Ultra-sensitive and rapid detection of toxic heavy metal, chemical toxins and biomolecules using calorimetric, fluorescence, electrochemical, Quart Crystal Microbalance (QCM) and Surface Enhanced Raman Spectroscopy (SERS) sensing platforms based on nanostructured metal surfaces, an active area of research due to their applications in environmental and biomedical sciences. We have fabricated variety of metal nanostructures using chemical and electrochemical methods and focussing on their applications in QCM based Mercury vapour sensing and SERS based chemical detection and bio diagnosis. Gold spikes and prisms were electro-deposited on the electrode surface of the QCM crystal and these materials have been demonstrated as very good mercury vapour sensing platforms, especially designed for alumina refineries. These sensor platforms were specific to mercury vapour even in a mixture of other vapours, have good thermal stability and long operational hours. On the other hand, we have fabricated metal dendritic nanostructures of silver, gold and copper using electrochemical methods and how the nanometre gaps present within the branched nanostructures can function as substrates for SERS based sensing of dyes. We have extended our SERS sensing approach to detect markers for infectious diseases such as malaria and anthrax. Malaria has a specific bio-marker called Hemozoin, after their interaction with gold nanorods, their Raman signals were found to enhance considerably under NIR laser excitation. The same method was used to detect the malaria pigment from an infected blood to establish the selectivity and sensitivity of this technique.