Supplementary Material A novel nitrite sensor fabricated through anchoring nickel-tetrahydroxy-phthalocyanine and polyethylene oxide film onto glassy carbon electrode by a two-step covalent modification approach Yan-Ying Wu, [a] Cong Li, [a] Zhi-Yu Dou, [a] Li-Li Cui, [a] Da-Jun Liu, [a] Xing-Quan He *[a] a Jilin Province Key Laboratory of Applied Chemistry and Nanotechnology, Changchun University of Science and Technology, Changchun 1322, P. R. China. * Corresponding author. Tel: +86-431-8558343 E-mail: hexingquan@hotmail.com 1
1. Supplementary data Fig. S1. Tapping mode AFM images of the NiPc(OH) 4 -GCE, (a) 2D and (b) 3D, and the NiPc(OH) 4 /PEO- GCE, (c) 2D and (d) 3D. 2
15 135 9 15 135 9 1 45-45 1 45-45 5-5 -9-135.16.24.32.4 2 i / A 5-5 -9-135.16.24.32.4 2-1 2-1 2-15 -15.5.4.3.2.1..5.4.3.2.1. 15 135 9 15 135 9 1 45-45 1 45-45 5-9 -135.16.24.32.4 5-9 -135.16.24.32.4-5 2-5 2-1 2-1 2-15 -15.5.4.3.2.1..5.4.3.2.1. 15 135 9 1 45-45 5-5 -9-135.16.24.32.4 2-1 2-15.5.4.3.2.1. Fig. S2. Cyclic voltammograms of five different [NiPc(OH) 4 /PEO)] ad -GCE in 5 mm Fe(CN) 6 3-/4- /1 M KCl at various scan rates from 2 to 2 mv s -1, respectively. Inset: plot of peak current vs. υ 1/2. 3
1 8 4 1 15 7 35 i / A 5-4 -8.1.15.2.25.3.35.4.45 2 i / A 5-35 -7-15.1.15.2.25.3.35.4.45 2-5 2-5 2-1 -1.5.4.3.2.1..5.4.3.2.1. 1 5 9 6 3-3 -6 1 5 9 6 3-3 -6 i / A -5-9.12.18.24.3.36.42 2 2 i / A -5-9.1.15.2.25.3.35.4.45 2 2-1 -1.5.4.3.2.1..5.4.3.2.1. 1 5 9 6 3-3 -6-9 i / A.12.18.24.3.36.42 2-5 2-1.5.4.3.2.1. Fig. S3. Cyclic voltammograms of five different [NiPc(OH) 4 /PEO)] bd -GCE in 5 mm Fe(CN) 6 3-/4- /1 M KCl at various scan rates from 2 to 2 mv s -1, respectively. Inset: plot of peak current vs. υ 1/2. 4
Fig. S4. Cyclic voltammograms of the NiPc(OH) 4 /PEO-GCE with electroadsorption of the NiPc(OH) 4 for, 3, 5 and 1 cyclic potential sweeps (a-d) in PBS (ph=7.) containing 1 mm nitrite. E p / V (vs. SCE).85.84.83.82.81.8.79.78-4. -3.5-3. -2.5-2. -1.5 ln ( mv s -1 ) Fig. S5. The relation between the peak potential and the ln υ. Scan rate: 5 mv s -1. 5
Fig. S6. DPVs of various concentrations of nitrite at the [NiPc(OH) 4 /PEO)] bd -GCE in ph 7. PBS. Inset: the relation between the peak currents and the nitrite concentrations. Scan rate: 5 mv s 1, pulse amplitude: 5 mv, pulse width: 2 ms. Figure S6 illustrates the DPVs at various concentrations of nitrite at the[nipc(oh) 4 /PEO)] bd -GCE in ph 7. PBS, the plot of i pa versus the concentration of nitrite is a well linear relationship in the concentration range of 2 to 5 μm. The linear regression equation is expressed as i pa (μa)=.253c(μm)+.73, with a correlation coefficient r=.9998 (the inset curve). The detection limit was found to be 3.74 1-7 M at a signal to noise ratio of 3. The performance of the fabricated [NiPc(OH) 4 /PEO)] bd -GCE is compared with [NiPc(OH) 4 /PEO)] ad -GCE, as seen in Table S3. It is very exciting to note that the detection limit, linear range and sensitivity have been obviously improved after drying under an infrared lamp. This should be attributed to the enlarged electrochemical effective surface area of the fabricated [NiPc(OH) 4 /PEO)] ad -GCE, which promote charge transfer and make the modified electrode more sensitive for the determination of nitrite. 6
