Mesoporous silica nanoparticles with tunable pore size for tailored gold nanoparticles

The aim of this paper was to verify a possible correlation between the pore-size of meso- porous silica nanoparticles (MSNs) and the sizes of gold nanoparticles (AuNPs) obtained by an impreg- nation of gold(III) chloride hydrate solution in the MSNs, followed by a specific thermal treatment. Mesoporous silica nanoparticles with tunable pore diameter were synthesized via a surfactant-assisted method. Tetraethoxysilane as silica precursor, cetyl- trimethylammonium bromide (CTAB) as surfactant and toluene as swelling agent were used. By varying the CTAB–toluene molar ratio, the average dimension of the pores could be tuned from 2.8 to 5.5 nm. Successively, thiol groups were grafted on the surface of the MSNs. Finally, the thermal evolution of the gold salt, followed by ‘‘in situ’’ X-ray powder diffraction (XRPD) and thermogravimetric analysis (TGA), revealed an evident correlation among the degradation of the thiol groups, the pore dimension of the MSNs and the size of the AuNPs. The samples were characterized by means of nitrogen adsorption– desorption, transmission electron microscopy, small- angle X-ray scattering, XRPD ‘‘in situ’’ by synchro- tron radiation, and ‘‘ex situ’’ by conventional tech- niques, diffuse reflectance infrared Fourier transform spectroscopy, and TGA

Structural and luminescence properties of europium(III)-doped zirconium carbonates and silica-supported Eu3+-doped zirconium carbonate nanoparticles

The synthesis, morphology and luminescence properties of europium(III)-doped zirconium carbonates prepared as bulk materials and as silica-supported nanoparticles with differing calcination treatments are reported. Transmission electron microscopy and X-ray diffraction analyses have, respectively, been used to study the morphology and to quantify the atomic amount of europium present in the optically active phases of the variously prepared nanomaterials. Rietveld analysis was used to quantify the constituting phases and to determinate the europium content. Silica particles with an approximate size of 30 nm were coated with 2 nm carbonate nanoparticles, prepared in situ on the surface of the silica core. Luminescence measurements revealed the role of different preparation methods and of europium-doping quantities on the optical properties observed

Structural and luminescence properties of europium(III)-doped zirconium carbonates and silica-supported Eu3+-doped zirconium carbonate nanoparticles

The synthesis, morphology and luminescence properties of europium(III)-doped zirconium carbonates prepared as bulk materials and as silica-supported nanoparticles with differing calcination treatments are reported. Transmission electron microscopy and X-ray diffraction analyses have, respectively, been used to study the morphology and to quantify the atomic amount of europium present in the optically active phases of the variously prepared nanomaterials. Rietveld analysis was used to quantify the constituting phases and to determinate the europium content. Silica particles with an approximate size of 30 nm were coated with 2 nm carbonate nanoparticles, prepared in situ on the surface of the silica core. Luminescence measurements revealed the role of different preparation methods and of europium-doping quantities on the optical properties observed

Photoluminescence properties of YAG:Ce3+,Pr3+ phosphors synthesized via the Pechini method for white LEDs

We describe a facile route for synthesize YAG nanophosphors via Pechini-type sol–gel process for white light-emitting diodes technology. The wettype synthesis was followed by a heat treatment at 1,000 C for 4 h. We carried out a study of the luminescent properties of the YAG:Ce,Pr system varying the concentration of praseodymium from 0.125 to 2 mol% maintaining the quantity of cerium constant at 2 mol%. The diffractometric analysis confirmed the purity of the YAG phase. The luminescent analysis showed the typical Ce3? emission arising from the 5d ! 4f transitions overlapped with the sharper Pr3? emissions in the red region of the spectrum. The presence of energy transfer phenomenon was confirmed by PLE spectra of the samples and the appearance of concentration quenching at 0.5 mol% Pr was observed thanks to the decrease both of the intensity of praseodymium emission and mean lifetime