Mesoporous silica particle embedded functional graphene oxide as an efficient platform for urea biosensing

The mesoporous silica particle embedded graphene oxide (GO) hybrid system is a promising platform for electrochemical biosensing owing to its large 2-dimensional structure, fast electron transfer kinetics, improved hydrophilic nature and surplus functional groups. Here, GO sheets were synthesized by Hummer's improved method and sub-micron sized homogeneous mesoporous silica (SiO2) particles were prepared by Stober's method. The SiO2 particles were embedded on the GO surfaces and were optimized with different concentrations for better applicability and hydrophilicity. Micro-structural and spectroscopic characterization of as-synthesized materials was carried out to confirm the successful synthesis as well as the functionalities required for biosensing. Scanning electron microscopy investigations suggest that the average size of the SiO2 particles decorated on the GO surface is _500 nm. Raman investigation provides information regarding the increase in defects and disorder on the GO surface with the increase in the SiO2 content. The optimized GO–SiO2 (GOS) composite electrode was prepared by the electrophoretic deposition technique and was used for the attachment of urease and glutamate dehydrogenase enzymes for urea detection employing the cyclic voltammetry method. The reproducibility, specificity and stability of the fabricated biosensor were found to be excellent for the urea sensing. Such an easy and cost effective material based GOS urea sensor showed a high sensitivity (2.6 mA mM_1 cm_2) and a good detection limit (14 mg dL_1).