Electrochemical Sensing of Bisphenol A on Facet-Tailored TiO 2 Single Crystals. Engineered by Inorganic-Framework Molecular Imprinting Sites

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1 Supporting information for Electrochemical Sensing of Bisphenol A on Facet-Tailored TiO 2 Single Crystals Engineered by Inorganic-Framework Molecular Imprinting Sites Dan-Ni Pei 1, Ai-Yong Zhang *1,2, Xiao-Qiang Pan 1, Yang Si 1, Han-Qing Yu *,1 1 Department of Chemistry, University of Science and Technology of China, Hefei, , China 2 Department of Municipal Engineering, Hefei University of Technology, Hefei, , China *Corresponding authors: Dr. Ai-Yong Zhang, Fax: , ayzhang@hfut.edu.cn Prof. Han-Qing Yu, Fax: , hqyu@ustc.edu.cn S-1

2 Table of Contents 1. Experimental details p. S-4 ~ S-8 2. Table S1. Main physical structural parameters of the three TiO 2 electrode materials. p. S-9 3. Table S2. Initial surface concentration (Γ), anodic peak current (i) and signal retention efficiency (η) of BPA detection on the MI-TiO 2 SCs under various analytical conditions. p. S-10 ~ S Table S3. Electrochemical detection of trace BPA in real industrial samples with the MI-TiO 2. p. S Figure S1. X-ray diffraction pattern of Degussa P25 benchmark with anatase-rutile mixed crystal phase. p. S Figure S2. SEM images of the MI-TiO 2 with BPA doage of (a), 5.0 (b), 2 (c) and 5 mg (d). p. S Figure S3. XPS (a and b), valance band spectra (c) and Brunauer-Emmett-Teller adsorption-desorption curves of liquid nitrogen (d) of TiO 2, BPA-entrapped TiO 2 and MI-TiO 2 with BPA dosage of 5.0 mg. p. S Figure S4. Cyclic voltammetry (a), Nyquist diagrams (b) and Q-t curves after background subtracted (c, d) of pure, P25-, TiO 2 -, BPA-entrapped TiO 2 - and MI-TiO 2 -modified GCE. p. S Figure S5. Interfacial diffusion coefficient D (a) and initial surface concentration Γ (b) of different BPA concentrations on the MI-TiO 2 -, facet-tailored TiO 2 - and Degussa P25-modified GCE. p. S Figure S6. i-t curves (a, c and e) and their calculated BPA diffusion coefficients (b, d and f) onto the MI-TiO 2 -, facet-tailored TiO 2 - and Degussa P25-modified GCE from 5.0, 1 and 2 µm aqueous solutions with 0.1 M KCl and 0.1 M phosphate buffer solution (ph = 7.0). p. S Figure S7. LSV voltammograms of P25- (a), TiO 2 - (b), BPA-entrapped TiO 2 - (c) and MI-TiO 2 - (d) modified GCE. p. S Figure S8. Relationship between the anodic peak current and the scanning rate and their calculated initial surface concentration in the LSV voltammograms of P25- (a), TiO 2 - (b), BPA-entrapped TiO 2 - (c) and MI-TiO 2 - (d) modified GCE. p. S Figure S9. BPA detection on the pure, P25-, TiO 2 -, BPA-entrapped TiO 2 - and MI-TiO 2 -modified GCE: detection material (a, b) and deposition amount of detection material (c, d). p. S Figure S10. BPA detection on the MI-TiO 2 -based electrochemical sensor at different phs without accumulation (a), accumulation time at 100 mv (b) and accumulation potential for 100 s (c). p. S Figure S11. BPA detection on the MI-TiO 2 -based electrochemical sensor at different solution ph (a, b) and electro-static pre-accumulation (c, d). p. S Figure S12. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of phenol (HB), 4-nitrophenol (p-np), 4-nitroaniline (p-na), humic acid (HA), methanol (CH 3 OH), ethanol (C 2 H 5 OH), chlorine (Cl - ) and 0.1 M phosphate buffer solution (ph = 7.0) (a) and different organic and inorganic S-2

