S-1
Electronic Supplementary Information (ESI)
Characterization of Mixed-Ligand Shells on Gold Nanoparticles by Transition Metal and Supramolecular Surface Probes
Mohamed Nilam,a Mostafa Ahmed,a,b Mohammad A. Alnajjar,a Andreas Hennig*,a
a Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759
Bremen, Germany
b Department of Chemistry, Faculty of Science (New Valley), Assuit University, Egypt
* Corresponding author: [email protected]
Table of Contents
Abbreviations....................................................................................................................................S-2
Molecular Structure of Ligands ........................................................................................................S-2
DTNB Assay.....................................................................................................................................S-3
Analysis of Particle Size Distribution by TEM ................................................................................S-4
Thermogravimetric analysis (TGA)..................................................................................................S-5
Other Supporting Figures and Tables ...............................................................................................S-5
Electronic Supplementary Material (ESI) for Analyst.This journal is © The Royal Society of Chemistry 2018
S-2
Abbreviations
AMADA-Put: N-adamantylmethylbutane-1,4-diamine; AO: acridine orange; AuNPs: gold
nanoparticles; CB7: cucurbit[7]uril; DTNB: 5,5´-dithio-bis-(2-nitrobenzoic acid) (Ellman’s
reagent); EDC: 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride salt; Hepes: 2-[4-
(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid; MES: 2-(N-morpholino)ethanesulfonic acid;
MPA: sodium 3-mercaptopropionate; MPS: sodium 3-mercapto-1-propanesulfonate; MUA: sodium
11-mercaptoundecanoate; PV: pyrocatechol violet; TEG: triethylene glycol mono-11-
mercaptoundecyl ether.
Molecular Structure of Ligands
O
O-Na+HS Na+S
O
O O-HS
Sodium 3-mercaptopropanoate (MPA) Sodium 3-mercapto-1-propanesulfonate (MPS)
O
O-Na+HS
Sodium 11-mercaptoundecanoate (MUA)
OO
OOH
HS
Triethylene glycol mono-11-mercaptoundecyl ether (TEG)
Chart S1. Molecular structures of ligands.
S-3
DTNB Assay
Stock solutions of DTNB and MPA were prepared in 0.1 M NaH2PO4, 1 mM EDTA, pH 8.0.
Varying concentrations of MPA (5-25 µM) and 40 µM DTNB were added to each solution.
Solutions were mixed and incubated at room temperature for 5 minutes, and then absorption spectra
were recorded. The prepared stock solutions of the AuNPs (ca. 1.5 µM AuNPs) were centrifuged
for 25 min at 16400 rcf, and then, 40 µM DTNB was added to the supernatant and absorption
spectra were recorded.
5 10 15 20 25
0.1
0.2
Abso
rban
cce
[MPA] M)
b)
300 400 500
0.00
0.15
0.30
Abs
orba
nce
Wavelength (nm)
Supernatant of MPA/MPS-AuNPs
a)
300 400 5000.00
0.25
0.50
0.75
Abs
orba
nce
Wavelength (nm)
Au/MPA-MPS 1:5 Au/MUA-TEG 1:1 Au/MUA-TEG 1:100 Au/MPA-MPS 1:83
c)
Fig. S1 a) Absorption spectra of 40 µM DTNB with varying concentration of MPA (5-25 µM) and
MPA/MPS-AuNPs nanoparticles in 0.1 M NaH2PO4, 1 mM EDTA, pH 8.0. b) Corresponding plot
of the absorbance at 412 nm against the concentration of MPA. The limit of detection (LOD) of
DTNB assay was calculated using the equation; LOD = 3sa/b where, sa is the standard deviation of
the blank and b is the slope of the calibration line. c) Absorption spectra of 80 µM DTNB with
different molar ratio of the ligand capped nanoparticles (after five months storage at 4 ˚C) in 0.1 M
NaH2PO4, 1 mM EDTA, pH 8.0.
S-4
Analysis of Particle Size Distribution by TEM
The synthesized mixed-ligand nanoparticles (ca. 1.5 µM) were fivefold diluted with NANOpure
water and then deposited onto a carbon film-coated copper net TEM grid (PLANO GmbH).
