Synthesis and characterization of luminescent SiO2 @Eu(phen-Si) core-shell nanospheres

Four core-shell structured nanometre luminescent composites with different kernel sizes and different shell layer thicknesses (SiO₂₍₅₀₀₎ @Eu (phen-Si)₍₅₀₎ , SiO₂₍₅₀₀₎ @Eu (phen-Si)₍₁₅₎ , SiO₂₍₂₅₀₎ @Eu (phen-Si)₍₅₎ and SiO₂₍₂₅₀₎ @Eu (phen-Si)₍₁₀₎ ) were made by changing synthesis conditions. Here, initial subscript numbers in parentheses refer to the particle size of the SiO₂ core, whereas the final subscript numbers in parentheses refer to shell layer thickness. In these composites, silica spheres of 500 nm or 250 nm were identified as the core. The shell layer was composited of silicon, 1,10-phenanthroline and europium perchlorate, abbreviated as Eu(phen-Si); the chemical formula of phen-Si was phen-N-(CONH (CH₂ )Si(OCH₂ CH₃ )₃ )₂ . The composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and infrared spectroscopy. The monodispersed spherical SiO₂ showed characteristics of a regular microstructure and a smooth surface, as well as the advantage of dispersity, shown by SEM. The Eu(phen-Si) complex was able to self-assemble into monodispersed SiO₂ spheres, as seen using TEM. Fluorescence spectra indicated that the four composites had excellent luminescence properties. Furthermore, composites composed of a SiO₂ core and a 250 nm kernel size exhibited stronger fluorescence than 500 nm kernel-sized composites. Fluorescence properties were affected by shell thickness: the thicker the shell, the greater the fluorescence intensity. For the four composites, quantum yield values and fluorescence lifetime corresponded to fluorescence emission intensity data as quantum yield values and fluorescence lifetime were higher, and luminescence properties increased.

Organoindium-modified monodisperse ellipsoid-/platelet-like periodic mesoporous silicas

Indium-modified mondisperse ellipsoid-/platelet-like large-pore periodic mesoporous silica nanoparticles (MMSNs) SBA-15 have been prepared via molecular grafting of In[N(SiMe₃)₂]₃. Surface ligand exchange led to the formation of heteroleptic In species, and the resulting surface In species were converted into crystalline In₂O₃ nanoparticles by calcination.

Hybrid luminescence materials assembled by [Ln(DPA)3](3-) and mesoporous host through ion-pairing interactions with high quantum efficiencies and long lifetimes

A kind of mesoporous hybrid luminescence material was assembled through the ion exchange method between [Ln(DPA)₃]³⁻ and ionic liquid functionalized SBA-15. [Ln(DPA)₃]³⁻ was successfully anchored onto positive-charge modified SBA-15 by the strong electrostatic interaction. In [Ln(DPA)₃]³⁻, Ln³⁺ ions are in 9-fold coordination through six oxygen atoms of carboxyl groups and three nitrogen atoms of pyridine units, leaving no coordination site for water molecules. Therefore the hybrids possess prominent luminescent properties, SBA-15-IMI-Tb(DPA)₃ and SBA-15-IMI-Eu(DPA)₃ exhibit high quantum yield values of 63% and 79%, and long lifetimes values of 2.38 ms and 2.34 ms, respectively. Especially, SBA-15-IMI-Eu(DPA)₃ presents a high color purity, and the red/orange intensity ratio is as high as 7.6. The excellent luminescence properties and ordered mesoporous structures give rise to many potential applications in optical and electronic areas.

Semiconducting polymer encapsulated mesoporous silica particles with conjugated Europium complexes: toward enhanced luminescence under aqueous conditions

Immobilization of lanthanide organic complexes in meso-organized hybrid materials for luminescence applications have attracted immense interest due to the possibility of controlled segregation at the nanoscopic level for novel optical properties. Aimed at enhancing the luminescence intensity and stability of the hybrid materials in aqueous media, we developed polyvinylpyrrolidone (PVP) stabilized, semiconducting polymer (poly(9-vinylcarbazole), PVK) encapsulated mesoporous silica hybrid particles grafted with Europium(III) complexes. Monosilylated β-diketonate ligands (1-(2-naphthoyl)-3,3,3-trifluoroacetonate, NTA) were first co-condensed in the mesoporous silica particles as pendent groups for bridging and anchoring the lanthanide complexes, resulting in particles with an mean diameter of ∼ 450 nm and a bimodal pore size distribution centered at 3.5 and 5.3 nm. PVK was encapsulated on the resulted particles by a solvent-induced surface precipitation process, in order to seal the mesopores and protect Europium ions from luminescence quenching by producing a hydrophobic environment. The obtained polymer encapsulated MSN-EuLC@PVK-PVP particles exhibit significantly higher intrinsic quantum yield (Φ(Ln) = 39%) and longer lifetime (τ(obs) = 0.51 ms), as compared with those without polymer encapsulation. Most importantly, a high luminescence stability was realized when MSN-EuLC@PVK-PVP particles were dispersed in various aqueous media, showing no noticeable quenching effect. The beneficial features and positive attributes of both mesoporous silica and semiconducting polymers as lanthanide-complex host were merged in a single hybrid carrier, opening up the possibility of using these hybrid luminescent materials under complex aqueous conditions such as biological/physiological environments.