Supplementary Materials

Selective capture of Pb2+ in rice phloem sap using glutathione-functionalized gold

nanoparticles/multi-walled carbon nanotubes: enhancing anti-interference

electrochemical detection

Min Jiang†ab, Hui-Ru Chen†bc, Shan-Shan Li†ab, Rui Liangbc , Jin-Huai Liuab, Yang

Yang*bc, Yue-Jin Wubc, Meng Yang*ab and Xing-Jiu Huang*ab

a Key Laboratory of Environmental Optics and Technology, And Institute of

Intelligent Machines, Chinese Academy of Sciences, Hefei 230031, People’s

Republic of China

b University of Science and Technology of China, Hefei 230026, People’s Republic of

China

c Key Laboratory of High Magnetic Field and Ion Beam Physical Biology, Hefei

Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, People’s

Republic of China

† M.J., H.R.C. and S.S.L. contributed equally to this work.

* Correspondence should be addressed to X.J.Huang, M. Yang and Y.Yang.

E-mail: xingjiuhuang@iim.ac.cn (X.J.H); myang@iim.ac.cn (M.Y);

yangyang19860207@163.com (Y.Y).

Tel.: +86-551-65591167; fax: +86-551-65592420.

Electronic Supplementary Material (ESI) for Environmental Science: Nano.This journal is © The Royal Society of Chemistry 2018

Contents

1. Experimental section and discussion

1.1. Apparatus

1.2. Electrochemical detection of Pb2+

1.3. The discussion of cyclic voltammetry and electrochemical impedance

spectroscopy

2. Figure

Fig. S1. The real picture of collection of phloem sap and corresponding collection

device

Fig. S2. Pathway of electron transfer through the MWCNTs-GSH-Au-GSH

Fig. S3. TEM image of (a) MWCNTs-Au-GSH and (b) MWCNTs-GSH-Au-GSH

Fig. S4. Typical SWASV response of MWCNTs-GSH-Au-GSH modified GCE for

analysis of Pb2+ mixed with rice phloem sap for 1 minute and 24 hours

Fig. S5. Optimal experimental conditions at MWCNTs-GSH-Au-GSH electrode

Fig. S6. SWASV response of bare, MWCNTs, MWCNTs-GSH, MWCNTs-GSH-Au,

and MWCNTs-Au-GSH GCE for analysis of Pb2+

Fig. S7. SWASV response of 0.1 M Pb2+ at MWCNTs-GSH-Au-GSH GCE in the

presence of 100 M Cl-, 100 M K+, 0-22 M Fe3+, 100 M Ca2+, 100 M Mg2+, 100

M Mn2+, 0-1 M Zn2+, and 0-0.5 M Cu2+ in 0.1 M HAc-NaAc solution

Fig. S8 SWASV detection of 1 M Pb2+ in the absence and presence of main

coexisting inorganic ions on glassy-carbon electrode

Fig. S9. Fourier transforms (FTs) of EXAFS data with fits to spectra

Fig. S10. Cyclic voltammograms and electrochemical impedance spectra at

MWCNTs-GSH-Au-GSH electrode

Fig. S11. Scan rate study at MWCNTs-GSH-Au-GSH electrode

3. Table

Table S1. Soil physical and chemical properties

Table S2. Comparison of electrochemical performance for voltammetric detection of

Pb2+

Table S3. Results of EXAFS analysis

Table S4. Results of XPS analysis

4. Reference

1. Experimental section and discussion

1.1. Apparatus and instruments

Electrochemical measurements were performed with CHI 660D computer-controlled

potentiostat (Chenhua Instruments Co., Shanghai) with the MWCNTs-GSH-Au-GSH

modified glassy-carbon electrode (GCE) as working electrode, Ag/AgCl electrode as

reference electrode, and Pt wire as counter electrode. Nanomaterials were conducted

by SEM images (FESEM, Quanta 200 FEG, FEI Company). TEM and HRTEM as

well as EDS (JEM-2010), XRD (Philips X’Pert Pro X-ray diffractometer), FT-IR

spectrometer (Nicolet Nexus-670), XPS (VG ESCALAB MKII spectrometer), XAFS

(BL14W1 beamline of the Shanghai Synchrotron Radiation Facility). The main

coexisting inorganic ions in the phloem sap were determined by ICPMS (Plasma

Quad 3, Thermo Electron Co., United States).

1.2. Electrochemical detection of Pb2+

Pb2+ was gradually added to NaAc-HAc solution, performing a deposition voltage (-1

V) for 210 s, then stripping and finally applying a deposition voltage (0.8 V) for

desorption. SWASV responses was performed with frequency of 15 Hz, amplitude of

25 mV and a step potential of 4 mV.

1.3. The discussion of cyclic voltammetry and electrochemical impedance

spectroscopy

Cyclic voltammetry (CV, Figure S8a) and electrochemical impedance spectroscopy

(EIS, Figure S8b) of bare, MWCNTs, MWCNTs-GSH, MWCNTs-GSH-Au,

MWCNTs-Au-GSH and MWCNTs-GSH-Au-GSH electrodes were tested in

potassium ferricyanide (K3Fe(CN)6) solution. Peak current of these six kinds of

electrodes reveal similar and great electron-transfer kinetics for K3Fe(CN)6 redox

probe. Electron transfer impedance values are all small, indicating the good

conductivity of these nanomaterials and the good capability for electrons transfer.

Real electrochemical surface areas (RESA, Figure S9) of the bare, MWCNTs,

MWCNTs-GSH, MWCNTs-GSH-Au, MWCNTs-Au-GSH and MWCNTs-GSH-Au-

GSH modified electrodes are 0.068, 0.056, 0.052, 0.059, 0.063 and 0.052 cm2,

respectively.

