Electronic Supporting Material
Photoelectrochemicalamperometric sensing of cyanide using a glassy carbon electrode modified with graphene oxide and titanium dioxide nanoparticles
Rahman Hallaj *, NasibehHaghighi
*Corresponding author
Electrochemical investigation of modified electrode
The recorded voltammograms (Fig.S1A.) showed any remarkable redox couple, implying to unsuccessful immobilization of nitrophenol reduction products on the surface of a: bare GC, b): GC/GO)c): GC/GO/TiO2(electrodes. And well define redox peak are shown after immobilization on toGC/GO/ TiO2-AS.
The stability of modified electrode was proved by the repetitive cyclic voltammetry. As shown, the peak current remained nearly unchanged after 100 cycles in the electrolyte solution, indicating high stability of modified electrode pH=7 (Fig.S1B.).
Fig.S1.A: CV responses of GC (a), GC/GO (b) GC/GO/TiO2 (c) and GO/TiO2-AS/O-rNPh (d) modified GC electrodes in 0.1 M phosphate buffered solution (pH 7.0) at a scan rate of 0.01 Vs-1. The CV response of GO/TiO2-AS/O-NPh-r after 1 and 100th scan at the same condition such as A.
The effect of pH on the electrochemical behavior of GC/GO/ TiO2-AS-rNPh electrode in different pH values (2-12) are shown in fig.S2.
Fig.S2. Cyclic voltammograms of GO/TiO2-AS/rNPh electrode in different pH solutions, from left to right, 2 to 12, scan rate 50mVs−1. The inset plot shows the variation of peak potential in various pH.
Photo-electrocatalytic activity
The photo-electrocatalytic activity of GC/GO/TiO2-AS-rNPh electrode was studied in presence of cyanide ion, using recorded cyclic voltammograms in light and dark conditions. These results are shown in fig.S3.
Fig.S3. (A) CV of GC/GO/TiO2-AS/rNPh electrode in 0.1 M phosphate buffered solution (pH 7.0) at a scan rate of 10mVs-1 in the presence 6.0 mM cyanide without (a) and with light irradiation (b).
The typical amperometric and photoamperometric responses at the GC/GO/TiO2-AS-rNPhelectrode obtained by successive additions of 0.6mMCyanide at 0.1 V in phosphate buffered solution (pH 7.0) without (a) and with irradiation (b). As it can be seen (fig.4), the current response obtained upon photoirradiationexplains clearly larger than that in the absence of irradiation.Fig.S4. shows the dependence of the electrocatalytic and photo electrocatalytic current responses to concentrations of cyanide.Calibration curves were plotted as seen in the field of electrocatalytic curve A in Fig.S4.andPhotoelectrochemical and catalytic curve B are based on the concentration of cyanide, two straight lines obtained by the following equations
Fig.S4.Amperometric (A) and photo amperometric (B) responses at the rotating GO/TiO2-AS/rNP modified GC electrode (rotating speed 1000 rpm) in 0.1 M phosphate buffered solution (pH 7.0), applied potential 0.35 V vs. Ag/AgCl, for successive addition of 1 M Cyanide. Inset is the corresponding calibration plots of amperometric (A) and photo amperometric(B) responses vs. the concentration of Cyanide. (C) Transient photocurrent responses of modified electrode in 30 M Cyanide aqueous solution under light irradiation at 0.35 V vs. Ag/AgCl.
The interferences effect
Thetypical amperometric responses of some common interfering ions (1-NO3-, 2-SCN-, 3-IO3-, 4-S2O32-, 5-I-, 6-CH3COO-, 7-NO2- and 500M of 8-SO32-)were investigated for GC/GO/TiO2-AS –rNPh electrode during the interval additions of 10 M of cyanide and 1mM of different interfering substances.
Fig.S5..Amperometric response of GO / TiO2-AS /rNPh modified GC electrode (rotating speed 1000 rpm) in 0.1 M phosphate buffered solution (pH 7.0), at applied potential of 0.35 V vs. Ag/AgCl during successive addition of 10M cyanide and 1mMof 1-NO3-, 2-SCN-, 3-IO3-, 4-S2O32-, 5-I-, 6-CH3COO-, 7-NO2- and 500M of 8-SO32-.