Samples were allowed to air dry and then dried under high vacuum before characterization by TEM
at 80 kV. To obtain the size of distribution of the nanoparticles from TEM images, ImageJ 1.47d
(National Institute of Health, USA) was used and at least 200 AuNPs from various areas of the grid
were considered.
10 15 20 25 300
20
40
60
80
Cou
nts
Diameter (nm)
10 15 20 25 300
20
40
60
Cou
nts
Diameter (nm)
Fig. S2 TEM images of MPA/MPS-AuNPs (top) and MUA/TEG-AuNPs (bottom) and respective
size distribution histograms.
S-5
Thermogravimetric analysis (TGA)
Thermogravimetric analysis (TGA) was performed with a SDT Q600 (TA Instruments).
MUA/TEG-AuNP samples (2 - 5 mg) were prepared by drying and the temperature range between
20 ˚C and 700 ˚C was scanned at a rate of 5 ˚C/min under a nitrogen flow of 100 mL/min.
Other Supporting Figures and Tables
400 500 600 700 800
0.0
0.5
1.0
Abs
orba
nce
Wavelength (nm)
MPA:MPS 1:2 MPA:MPS 1:5 MPA:MPS 1:10 MPA:MPS 1:15 MPA:MPS 1:20 MPA:MPS 1:50
a)
400 500 600 700 8000.0
0.5
1.0
Abs
orba
nce
Wavelength (nm)
MUA:SPEG 1:1 MUA:SPEG 1:2 MUA:SPEG 1:5 MUA:SPEG 1:10 MUA:SPEG 1:20 MUA:SPEG 1:100
b)
Fig. S3 Normalized absorption spectra of functionalized particles: a) MPA/MPS-AuNPs,
b) MUA/TEG-AuNPs.
S-6
Fig. S4 1H NMR spectra of MUA/TEG-AuNPs with varying molar ratio of MUA and TEG after
digestion with aqua regia and subsequent dilution with D2O (pD 1.6). a) MUA only and MUA/TEG
molar ratio b) 1:1, c) 2:1, d) 5:1, e) 10:1, f) 20:1, g) 100:1.
100 200 300 400 500 600 70050
75
100
Wei
ght L
oss
(%)
Temperature (C)
MUA/TEG(10:1)-AuNPs: 1.46 ligands/nm2 MUA/TEG(5:1)-AuNPs: 1.30 ligands/nm2
Fig. S5 TGA plots of MUA/TEG-AuNPs coated with different molar ratios of MUA and TEG.
S-7
Fig. S6 Reproducibility measurements of different batches of MPA/MPS(1:5)-AuNPs by 1H NMR
spectroscopy of after digestion with aqua regia and subsequent dilution with D2O (pD 1.6).
S-8
0 20 40 60 80 1000.15
0.20
0.25
0.30
Abs
orba
nce
Volume of AuNP stock solution (L)
a)
0 50 100
0.1
0.2
0.3
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
0 20 40 60 80
0.15
0.20
0.25
0.30
0.35
Abs
orba
nce
Volume of AuNP stock solution (L)
b)
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
0 20 40 60 800.15
0.20
0.25
0.30
Abs
orba
nce
Volume of AuNP stock solution (L)
c)
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
0 20 40 60 80 100
0.15
0.20
0.25
0.30
Abs
orba
nce
Volume of AuNP stock solution (L)
d)
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
0 50 100 150 200
0.15
0.20
0.25
0.30
Abs
orba
nce
Volume of AuNP stock solution (L)
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
e)
0 20 40 60 800.15
0.20
0.25
0.30
Abs
orba
nce
Volume of AuNP stock solution (L)
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
f)
Fig. S7 Results of NiPV assay for quantification of negatively charged surface functional groups on
AuNPs. Dependence of the absorbance at 650 nm versus the volume of particles a) MPA only and
MPA/MPS molar ratio b) 1:5, c) 1:10, d) 1:30, e) 1:50, f) 1: 83.
