Silver nanodendrite modified graphene rotating disk electrode for nonenzymatic hydrogen peroxide detection

Abstract

Although silver nanostructures have been widely used for H₂O₂ detection, the development of silver based nanomaterials with higher performance toward H₂O₂ detection is still needed. In this work, metallic silver nanodendrite (AgND) modified reduced graphene oxide (rGO) electrode with open pore structure was prepared by an electrodeposition method and used for H₂O₂ detection. The rotating disk electrode (RDE) was used to study the convective diffusion effect of H₂O₂ to the electrode. The performance of the AgND/rGO electrode toward H₂O₂ detection significantly depends on the rotation rate of the electrode. At the rotation rates of 0 and 100 rpm, the as-fabricated electrode could not detect H₂O₂. At higher rotation rates, wide linear ranges of detected H₂O₂ concentrations with a determination coefficient R² of over 0.99 are found to be 1–100, 0.5–100, 0.1–100, and 0.05–30 mM at the electrode rotation rates of 500, 1000, 2000, and 6000 rpm, respectively. The LOD values determined at a signal-to-noise ratio of ca. 3 are about 100, 50, 30, and 10 μM at 500, 1000, 2000, and 6000 rpm, respectively. The as-fabricated electrode can detect diluted H₂O₂ in milk demonstrating its potential sensing application.

Introduction

Metal nanoparticle/graphene nanocomposites have been proved to be one of the most promising materials owing to the outstanding synergetic properties of metal nanoparticles and graphene. The composites are useful for various applications e.g., electrocatalysis, electroanalysis, and electrochemical sensors [1], [2], [3], [4], [5].

An accurate detection of H₂O₂ is very important in chemical, biological, clinical, foods, environmental and many other fields [6], [7]. H₂O₂ is a common reactive oxygen species (ROS) in living cells. The amounts of H₂O₂ in different systems are from micromolar for in vivo conditions to millimolar for bleaching applications [7]. A number of methods i.e., spectrophotometry based on horseradish peroxidase enzyme, titration, and chronoamperometry are being used to determine H₂O₂ concentrations [7]. The enzyme-based sensors show poor stability and tolerance in experimental conditions as well as high cost. Titration is rather poor in selectivity and cannot detect H₂O₂ at diluted concentration. On the other hand, the electrochemical technique chronoamperometry has been well accepted as a superior promising technique due to its many advantages such as cost-effectiveness, simultaneous detection, fast response, stability, highly sensitivity, and selectivity [6], [8]. However, it was found that previous work based on the H₂O₂ detection using the chronoamperometry was carried out in the stirring solution but the missing quantitative information about the stirring solution leads to an unclear conclusion about the electrode performance. The stirring process is rather important to the electrode performance since it affects the flux of H₂O₂ to the electrode surface.

There are a number of methods used for synthesizing silver nanoparticle (AgNP)-graphene nanocomposites for example, a chemical reduction of AgNO₃ with reduced graphene oxide (rGO) [2], [9], a microwave-assisted synthesis [3], and a combining sonication with sol–gel technique [10]. The resulting Ag-rGO composite used for H₂O₂ detection provided the wide linear detection range, 0.1–80 mM, determined by the chronoamperometry and the limit of detection (LOD) of 7.1 μM at a signal-to-noise ratio (S/N) of ca. 3 [2]. More recently, the AgNP–rGO nanocomposite was prepared by an electrodeposition method from graphene oxide (GO) and AgNO₃ on indium tin oxide (ITO) electrode [1]. The composite, used for H₂O₂ detection using the chronoamperometry in the stirring solution, exhibited a fast amperometric response toward H₂O₂ detection with a linear detection range of 0.1–100 mM (R² = 0.9992) [1].

AgNPs themselves were previously produced in various shapes such as spheres, polyhedrons, rods, ribbons, wires, and dendrites. Among them, Ag nanodendrite (AgND) has a particular attractive structure since it is one of the most effective materials for surface enhanced Raman spectroscopy (SERS), fast charge transfer due to its unique tree-like structure with ultrahigh conducting property, and open pore structure [11], [12], [13]. As a result, the AgND could be an ideal material to be used as an electrochemical sensor electrode. The AgND were previously produced by chemical methods using surfactants or templates [13].

In this work, the AgND was electrodeposited onto the surface of rGO modified glassy carbon rotating disk electrode (GC RDE) at room temperature without using surfactants. Note that the as-prepared graphene material in this work is so-called ‘‘rGO’’ according to the recommended nomenclature [14]. The RDE was used as a working hydrodynamic electrode to accelerate H₂O₂ to the electrode surface overcoming the diffusion limit of the analyte. Although the AgND has not yet been coated on graphene-related materials, it has been previously coated on other substrates by using the electrodeposition method [15]. The as-fabricated AgND/rGO electrode in this work shows excellent sensing linear signals to broad concentration ranges of H₂O₂, high stability, and fast response at a physiological condition (pH 7.4).