A facile and green fabrication of Cu₂O-Au/NG nanocomposites for sensitive electrochemical determination of rutin

Highlights

• Cu₂O-Au/NG (nitrogen-doped graphene) nanocomposite was fabricated by a facile and green method.

• The nanocomposite has excellent electrochemical activity towards the oxidation of rutin.

• The detection range of rutin is 0.06–512.90 μM with a detection limit of 30 nM.

Abstract

Rutin has a broad range of physiological activities and often used clinically as therapeutic medicine on humans, and it is important to develop sensitive analytical methods for rutin determination. The nanocomposites, consisting of Cu₂O, Au nanoparticles and nitrogen-doped graphene (denoted as Cu₂O-Au/NG), were successfully fabricated by a facile and green method and used for highly sensitive detection of rutin. The electrochemical methods, such as cyclic voltammetry (CV) and differential pulse voltammetry (DPV) have been used to investigate the electrochemical properties of the fabricated sensors for rutin detection. The results showed that under optimal conditions, Cu₂O-Au/NG/GCE exhibited highest sensitivity of 114.94 μA·mM^− 1 than the other modified electrodes, and a low detection limit of 30 nM could be achieved with a linear concentration response range from 0.06 to 512.90 μM. The enhanced electrochemical performances could be attributed to the synergistic effect between Cu₂O-Au and NG and the outstanding catalytic effect of the Cu₂O-Au nanoparticles. Finally, the sensor was successfully used to analyze rutin tablets, showing high potential for practical applications.

Introduction

High blood pressure and cerebral hemorrhage are kinds of serious diseases, which can cause dizziness, vomiting and disturbance of consciousness. More and more people pay attention to these health problems now. Medical research displays that rutin, also named vitamin P, is one of effective components in drugs for the treatment of high blood pressure and cerebral hemorrhage [1], [2]. Besides, rutin also has functions of anti-inflammatory, anti-tumor and anti-oxidant, and it shows certain reactive oxygen intermediate scavenging activities, such as, hydroxyl radical, superoxide radical and peroxy radical [3], [4], [5], [6], [7]. Based on these good performances, rutin is widely used in medicine and in the human diet. Thus, it is important to develop simple, economic and sensitive methods for rutin detection. In the past decades, tremendous efforts have been devoted to this area. For example, there are some conventional methods of analysis like HPLC, HPLC-UV and UPLC, but they are time-consuming, expensive and usually need complicated pretreatments [8], [9], [10]. By contrast, electrochemical technique is considered as a good alternative to determine rutin. Compared with those conventional analysis techniques, electrochemical method has many advantages, such as low detection limit, high sensitivity and low cost [11]. For instance, Yang et al. developed NMP-exfoliated graphene/GCE to detection rutin, and a detection limit 3.2 nM/L was achieved. Serkan Elcin et al. got a good linear range 0.0001–100 μM for rutin determination on the RuNPs/C₄A₅/RGO/GCE [12], [13].

Until now, various materials, including graphene, carbon nanotubes and nitrogen-doped graphene, have been used for electrochemical determination of rutin, and proved to display good electrochemical performance. Especially the nitrogen-doped graphene, has some enhanced properties [13], [14], [15], [16]. It was found that the N doping leads to a high catalytic activity because it could introduce high positive spin density and asymmetry atomic charge density [17], [18], [19], [20], [21]. Sun et al. used nitrogen-doped graphene to modify carbon ionic liquid to detection rutin, obtaining a low detection limit of 0.23 nM/L, which is lower than that many values from similar materials reported in the literature [3]. Meanwhile, some noble metallic nanoparticles like Pt, Au and Ag nanoparticles have been also used for rutin determination due to their unique advantages of enhanced mass transport, size controlled electrical, chemical and optical properties [1], [2], [22], [23]. Mehmet Lütfi Yola et al. modified GCE with AuNPs/p-MWCN nanocomposites, which was successfully applied to detect rutin [24]. Besides, semiconductor materials also attract considerable attention in electrochemical applications. Cuprous oxide (Cu₂O) is a narrow band p-type semiconductor with a direct band gap of 2.0–2.2 eV, which has unique optical, electrical properties and other properties such as easy to prepare and low cost, nontoxic nature and abundance. It has been applied to various fields, such as sensors, catalysts, photoelectrochemical cells and batteries [25], [26].

Au nanoparticles modified on metal oxides have been proved to be an effective strategy to improve electrochemical properties of metal oxide. It is well known that Cu₂O-Au nanocomposites can apply to determine H₂O₂ and glucose, and the nanocomposite electrode displays good detection limit and wide detection range [27], [28]. However, using Cu₂O-Au nanocomposites for rutin determination has been rarely reported. In this work, Cu₂O-Au/NG nanocomposites have been fabricated by a simple and green method and apply for rutin determination. A sprinkling of nitrogen-doped graphene is aiming at improving the dispersion of Cu₂O-Au nanocomposites. For comparison, the electrocatalytic performances of Cu₂O-Au modified GCE, Cu₂O/NG and NG modified GCE towards rutin oxidation were also studied.