-Z'' / ohm -Z'' / ohm 36 24 12 12 1 8 6 4 2 25 5 75 1 Z' / ohm a 3 25 2 15 1 5 b d c b e a 3 27 24 21 18 15 12 2 4 6 8 1 12 14 16 Cycles 1 2 3 4 Z' / ohm 1.2 1..8.6.4.2 Fig. S7. (a) Impedance spectra of the NiPc(OH) 4 -GCE with electroadsorption of the NiPc(OH) 4 for 3, 5, 7, 1 and 15 cyclic potential sweeps in 5. mm K 3 Fe(CN) 6 containing.1 M KCl, respectively. (b) Cyclic voltammograms of the NiPc(OH) 4 -GCE with electroadsorption of the NiPc(OH) 4 for 3, 5, 7, 1 and 15 cyclic potential sweeps (a-e) in PBS (ph=7.) containing 1 mm nitrite. Inset: the relationship between peak currents and cycles. In order to obtain suitable CV sweeps for the preparation of the NiPc(OH) 4 -GCE, impedance measurements were performed by employing electrochemical impedance spectroscopy (EIS) method for studying the interface properties of the modified electrode. Figure S7a gives the Nyquist plots of the electrochemical impedance spectroscopy measurement of the NiPc(OH) 4 -GCE in the presence of equivalent amounts of 5. mm K 3 Fe(CN) 6 and.1 M KCl. As can be seen, well defined semicircular Nyquist impedance spectra can be observed on the NiPc(OH) 4 -GCE for 3, 5, 7, 1 and 15 CV scans and the NiPc(OH) 4 film adsorbed by less cycles has a lower arc radius with a smaller charge transfer resistance R ct. This phenomenon suggests that the value of the charge transfer resistance at the electrode interface increases with increasing the number of sweep cycles. We also investigated the electrocatalytic activity of the NiPc(OH) 4 -GCE for the oxidation of nitrite with different sweep cycles (shown in Fig. S7b). It is found that the largest anodic current of nitrite was obtained for 1 cyclic potential sweeps. Under the circumstances, a value of 1 cyclic potential sweeps is employed in the following study. 7
Fig. S8. DPVs of various concentrations of nitrite at the NiPc(OH) 4 -GCE in ph 7. PBS. Inset: the relation between the peak currents and the nitrite concentrations. Scan rate: 5 mv s 1, pulse amplitude: 5 mv, pulse width: 2 ms. Figure S8 illustrates the DPVs at various concentrations of nitrite at the NiPc(OH) 4 -GCE in ph 7. PBS, the plot of i pa versus the concentration of nitrite is a well linear relationship in the concentration range of 1 to 45 μm. The linear regression equation is expressed as i pa (μa)=.82c(μm)+.727, with a correlation coefficient r=.9973 (the inset curve). The detection limit was found to be 3.66 1-6 M at a signal to noise ratio of 3. The performance of the fabricated NiPc(OH) 4 -GCE is compared with NiPc(OH) 4 /PEO-GCE. The results are shown in Table S3. As compared with NiPc(OH) 4 -GCE, the sensitivity and the detection limit of the NiPc(OH) 4 /PEO-GCE are outstanding. 8
4 3 i / A 2 1-1 1.2 1..8.6.4.2 Fig. S9. Cyclic voltammograms of five different [NiPc(OH) 4 /PEO)] ad -GCE in PBS (ph=7) containing 1 mm nitrite at a scan rate of 5 mv s -1. 35 3 25 2 i / A 15 1 5-5 -1 1.2 1..8.6.4.2 Fig. S1. Cyclic voltammograms (CVs) of 5 times with the same modified electrode in PBS (ph=7) containing 1 mm nitrite at a scan rate of 5 mv s -1. 9
4 3 b a i / A 2 1-1 1.2 1..8.6.4.2 Fig. S11. The storge stability of [NiPc(OH) 4 /PEO)] ad -GCE by cyclic votammograms scanning in PBS containing 1mM nitrite with ph=7., curve (a ) for 2 month before and curve (b) for 2 month later. 1
