Sensors are the devices, which are composed of an active sensing material with a signal "transducer". The role of these two important components in sensors is to transmit the signal without any amplification from a selective compound or from a change in a reaction. These devices produce any one of the signals as electrical, thermal or optical output signals which could be converted in to digital signals for further processing. One of the ways of classifying sensors is done based on these output signals. Among these, electrochemical sensors have more advantage over the others because; in these, the electrodes can sense the materials which are present within the host without doing any damage to the host system. On the other hand, sensors can be broadly classified in to two categories as chemical sensors and biosensors. The biosensors can be defined in terms of sensing aspects, where these sensors can sense biochemical compounds such as biological proteins, nucleotides and even tissues [1-4]. Within these sensors, the active sensing material on the electrode should act as a catalyst and catalyze the reaction of the biochemical chemical compounds to obtain the output signals [1,5, 6]. The combination of these two different ways of classifications has given rise to a new type of sensors which are called electrochemical biosensors, where the electrochemical methods are applied for the construction and working of a biosensor [ l, 7-9].

The selection and development of an active material is a challenge. The active sensing materials may be of any kind as whichever acts as a catalyst for sensing a particular analyte or a set of analytes. The recent development in the nanotechnology has paved the way for large number of new materials and devices of desirable properties which have useful functions for numerous electrochemical sensor and biosensor applications [l, 10-14]. Basically by creating nanostructure, it is possible to control the fundamental properties of materials even without changing their chemical composition. In this way the attractive world of low dimensional systems, together with the current tendencies on the fabrication of functional nanostructured arrays could play a key role in the new trends of nanotechnology [ 1, 15-17]. Further, the nanostructures can be used for both efficient transport of electrons and optical excitation, and these two factors make.