Hello Dr. Arasu,

This is a review paper which provides a comprehensive analysis of new synthetic routes, characterization methodologies, and functionalization protocols of magnetic and gold-coated magnetic iron oxides nanoparticles. Applications of these materials for biosensing are also discussed.

http://www.eurekaselect.com/74527/article

Also the implications of some of the research findings to address both fundamental and practical issues related to gold-coated magnetic oxide nanoparticles are also briefly discussed in:

http://pubs.rsc.org/en/content/articlelanding/2008/jm/b719096d#!divAbstract

Synthesis of shell Au NPs is described briefly in the pdf.

Hopefully this helps you. Do provide some feedback.

Regards.

Hi, in case you have a pulsed laser at hand, this method is also easy to adapt. 

http://www.nature.com/articles/srep23352

If you need further info on pulsed laser ablation in liquids let me know.