Environmental contamination by toxic metals—such as Pb²⁺, Cr³⁺, and Hg²⁺—and organometallic species like monomethylmercury (MeHg) presents one of the most persistent global challenges due to their bioaccumulation, long-term toxicity, and resistance to degradation. This thesis addresses this critical issue through a multidisciplinary approach combining nanotechnology, environmental chemistry, biosensor engineering, and …