Supplementary Information for
Silver Nanoislands on Cellulose Fibers for Chromatographic Separation and Ultrasensitive
Detection of Small Molecules
Hyukjin Jung, Moonseong Park, Minhee Kang, and Ki-Hun Jeong*
Figure S1 Wafer-level nanofabrication of silver nanoislands on cellulose fiber matrices of
paper. The photographic images of a chromatography paper, a paper with an initial silver film
thickness of 10 nm before thermal annealing, and a paper with silver nanoislands after thermal
annealing (scale bar: 1 cm).
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Figure S2 Size-controlled silver nanoislands on cellulose fiber matrices and their measured
and calculated extinctions. (a) The statistical size distribution of silver nanoislands on cellulose
fiber matrices were moderately controlled with an initial silver film thickness from 5 nm to 20
nm. (b) The measured extinction spectra of silver nanoislands depend on the initial silver film
thickness. (c) The calculated extinction spectra of NP-paper depend on the thickness of the initial
silver film. Both the measured extinctions and the calculated extinctions were normalized by the
maximum extinction intensity of the initial silver thickness of 10 nm.
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Figure S3 Extinction spectra and SERS signals from crystal violet with different
concentrations spotted on NP-paper. (a) Extinction spectra of CV molecules with nanomolar to
micromolar concentrations. The LSPR wavelength shift effectively allows the detection of CV
molecules at low concentration, whereas the absorbance is dominant to detect those with high
molar concentrations. (b) SERS intensities at a signature peak (1590 cm-1) of CV depending on
the molar concentration. The inset shows the SERS spectra of CV from 10 nM to 1 mM. The five
SERS peaks of the CV molecule are located at 1590, 1355, 1167, 907, and 786 cm-1, which
correspond to the following molecular vibrational modes: ring breathing, asymmetric stretching
of phenyl-C-phenyl and C-N, asymmetric in-plane stretching of C-H and C-phenyl, ring
breathing, and asymmetric phenyl aromatic ring-H out-of-plane bending, respectively. The
signature SERS peaks of CV increase with the number of adsorbed molecules near hotspots from
10 nM to 100 μM, whereas more than 100 μM of CV obstructs further increases in the SERS
intensity. Upon increasing the concentration of CV, both the surfaces of the silver nanoislands
and the cellulose matrices in the detection volume are covered by the CV multilayer, thus
reducing the contribution of the first layer on silver nanoislands to the overall SERS spectra.
Therefore, the pronounced SERS with a maximum intensity appears only at the monomer
coverage, where both the charge transfer and electromagnetic enhancement contribution reach
maxima. The limit of detection of CV was 50 nM, which corresponds to 2 pg per detection spot
on the NP-paper. The SERS excitation wavelength is 488 nm (power: 0.5 mW, integration time:
0.5 sec).
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Figure S4 MEF sensitivity of different dye molecules adsorbed on NP-paper. (a)
Comparisons of the limit of detection (LOD) for SO and CR between normal chromatography
paper and NP-paper. (b) The LOD for TB was 5 pM (185 ag per detection spot) adsorbed on NPpaper.
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Figure S5 Normalized SERS spectra of analytic molecules at each chromatogram on NPpaper. (a) CV (5 mM). (b) TB (40 mM). (c) CR (50 mM). At position 1, Raman bands of CR
appear at 1163 cm-1, 1345 cm-1, and 1593 cm-1. Those bands are related to phenyl ring-N=N
stretching, naphthyl aromatic ring mode, and phenyl aromatic ring mode for each. Position 2
indicates TB according to Raman bands at 1385 cm-1, 1434 cm-1, and 1605 cm-1. The band at
1385 cm-1 is attributed to ring C-C stretching and ring C-N stretching. The band at 1434 cm-1 is
ascribed to ring C-C stretching and asymmetric C-N stretching. The band at 1605 cm-1 is related
to aromatic ring C-C in-plane stretching. The position 3 refers to CV according to Raman bands
at 813 cm-1, 919 cm-1, 1179 cm-1, and 1370 cm-1 (Figure 4a in manuscript text). SERS spectra
were measured at 488 nm of excitation wavelength (power: 0.5 mW, integration time: 1 sec).
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Figure S6 Fluorescence detection of mixed dye molecules at ultra-low concentrations after
chromatographic separation. Fluorescence signals were acquired by spectral filtering with 530600 nm for SO (λex: 488 nm), 560-615 nm for CR (λex: 514 nm), and > 650 nm for TB (λex: 633
nm).
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