Supplementary material

Efficient Enhancement of Electrochemiluminescence from Tin

Disulfide Quantum Dots by Hollow Titanium Dioxide

Spherical Shell for Highly Sensitive Detection of

Chloramphenicol

Peng-Cheng Li, Jie Yu, Kang Zhao, An-Ping Deng*, Jian-Guo Li*

The Key Lab of Health Chemistry & Molecular Diagnosis of Suzhou, College of

Chemistry, Chemical Engineering & Materials Science, Soochow University, Suzhou

215123, P. R. China

* Correspondence authors: J.G. Li, Telephone: +86 51265882195, Fax: +86

51265882195, E-mail address: lijgsd@suda.edu.cn; A.P. Deng, Telephone: +86

51265882362, Fax: +86 51265882362, E-mail address: denganping@suda.edu.cn

Table of Content

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Instruments and Chemicals................................................................S-3

Buffers and Solutions..........................................................................S-4

Figure S1...............................................................................................S-5

Figure S2...............................................................................................S-6

Figure S3...............................................................................................S-7

Figure S4...............................................................................................S-8

Figure S5...............................................................................................S-9

Figure S6.............................................................................................S-10

Figure S7.............................................................................................S-11

Table S1...............................................................................................S-12

Table S2...............................................................................................S-13

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Instruments and Chemicals

The ECL measurements were performed by a MPI-A multi-functional

electrochemical and chemiluminescent analytical system (Xi’An Remax Elcetronic

Science & Technology Co., Ltd., Xi’An, China) with the voltage of the photomultiplier

tube (PMT) being biased at -550 V and the potential scanning from 0 to -2.0 V in the

course of detection. Three electrode system was used in the experiment, which contained

the modified glassy carbon electrode (GCE, Ф = 3 mm) as working electrode, platinum

as the counter electrode and Ag/AgCl (saturated KCl solution) electrode as reference

electrode. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV)

were carried out with a RST 5000 electrochemical working station (Suzhou Risetest

Instrument Co, Ltd, Suzhou, China). X-ray photoelectron spectroscopy (XPS) was

performed on an ESCA-Lab 220i-XL electron spectroscopy from VG Scientific (Thermo

VG Scientific, USA). Scanning Electronic Microscopy (SEM) was carried out using a

Hitachi SU8010 SEM (Hitachi Co., Ltd. Japan). Transmission Electron Microscope

(TEM) images and High Resolution Transmission Electron Microscopy (HRTEM)

images were obtained from Tecnai G2 F20S-TWIN 200KV (FEG, FEI Co., USA).

Fluorescence emission spectra were obtained from F-2500 fluorescence spectrometer

(Hitachi, Japan). UV absorption spectroscopy was performed on a TU-1901 dual-beam

UV-Vis spectrophotometer (Persee, Beijing). The recovery test was verified with Q-6545-

TOF LC/MS system (Agilent, USA).

Chloroauric acid (HAuCl4·4H2O, 47.8%), potassium hexacyanoterrate trihydrate

(K4[Fe(CN)6]·3H2O, AR), potassium chloride (KCl, AR), potassium dihydrogen

phosphate (KH2PO4, AR), potasium ferricyanide (K3[Fe(CN)6], AR), potassium

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peroxydisulfate (K2S2O8, AR), L-cysteine (C3H7NO2S, BR) and ammonia solution

(NH3·H2O, AR) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai,

China). L-ascorbic acid (AA, AR), sodium phosphate dibasic dodecahydrate

(Na2HPO4·12H2O, AR), sodium3hydroxide (NaOH, AR) and titanium butoxide (TBT,

99%) were bought form Shanghai Titan Scientific Co., Ltd. (Shanghai, China).

Polyethyleneimine (PEI, M.W.600, 99%) and (3-aminopropyl) triethoxysilane (APTES,

99%) were obtained from Aladdin Industrial Corporation (Shanghai, China). Tetraethyl

orthosilicate (TEOS, 98%), Ethyl-3-(dimethyl aminopropyl) carbodiimide (EDC, 98%),

N-hydroxysuccinimide (NHS, 97%) were supplied by J&K Scientific (Beijing, China).

Tinchloride pentahydrate (SnCl4·5H2O, 99%) was acquired from Energy Chemical

(Shanghai, China). Bovine serum albumin (BSA, 98%) and ovalbumin (OVA) were

purchased from Sigma-Aldrich Co., Ltd. (St. Louis, MO, USA). Aluminum oxide

polishing powder (Al2O3, 0.3 and 0.05 μm) was obtained from Tianjin Aidahengsheng

Technology Co., Ltd. (Tianjin, China). All other reagents and materials were

commercially available and of analytical reagent grade.

