Europium Polyoxometalates Encapsulated in Silica Nanoparticles - Characterization and Photoluminescence Studies

• Published in: European journal of inorganic chemistry Vol. 2013; no. 16; pp. 2877 - 2886
• Main Authors: Neves, Cristina S., Granadeiro, Carlos M., Cunha-Silva, Luís, Ananias, Duarte, Gago, Sandra, Feio, Gabriel, Carvalho, Patricia A., Eaton, Peter, Balula, Salete S., Pereira, Eulália
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01-06-2013; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Biocompatibility; Encapsulation; Europium; Luminescence; Microemulsions; Nanomaterials; Nanoparticles; Nanostructure; Photoluminescence; Polyoxometalates; Silica; Silicon dioxide; X-rays
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201201482

The incorporation of europium polyoxometalates into silica nanoparticles can lead to a biocompatible nanomaterial with luminescent properties suitable for applications in biosensors, biological probes, and imaging. Keggin‐type europium polyoxometalates Eu(PW11)x (x = 1 and 2) with different europium coordination environments were prepared by using simple methodologies and no expensive reactants. These luminescent compounds were then encapsulated into silica nanoparticles for the first time through the water‐in‐oil microemulsion methodology with a nonionic surfactant. The europium polyoxometalates and the nanoparticles were characterized by using several techniques [FTIR, FT‐Raman, 31P magic angle spinning (MAS) NMR, and TEM/energy‐dispersive X‐ray spectroscopy (TEM‐EDS), AFM, dynamic light scattering (DLS), and inductively coupled plasma MS (ICP‐MS) analysis]. The stability of the material and the integrity of the europium compounds incorporated were also examined. Furthermore, the photoluminescence properties of the Eu(PW11)x@SiO2 nanomaterials were evaluated and compared with those of the free europium polyoxometalates. The silica surface of the most stable nanoparticles was successfully functionalized with appropriate organosilanes to enable the covalent binding of oligonucleotides.
Europium polyoxometalates with distinct europium coordination are encapsulated in silica nanoparticles by a microemulsion methodology. Their surface is further functionalized with appropriate organic groups to originate biocompatible nanomaterials with suitable photoluminescent properties.