In this work, we present the synthesis of amphiphilic diblock copolymer poly(ethylene oxide-block-methylmethacrylate) (PEO-b-PMMA) using atom transfer radical polymerization and demonstrate its application for the fabrication of recessed nanodisk-array electrode (RNE) as a platform for protein detection. For the fabrication of thin-film, PEO-b-PMMA was spin-coated on the silicon wafer and the phase separation was achieved by a unique direct immersion annealing technique followed by washing with the water/methanol solution to remove the PEO phase. The microphase separation and comprehensive porosity characterizations were done using AFM and electron microscopy. Later, the thin film was loaded on the surface of the glassy carbon electrode by wedge transfer technique and the RNE property of the mesoporous thin film was confirmed using cyclic voltammetry (CV). For the protein sensing application, the thin film-coated electrode was biotinylated using EDC-NHS chemistry, followed by the blocking of the non-specific sites using bovine serum albumin (BSA). The reduction in the CV current and the increase in the channel resistance in EIS at each stage of fabrication confirmed the successful immobilization. For the streptavidin detection, the RNE displayed an ultra-low detection limit of 0.15 fg/ml with enhanced selectivity which confirms the potential of PEO-b-PMMA based RNE as an ultrasensitive immunosensor platform for any biomarker detection. © 2021 Elsevier B.V.