Diabetes mellitus is a metabolic disorder characterized by elevated levels of blood glucose. The number of people with diabetes mellitus is increasing every year. In 2017, the International Diabetes Federation (IDF) estimated that 1 in 11 adults aged 20–79 years (451 million adults) had diabetes mellitus globally and that the number would increase to 693 million in 2045 . According to the IDF, approximately 5 million deaths worldwide were related to diabetes in the 20–99 years age range in 2017, which accounts for 9.9% of the global mortality for people in this age range . Therefore, the detection and monitoring of the glucose levels is essential for the prevention, the diagnosis, and the treatment of diabetes. Many glucose sensors were developed using enzymes to obtain a high sensitivity and good selectivity . However, the sensitivity, the selectivity, and the stability of enzyme-based glucose sensors largely depend on the activity of the enzymes. The pH, the humidity, and the temperature influence the activity of glucose enzymes .
To overcome these issues, non-enzymatic glucose sensors have been developed as alternatives [5–8]. Overall, non-enzymatic glucose sensors have many strong advantages, such as a high reproducibility, a high stability, and structural simplicity. To date, many noble metals (Pt, Au, and Pd), transition metals (Cu, Ni, and Co) and their oxides or hydroxides have been used in non-enzymatic glucose sensors [9–15]. Among them, Au is widely used because it produces a high glucose oxidation current in neutral or alkaline conditions [16, 17]. Furthermore, Au nanoparticles (AuNPs) are glucose catalysts that have attracted much attention because of their large surface area, their excellent catalytic activity, and a high resistance to toxic Cl− . In addition, the favorable structure of the carrier-catalyst composite is a major advantage for sensors [19–21]. The carrier can affect the dispersion of the catalyst, enhance the conductivity and the stability of the material, and make the catalyst work more effectively. Single-walled carbon nano-horns (SWCNHs) are a nanostructured carbon material with horn-shaped sheaths composed of graphene sheets and has a conical structure with a particularly sharp apical angle . Their excellent electrical conductivity, their high specific surface area, and the vast internal space of the SWCNHs make it an excellent carrier for other particles. Moreover, SWCNHs are produced without using any metal catalyst at a high purity and can be used directly without further purification .
Considering the many merits of AuNPs and SWCNHs, we first developed an Au electrode modified with an AuNPs and SWCNHs composite for the detection of glucose. Covalent bonding is used in the preparation of the Au-SWCNHs composite. The method is simple and has a low cost. Additionally, it avoids the use of toxic reagents and the composite performs very well for the electrochemical detection of glucose. SWCNHs have a large surface area and good electrochemical properties , which gives the composite prepared a stable structure and a high catalytic activity for glucose. There are enough binding sites for the gold nanoparticles on the modified SWCNHs to enable the formation of s-Au bond. Glucose sensing tests confirmed that the fabricated electrode had high sensitivity, good stability, anti-interference and reproducibility, which is used as the basis for developing the glucose sensor.