Financial support from ‘Plan Nacional de I+D+I’ (Spanish Ministry of Science and Innovation and FEDER Program) through CTQ2010-16636 and MAT2010-20921 is acknowledged. Also we express our gratitude to both the Hedi Mattoussi’s Research Group at Florida State University for the supply of the functionalized ligand (TA-PEG-COOH) and the Organic Synthesis Research Group of the University of Oviedo for providing the equipment for the TAPEG- OMe ligand synthesis. We thank Dr Zakariae Amghouz from the Unit of Electron Microscopy of University of Oviedo for his assistance in the HR-TEM analysis. Finally, LTA. and MMM acknowledge pre-doctoral fellowships from the FPU program (Ref: AP2008-01504) from the Spanish Education Ministry and Severo Ochoa program (Ref: BP12046) from the Principado de Asturias, respectively.