A facile method for the synthesis of metal nanostructures decorated two-dimensional (2D) semiconductor nanosheets was developed. The solution-processable molybdenum trioxide (MoO3) nanosheets were used as templates for direct liquid-phase growth of platinum nanoparticles (Pt NPs) at ambient conditions. Results show that the Pt NPs with the size of 1-3 nm were uniformly grown on the MoO3 surface. Importantly, the Pt-MoO3 hybrid nanomaterials exhibit an enhanced peroxidase-like catalytic activity compared to the MoO3 nanosheets, Pt NPs, and their physical mixture under same conditions. As a proof-of-concept application, the Pt-MoO3 hybrid nanomaterials were used as a high-efficiency peroxidase-mimic for ultrasensitive colorimetric detection of glucose in serum samples. This work provides a promising strategy for design and development of biomimetic catalysts by smart assembly of different dimensional nanomaterials.