Dendrite-like Self-assembly of Magnetite Nanoparticles on Porous Silicon** Sivakumar Balakrishnan, Yurii K. Gun’ko,* Tatiana S. Perova, Robert A. Moore, Munuswamy Venkatesan, Alexios P. Douvalis and Paul Brouke. [*] S. Balakrishnan, Dr. Y. K. Gun’ko School of Chemistry, Trinity College Dublin, Dublin 2 (Ireland) Fax: (+353)1-6712826 E-mail: igounko@tcd.ie Dr. T. S. Perova, Dr. R. A. Moore Department of Electronic & Electrical Engineering, University of Dublin, Trinity College, Dublin 2 (Ireland) Dr. M. Venkatesan School of Physics, Trinity College, University of Dublin, Dublin 2 (Ireland) Dr. A. P. Douvalis Department of Materials Science and Engineering, University of Ioannina, P.O. Box 1186, 45110, Ioannina (Greece) Dr. P. Brouke Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122 (Australia) [**] The authors acknowledge Science Foundation Ireland (Grant 04/BR/P0698) and HEA PRTLI programme for financial support, and staff members of the Electron Microscopy Unit (TCD) for SEM images. The authors like to thank Prof. J. M. D. Coey for providing access to his lab facilities and useful discussions, and also the Mössbauer Lab of the Physics Department of the University of Ioannina, for additional Mössbauer spectroscopy measurements.