3 interfering compounds (b-f). p. S Figure S13. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of phenylalanine (PA) (a, b), diphenylalanine (DPA) (c, d) and their mixture (PA+DPA) (e, f) at different molar ratios. p. S Figure S14. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of four structural analogues: BPAF (a, b), BPS (c, d), HBP (e, f) and HBPA (g, h). p. S Figure S15. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of four structural analogues: BPAF+BPS (a), BPAF+HBP (b), BPAF+HBPA (c), BPS+HBP (d), BPS+HBPA (e) and HBP+HBPA (f). p. S Figure S16. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of four structural analogues: BPAF+BPS+HBP (a), BPAF+BPS+HBPA (b) and BPAF+BPS+HBP+HBPA (c). p. S Figure S17. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of humic acids: distilled water (a, b) and practical water (c, d). p. S Figure S18. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of typical metal ions and inorganic anions: Fe 2+ (a), Fe 3+ (b), Mn 2+ (c), Cl - (d) and HCO 3 - (e). p. S Figure S19. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of humic acids and typical ions: Cl - + Fe 2+ (a), Fe 2+ + Mn 2+ + Cl - (b), Mn 2+ + Cl - (c), Cl - + HCO 3 - (d) and Cl - + HCO Mn 2+ + Fe 2+ + Fe 3+ (e). p. S-31 S-3

4 Characterization of TiO 2 SCs and MI-TiO 2 SCs Morphology of the samples was imaged with a field emission scanning electron microscope (SEM, JEOL Co., Japan) and a transmission electron microscope (TEM) (JSM-6700F and JEM-2011, JEOL Co., Japan). X-ray diffraction (XRD) patterns were recorded by a diffract meter with Cu Kα radiation (XPert, Philips Inc., the Netherlands). X-ray photoelectron spectra (XPS) were recorded by an electron spectrometer (ESCALAB 250, Thermo-VG, USA). Fourier transform infrared (FTIR) spectra were recorded by a spectrometer with KBr as matrix (Vertex 70, Bruker Co., Germany). Brunauer-Emmett-Teller (BET) and Barret-Joyner-Halender (BJH) analyses were performed by nitrogen adsorption-desorption isotherms at o C with automatic specific surface and pore size analyzer (Tristar II 3020M, Micromeritics Co., USA). All electrochemical experiments were conducted on a workstation (CHI760e, Chenhua Co., China) with a 20 ml home-made three-electrode glass cell. A bare or modified glass carbon electrode (GCE, 3 mm in diameter) was used as the working electrode, a saturated Ag/AgCl electrode and a Pt wire as the reference electrode and counter electrode (Wuhan Gaossunion Co., China) respectively. The bulk solution ph was measured using a PHS-3C digital meter (Shanghai Leici Co., China). Morphological and Structural Properties of P25 Benchmark Degussa P25, the most widely used commercial TiO 2 product in the world, was employed as the reference in our work. The polycrystalline P25 benchmark has a S-4

5 mean particle size of about 25 nm, anatase/rutile = 80:20, BET surface area of ca. 50 m 2 /g (Table S1 and Figs. S3d and S4), and a low-energy {101} facet of less than 5%. Calculation of Electrochemical Surface Area The electrochemical effective surface area (A eff ) of the electrodes was further measured by chronocoulometry in 0.1 mm K 3 [Fe(CN) 6 ] and 20 µm BPA target solutions (Fig. 2c and d), and calculated with the Anson equation: ( )= + + (1) = (2) where n is electron transfer number of reaction, c is concentration of substrate, D is diffusion coefficient of substrate, F is Faradic constant (F= C mol -1 ), Q dl is double layer charge, Q ads is Faradic charge, Γ s is adsorption capacity. In the K 3 [Fe(CN) 6 ] model solution, n = 1, D = cm 2 s -1 and c = 0.1 mm. Calculation of Anodic Oxidation Peak Potential For an adsorption-controlled and totally irreversible electrode process, E p is defined by the following equation: E p = E 0 + (2.303RT/αnF) lg(rtk 0 /αnf) + (2.303RT/αnF) lgv (3) where α is transfer coefficient, k 0 is standard reaction rate constant, n is electron transfer number, v is scan rate, E 0 is formal redox potential, R is gas constant, T is absolute temperature and F is Faraday constant. S-5