2. Figure

Fig. S1 The real picture of (a) collection of phloem sap, (b) corresponding collection device, (c) centrifuge tube, and (d) absorbent cotton wool.

Fig. S2 Pathway of electron transfer through the MWCNTs-GSH-Au-GSH.

Fig. S3 TEM image of (a) MWCNTs-Au-GSH and (b) MWCNTs-GSH-Au-GSH.

Fig. S4 Typical SWASV response of MWCNTs-GSH-Au-GSH modified GCE for analysis of Pb2+ mixed with rice phloem sap for (a) 1 minute, (b) 24 hours.

Fig. S5 Optimum experimental conditions. Influence of (a) supporting electrolytes;(b) pH value; (c) deposition potential; and (d) deposition time on SWASV response of MWCNTs-GSH-Au-GSH electrode. Data were evaluated of 0.3 M Pb2+.

Fig. S6 SWASV response of (a) bare, (b) MWCNTs, (c) MWCNTs-GSH, (d) MWCNTs-GSH-Au, and (e) MWCNTs-Au-GSH electrode for analysis of Pb2+ in different concentration ranges. Inset in panel a, b, c, d and e are the corresponding linear calibration plot of peak current against Pb2+ concentrations, respectively.

Fig. S7 SWASV response of 0.1 M Pb2+ at MWCNTs-GSH-Au-GSH modified GCE in the presence of (a) 100 M Cl-, (b) 100 M K+, (c) 0-22 M Fe3+, (d) 100 M Ca2+, (e) 100 M Mg2+, (f) 100 M Mn2+, (g) 0-1 M Zn2+, and (h) 0-0.5 M Cu2+ in HAc-NaAc solution.

Fig. S8 SWASV detection of 1 M Pb2+ in the absence and presence of main coexisting inorganic ions on glassy-carbon electrode.

Fig. S9 (a) The k3-weighted Cu K-edge XAFS spectra of MWCNTs-GSH-Au-GSH-Cu2+, k3-weighted Fe K-edge XAFS spectra of MWCNTs-GSH-Au-GSH-Fe3+ and k3-weighted Zn K-edge XAFS spectra of MWCNTs-GSH-Au-GSH-Zn2+. (b) Fourier transforms of EXAFS data with fits to spectra.

Fig. S10 CV (a) and EIS (b) for bare, MWCNTs, MWCNTs-GSH, MWCNTs-GSH-Au, MWCNTs-Au-GSH, and MWCNTs-GSH-Au-GSH modified GCE in K3Fe(CN)6 solution. Scan rate: 100 mV s-1.

Fig. S11 Scan rate test in K3Fe(CN)6 solution on bare, MWCNTs, MWCNTs-GSH, MWCNTs-GSH, MWCNTs-GSH-Au, MWCNTs-GSH-Au-GSH, and MWCNTs-Au-GSH modified electrode, respectively. Inset is the corresponding plots of current versus the square root of the scan rate with a linear trend line.

3. Table

Table S1 Soil physical and chemical properties.Organic matter

(g / kg) pH Pb (mg/kg)

Total nitrogen (g/kg)

Total phosphorus (g/kg)

Available potassium (mg/kg)

20.3 6.8 30 0.95 1.32 101.46

Table S2 Comparison of electrochemical performance for voltammetric detection of Pb2+.

Electrode material Linear range (μM) SensitivityμA μM−1

LOD (μM) Sample Ref.

nanoplate-stacked Fe3O4 0.04-0.2 24.6 0.0152 water 1

Terephthalic acid - iron oxide 0.06-1.1 12.149 0.04 water 2

O2-plasma oxidized MWCNTs 0.5–4.5 3.55 5.7×10-5 water 3

amino-carbon microspheres 0.6-1.8 16.13 0.38 water 4

TCA-MWCNTs. 0.0002 -0.01 7548 4 × 10−5 water 5

fluorinated graphene oxide 0.3-5.0 10.32 0.01 water 6

Au NPs 0.2-1.4 17.63 ------ water 7

AlOOH-RGO 0.3-1.1 2.97 7.6×10-5 water 8

N-doped graphene 0.01-9 4.946 0.005 water 9

G/MWCNTs/Bi 0.0024 -0.14 29.4 0.001 water 10

MWCNT-GSH-Au-GSH 0.02-0.35 58.4 0.01rice phloem

sapthis

work

Table S3 Results of EXAFS analyses. CN = coordination number, R = interatomic distance, σ2 = Debye-Wailer factor and ΔE0 = phase shift.

Sample first shell CN R(Å) s2(Å2) E0 (eV) ΔE0 (eV)

MWCNTs-GSH-Au-GSH-Cu2+ Cu--O/N 3.46 1.95 0.07 -2.23 1.37

MWCNTs-GSH-Au-GSH-Fe3+ Fe--O/N 4.71 1.99 0.06 -2.24 1.26

MWCNTs-GSH-Au-GSH-Zn2+ Zn--S 4.58 2.21 0.03 -4.37 1.81

MWCNTs-GSH-Au-GSH-Pb2+ Pb--O/N 3.51 2.43 0.15 -3.92 2.61

Table S4 Results of XPS analysis. MWCNTs-GSH-Au-GSH adsorbed coexisting ions of Pb2+, Cu2+, Fe3+ and Zn2+ for different times.

210 s 2 hours 4 hoursPb/C (%) 0.43 0.49 0.5Cu/C (%) 0.14 0.19 0.26Fe/C (%) 0.18 0.19 0.27

Zn/C (%) 0 0 0.04

Atom RatioAdsorption Time

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