Electronic supplementary material
1. Cyclic voltammetry characterization of self-assembly process
Fig. 1Sshowed CV of modified electrodes in different composites in 5.0 mM [Fe(CN)6]4−/3− with a scan rate of 50 mV/s. It can be seen that a well-defined oxidation and reduction peaks of [Fe(CN)6]4−/3−were observed with the bare GCE (Fig. 1S curve a). A remarkable peak current increase was obtained (Fig. 1S curve b) after PPy nanowires film was coveredonto the electrode. The reason may be that electrostatic force between negatively charged Fe(CN)64−/3− and the positively charged PPy nanowires. Compared with curve b, peak current further increase was observed (Fig. 1S curve c) when Pt hollow nanospheres were spread onto the PPy nanowires modified electrode, owing to the Pt nanoparticles which played an important role similarly toa conducting wire or electron conduction tunnel. The above results could clearly confirm the success of the assembly of the electrode.
Fig. 1S. CVs of the different electrodes were recorded in 5.0 mM [Fe(CN)6]4−/3−: (a) bare GCE, (b) PPy nanowires-GCE, (c) Pt hollow nanospheres-PPy nanowires-GCE with scan rate of 50 mV/s.
2. Influence of workpotential and pH on sensor response
In order to obtain an efficient sensor for H2O2, the influence of potential on the response of modified electrode were investigated. Fig. 2S showed the dependence of the chronoamperometric current response to constant concentration 0.35 mM H2O2 on the applied potential in the range from 0 V to -0.6 V. As can be seen, the response current increased gradually from 0 V to -0.6 V. A potential of -0.3 V was selected as work potential in all the subsequent amperometric detection, because it not only could obtain sufficient current responses but also could minimize the risk for interfering reactions of other electroactive species in the solution.
The effect of pH on the performance of sensor was investigated. The change of chronoamperometric current with the pH under constant H2O2 concentration (0.35 mM) is shown in Fig. 3S. As can be seen, the current response increased from pH 4.5 to 7.0, When the then pH is more larger than 7.0, the response current decreases roughly, therefore, pH 7.0 of the working buffer was selected.
Fig. 2S. Effect of the work potential to PPy-Pt hollow spheres nanocomposite modified GCE in the presence of 0.35 mM H2O2. Applied potential: -0.3 V. Solution: in 0.1 M PBS.
Fig. 3S. The influence of pH on the response of the sensor in 0.1 M PBS containing 0.35 mM H2O2.
Fig. 4S.The stepwise fabrication processes of the modified electrode.