6 Calculation of Diffusion Coefficient Chronoamperometry measurements were carried out with BPA aqueous solutions of 5, 10 and 20 µm to determine its diffusion coefficient onto the modified GCE surface (Figure S6a, c and e). The plot of current (I) versus t -1/2 at various BPA concentrations gives straight lines with different slopes (Figure S6b, d and f). From the resulting slopes, a specific diffusion coefficient could be calculated using the Cottrell equation. I = (4) where I is the time-dependent faradic current, n is the number of electrons (n = 2), F is the Faraday's constant (F C mol -1 ), A is the working electrode geometric area (A = cm 2 ), D is the BPA diffusion coefficient (cm 2 s -1 ), C is the BPA concentration in solution (mol cm -3 ) and t is the time (s). Calculation of Initial Surface Concentration The initial surface concentration Γ indicates the adsorption capacity of BPA at the anodic electrodes, which was obtained from the LSVs of BPA at the MI-TiO 2 anode at various potential scan rates (υ) (Figure S7). When the potential scan rate increased, the oxidation peaks of BPA shifted toward more anodic potentials, and a linear variation of the peak potential (E p ) with ln υ was observed, confirming that the electrochemical oxidation of BPA was irreversible. In the case of an irreversible electrochemical reaction of an adsorbed species, the oxidation peak current (I p ) could be expressed as: S-6

7 α. (5) where I p is the peak current (in A), n is the total number of electrons exchanged in the electrochemical process (n = 2 in this case), α is the charge transfer coefficient (usually considered to be 0.5), n a is the number of electrons exchanged in the limiting electron transfer step (n a = 2 in this case), A is the electrode surface area (in this case, A = cm 2 ), F is the faraday constant (F = C mol -1 ), R is the molar gas constant (R = 8.3 J mol -1 K -1 ), T is the thermodynamic temperature (T = 298 K in this case), Γ is the initial surface concentration of BPA (mol - ), and υ is the potential scan rate in LSV measurements (V s -1 ). Therefore, the initial surface concentration Γ could be calculated from the slope of the linear variation of I p with υ (Figure S8) according to the following equation: =. [ ] α (6) Collection and Sampling Conditions of Real Environmental Samples All real water samples were filtered by 0.45 µm membrane for analysis at ambient temperature. The tap water sample was collected from our laboratory without any further purification. The lake water was collected at different positions in Chaohu Lake in Hefei City, Anhui, China, which is one of the greatest freshwater lakes in China. The river water samples were collected at different positions in Nanfeihe River in Hefei City, China. The sewage and sludge samples were collected from a municipal wastewater treatment plant in Hefei City, China. The wastewater samples were collected from the secondary effluent (after biological treatment and before S-7

8 chlorination disinfection). The lake water, river water and wastewater samples were subjected to the same pre-treatment by centrifugation, and the supernatants were used for BPA analysis. The sludge samples were collected from the secondary sedimentation tank and then mixed with 30 ml 0.1 M PBS (ph 7.0) at 50 o C in sealed conical flasks, which were shaken at 30 o C for 1~5 d. After that, the precipitate was removed by centrifugation and the supernatant was used for BPA analysis. S-8

9 Table S1. Main physical structural parameters of the three TiO 2 electrode materials. a materials A BET (m 2 g) V Pore (cm 3 g) D Pore (nm) MI-TiO 2 SCs TiO 2 SCs P a the mean value of three parallel measurements (n = 3), with relative standard deviation less than 1% (RSD < 1%). S-9

