Metallic nanomaterials exhibiting distinct surface-plasmon-resonance effects have gained increasing attention over the past few years due to their broad applications in photonics, biological imaging, drug delivery, sensing and surface enhanced Raman spectroscopy (SERS). One of the main drivers for the development of plasmonic materials is the desire to improve the sensitivity of SERS for exploring structure and reaction pathways at surfaces as well as for sensing. The development of nanofabrication methodologies for tailoring both particle shape and size has been intensified recently, giving special attention to the preparation of noble metal nanoparticles (Cu, Ag, Pt, Pd, and Au). Over a wide range of studies, the challenge is to develop metallic substrates combining high sensitivity, reproducibility, stability and easy of preparation. The sensing feature of MNPs results from their collective charge density oscillations and is known as localized surface plasmon resonance (LSPR). In recent studies, we reported a new method of fabrication of MNPS based on the self-assembly of metallic precursor-loaded homopolymer dispersion. Then, the deposition of this dispersion on a given substrate (glass, silicon, functionalized surface, etc.) allows the formation of highly sensitive nano-objects particularly relevant for sensing and SERS. Herein we report a facile way to detect few biomolecules (picomol) using highly sensitive silver nanoparticles. In the present communication, we investigate the physico-chemical mechanism of formation of MNPs in order to tune their physical and optical properties, which is essential for sensing applications. We particularly highlight the possibility to measure few molecules of bacteria.