Zhaojing Yin, Jiajia Wu, Zhousheng Yang*

Electronic Supplementary Material

A sensitive mercury (II) sensor based on CuO nanoshuttles/poly(thionine) modified glassy carbon electrode

Zhaojing Yin, Jiajia Wu, Zhousheng Yang*

Anhui Key Laboratory of chemo-Biosening, College of Chemistry and Materials Science, Anhui Normal University,Wuhu 241000, PR China.

*Corresponding author. Fax: +86-553-3869303

E-mail address: (Z.S. Yang)

Results and discussion

Characterization of theCuO/PTH/GCE

Fig S1. Nyquist plots at bare GCE (a), PTH/GCE (b) and CuO/PTH/GCE (c) in an aqueous solution of 5.0 mM [Fe(CN)6]3−/ 4− containing 0.1M KCl.

EIS was carried out to probe the interfacial electron-transfer resistance (Ret) at the modified electrode [30]. The Ret value can be directly measured as the semicircle diameter. Fig.S1 showed the Nyquist diagrams of different modified electrodes in 5.0 mM [Fe(CN)6]3−/ 4− containing 0.1M KCl. The Ret value for PTH/GCE (110Ω, Fig. S1b) was higher than that for bare GCE (Fig. S1a) which is ascribed to The PTH film binding on electrode surface blocked the redox probe of Fe(CN)63−/ 4− in some degree. When the nano-CuO particles were immobilized onto the surface of PTH/GCE, the Ret value (450Ω) decreased dramatically (Fig. S1c), indicating that nano-CuO particles form high electron conduction pathways between the electrode and electroactive indicator. Here, the changes of RCT manifested that the PTH and nano-CuO particles were assembled onto the surface of GCE in proper order.

Effect of scan rate

Fig S2. CVs of CuO nanoshuttles and PTH modified GCE in phosphate buffer solutions (containing 6 M Hg2+) at scan rates of 10～150 mV s-1 (from internal to external). Inset (A) Plot of anodic peak current (a) and cathodic peak current (b) vs. v1/2.

Fig. S2 showed the dependence of Hg2+ redox peak current on scanning rate on nano-CuO/PTH/GCE. With an increasing scan rate, the both cathodic and anodic peak currents increased and the peak potential Ep changed slightly in the scan rates range of 10～150 mV s-1. The values of △Ep were increased slightly. Both cathodic and anodic peak currents of Hg2+ redox on nano-CuO/PTH/GCE increased linearly with the square root of scan rates. A linear relationship between the peak current and the scan rate was found as Ipa (μA) =0.3119+0.0132 V1/2 [ (mV s-1) 1/2] (R2=0.999), Ipc (μA)=－0.5061－0.0148 V1/2 [(mV s-1)1/2] (R2=0.998). This result suggested that the electrochemical reaction of Hg2+ on nano-CuO/PTH/GCE was a non-surface controlled electrode process, which might be attributed to a slow electron hoping across the matrix of the composite membrane. The result was consistent with other previous studies [31].

Fig S3. CVs in 0.1 M phosphate buffer solutions (pH=7.0), in the presence of Hg2+ from a to b: 0, 2, 4, 6, 8, 10, 12M.

Fig S4. Current responses obtained at the Cu/PTH/GCE for the additions (indicated by arrows) of a, 10 Hg2+; b, 20 Hg2+; c→g, 10  Cd2+, Cu2+,Cr3+, Ag+, Pb2+; h, 20 Hg2+. Applied potential: 0.26 V. Other conditions were as Fig. 5.

Reference

30. Suni II (2008)Impedance methods for electrochemical sensors using nanomaterials. Trends Anal Chem 27: 604

31. Tripathi VS, Kandimalla VB, Ju H (2006) Amperometric biosensor for hydrogen peroxide based on ferrocene-bovine serum albumin and multiwall carbon nanotube modified ormosil composite. Biosens Bioelectron 21: 1529