Water-dispersible triethylenetetramine-functionalized graphene: Preparation, characterization and application as an amperometric glucose sensor

The triethylenetetramine-functionalized graphene (TFGn) was prepared using graphene oxide (GO) and triethylenetetramine as raw materials through a one-step reaction under alkaline condition. The triethylenetetramine not only acted as cross-linker to combine GO, but also as reductant of GO. The TFGn was characterized by its ultraviolet spectrum (UV), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and Scanning electron microscopy (SEM). The results showed that triethylenetetramine was successfully grafted onto the surface of the GO through covalent bonding between amine and epoxy groups. The resultant TFGn was uniformly dispersed in water over several weeks, suggesting that the introduction of amino groups greatly increased the hydrophilicity of TFGn. The triethylenetetramine-functionalized graphene was then applied to fabricate glucose biosensors with IO₄⁻ oxidized glucose oxidase (GOx) through layer-by-layer (LBL) self-assembly by the covalent bonding between the aldehyde groups of GOx and amino groups of TFGn. The gold electrodes modified with the (GOx/TFGn)_n multilayer films were studied by cyclic voltammetry (CV) and showed outstanding electrocatalytical response to the oxidation of glucose when ferrocenemethanol was used as an artificial redox mediator. The response increased with an increasing number of GOx/TFGn bilayers, indicating that the analytical performance, such as the sensitivity of the glucose biosensor, could be adjusted by tuning the number of deposited GOx/TFGn bilayers. The linear response range of the biosensor constructed with six bilayers of GOx/TFGn to the concentration of glucose can extend to at least 8 mM with a sensitivity of 19.9 μA mM⁻¹ cm⁻². In addition, the sensor exhibited good stability due to the covalent interactions between the GOx and TFGn. - Highlights: • Water-dispersible triethylenetetramine-functionalized graphene (TFGn) was prepared through a one-step reaction. • The triethylenetetramine not only acted as cross-linker to combine GO, but also as reductant of GO. • A feature of this assembly process of the sensors is the formation of a covalent bond between the TFGn and GOx. • The sensitivity of the glucose biosensors could be adjusted by tuning the number of deposited GOx/TFGn bilayers.