S-9
0 20 40 60 80
0.15
0.20
0.25
0.30
0.35
0.40
Abs
orba
nce
Volume of AuNP stock solution (L)
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
a)
0 50 100 150 200 2500.15
0.20
0.25
0.30
Abs
orba
nce
Volume of AuNP stock solution (L)
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
b)
0 50 100 1500.15
0.20
0.25
0.30
Abs
orba
nce
Volume of AuNP stock solution (L)
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
c)
0 50 100 150 2000.15
0.20
0.25
0.30
Abs
orba
nce
Volume of AuNP stock solution (L)
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
d)
0 50 100 150 200 2500.15
0.20
0.25
0.30
Abs
orba
nce
Volume of AuNP stock solution (L)
400 600 8000.0
0.2
0.4
Abs
orba
nce
Wavelength (nm)
e)
0 100 200 300 4000.20
0.25
0.30
Abs
orba
nce
Volume of AuNP stock solution (L)
400 600 8000.0
0.2
0.4A
bsor
banc
e
Wavelength (nm)
f)
Fig. S8 Results of NiPV assay for quantification of negatively charged surface functional groups on
AuNPs. Dependence of the absorbance at 650 nm versus the volume of particles a) MUA only and
MUA/TEG molar ratio b) 100:1, c) 20:1, d) 10:1, e) 5:1, f) 2:1.
S-10
Table S1. Reproducibility measurements of MPA/MPS(1:5)-AuNPs by the NiPV assay.
Au-MPA/MPS Ligand density (ligands/nm2)Sample 1 5.449Sample 2 5.374Sample 3 5.426Sample 4 5.415Sample 5 5.578
Sample 6 (different batch) 5.454Average 5.449 ± 0.070Coefficient of Variation (%) 1.3
Table S2. Reproducibility measurements of MPA/MPS(1:5)-AuNPs by the CB7 assay.
Au-MPA/MPS Ligand density (ligands/nm2)Sample 1 0.07798Sample 2 0.07559Sample 3 0.07902Sample 4 0.09128Sample 5 0.08533Sample 6 0.09279Average 0.0837 ± 0.0073Coefficient of Variation (%) 8.6
S-11
0 20 40 60 80
5
10
Fluo
resc
ence
Volume (L)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
b)
0 20 40 60 80
5
10
Fluo
resc
ence
Volume (L)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
c)
0 30 60 90 120 150
5
10
Fluo
resc
ence
Volume (L)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
d)
0 50 100 150 200
5
10
Fluo
resc
ence
Volume (L)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
f)
Fig. S9 Results of CB7 assay for quantification of accessible surface functional groups on
MPA/MPS-AuNPs a) MPA only and MPA/MPS molar ratio b) 1:5, c) 1:10, d) 1:15, e) 1:30,
f) 1:83. Shown is the variation of fluorescence spectra with increasing volume of AuNPs stock
solution (see main text for details) (λem = 510 nm, λexe = 450 nm).
0 10 20 30 40
5
10
Fluo
resc
ence
Volume (L)
a)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
0 30 60 90 120 150
5
10
Fluo
resc
ence
Volume (L)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
e)
S-12
0 10 20 30 40
5
10
Fluo
resc
ence
Volume (L)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
a)
0 40 80 120 160
5
10
Fluo
resc
ence
Volume (L)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
b)
0 30 60 90 120 150
5
10
Fluo
resc
ence
Volume (L)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
c)
0 40 80 120 160
5
10
Fluo
resc
ence
Volume (L)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
d)
0 50 100 150
5
10
Fluo
resc
ence
Volume (L)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
e)
0 50 100 150 200 250
5
10
Fluo
resc
ence
Volume (L)
f)
500 600 7000
5
10
Fluo
resc
ence
Wavelength (nm)
Fig. S10 Results of CB7 assay for quantification of accessible surface functional groups on
MUA/TEG-AuNPs a) MUA only and MUA/TEG molar ratio b) 100:1, c) 20:1, d) 10:1, e) 5:1,
f) 2:1. Shown is the variation of fluorescence spectra with increasing volume of AuNPs stock
solution (λem = 510 nm, λexe = 450 nm).