10 Table S2. Initial surface concentration (Γ), anodic peak current (i) and signal retention efficiency (η) of BPA detection on the MI-TiO 2 SCs under various analytical conditions. analytical condition Γ a ( M cm -2 ) BPA detection i η b (%) BPA 9.83±7 18±41 100±3.37 BPA+HB 8.67± ±44 103±3.61 BPA+p-NP 9.02± ± ±4.11 BPA+p-NA 10.48±4 22±43 103±3.53 BPA+HA 9.39± ± ±4.27 BPA+CH 3 OH 11.14±7 28± ±3.04 BPA+C 2 H 5 OH 9.28±9 03± ±2.87 BPA+HB+p-NP 8.40± ± ±3.69 BPA+HB+p-NA 7.19±1 05± ±3.61 BPA+p-NP+p-NA 10.52±5 31± ±3.20 BPA+HB+HA 9.03± ±38 94±3.12 BPA+p-NP+HA 8.15±6 73± ±3.37 BPA+p-NA+HA 9.27± ± ±2.38 BPA+HB+p-NP+p-NA 10.59± ±34 99±2.79 BPA+p-NP+p-NA+HA 7.45± ± ±3.45 BPA+HB+p-NP+HA 8.02± ± ±3.69 BPA+HB+p-NA+HA 8.48±5 22±44 103±3.61 BPA+HB+p-NP+p-NA+HA 7.07± ± ±3.12 BPA+100HB 6.53± ± ±4.27 BPA+100p-NP 8.69± ± ±5.17 BPA+100HB+100p-NP 11.14± ± ±4.19 S-10

11 BPA+100HB+100p-NA 19±4 06± ±2.96 BPA+100HB+100HA 9.01± ± ±3.45 BPA+100p-NP+100p-NA 7.46± ± ±3.86 BPA+100p-NP+100HA 8.20± ± ±3.20 BPA+100HB+100p-NP+100p-NA 18± ± ±3.04 BPA+100p-NP+100p-NA+100HA 7.04± ± ±2.87 BPA+100HB+100p-NP+100HA 8.29± ± ±4.68 BPA+100HB+100p-NA+100HA 7.46± ± ±4.27 BPA+100HB+100p-NP+100p-NA+100HA 9.01±4 19±36 108±2.96 BPA+HB+p-NP+p-NA+HA+CH 3 OH+C 2 H 5 OH 6.38± ± ±3.45 a =. [ ], I p : peak current (A), n: total number of electrons exchanged (n = 2), α: charge transfer coefficient (α = 0.5), n a : number of electrons exchanged in limiting electron transfer step (n a = 2), A: electrode surface area (A = cm 2 ), F: faraday constant (F = C mol -1 ), R: molar gas constant (R = 8.3 J mol -1 K -1 ), T: thermodynamic temperature (T = 298 K), Γ: initial surface concentration (mol), υ: potential scan rate (V s -1 ). b η=i/i 0 100, i: detection current with interfere, i 0 : detection current without interfere. c the mean value of five parallel measurements (n = 5), with relative standard deviation less than 5.0% (RSD < 5.0%). S-11

12 Table S3. Electrochemical detection of trace BPA in real industrial samples with the MI-TiO 2. a industrial samples testing series measured (nm) spiked (nm) b found (nm) RSD (%) recovery efficiency (%) baby nipple 23.3± ± ±3.62 PC water bottle 26.2± ± ±2.87 beverage bottle 27.5± ± ±2.66 food package 36.1± ± ±3.30 fresh film 46.2± ± ±1.40 instant food 4± ± ±2.55 a the mean value of five parallel measurements (n = 5), with relative standard deviation less than 5.0% (RSD < 5.0%). b diluted from 2 µm stock solution at appropriate folds with or without 0.1 M KCl mineral as supporting electrolyte. S-12

