Size-control of species via wavelength to selectively synthesize Ag quantum clusters (QCs) was utilized and the synthesis conditions of this system (AgNO3, poly(methacrylic acid) (PMAA) with light) were optimized by changing a variety of parameters. Silver QCs, stabilized by PMAA with different compositions, have been synthesized in aqueous solution by tuning the irradiation monochromatic light wavelengths (300 or 365 nm) and AgNO3/MAA ratio (1 or 2). The novel preparation procedure has demonstrated a new approach to enlarge the population of the Ag QC family and proved the effectiveness of size control to prepare Ag QCs by tuning the light wavelength. Naked Ag QC species Agn (n = 2-9, 11, and 13) in polymer matrices are fully characterized by mass spectrometer, thus providing finger-printing evidence of their presence. Details regarding the photolysis reaction procedure, Ag QC optical properties, and the origins of fluorescence are discussed. Through a combination of results obtained from mass spectroscopy, fluorescence, and time-dependent density functional theory, we can assign the origin of fluorescence from a small silver cluster of Ag2 in organic scaffolds. The kinetics of the photolysis reaction follows first-order kinetics (k = 0.1/h). After thiolphenol (C6H5SH) ligand functionalization of the generated silver clusters in aqueous solution, the low or high resolution mass spectra showed the constant species composites with a molecular formula AgnLn-1 (n = 2-9 and L = C6H5S). More evidence indicated the formation of polymer-wrapped silver clusters. Their antibio property was explored, and we confirmed that they indeed show efficient activity.