Abstract
There are more and more people getting diabetes all over the world and the patients suffer from bad life quality because of the fluctuating blood glucose concentration. To fabricate a good glucose biosensor, there are several criteria to be satisfied. The stability and specificity of the sensor itself, control of hydrophilicity for good electron transfer ability and larger surface areas are the key points to improve the sensing results. Glucose oxidase is an enzyme specifically binding with glucose and is usually used to sense blood glucose. This study aims to combine a cheap, stable and non-toxic SnS2 with multi-wall carbon nanotubes (MWCNT) to improve the sensitivity toward glucose. SnS2 is a layer structure material. The van der Waals force between the layers can be separated and thus the material exfoliated with ultrasonication. After centrifuguration in 13500 rpm, the size and thickness of the exfoliated SnS2 (E-SnS2) collected from the top portion become smaller so the surface area is much larger at the same concentration. X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are used to characterize E-SnS2. TEM images show the same crystal lattice (001), (110) and (100), echoing the results in XRD. The binding energies of electrons match those of the database of SnS2. The atomic proportion of Sn and S is approximately 1:2 from scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). The thickness of SnS2 decreases from 36, 43 nm to 8.2 nm as measured by an atomic force microscope (AFM) and the size also decreases from 934±804 nm to 24±8 nm as estimated from SEM images. The current density in cyclic voltammetry of the redox reaction increases when the E-SnS2 is added. The current becomes larger when the scan rate increases which means that the electrochemical reaction is a surface control process. The most important goal in biosensor is sensitivity. This work achieved a high sensitivity of 28.9 μA/mM cm2, which shows a great improvement in sensing ability. The linear range is from 0.0625 to 2.8 mM and the detection limit is 0.0125 mM.