Multivariate optimization of a new 4-chlorophenol sensor fabricated by modification of glassy carbon electrode using Ni(OH)2 nanoparticles-carbon nanotubes (NNH–MWCNTs)

In this study a simple method was developed to fabricate a glassy carbon electrode (GCE) modified by a composition of multi-wall carbon nanotubes (MWCNTs) and nano nickel hydroxide (NNH). The NNH powder was synthesized by coordination homogeneous precipitation (CHP) method and characterized by means of SEM and XRD techniques. Applicability and suitability of NNH–MWCNTs/GC electrode for determination of 4-chlorophenol (4-CP) were subsequently checked in details using different methods such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and chronocoulometry (CC). The DPV data showed that NNH–MWCNTs/GCE enhances significantly the oxidation peak current of 4-CP in compare with bare GCE and MWCNTs/GCE, which it indicates that Ni(OH)2 possesses an active surface area toward 4-CP oxidation. Response surface methodology (RSM) was used to optimize voltammetric response of modified electrode for determination of 4-CP. Initial solution pH, nickel hydroxide amount in modifier matrix and dropping volume of this mixture were considered as three important operating factors through experimental design methodology. The central composite design (CCD) as a response surface approach was applied for obtaining the optimum conditions as well as the maximum height of 4-CP oxidation peak. Under the optimal experimental conditions, the current oxidation peak was proportional to the 4-CP concentration in a range of 1.0–750 μM with a detection limit (S/N = 3.0) of 0.5 μmol L−1. Using the proposed method, 4-CP was successfully determined in water samples with standard addition method, suggesting that this method can be applied to determine 4-CP in water samples.