Fig. S12. a Cyclic voltammograms of [NiPc(OH) 4 /PEO)] ad -GCE in PBS containing 1mM nitrite with ph=7., curve (a) for adding 2 mm Ca 2+, Ba 2+, Na +, Mn 2+, Zn 2+, K +, H 2 PO - 4, HPO 2-4, Cl -, NO - 3 and SO 2-3 before and curve (b) for adding 2 mm Ca 2+, Ba 2+, Na +, Mn 2+, Zn 2+, K +, H 2 PO - 4, HPO 2-4, Cl -, NO - 3 and SO 2-3 after. b Cyclic voltammograms of [NiPc(OH) 4 /PEO)] ad -GCE in PBS containing 1 mm nitrite with ph=7., curve (a) for adding.1 M adding glucose and H 2 O 2 before and curve(b) for adding.1 M adding glucose and H 2 O 2 after. c Cyclic voltammograms of [NiPc(OH) 4 /PEO)] ad -GCE in PBS containing 1mM nitrite with ph=7., curve (a) for adding 5 μm DA, 5 μm UA, 1 μm EP and 5 μm AA before and curve(b) for adding 5 μm DA, 5 μm UA, 1 μm EP and 5 μm AA after. d Cyclic voltammograms of [NiPc(OH) 4 /PEO)] ad -GCE in PBS containing 1mM nitrite with ph=7., curve (a) for adding 2 mm Fe 3+ before and curve (b) for adding 2 mm Fe 3+ after. e Cyclic voltammograms of [NiPc(OH) 4 /PEO)] ad -GCE in PBS 11
containing 1mM nitrite with ph=7., curve (a) for adding 2 mm HCO 3 - /CO 3 2- before and curve (b) for adding 2 mm HCO 3 - /CO 3 2- after. 12
Table Table S1. R s, R ct, CPE, n and Z w values obtained from impedance studies for different modified GCEs, error values are in parentheses. Type of the electrode R s (kohm) R ct (kohm) CPE (μf) n Z w (kohm cm 2 ) Bare GCE.152 (.962%).293 (2.8%) 1.182 (2.844%) 1 2.769 (.935%) NiPc(OH) 4 -GCE.149 (.71%) 3.253 (1.189%) 4.82 (3.11%).812 (.593%) 2.52 (1.518%) PEO-GCE.145 (.642%) 1.3 (1.73%) 5.49 (2.142%).813 (.428%) 8.945 (1.297%) [NiPc(OH) 4 /PEO] bd -GCE.144 (.625%) 7.134 (1.454%) 4.913 (2.267%).815 (.442%) 6.414 (1.21%) [NiPc(OH) 4 /PEO] ad -GCE.144 (.635%) 5.843 (1.28%) 4.751 (2.378%).816 (.46%) 4.466 (1.289%) Table S2. The results of electrochemical effective surface area of the [NiPc(OH) 4 /PEO)] bd -GCE and [NiPc(OH) 4 /PEO)] ad -GCE. A 1 [cm 2 ] a A 2 [cm 2 ] b 1.111.714 2.199.712 3.13.744 4.171.729 5.129.739 SE of mean c 2.4 1-3 6.44 1-4 RSD d (%) 4.292 1.98 a obtained from Fig. S 2 b obtained from Fig. S 3 c Standard error of mean d Relative standard deviation 13
Table S3. comparison of the performance of some modified electrodes used in the electrocatalysis of nitrite Type of the electrode Linear regression equation Linear range (μm) Detection limit (μm) Sensitivity (µa/mm) [NiPc(OH) 4 /PEO] ad -GCE [NiPc(OH) 4 /PEO] bd -GCE NiPc(OH) 4 -GCE i pa (μa)=.594c (μm) +.592 i pa (μa)=.253c (μm) +.7297 i pa (μa)=.82c (μm) +.7267.1-53.522 59.4 2-5.374 25.3 1-45 3.66 8.2 Table S4. The results of the quantitation of peak potential and peak current of the [NiPc(OH) 4 /PEO)] ad -GCE. E p [V] a I p [μa] a 1.82 34.92 2.792 36.64 3.86 36.18 4.814 35.19 5.85 36.9 SE of mean 2.2 1-3.323 RSD (%).989 2.14 a obtained from Fig. S 9 14
Table S5. The results of the currents at different potentials. Potential (V vs. SCE).7.75.8.85.9 1 13.78 28.67 34.88 33.17 3.25 2 13.5 3.69 36.44 33.84 3.92 Current 3 12.24 27.99 36.5 34.9 3.57 (μa) 4 12.83 27.49 34.8 33.88 3.82 5 12.7 27.85 36.2 34.2 3.64 Mean 13.1 28.538 35.638 33.8 3.64 SD.6234 1.2768.7476.3665.2588 SE of mean.2788.571.3343.1639.1157 Variance.3886 1.631.5589.1344.667 RSD (%) 4.79 4.47 2.1 1.8.84 Table S6. The results of between-groups statistical differences of the current densities at different potentials by using SPSS analysis. ANOVA VAR1 Sum of Squares df Mean Square F Sig. Between Groups 1617.47 4 44.262 727.367 2.45 1-21 Within Groups 11.116 2.556 Total 1628.163 24 Table S7. The results of within-groups statistical differences of the current densities at different potentials by using SPSS analysis. Student-Newman- Keuls a VAR2 VAR1 N.7 5 13.1.75 5 28.538 Subset for alpha =.5 1 2 3 4 5.9 5 3.64.85 5 33.8.8 5 35.638 Sig. 1. 1. 1. 1. 1. Means for groups in homogeneous subsets are displayed. a Uses Harmonic Mean Sample Size = 5.. 15
