Electronic Supplementary Material
An indium tin oxide electrode modified with gold nanorods for use in potentialcontrolled surface plasmon resonance studies
Emily C. Heider1, Khang Trieu1, Victor M. Diaz1, Karin Y. Chumbimuni-Torres1, Andres
D. Campiglia1*, Steven J. Duranceau2
1. Department of Chemistry, P.O. Box 25000, University of Central Florida, Orlando,
Florida 32816-2366
2. Civil, Construction and Environmental Engineering Department, P.O. Box 162450,
University of Central Florida, Orlando, Florida 32816-2366
* Corresponding author: +1 407 823 4162; fax: +1 407 823 2252, e-mail:
andres.campiglia@ucf.edu
Optimizing preparation conditions for AuNR-modified ITO electrodes
Reaction conditions for forming self-assembled monolayers of MPTMS on ITO
substrates were tested under a variety of conditions. Immersing cleaned, NH4OHpretreated ITO slides in 10% (volume percent) MPTMS in ethanol both at room
temperature for an hour and under reflux conditions for an hour yielded similar MPTMS
surface coverage. The similar MPTMS coverage is indicated in the cyclic voltammetry
curves for the MPTMS-modified slides shown below. The CV curves were obtained for
the slides in 1 mM K4Fe(CN)6 and 0.1 M KNO3. Both bare ITO slides (black line in the
figure), and ITO slides treated with 10% MPTMS for 60 minutes under reflux (blue line –
Method 1 in Table 1) or 60 minutes at room temperature (red line – Method 2 in Table 2)
are shown.
3.0x10-4
2.0x10-4
Current (A)
1.0x10-4
0.0
-1.0x10-4
-2.0x10-4
-3.0x10-4
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2
Potential (V)
After determining that the slides had been modified with MPTMS, AuNR were
immobilized on the surface. Immersing the slides in AuNR solution without pretreatment
for several hours yielded slides modified with AuNR, but with absorbance spectra
showing inadequate signal-to-noise. The spectra are shown in the figure below, where the
different curves correspond to different MPTMS monolayer pretreatment reaction
conditions. The different MTPMS treatment conditions are detailed in Table 1 in the text
of this article.
0.012
Method 1
Method 2
Method 3
0.010
Absorbance
0.008
0.006
0.004
0.002
0.000
-0.002
-0.004
400
500
600
700
Wavelength (nm)
800
Detection of mercury with SPR and applied potential
Hg(II) was reduced to Hg(0) to deposite onto the NRs using potential sweep
voltammetry (+1.0 V to -0.6 V at 25 mV/sec). The peak for mercury reduction was
observable at ~0.28 V. The background corrected sweep data are shown here.
5x10-5
4x10-5
3x10-5
Current (A)
2x10-5
1x10-5
0
-1x10-5
3 M Hg(II)
4 M Hg(II)
5 M Hg(II)
6 M Hg(II)
7 M Hg(II)
-2x10-5
-3x10-5
-4x10-5
-5x10-5
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Potential (V)