13 Intensity θ ( ) Figure S1. X-ray diffraction pattern of Degussa P25 benchmark with anatase-rutile mixed crystal phase. S-13

14 Figure S2. SEM images of the MI-TiO 2 with BPA doage of (a), 5.0 (b), 2 (c) and 5 mg (d). S-14

15 Ti 2p TiO 2 BPA-TiO 2 MI-TiO 2 O 1s TiO 2 BPA-TiO 2 MI-TiO 2 (a) (b) VB TiO 2 BPA-TiO 2 MI-TiO 2 (c) Binding Energy (ev) Binding Energy (ev) Quantity Adsorbed (cm 3 g -1 ) Pore Volume (mm 3 g -1 A) Binding Energy (ev) Pore Diameter (nm) (d) P/P 0 P25 TiO 2 MI-TiO 2 Figure S3. XPS (a and b), valance band spectra (c) and Brunauer-Emmett-Teller adsorption-desorption curves of liquid nitrogen (d) of TiO 2, BPA-entrapped TiO 2 and MI-TiO 2 with BPA dosage of 5.0 mg. S-15

16 MI-TiO 2 BPA-TiO 2 TiO 2 P25 GCE (a) -Z'' (ohm) (b) MI-TiO 2 BPA-TiO 2 TiO 2 P25 GCE Charge (µc) Charge (µc) (c) sqrt Time (s 1/2 ) Time (s) MI-TiO 2 BPA-TiO 2 TiO 2 P25 GCE Charge (µc) Charge (µc) Z' (ohm) sqrt Time (s 1/2 ) (d) MI-TiO Time (s) Figure S4. Cyclic voltammetry (a), Nyquist diagrams (b) and Q-t curves after background subtracted (c, d) of pure, P25-, TiO 2 -, BPA-entrapped TiO 2 - and MI-TiO 2 -modified GCE. Measuring conditions: CV (Solution: 0.1 M KCl mm [Fe(CN) 6 ] 3- /[Fe(CN) 6 ] 4- (1:1) M phosphate buffer solution, ph = 7.0, potential range = -0.2 ~ V, scan rate = 100 mv s -1 and effective anode area = cm 2 ), Nyquist diagrams (solution = 0.1 M KCl mm [Fe(CN) 6 ] 3- /[Fe(CN) 6 ] 4- (1:1) M phosphate buffer solution, ph = 7.0, voltage amplitude = 5 mv, frequency range = 10 5 ~ 10-2 Hz, bias = open-circuit potential and effective anode area = cm 2 ) and chronocoulometry (Solution 1: 0.1 M KCl mm [Fe(CN) 6 ] 3- /[Fe(CN) 6 ] 4- (1:1) M phosphate buffer solution, Solution 2: 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 7.0, chronometer time = 0.25 second and effective anode area = cm 2 ). S-16

17 7.5 (a) 6.0 MI-TiO 2 SC TiO 2 SC P25 D (cm 2 s -1 ) Γ ( M cm 2 ) (b) BPA concentration (µμ) 20 µm 0 P25 TiO2 MI-TiO2 Detection material Figure S5. Interfacial diffusion coefficient D (a) and initial surface concentration Γ (b) of different BPA concentrations on the MI-TiO 2 -, facet-tailored TiO 2 - and Degussa P25-modified GCE. S-17

