Graphene oxide/silica-cobalt (GO/Si-10Co) mesostructured nanocomposite was prepared via simple sol-gel method followed by hydrothermal treatment. Calcination of the material at 540 degrees C for 24 h gave reduced graphene oxide/silica-cobalt (rGO/Si-10Co). The FT-IR and Raman spectroscopies of the GO/Si-10Co confirms the interaction between graphene oxide, silica and cobalt. The characteristic structure of the mesoporous silica with parallel and cylindrical pores stacked in a hexagonal array, the graphene sheet and the distribution of cobalt nanoparticles were clearly viewed through FESEM, TEM and EDS-mapping analyses. The BET specific surface areas were found to be 588 m(2) g(-1) for GO/Si-10Co and 843 m(2) g(-1) for rGO/Si-10Co. Nitrogen sorption analysis exhibits that both the materials having type IV isotherms with H1 hysteresis loops, revealed the mesoporosity nature of the materials. The synergistic effect between GO sheets, silica and Co species fashioned the multifunctional applications of the synthesized materials. Under optimal experimental conditions, the GO/ Si-10Co showed excellent catalytic activity toward the liquid-phase oxidation of phenol with H2O2. Furthermore, rGO/Si-10Co mesostructured nanocomposite showed good electrocatalytic activity towards the reduction of H2O2 as compared to GO/Si-10Co due to the large surface area, excellent electrical conductivity and enhanced electrochemical activity. The developed nanocomposites were also tested as an aptasensor, and it is demonstrated a low detection limit of similar to 10(1) cfu mL(-1) towards Salmonella spp. The EIS result indicates, the electron transfer was blocked as more Salmonella spp was captured on the rGO/Si-10Co-aptamer/GCE electrode. Besides, the nanocomposites also showed photoluminescence properties in visible range due to the cobalt nanoparticles and magnetic properties. These properties are important for applications in optoelectronics and biological labelling.