Is there way to detect surface area of nanoparticle by electrochemical technique?
Dynamic light scattering is commonly used to measure nanoparticle size: http://en.wikipedia.org/wiki/Dynamic_light_scattering

Whether you can measure this sort of thing electrochemically depends a lot on the type of nanoparticle. Conductive nanoparticles, you might be able to estimate the surface area by measuring adsorptive behaviours of various things, like CO for Pt and Pd: http://www.sciencedirect.com/science/article/pii/S1388248113000933 Non-conductive particles might be measured by how they impede diffusion to a surface. Electrochemical techniques could suffer from problems related to the shapes of the nanoparticles, as well.

The most straightforward ways of examining the surface features of nanoparticles would be electron microscopy or AFM.

Without further details of your application, it's difficult to recommend a specific technique. If the nanoparticles are being used as an electrode, the apparent electrochemical surface area may be all you care about, even though this is not necessarily the same as the geometric surface area.