18 I I I (a) MI-TiO (c) t (s) 5 µm 10 µm 20 µm (e) t (s) TiO 2 P25 5 µm 10 µm 20 µm t (s) 5 µm 10 µm 20 µm I I I (b) 5 µμ 10 µμ 20 µμ MI-TiO 2 k = R 2 = 99 k = R 2 = 99 k = R 2 = (d) 1.0 (f) µm 10 µm 20 µm TiO 2 t -1/2 (s -1/2 ) k = R 2 = 99 k = R 2 = µμ 10 µμ 20 µμ P25 t -1/2 (s -1/2 ) k = 30 R 2 = 99 k = 64 R 2 = 99 k = R 2 = 99 k = 47 R 2 = t -1/2 (s -1/2 ) Figure S6. i-t curves (a, c and e) and their calculated BPA diffusion coefficients (b, d and f) onto the MI-TiO 2 -, facet-tailored TiO 2 - and Degussa P25-modified GCE from 5.0, 1 and 2 µm aqueous solutions with 0.1 M KCl and 0.1 M phosphate buffer solution (ph = 7.0). Measuring conditions: solution 1 = 0.1 M KCl µm BPA M phosphate buffer solution, solution 2 = 0.1 M KCl + 1 µm BPA M phosphate buffer solution, solution 3 = 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 7.0, chronometer time = 120 second and effective anode area = cm 2. S-18

19 mv s -1 (a) 20 mv s mv s -1 P25 40 mv s mv s mv s mv s -1 (b) 20 mv s mv s mv s mv s mv s -1 TiO Potential (V, SCE) mv s -1 (c) 20 mv s mv s mv s mv s mv s -1 BPA-TiO Potential (V, SCE) 10 mv s mv s mv s -1 MI-TiO 40 mv s mv s mv s -1 (d) Potential (V, SCE) Potential (V, SCE) Figure S7. LSV voltammograms of P25- (a), TiO 2 - (b), BPA-entrapped TiO 2 - (c) and MI-TiO 2 - (d) modified GCE. Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 7.0, potential range = ~ 1.0 V, scan rate = 5, 10, 20, 30, 40, 50 and 100 mv s -1, and effective anode area = cm 2. S-19

20 6.0 P25 (a) 6.0 TiO 2 (b) = ν = ν R 2 = ν (V s -1 ) 6.0 BPA-TiO 2 (c) R 2 = ν (V s -1 ) 6.0 MI-TiO 2 (d) = ν = 53 ν R 2 = ν (V s -1 ) R 2 = ν (V s -1 ) Figure S8. Relationship between the anodic peak current and the scanning rate and their calculated initial surface concentration in the LSV voltammograms of P25- (a), TiO 2 - (b), BPA-entrapped TiO 2 - (c) and MI-TiO 2 - (d) modified GCE. Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 7.0, potential range = ~ 1.0 V, scan rate = 5, 10, 20, 30, 40, 50 and 100 mv s -1, and effective anode area = cm 2. S-20

21 2.0 MI-TiO 2 (a) BPA-TiO TiO 2 P25 GCE (b) µl 5 µl 10 µl (c) (d) Blank P25 TiO2 BPA-TiO2 MI-TiO2 Detecting material 0.4 MI-TiO ul 5 ul 10 ul Dosage Figure S9. BPA detection on the pure, P25-, TiO 2 -, BPA-entrapped TiO 2 - and MI-TiO 2 -modified GCE: detection material (a, b) and deposition amount of detection material (c, d). Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, anodic material = P25-, TiO 2 -, BPA entrapped TiO 2 - and MI-TiO 2 -modified GCEs and effective anode area = cm 2. S-21

22 ph=3.0 ph=5.0 ph=7.0 ph=9.0 ph=11.0 ph=13.0 ph=4.0 ph=6.0 ph=8.0 ph=1 ph=12.0 (a) s 100 s (b) s 200 s 300 s s mv (c) 100 mv mv 300 mv 400 mv mv Figure S10. BPA detection on the MI-TiO 2 -based electrochemical sensor at different phs without accumulation (a), accumulation time at 100 mv (b) and accumulation potential for 100 s (c). Measuring conditions of panel (a): solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 3.0 ~ 13.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, and effective anode area = cm 2. Measuring conditions of panel (b): solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, accumulation potential =10 mv, accumulation time = 5 ~ 50 seconds and effective anode area = cm 2. Measuring conditions of panel (c): solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, accumulation potential = -10 ~ 50 mv, accumulation time = 10 seconds and effective anode area = cm 2. S-22