Table S8. The results of the potentials at different currents. Current (μa) 26. 28. 3. 32. 34. Potential (V vs. SCE) 1.74.747.756.767.783 2.734.74.747.755.766 3.743.75.757.766.777 4.748.756.764.774.789 5.744.751.758.766.777 Mean.7418.7488.7564.7656.7784 SD 5.22 1-3 5.89 1-3 6.11 1-3 6.8 1-3 8.53 1-3 SE of mean 2.33 1-3 2.63 1-3 2.73 1-3 3.4 1-3 3.82 1-3 Variance 2.72 1-5 3.47 1-5 3.73 1-5 4.63 1-5 7.28 1-5 RSD (%).7.79.81.89 1.1 Table S9. The results of between-groups statistical differences of the potentials at different current densities by using SPSS analysis. ANOVA VAR1 Sum of Squares df Mean Square F Sig. Between Groups 4.11 1-3 4 1.29 1-3 23.573 2.49 1-7 Within Groups 8.732 1-4 2 4.366 1-5 Total 4.99 1-3 24 Table S1. The results of within groups statistical differences of the potentials at different current densities by using SPSS analysis. Student-Newman- Keuls a VAR 2 VAR1 N 26. 5.742 28. 5.749 Subset for alpha =.5 1 2 3 4 5 3. 5.756 32. 5.766 34. 5.778 Sig..11.84 1. 1. 1. Means for groups in homogeneous subsets are displayed. a Uses Harmonic Mean Sample Size = 5.. 16
Table S11. The results of the quantitation of peak potential and peak current of the [NiPc(OH) 4 /PEO)] ad -GCE. E p [V] a I p [μa] a 1.829 29.64 2.832 29.77 3.834 29.45 4.832 29.45 5.834 29.2 SE of mean 9.165 1-4.968 RSD (%).245.734 a obtained from Fig S 1. Table S12. The results of the currents at different potentials. Potential (V vs. SCE).7.75.8.85.9 1 8.574 18.95 28.6 29.57 27.67 2 8.255 18.87 28.11 29.59 27.55 Current 3 8.53 18.5 27.72 29.33 27.32 (μa) 4 8.27 18.46 27.67 29.27 27.26 5 7.894 18.16 27.29 29. 27.11 Mean 8.161 18.588 27.77 29.352 27.382 SD.265.323.333.243.226 SE of mean.118.145.149.18.11 Variance.7.14.111.588.51 RSD (%) 3.24 1.74 1.2.83.82 Table S13. The results of between-groups statistical differences of the current densities at different potentials by using SPSS analysis. ANOVA VAR1 Sum of Squares df Mean Square F Sig. Between Groups 1595.838 4 398.96 55.271 9.846 1-3 Within Groups 1.58 2.79 Total 1597.418 24 17
Table S14. The results of within-groups statistical differences of the current densities at different potentials by using SPSS analysis. Student-Newman- Keuls a VAR 2 VAR1 N.7 5 8.161.75 5 18.588 Subset for alpha =.5 1 2 3 4 5.9 5 27.382.8 5 27.77.85 5 29.352 Sig. 1. 1. 1. 1. 1. Means for groups in homogeneous subsets are displayed. a Uses Harmonic Mean Sample Size = 5.. Table S15. The results of the potentials at different currents. Current (μa) 2. 22. 24. 26. 29. Potential (V vs. SCE) 1.754.763.773.784.811 2.755.763.773.784.81 3.756.765.775.787.82 4.757.765.775.787.819 5.758.767.777.79.83 Mean.756.765.775.786.818 SD 1.58 1-3 1.67 1-3 1.67 1-3 2.51 1-3 8.9 1-3 SE of mean 7.7 1-4 7.48 1-4 7.48 1-4 1.12 1-3 3.62 1-3 Variance 2.5 1-6 2.8 1-6 2.8 1-6 6.3 1-6 6.55 1-5 RSD (%).21.22.22.32.99 Table S16. The results of between-groups statistical differences of the potentials at different current densities by using SPSS analysis. ANOVA VAR1 Sum of Squares df Mean Square F Sig. Between Groups.116 4.291 182.44 1.999 1-15 Within Groups 3.196 1-4 2 1.598 1-5 Total.12 24 18
Table S17. The results of within groups statistical differences of the potentials at different current densities by using SPSS analysis. Student-Newman- Keuls a VAR 2 VAR1 N 2. 5.756 22. 5.765 Subset for alpha =.5 1 2 3 4 5 24. 5.775 26. 5.786 29. 5.818 Sig. 1. 1. 1. 1. 1. Means for groups in homogeneous subsets are displayed. a Uses Harmonic Mean Sample Size = 5.. 19