Among the various hazardous materials, phenolic compounds constitute a family of pollutants particularly toxic to environment and human health. Hydroquinone (HQ) is one of the phenolic compounds, which is important in a wide number of biological and industrial processes such as dyes, cosmetics, pesticides, coal–tar production, paper manufacturing and photographic developers [1]. Hence, the HQ widely exists in environment as a kind of important pollutant because they are toxic to human and animals and also difficult to be degraded in the ecological condition [2] and [3]. Further, it has been included in the lists of priority pollutants to be monitored in the aquatic environment by US Environmental Protection Agency (EPA) and European Union (EU) [4]. Therefore, it is of great importance to accurately monitor HQ for public health, environmental and chemical industries. Up to now, several methods such as fluorescence [5], chemiluminescence [6], high performance liquid chromatography (HPLC) [7], pH based-flow injection analysis [8], solid-phase extraction [9] and pulse radiolysis [10] have been established for the determination of HQ. The determination of HQ using these techniques shows high sensitivities, but these methods are generally carried out at sophisticated laboratories, involve expensive instruments, requiring highly trained persons for operate, lengthy sample preparations and complicated analysis procedures, which limit their application for the real-time analysis.
Compared to these methods, electrochemical method can provide compact, relatively inexpensive, reliable, fast response, sensitive and real-time analysis [11] and [12]. Moreover, electrochemical oxidation of HQ is possible due to its electroactive group of hydroxyl in benzene ring. However, phenol compounds were usually hard to be detected directly at conventional working electrodes (Au and GC) because of the poor electrochemical response and surface fouling of the electrode surface due to the oxidation products. Hence, it is highly important to design electrodes that are selective and sensitive towards HQ analyte. Recently, different kinds of electrochemical HQ sensors have been fabricated based on the chemical modification of electrodes [13], [14], [15], [16], [17], [18], [19], [20] and [21].
Many researchers have carried out electrochemical detection of HQ based on conducting polymer [22], carbon nanostructures [18] and [20] and other nanomaterials [14] and [23]. However, compared with composite materials, the application prospects of single materials are limited due to their poor electrocatalytic properties. Further, composite nanomaterials with unique structures are of great interest because of their superior catalytic properties compared with their pure counter parts. Recently, much attention has been focused on Fe2O3/PANi [24] and [25], graphene/PANi [26] and [27] and Fe2O3/graphene[12] and [28] composite with unique structure, which have a superior catalytic behavior between each component. These binary composite have been used for multi-functional applications [24], [25], [26],[27] and [28]. Furthermore, preparation of the nanostructure composite materials is another issue currently limiting their application in electrochemical sensor. However, a simple, efficient, controlled and large-scale synthesis method for the preparation of composite material is still lacking. In the present investigations, a simple, two-step fabrication of PANi–Fe2O3–rGO ternary composite with high yield and successfully applied for HQ determination for the first time.
In this work, we report the fabrication, characterization and analytical performance of HQ sensor based on the PANi–Fe2O3–rGO composite modified glassy carbon (GC) electrode. The performance of the newly fabricated HQ sensor was studied using cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV) and the results are discussed. The fabricated sensor showed high sensitivity, stability and satisfactory reproducibility