23 E p (V/SCE) 0.8 (a) (b) (c) ph (d) ph T acc (s) E acc (mv) Figure S11. BPA detection on the MI-TiO 2 -based electrochemical sensor at different solution ph (a, b) and electro-static pre-accumulation (c, d). Measuring conditions of panel (a) and (b): solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 3.0 ~ 13.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, anodic material = MI-TiO 2 -modified GCEs and effective anode area = cm 2. Measuring conditions of panel (c): solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, accumulation potential =10 mv, accumulation time = 5 ~ 50 seconds, anodic material = MI-TiO 2 -modified GCEs and effective anode area = cm 2. Measuring conditions of panel (d): solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, accumulation potential = -10 ~ 50 mv, accumulation time = 10 seconds, anodic material = MI-TiO 2 -modified GCEs and effective anode area = cm 2. S-23

24 2.1 BPA HB (a) p-np p-na HA CH 3 OH C 2 H 5 OH Cl - PBS BPA BPA+HB+p-NP (c) BPA+HB+p-NA BPA+p-NP+p-NA BPA+HB+HA BPA+p-NP+HA BPA+p-NA+HA 2.1 BPA BPA+HB (b) BPA+p-NP BPA+p-NA BPA+HA BPA+CH 3 OH BPA+C 2 H 5 OH BPA BPA+HB+p-NP+p-NA (d) BPA+p-NP+p-NA+HA BPA+HB+p-NP+HA BPA+HB+p-NA+HA BPA BPA+HB+p-NP+p-NA+HA (e) BPA+HB+p-NP+p-NA+HA+CH 3 OH+C 2 H 5 OH+Cl BPA+100HB BPA+100p-NP BPA+100HB+100p-NP BPA+100HB+100p-NA BPA+100HB+100HA BPA+100p-NP+100p-NA BPA+100HA+100p-NA BPA+100HB+100p-NP+100p-NA BPA+100p-NP+100p-NA+100HB BPA+100HB+100p-NP+100HA BPA+100HB+100p-NA+100HA BPA+100HB+100p-NP+100p-NA+100HA (f) Figure S12. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of phenol (HB), 4-nitrophenol (p-np), 4-nitroaniline (p-na), humic acid (HA), methanol (CH 3 OH), ethanol (C 2 H 5 OH), chlorine (Cl - ) and 0.1 M phosphate buffer solution (ph = 7.0) (a) and different organic and inorganic interfering compounds (b-f). Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution + interfering compounds, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, and effective anode area = cm 2. S-24

25 PA BPA+PA BPA+5PA BPA+10PA BPA+50PA BPA+100PA (a) (b) DPA BPA+DPA (c) BPA+5DPA BPA+10DPA BPA+50DPA BPA+100DPA PA+DPA BPA+PA+DPA (e) BPA+100PA+DPA BPA+PA+100DPA BPA+100PA+100DPA PA (µm) (d) DPA (µm) (f) PA+DPA (µm) Figure S13. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of phenylalanine (PA) (a, b), diphenylalanine (DPA) (c, d) and their mixture (PA+DPA) (e, f) at different molar ratios. Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution + interfering compounds, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, and effective anode area = cm 2. S-25

26 BPAF BPA+BPAF (a) (b) BPAF BPA+BPAF BPAF BPS BPA+BPS (c) (d) BPA BPAF BPS BPA+BPS BPS HBP BPA+HBP (e) (f) BPA BPS HBP BPA+HBP HBP HBPA BPA+HBPA (g) (h) BPA HBP HBP BPA+HBPA HBPA BPA HBPA Figure S14. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of four structural analogues: BPAF (a, b), BPS (c, d), HBP (e, f) and HBPA (g, h). Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution + 2 µm BPAF/BPS/HBP/HBPA, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, and effective anode area = cm 2. S-26

