Dalton Transactions PAPER Cite this: DOI: 10.1039/c4dt00760c Received 13th March 2014, Accepted 6th May 2014 DOI: 10.1039/c4dt00760c www.rsc.org/dalton Structural and photophysical properties of rare-earth complexes encapsulated into surface modified mesoporous silica nanoparticles† Chandrashekhar Malba, a Umayal P. Sudhakaran, b Silvia Borsacchi, b Marco Geppi,* b Francesco Enrichi, c,d Marta Maria Natile, e Lidia Armelao, e Tiziano Finotto, a Riccardo Marin, a Pietro Riello a and Alvise Benedetti* a The encapsulation of [Eu(dbm) 3 phen] into functionalized mesoporous silica nanoparticles (MSN) has been carried out to study the effect of chemical environments on the photoluminescence properties of the rare-earth complex. Surface functionalization was achieved by the reaction of the silanol groups on the surface of mesoporous silica with different organosilylating agents such as (3-aminopropyl)-triethoxy- silane (APTES), (3-mercaptopropyl)-trimethoxysilane (MPTMS), and ethoxytrimethylsilane (ETMS). A change in the luminescence properties of the Eu(dbm) 3 phen complex has been observed on its encapsu- lation into surface modified mesoporous silica nanoparticles. The modification of photophysical pro- perties is attributed to the interaction of Eu(dbm) 3 phen with the different chemical environments in the functionalized mesoporous silica nanoparticles (MSN). The luminescence properties of the rare-earth complex in surface-modified MSN increase in the order MSN < MSN–ETMS < MSN–MPTMS < MSN– APTES. The Eu(dbm) 3 phen complex encapsulated in the functionalized mesoporous silica nanoparticles shows an enhanced luminescence and an increased lifetime compared to the pure rare-earth complex in the solid state and that in unmodified MSN. This implies that some interactions of the lanthanide com- plexes take place during their incorporation process into the organically modified mesoporous silica nanoparticles. The organically modified mesoporous silica nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR) and N 2 adsorption desorption measurements. The luminescence properties of the encapsulated Eu(dbm) 3 phen were studied in detail. Moreover, the effect of functionalized MSNs on the structural behaviour of the Eu(dbm) 3 phen was investigated by solid state nuclear magnetic res- onance (SSNMR) techniques using an analogous diamagnetic model complex, Y(dbm) 3 phen, encapsulated into functionalized MSNs. These studies indicate that the encapsulated rare-earth complex shows some interactions with the functional groups anchored on the surface of MSNs. Introduction There is increasing interest in the development of lanthanide based luminescent materials, especially those of Eu 3+ and Tb 3+ with organic ligands which often show excellent luminescence characteristics. 1 Weissman first reported the light-emission characteristics of lanthanide complexes of β-diketonates in 1942. 2 However, the lanthanide complexes have been excluded from practical applications due to their poor thermal stability and mechanical properties. In attempting to solve these pro- blems, some research groups have incorporated the complexes into inorganic 1e,3 and polymeric materials. 1b,4 The incor- poration of lanthanide complexes within silica matrices 5 or organic–inorganic hybrid matrices 6 has also been extensively investigated. These studies have indicated that the matrix not only improves the thermal stability 7 and mechanical † Electronic supplementary information (ESI) available. See DOI: 10.1039/ c4dt00760c a Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, INSTN and Centro di Microscopia Elettronica “Giovanni Stevanato”, via Torino 155/b, 30170 Venezia-Mestre, Italy. E-mail: benedett@unive.it; Fax: +39-041-234-8594; Tel: +39-041-234-8544 b Dipartimento di Chimica e Chimica Industriale, Università di Pisa and INSTM, v. Risorgimento 35, 56126 Pisa, Italy. E-mail: marco.geppi@unipi.it; Fax: +39-050-2219260; Tel: +39-050-2219289 c Laboratorio Nanofab, Veneto Nanotech SCpA, via delle Industrie 5, 30175 Venezia-Marghera, Italy d CNR-IFN, Istituto di Fotonica e Nanotecnologie, Labortorio CSMFO, via alla Cascata 56/C, 38123 PovoTrento, Italy e CNR-IENI, INSTM, Dipartimento di Scienze Chimiche – Università di Padova, Via F. Marzolo 1, 35131 Padova, Italy This journal is © The Royal Society of Chemistry 2014 Dalton Trans. Published on 06 May 2014. Downloaded by UNIVERSITA CA FOSCARI VENEZIA on 30/05/2014 06:54:19. View Article Online View Journal