The network polysilanes (polysilynes) [RMe2SiCH2CH2Si]n, [R=Ph (1), 2‐Furyl (2)] have been synthesized by room temperature reaction of the corresponding organotrichlorosilane with Na dispersion in tetrahydrofuran (THF) medium. The method allows the formation of high molecular weight polymers [Mw/PDI = 10,504/2.2 (1), 9176/1.5 (2)] in improved yields than those obtained from classical Wurtz coupling reaction (Na, toluene, 110 °C). These polymers act as reducing agents for Ag(I) and Au(III) ions to afford stable metal nanoparticles of 4–8 nm size domains in toluene medium. The corresponding polymer–silver nanocomposites, 1a and 2a, are fluorescent in the green light region (λmax = ∼ 530 nm) due to the formation of silver nanoclusters (AgNCs) along with the nanoparticles (AgNPs). A simple chemical approach has been developed to modulate the plasmonic and emission intensities of the nanocomposite 1a by reacting with varying concentrations (10−12 to 10−7M) of HgI2 in toluene. The method allows enhancement of the fluorescence intensity associated with AgNCs. The results are explained by invoking coupling between the energies of surface plasmon resonance and the nanocluster electronic transition. The polymer–gold nanocomposites, 1b and 2b, are non‐fluorescent and the plasmonic resonance at 530 nm associated with AuNPs is found to be insensitive to Hg(II) ions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012