27 Figure S15. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of four structural analogues: BPAF+BPS (a), BPAF+HBP (b), BPAF+HBPA (c), BPS+HBP (d), BPS+HBPA (e) and HBP+HBPA (f). Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution + 1 µm BPAF/BPS/HBP/HBPA, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, and effective anode area = cm 2. S-27

28 Current ( µa) BPA+BPAF+BPS+HBP (a) BPA+BPAF+BPS+HBPA BPA+BPAF+BPS+HBP (b) BPA+BPAF+BPS+HBP+HBPA BPA+BPAF+BPS+HBPA (c) BPA+BPAF+BPS+HBP+HBPA Figure S16. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of four structural analogues: BPAF+BPS+HBP (a), BPAF+BPS+HBPA (b) and BPAF+BPS+HBP+HBPA (c). Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution + 1 µm BPAF/BPS/HBP/HBPA, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, and effective anode area = cm 2. S-28

29 10 mg L -1 HA 30 mg L -1 HA 50 mg L -1 HA (a) HA (mg L -1 ) 20 µm BPA + 10 mg L -1 HA 20 µm BPA + 30 mg L -1 HA 20 µm BPA + 50 mg L -1 HA (b) Surface water 1 Surface water 2 Surface water 3 (c) sample1 sample 2 sample 3 HA (mg L -1 ) Surface water 1+BPA Surface water 2+BPA Surface water 3+BPA (d) Figure S17. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of humic acids: distilled water (a, b) and practical water (c, d). Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution + 1 ~ 5 mg L -1 HA (a, b), solution = surface water + 2 µm BPA M phosphate buffer solution + 2 µm BPA (c, d), ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, and effective anode area = cm 2. S-29

30 Fe(ii) 100Fe(ii) BPA + Fe 2+ BPA + 100Fe 2+ (a) Fe(iii) 100Fe(iii) BPA + Fe 3+ BPA + 100Fe 3+ (b) Mn(ii) 100Mn(ii) BPA + Mn 2+ BPA + 100Mn 2+ (c) Cl 100 Cl BPA + Cl - BPA + 100Cl - (d) HCO3 100 HCO3 - BPA + HCO 3 - BPA + 100HCO 3 (e) Figure S18. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of typical metal ions and inorganic anions: Fe 2+ (a), Fe 3+ (b), Mn 2+ (c), Cl - (d) and HCO 3 - (e). Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution + 2 ~ 200 µm Fe 2+ /Fe 3+ /Mn 2+ /Cl - /HCO 3 -, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, and effective anode area = cm 2. S-30

31 BPA+Cl+Fe+HA (a) Current ( µa) BPA+Cl - +Fe 2+ +HA BPA+Mn(ii)+Cl(i)+HA BPA+Cl(i)+HCO3(i)+Mn(ii)+Fe(ii)+Fe(iii)+HA (c) BPA+Mn 2+ +Cl - +HA (e) BPA+Cl - +HCO 3 - +Mn 2+ +Fe 2+ +Fe 3+ +HA Current ( µa) BPA+Fe(ii)+Mn(ii)+Cl(i)+HA (b) BPA+Cl(i)+HCO3(i)+HA BPA+Fe 2+ +Mn 2+ +Cl - +HA (d) BPA+Cl - +HCO 3 - +HA Figure S19. BPA detection on the MI-TiO 2 -based electrochemical sensor in the presence of humic acids and typical ions: Cl - + Fe 2+ (a), Fe 2+ + Mn 2+ + Cl - (b), Mn 2+ + Cl - (c), Cl HCO 3 (d) and Cl HCO 3 + Mn 2+ + Fe 2+ + Fe 3+ (e). Measuring conditions: solution = 0.1 M KCl + 2 µm BPA M phosphate buffer solution + 2 µm Fe 2+ /Fe 3+ /Mn 2+ /Cl - /HCO mg L -1 HA, ph = 7.0, potential range = ~ 1.0 V, scan rate = 100 mv s -1, and effective anode area = cm 2. S-31