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Supporting Information

Ultrafine gold nanoparticle embedded poly(diallyldimethylammonium

chloride)-graphene oxide hydrogels for voltammetric determination of

antimicrobial drug (Metronidazole)†

Pitchaimani Veerakumar*,a,b Arumugam Sangili,c Shen-Ming Chen*,c and King-Chuen

Lin*,a,b

aDepartment of Chemistry, National Taiwan University, No. 1, Roosevelt Road, Section 4, Taipei

10617, Taiwan, ROCbInstitute of Atomic and Molecular Sciences, Academia Sinica, No. 1, Roosevelt Road, Section 4,

Taipei 10617, Taiwan, ROCcDepartment of Chemical Engineering and Biotechnology, National Taipei University of

Technology, No. 1, Chung-Hsiao East Road, Section 3, Taipei 10608, Taiwan, ROC

*Corresponding Authors

E-mail: spveerakumar@gmail.com (P. Veerakumar); Tel.: +886-2-23668230; Fax: +886-2-

23620200

E-mail: smchen78@ms15.hinet.net (S.-M. Chen); Fax: +886-2-27025238; Tel: +886-2-27017147

E-mail: kclin@ntu.edu.tw (K.-C. Lin); Tel.: +886-2-33661162; Fax: +886-2-23621483

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry C.This journal is © The Royal Society of Chemistry 2020

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Calculation of Au NP particle size

While considering the peak at degrees, average particle size has been estimated by using Debye-

Scherrer formula.S1

𝐷 =0.89 𝜆𝛽 𝐶𝑜𝑠𝜃

(𝑆1)

where D = Crystallite size in Å; λ = X-ray wavelength, 1.540598 nm for Cu Kα Radiation; β = Full

width at half maximum (FWHM) of the highest intensity peak, in Radians (0.312π/180); θ = Peak

position (2θ = 38.1). In the present case, substituting the known values yields

= 269.9 Å ≈ 26.9 nm.

𝐷 =0.89 1.540598

(0.312𝜋180 )𝐶𝑜𝑠(

38.12

)

Fig. S1. N2-adsorption/desorption (77 K) isotherms of GO, GO@PDDA, and Au NP@PDDA/GH.

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Fig. S2. FE-SEM images of the as-synthesized (a) GO, (b-d) GO@PDDA at different

magnifications.

Fig. S3. The size distributions of Au NP corresponding to the Au NP@PDDA/GH.

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Fig. S4. (a) UV–vis spectra of PDDA, HAuCl4 solution, and PDDA/Au NP (Inset Corresponding

photographs) and (b) UV-vis spectra of the GO, GO@PDDA, Au NP, and Au NP@PDDA/GH.

Fig. S5. The Nyquist plots of the bare GCE, Au NP@PDDA, GO, GO@PDDA, Au NP@GO, and

Au NP@PDDA/GH-modified GCE.

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Fig. S6. (a) CV curves of different catalyst dosage, (b) the corresponding plot of reduction peaks

current vs. catalyst dosage, (c) CV curves of various MZ concentration at 50250 µM in the

presence of Au NP@PDDA/GH-modified GCE, and (d) their corresponding current versus MZ

concentration. All measurements performed under N2-saturated in 0.05 M PB solution (7.0).

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Figure S7. The linear plot of reduction peak potential vs. log scan rate. All measurements recorded

in N2-saturated PBS with MZ (200 µM) in the presence of Au NP@PDDA/GH-modified GCE

(scan rate of 50 mV s1).

Fig. S8. (a) The CV response peak current for electro reduction of MZ with the Au

NP@PDDA/GH-modified GCE which was kept for 5 weeks, (b) Current with variation of

electrodes, (c) Fifty overlapped CV curves of Au NP@PDDA/GH/GCE in the absence of MZ, and

(d) EIS spectra recorded before and after 50 cycles with Au NP@PDDA/GH-modified GCE. All

measurements recorded in N2-saturated 0.05 M PB solution (pH 7.0) with 200 µM MZ (scan rate

of 50 mV s1).

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Fig. S9. (a) CV curves of different size of Au NP (20 nm, 25 nm, 30 nm, 45 nm) loaded catalyst

dosage, (b) Extended image, and (c) Corresponding bar diagrams in the presence of MZ (50 µM)

in N2-saturated 0.05 M PB solution (pH 7.0).

Fig. S10. The time-dependent UV-vis spectra of (a) MZ-Tab-1, (b) MZ-Tab-2, and (c) MZ-Tab-3

in the presence of Au NP@PDDA/GH catalyst after the addition of NaBH4 solution.

Table S1. Raman characteristics for Gr, GO, GO@PDDA, and Au NP@PDDA/GH composites.

Intensity (counts) Band position (cm1)Sample

D

band

G

band

ID/IG D

band

G

band

SBET

(m2 g 1)a

Vtot

(cm3 g 1)a

Gr 3028.7 1578.6

GO 11755.2 11865.4 0.9907 1361.2 1606.1 212.68 0.019

GO@PDDA 12864.7 12894.1 0.9977 1361.1 1612.3 168.45 0.014

Au NP@PDDA/GH 13980.1 13999.3 0.9992 1367.3 1606.4 112.71 0.011aSurface area (SBET) and pore volumes (Vtot) derived at P/P0 = 0.99.

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Table S2. The C 1s, O 1s, and N 1s XPS spectral bands based on the binding energies for GO, PDDA, PDDA/GH, and Au NP@PDDA/GH.

Sample C 1s

(eV)

Assignment O 1s

(eV)

Assignment N 1s

(eV)

Assignment Au 4f

(eV)

Assignment

GO 285.1;

286.3;

288.7;

290.9

sp2 (C=C); sp3 (CC,

C-H); (C-O/C-OH);

(C=O/O-C=O)

532.1;

533.2;

534.5

C=O/O-C=O; (O=C-

O-C=O)/(C-O-H); (O-

C=O)/(C-O-C)

PDDA 402.0 N+

GO@PDDA 285.0;

285.8;

288.1;

289.2

sp2 (C=C); sp3 (C-C,

C-H); (C-O/COH);

(C=O/O-C=O)

530.6;

532.5;

533.5

C=O/O-C=O; (O=C-

O-C=O)/(C-O-H); (O-

C=O)/(C-O-C)

401.4 N+

Au NP@PDDA/GH 284.8;

285.6;

287.8;

289.2

sp2 (C=C); sp3 (C-C,

C-H); (C-O/C-OH);

(C=O/OC=O)

530.3;

532.1;

533.2

C=O/O-C=O; (O=C-

O-C=O)/(C-O-H); (O-

C=O)/(C-O-C)

401.3 N+ 83.4;

87.1

Au 4f7/2; Au

4f5/2

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Table S3. Rate constants for the catalytic reduction of MZ with varying catalyst dosages.

Catalyst Dosage

(mg mL-1)

Time

(s)

k

(s1)

GO 0.2 100 0.018

GO@PDDA 0.2 100 0.021

Au NP@PDDA/GH 0.2 100 0.064

Au NP@PDDA/GH 0.5 70 0.1082

Au NP@PDDA/GH 0.8 60 0.1410

Au NP@PDDA/GH 1.2 50 0.1830

References

S1. A. Jafari, M. H. Alam, D. Dastan, S. Ziakhodadadian, Z. Shi, H. Garmestani, A. S.

Weidenbach and Ş. Ţălu, J. Mater. Sci. Mater. Electron., 2019, 30, 2118521198.