TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The nanoparticles: have a diameter of 1-100 nm, preferably 3-10 nm; and are of non-spherical, tetrahedron, triangular, prismatic, rod, hexagonal, cubical, ribbon, tubular, helical, dendritic, flower and/or star shapes. The nanocomposite comprises at least one of RGO-silver, RGO-gold, RGO-platinum, RGO-palladium, RGO-iron, RGO-rhodium, RGO-manganese oxide (MnOx), RGO-cobalt oxide, RGO-tellurium dioxide, RGO-cerium trioxide or RGO-chromium trioxide. In the adsorbent, the nanocomposite is supported on materials comprising at least one of alumina, zeolites, activated carbon, cellulose fibers, coconut fibers, clay, banana silks, nylon or coconut shell. The substrate comprises at least one of silica, alumina, zeolites, activated carbon, cellulose fibers, coconut fibers, clay, banana silks, nylon or coconut shell. In a batch setup the adsorbent is mixed with water contaminated with at least one heavy metal. In column setup water contaminated with at least one heavy metal is passed through an adsorbent bed into the adsorbent. In the method (I) the metal precursor comprises at least one of gold, silver, platinum, palladium, cobalt, manganese, iron, tellurium, rhodium, ruthenium, copper, iridium, molybdenum, chromium or cerium. The nanocomposite: has a width of 50 nm to 5 mu m; and is of spherical, tetrahedron, triangular, prismatic, rod, hexagonal, cubical, ribbon, tubular, helical, dendritic, flower shape, star and/or sheet shapes. The counter ions comprise at least one of chlorides, nitrates, acetates, sulfates or bicarbonates. In the method (I) graphite source comprises at least one of fossil fuels or sugars. Preferred Method: In method (I): the metal precursor is reduced by RGO at 40 degrees C or in-situ by the RGO; the RGO is obtained by chemical, biological, physical, photochemical or hydrothermal reduction of graphene oxide (GO); and the GO is obtained by oxidizing the graphite source. The method (I) further comprises: reducing the metal precursor and the GO; mixing pre-formed metal or pre-formed metal-oxide nanoparticles and the RGO; and varying size of the nanocomposite by varying the concentration of the metal precursor and the RGO.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The nanocomposite is bound to the substrate by at least one of chitosan, polyaniline, polyvinyl alcohol or polyvinylpyrrolidone. EXAMPLE - Pre-oxidized graphite was completely oxidized to obtain graphene oxide (GO). The GO was exfoliated by sonication and hydrazine hydrate solution (35 wt.% in water) was added and stirred. The ammonia solution (28 wt.% in water) was then added to above solution and heated at 90 degrees C. After 2 hours the GO was reduced to obtain purified reduced graphene oxide sheets (RGO). RGO (25 ml) was taken in beaker and calculated volumes of metal ion precursors (potassium permanganate, gold chloride, silver nitrate, chloroplatinic acid or palladium dichloride) were added to obtain final concentrations of 0.01 mM, 0.025 mM, 0.05 mM, 0.1 mM and 0.3 mM. The mixture was incubated for 12 hours at 30 degrees C. Later, all the solutions were dialyzed against distilled water for 5 days to obtain RGO-metal/metal oxide nanocomposites.