Graphdiyne oxides as new modifier for the simultaneous electrochemical detection of phenolic compounds

Highlights

• GDYO was prepared successfully in this work.

• GDYO was first used as a new modifier for the simultaneous detection of phenols.

• The sensor performed favorable properties.

Abstract

Graphdiyne (GDY) is a new two-dimensional carbon nanomaterial with rich carbon chemical bonds, large conjugation system, porous structure and excellent chemical catalytic properties. In this work, graphdiyne oxide (GDYO), the oxidized form of GDY, was first used to establish a new platform for the simultaneously detection of hydroquinone (HQ), catechol (CC), resorcinol (RC) and p-nitrophenol (p-NP). The microstructure and morphologies of the materials and the surface of the modified electrode were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic properties of graphene oxide (GO), GDY and GDYO for CC, HQ, RC and p-NP were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results show that the GDYO modified glassy carbon electrode (GDYO/GCE) exhibited excellent catalytic activities towards CC, HQ, RC and p-NP. The linear ranges of HQ, CC, RC and p-NP were 1 μM–980 μM, 0.6 μM–692 μM, 1 μM–300 μM and 0.6 μM–203 μM, 203 μM–692 μM with 0.3 μM, 0.2 μM, 0.3 μM and 0.2 μM, respectively. In addition, the electrochemical sensor showed good selectivity, sensitivity and stability. The application in real samples was also evaluated, and the recoveries suggesting that it could be used as an excellent potential material for the simultaneous determination of phenolic compounds in environmental samples.

Introduction

With the rapid development of modern industry, the environmental pollution is becoming more and more serious, which severely threatens the safety of organisms, especially human beings. Among all the pollutants, phenolic compounds are the most typical substances with high toxicity, slow degradation and bioaccumulation [[1], [2], [3], [4]]. They are mainly discharged into the environment through wastewater from coal mines, oil refining, dyes, pharmaceutical and other industries [5,6]. According to the literature, most of the phenolic pollutants (such as HQ, CC, RC and p-NP and so on) will cause irritation even carcinogenesis to the skin, central nervous and respiratory system [7]. Therefore, the monitoring and determination of phenolic pollutants is very important. Currently, the High-Performance Liquid Chromatography (HPLC) is the most commonly used method in the actual sample detection due to its high accuracy [8,9]. However, the expensive cost, complex and time-consuming sample pretreatment limit its application in the real-time and on-site detection.

In order to avoid these problems, electrochemical sensors have attracted more and more interest in the detection of phenolics. According to the different detection principles, there are two kinds of phenol electrochemical sensors, enzyme catalysis and direct electrocatalysis. Laccase is a polyphenol oxidase containing four copper ions, which belongs to the copper blue oxidase and exists in the form of monosaccharide protein [10]. It is an enzyme that is most commonly used to assemble on the electrode surface to oxidize phenol hydroxyl and produce some detectable signals. However, the active center of the enzyme is embedded in the center of the protein, which hinders the transmission of electrons [11]. Although this situation can be improved by adding nano materials and conducting polymers [12,13], the properties of enzyme itself, such as its performance is greatly affected by temperature and pH value, limit its application. Thus, in this work, direct electrocatalysis was used to simultaneously detect HQ, CC, RC and p-NP.

In the process of direct electrocatalysis, the performance of electrochemical sensors depends on the catalytic materials. Among all materials, carbon nanotubes (CNTs), graphene sheets (GS) and their composites are the most widely used catalytic materials, which are mainly due to their good adsorption, large specific surface area and high conductivity [[14], [15], [16], [17]]. GDY is a new two-dimensional all-carbon allotrope composed of benzene rings and alkyne unites with much intriguing properties especially highly π-conjugated structure, attractive electronic and chemical properties, good biocompatibility and well dispersion in aqueous solution [[18], [19], [20], [21], [22]]. Compared with GS, the introduction of acetylene to the benzene ring in GDY results in lower atomic density and natural holes [23]. These porous and layered structures can promote the diffusion of ions or small molecule in-plane and out of plane. Meanwhile, according to Compton's reports, these properties are conducive to the discrimination of many species which oxidize or reduce at similar potentials [24,25].

At present, many literatures about GDY have been reported in the field of semiconductor and solar cell [26,27], but few reports about GDY used in electrochemical sensors. In this work, GDYO, the oxidized form of GDY, was first used to modify GCE to construct a new electrochemical sensor (GDYO/GCE) for the simultaneously detection of HQ, CC, RC and p-NP. GDY was synthesized on the surface of copper foil by a cross coupling reactions using hexaethynylbenzene as precursor, as reported in Li Yuliang's team [28,29]. GDYO was prepared by improved Hummer's method. Compared with GDY, GDYO has more oxygen-containing groups and active sites. GO, GDY and GDYO are respectively immobilized on the glassy carbon electrode surface to form GO/GCE, GDY/GCE and GDYO/GCE. CV was used to study the catalytic capacity of GO, GDY and GDYO for HQ, CC, RC and p-NP. The linear range, detection limit, selectivity and stability of the modified electrode are investigated by DPV.