Electrochemically reduced graphene oxide and reduced graphene oxide-carbon nanotubes composite films on gold electrodes obtained from recordable compact disks as new plataform for the electrochemical sensors

Gold and platinum are the most widely used metal electrodes for electrochemical and electroanalytical purposes. The preference for these metals is attributed to their high purity, ease of machining and "inertia" in the presence of almost all reagents. Gold electrodes using recordable CDs (CD-R) is an alternative substrate with almost inexhaustible supply of thin layers of gold at low cost for use in surface modifications [1]. The objective of this work was to use the gold CD-R in the construction of electrodes and their modification with electrochemically reduced graphene oxide (ERGO) and the reduced graphene oxide-carbon nanotubes composite film (RGO-MWCNT) and to evaluate the performance in the determination of dopamine (DP) and hydrogen peroxide (HP) using the batch injection analysis (BIA) with amperometric detection. ERGO synthesis consisted in preparing a dispersion of graphene oxide in a solution of sodium phosphate [2]. The electrochemical synthesis was made by cyclic voltammetry (potential range from 0 to -1.7 V, 10 cycles and scan rate of 75 mV s-1) on gold CD-R electrode, in a cell with three electrodes. The composite film RGO-MWCNT was obtained through the interfacial method, within the interface between two immiscible liquid phases. The film was washed with distilled water, adsorbed on the gold CR-R and dried. Cyclic voltammetry of DP and HP on ERGO-modified, RGO-MWCNT-modified and unmodified gold CD-R revealed better sensitivity and slight decrease in the ΔE for DP in RGO-MWCNT and HP in ERGO. The parameters of batch-injection analysis (BIA) for amperometric detection were optimized (153 μL s-1 for dispensing rate and 100 μL injected volume) and analytical curves were constructed. For all evaluated analytes, the slopes of the analytical curves of ERGO and RGO-MWCN were much larger than those obtained on unmodified gold CD-R. For DP, the slope of RGO-MWCNT (0.1947 μA/μmol L-1) was higher than ERGO (0.1021 μA/μmol L-1). For HP, the slope of ERGO (0.1708 μA/μmol L-1) was slightly higher than RGO-MWCNT (0.1451 μA/μmol L-1). The limits of detection were lower for DP on RGO-MWCNT (2 μmol L-1) and for HP on ERGO (1 μmol L-1). The results showed that gold CD-R may be an inexpensive alternative to be used as a substrate for the modification with carbon nanomaterials. The determination of these molecules using ERGO-modified and RGO-MWCNT-modified gold CD-R electrode presented satisfactory analytical performance.