Lanthanopolyoxotungstates in silica nanoparticles: multi-wavelength photoluminescent core/shell materials

Abstract

Photoluminescent lanthanopolyoxotungstate core/shell nanoparticles are prepared by the encapsulation of lanthanide-containing polyoxometalates (POMs) with amorphous silica shells. The preparation of morphological well-defined core/shell nanoparticles is achieved by the hydrolysis of tetraethoxysilane in the presence of POMs using a reverse microemulsion method. The POMs used are decatungstolanthanoates of [Ln(W 5 9À type (Ln(III) ¼ Eu, Gd and Tb). Photoluminescence studies show that there is efficient emission from the POM located inside the SiO 2 shells, through excitation paths that involve O / Eu/Tb and O / W ligand-to-metal charge transfer. It is also shown that the excitation of the POM containing europium(III) may be tuned towards longer wavelengths via an antenna effect, by coordination of an organic ligand such as 3-hydroxypicolinate. The POM/SiO 2 nanoparticles form stable suspensions in aqueous solution having the advantage of POM stabilization inside the core and the possibility of further surface grafting of chemical moieties via well known derivatization procedures for silica surfaces. These features together with the possibility of tuning the excitation wavelength by modifying the coordination sphere in the lanthanopolyoxometalate, make this strategy promising to develop a new class of optical bio-tags composed of silica nanobeads with multi-wavelength photoluminescent lanthanopolyoxometalate cores.

Dependence of the Lifetime upon the Excitation Energy and Intramolecular Energy Transfer Rates: The 5D0 EuIII Emission Case

“…Materials and measurements: With the exception of EuCl 3 ·6 H 2 O (99.9 %, Aldrich), which was used as received, the compounds addressed in this paper have been reported elsewhere (Table 1). The corresponding preparation procedures can be found in the references (also listed in Table 1).These compounds are chosen as illustrative examples of the abovementioned classes of materials: 1) K 7 [Eu(a 2 -P 2 Mo 17 O 61 )]·8 H 2 O [8] and Na 9 A C H T U N G T R E N N U N G [EuW 10 O 36 ]·14 H 2 O [9] POMs;…”

“…2) Core/shell [EuA C H T U N G T R E N N U N G (W 5 O 18 ) 2 ]/SiO 2 NPs [10] and Gd 2 O 3 :Eu nanotubes; [11] 3) EuA C H T U N G T R E N N U N G (H 2 O) 5 [Mo(CN) 8 ] coordination polymer; [12] [13] EuA C H T U N G T R E N N U N G (btfa) 3 ·phen, [13] EuA [15] 5) Organic-inorganic hybrid materials; [14][15][16] 6) Macro-mesocellular foams; [17] 7) MCM-41 functionalized mesoporous silica embedding EuA [18] 8) Zn-Al-bdc/Eu [19] and ZnAl[EuW 10 O 36 9À ] [20] LDHs. ] LDH) to coordination complexes (e.g., EuA C H T U N G T R E N N U N G (btfa) 3 ·A C H T U N G T R E N N U N G (H 2 O) 2 ) and amorphous siloxane-based organic-inorganic hybrids (e.g., organosilica porous networks [17] and di-ureasils [14b, 15,16] incarcerating Eu III b-diketonate complexes).…”

Biofunctional Composites of Polysaccharides Containing Inorganic Nanoparticles

“…Silica encapsulation normally involves the growth of SiO 2 shells, very often following the hydrolysis of tetraethylortosilicate precursor, in the presence of the above mentioned fluorophores. The literature offers a number of examples of nanoparticles comprising amorphous silica encapsulating fluorophores, these include organic dyes (Ow et al, 2005), lanthanide complexes (Granadeiro et al, 2010;Soares-Santos et al, 2003), gold clusters (Guével et al, 2011) and quantum dots (Darbandi et al, 2005), among other luminescent systems (Burns et al, 2006). Silica coating of fluorophores provides a large surface area for which a number of functionalization procedures that are well known in chemistry can be directly applied.…”

The role of surface functionalization of silica nanoparticles for bioimaging

“…70,73,77 Granadeiro et al studied the°u orescence behavior of several lanthanopolyoxotungstates (Ln(III)-POM)) entrapped in SNP. 78 They successfully obtained a core-shell nanostructure with the Ln(III)-POM mainly located in the nanoparticle core. According to their results, the photophysical characteristics of the Ln(III) compounds could be adjusted by using an aromatic organic ligand as an antenna for energy transfer.…”