Buffers and Solutions

Phosphate buffered saline (PBS, pH =7.4, 0.1 mol L-1) was prepared using KCl (0.1

mol), NaCl (0.1 mol), Na2HPO4 (6.4 mmol) and KH2PO4 (1.0 mmol) throughout the entire

work. ECL detection buffer was prepared by PBS containing 0.1 mol K2S2O8. The

solution to activate bare GCE was prepared by 5.0 mmol K3[Fe(CN)6], 5.0 mmol

K4[Fe(CN)6] and 0.1 mol KCl. All aqueous solutions were prepared with sub-boiling

doubly distilled water.

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Figure S1

Figure S1. XPS survey spectra of (a) THS, (b) Au-THS, (c) Ti2p and (d) Au4f.

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Figure S2

Figure S2. Fluorescence emission spectra of hollow titanium dioxide: (A) excitation wavelength 280 nm and (B) excitation wavelength 480 nm. Fluorescence emission spectra of titanium dioxide: (C) excitation wavelength 280 nm and (D) excitation wavelength 480 nm.

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Figure S3

Figure S3. UV-vis absorption spectrum of THS and TiO2 (ethanol as solvent).

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Figure S4

Figure S4. CV curves of immunosensor without probe (a), ECL intensity of immunosensor at probe of (b) SnS2 QDs-Ab, (c) SnS2 QDs-PEI-TiO2 sphere-Ab and (d) SnS2 QDs-PEI- TiO2 hollow sphere-Ab.

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Figure S5

Figure S5. Selectivity of the proposed ECLIA against different targets: CAP, FFC, OFX, NOR and TAP (The concentration of the above substances are 10 ng mL-1). Abbreviations: CAP, chloramphenicol; FFC, florfenicol; OFX, ofloxacin; NOR, norfloxacin; TAP, thiamphenicol.

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Figure S6

Figure S6. The intra-assay precision investigated with six different electrodes and RSD is less than 5% (Continuous 5 cyclic scans of six different electrodes at 1 ng mL-1 CAP standard solutions in PBS containing 0.1 M S2O8

2-).

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Figure S7

Figure S7. Stability of proposed sensors stored at 4 °C for different times: (A) 24 hour, (B) 48 hours, (C) 72 hours and (D) 96 hours.

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Table S1

Table S1. Properties of comparable methods for the determination of CAP.

Methods LODs

(ng mL-1)

Analytical ranges

(ng mL-1)

References

GC-MS 0.05 0.1~100 Liu et al., 2014

LC-MS 0.019 0.15~3 Letícia et al., 2018

HPLC-DAD 4 20~2000 Karageorgou et al., 2018

ELISA 0.06 0.01~30 Yuan et al., 2017

SERS 33 100~100000 Ji et al., 2015

ECLIA 0.0031 0.01~100 This Work

Abbreviations: GC-MS, gas chromatography mass spectrometry; LC-MS, liquid chromatography mass spectrometry; HPLC-DAD, high performance liquid chromatography with diode-array detection; ELISA, enzyme-linked immunosorbent assay; SERS, surface-enhanced Raman scattering; ECLIA, electrochemiluminescence immunoassay.

Reference

Ji, W., Yao, W.R., 2015. Spectrochim. Acta A. 144, 125-310. DOI: 10.1016/j.saa.2015.02.029

Karageorgou, E., Christoforidou, S., Ioannidou, M., Psomas, E., Samouris, G., 2018. Foods 7 (6). DOI: 10.3390/foods7060082

Letícia, R.G., Patrícia, A.S.T., Maria, B.A.G., Christian, F., 2018. Food Chem. 262, 235-241. DOI: 10.1016/j.foodchem.2018.04.087

Liu, T.S., Xie, J., Zhao, J.F., Song, G.X., Hu, Y.M., 2014. Food Anal. Methods. 7, 814-819. DOI: 10.1007/s12161-013-9686-5

Yuan, Y., Zhao, Y.Y., Wu, K., Yang, H., Zhao, K., Li, J.G., Deng, A.P., 2017. Anal. Methods. 9 (39), 5806-5815. DOI: 10.1039/c7ay01628j

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Table S2Table S2. Molecular formula of chloramphenicol and four structurally similar interfering substances

Structural Formula Substance

Chloroamphenicol (CAP)

CAS No.: 56-75-7

Florfenicol (FFC)

CAS No.:73231-34-2

Thiamphenicol (TAP)

CAS No.:15318-45-3

Norfloxacin (NOR)

CAS No.: 70458-96-7

Ofloxacin (OFX)

CAS No.:82419-36-1

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