S.  Shukla, Priscilla, A., Banerjee, M., Bhonde, R. R., Ghatak, J., Satyam, P. V., and Sastry, M., ?Porous gold nanospheres by controlled transmetalation reaction: a novel material for application in cell imaging?, Chemistry of Materials, vol. 17, no. 20, pp. 5000-5005, 2005.