In this study, silica spheres (SiO2) nanomaterials were introduced as the support materials for glucose sensors. Glucose oxidase (GOx) was immobilized onto SiO2 spheres (SiO2/GOx) using physical adsorption (electrostatic interaction) method. The SiO2 spheres were synthesized in-house using a nonsurfactant template of palm oil derived fatty alcohols (PODFA). Based on FT-IR analyses, SiO2/GOx exhibited N-H absorbance at ca. 2990 cm-1 and O-H absorbance at ca. 3330 cm-1. One new absorbance peak was observed at ca. 2320 cm1 attributed to the bending vibration (νbend)of silane molecules (Si-H) obtained by the interaction of GOx and the surface silanols (Si-OH). UV-Vis analysis results exihibited the presence of a new broad peak for GOx/SiO2 sample at ca. 250 nm to 280 nm suggested to be assigned to H2O2, C=C and benzene ring from GOx. The optimum pH and optimum temperature for SiO2/GOx for GOx activity were ca. 7.0 and ca. 50°C respectively. The increase of glucose concentration from 2mM to 5mM resulted to the increment of absorbance value for both GOx and SiO2/GOxsuggesting succesful immobilization of GOx on SiO2 spheres. These materials were suitable for glucose detection at very small glucose concentrations particularly in salivary glucose detection.
Highly sensitive urine glucose detection by graphene field-effect transistors functionalized with electropolymerized nanofilms.
