Size-controlled synthesis of CoFe2O4 nanoparticles potential contrast
agent for MRI and investigation on their size-dependent magnetic
properties
Fujun Liua, Sophie Laurenta, Alain Rocha, Luce Vander Elsta, Robert N. Mullera, b, *
a Department of General, Organic and Biomedical Chemistry, NMR and Molecular Imaging
Laboratory, University of Mons, B-7000 Mons, Belgium
b Center for Microscopy and Molecular Imaging (CMMI), Académie Wallonie - Bruxelles, B6041 Charleroi-Gosselies, Belgium
Supporting Information
Contents:
1. Section on measurements of Fe and Co concentrations – page S2-S5
2. Fig. S3 – page S6
3. Fig. S4 – page S7
4. Fig. S5 – page S8
5. Fig. S6 – page S8
6. Fig. S7 – page S9
Page S1 of 10
Measurement of Fe concentration: As there were peak-overlaps between Fe and Co
absorption for inductively coupled plasma (ICP) measurements, the concentration of Fe was
confirmed by spectrophotography, using 1,10-phenanthrolin as the chromogenic agent. The
principle is that, Fe3+ ions were reduced to Fe2+, and the formed Fe2+ ions reacted with 1,10phenanthrolin into pink complex. Here CoFe2O4 NPs with hydrodynamic diameters of 12.98,
15.97, 19.25 28.35nm and 32.85nm were tested, denoted as SP1, SP2, SP3 SP4 and SP5,
respectively.
(1) Fe absorption curve
Standard Fe solution (1000mg/L), 1mL 1% hydroxylamine hydrochloride, 2mL HAc-NaAc
buffer and 2mL 0.1% 1,10-phenanthroline were mixed to prepare 10mL Fe solution of 1mg/L,
2mg/L, 5mg/L and 10mg/L. Using UV-vis at 510nm, the Fe standard absorption curve has been
obtained as shown in Fig. S1, and the equation is Abs=0.08995+0.19934x, where x is the
concentration of Fe3+ in mg/L.
2.2
2.0
1.8
y = a + b*x
Weight
No Weighting
Residual Sum
of Squares
7.99568E-4
Adj. R-Square
0.99934
Value
1.6
Absorption
Equation
1.4
Standard Erro
B
Intercept
0.08995
0.01628
B
Slope
0.19223
0.00286
1.2
1.0
experiment data
fitting
0.8
0.6
0.4
0.2
0
2
4
6
8
10
concentration of Fe (mg/L)
Fig. S1. The standard adsorption curve of Fe.
Page S2 of 10
(2) Concentration of Fe in Samples
1mL sample, 0.3mL H2O2 and 0.6mL HNO3 were mixed and treated by microwaves for 25
min, and subsequently diluted into 10mL. Then 1mL of the obtained solution was treated via the
same process as in (1) into 10mL and
its UV-Vis absorption was recorded. The Fe
concentrations were calculated as shown in Table S1.
Table S1. Calculation of Fe concentrations.
Sample
SP1
SP2
SP3
SP4
SP5
Abs
0.3844
0.9806
1.3390
1.5472
1.5839
[FeUV] (mg/L): (AbS0.08995)/0.19934
1.4772
4.4678
6.2660
7.3104
7.4945
[FeSP] (mg/L): 100∙[FeUV]
147.72
446.78
626.60
731.04
749.45
[FeSP] (mM): [FeSP] /55.847
2.65
8.01
11.22
13.09
13.42
Measurement of Co concentration: There is no special chromogenic agent specific for Co3+ or
Co2+ ions, so the concentration of Co was obtained through external standard method by
measuring the R1 values.
(1) Standard Co relaxation by proton relaxometry
A standard Co solution was mixed with 0.3 mL H2O2 and 0.6 mL HNO3 into 10 mL in total,
followed by microwave treatment to prepare a Co solution with different concentrations to get
the relaxation constant of Co via T1 measurements. The results are shown in Fig. S2, and are
fitted with the equation of R1`Co=1.833[Co]+0.2861, where R1`Co and [Co] are the relaxation rate
and concentration of Co ions, in S-1 and mM, respectively.
Page S3 of 10
35
experimental data
Linear fit
30
R /s
-1
25
R1=1.833[Co]+0.2861
20
15
10
5
0
2
4
6
8
10
12
14
16
18
[Co] /mM
Fig. S2. The R1 measurements of standard Co solutions and the fitting curve.
Page S4 of 10
(2) Measurement of Co concentration by proton relaxometry
0.2mL sample was microwave treated with 0.3 mL H2O2 and 0.6 mL HNO3, and diluted into
10 mL in total before measurement of T1 at 20 MHz. Based on the equation of
R1=11.4207[Fe]+0.2861, which is the relaxation rate of Fe3+ solution and obtained with the same
method as described above, concentrations of Co in samples were obtained by calculation. The
results are shown in Table S2.
Table S2. Calculation of Co concentrations
Sample
SP1
SP2
T1 /ms
1060.3 441.4
R1 /S-1: 1000÷T1
0.9431 2.2653 3.0539 3.5191 3.6049
[Fe]T1 /mM
0.0529 0.1600 0.2244 0.2618 0.2684
R1Fe /S-1: 11.4207×[Fe]T1
0.6041 1.8273 2.5628 2.9899 3.0653
R1 Co /S-1: R1-0.2861- R1 Fe
0.0529 0.1519 0.2050 0.2431 0.2535
[Co]T1 /mM: R1Co÷1.833
0.0289 0.0829 0.1118 0.1326 0.1383
[Fe]/[Co]
1.8304 1.9394 1.9016 1.9744 1.9415
[Co]SP /mM: 50×[Co]T1
1.445
4.145
SP3
SP4
SP5
327.4
284.2
277.4
5.59
6.63
6.915
Page S5 of 10
Fig. S3. TEM pictures of obtained CoFe2O4/H+/citrate NPs with diameters by PCS being a)
12.98, b) 15.97 nm, c) 19.25nm and d) 37.89nm, where the scale bars for left pictures and right
Page S6 of 10
ones are 100nm and 200nm, respectively, the diameters and PDIs for S3-a, S3-b, S3-c and S3-d
are 7.25nm and 1.1154, 8.51nm and 1.0941, 9.26nm and 1.0536, 11.02nm and 1.1735,
respectively.
Page S7 of 10
Fig. S4. Size distributions by intensity and statistics graphs of CoFe2O4/H+/citrate NPs by
photon correlation spectroscopy (PCS).
Page S8 of 10
Fig. S5. Nanocrystal formation: nucleation and growth processes, where csat. and ceq. are the
saturation concentration of monomers and the equilibrium concentration between monomers and
formed crystal, respectively.
Fig. S1. Comparison of the IR spectra acquired from CoFe2O4/citrate NPs and
CoFe2O4/H+/citrate NPs.
Page S9 of 10
Fig. S2. Transmission and backscattering profiles of CoFe2O4/H+/citrate with DPCS of 37.89nm
colloid by using Turbiscan Lab® Expert. The curves between 4 and 30mm (inside the red dashed
border) are the transmission/backscattering for different parts of measured colloid.
Page S10 of 10