Water pollution by heavy metals has become one of the most severe environmental problems today. In recent years, various methods for heavy metal detection from water have been extensively studied. The present article brings out a series of information on different varieties of core-shell nanocomposites such as SiO2@Au, SiO2@Ag, Ag@SiO2, Au@SiO2, etc., for water puriication. These nanocomposites provide high surface area and speciic afinity for heavy metal adsorption from aqueous systems. To date, it has become a hot topic to develop new technologies to synthesize different nanocomposites, to evaluate the detection of heavy metals under varying experimental conditions, to reveal the underlying mechanism responsible for metal removal based on modern analytical techniques (SEM, TEM, SERS, etc.) or mathematical models, and to develop materials of better applicability for practical use. This chapter mainly focuses

on nanocomposites preparation, their physicochemical properties, adsorption characteristics and mechanism, as well as their application in heavy metal detection. These materials exhibited strong aptitude to detect metal ions such as Pb(II), Cd(II), Zn(II), etc. Detection by different nanocomposites showed that concentration level can be successfully detectable down to the acceptable level of environmental standard.