / 3 )d

d d

eN r mQi

t t

(S1)

where i, ρ, mAg, NA and r are the theoretical current, density of silver, mass of silver atom, Avogadro’s constant,

and the radius of the particle, respectively.

In our previous study, SPR intensity is proportional to the nanoparticle volume [S1] and we obtain a quantitative

model

SPRlog 2.52 2.84 logI r (S2)

where ISPR and r are the SPRM intensity and the radius of the particle, respectively.

Combining Eqs. (S1) and (S2), we can calculate theoretical current.

At the same time, we can use Eq. (S1) to calculate the size of AgNP from electrochemical current, which was

generally consistent with the TEM characterization. Figure S5 shows the theoretical average diameter of 30

individual AgNPs was 45 ± 15 nm.

Figure S5 The theoretical size distribution of 30 individual AgNPs.

S6 Descriptions of movies

Movie S1 Collision and oxidation of three Ag nanoparticles (potential: 300 mV, and electrolyte: 0.1 M KNO3).

Reference

[S1] Fang, Y. M.; Wang, W.; Wo, X,; Luo, Y. S.; Yin, S. W.; Wang, Y. X.; Shan, X. N.; Tao, N. J. Plasmonic imaging of electrochemical

oxidation of single nanoparticles. J. Am. Chem. Soc. 2014, 136, 12584–12587.