title: Effect of pH on the synthesis and properties of luminescent SiO2/calcium phosphate:Eu3+ core-shell nanoparticles.
abstract: A novel method for the synthesis of luminescent SiO(2)/calcium phosphate (CaP):Eu(3+) core-shell nanoparticles (NPs) was developed via a sol-gel route followed by annealing at a temperature of 800 °C. The object of this study was the investigation of the effect of pH on the formation of a CaP shell around the silica core. The resulting annealed NPs exhibited an amorphous SiO(2) core and a crystalline luminescent shell. The formation of a CaP layer was possible at pH below 4.5 and above 6.5 during the coating step. The crystal structure of the shell was studied by X-ray diffraction analysis. Hydroxyapatite (HAp) and α-tricalcium phosphate were detected as crystal phases of the surrounding layer. However, NPs produced under basic conditions exhibited a higher crystallinity of the CaP layer than did samples coated at pH below 4.5. In the pH interval between 4.5 and 6.5, no shell growth but the formation of secondary NPs containing CaO and Ca(OH)(2) was observed. Furthermore, SiO(2)/CP:Eu(3+) core-shell NPs were investigated by transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, inductively coupled plasma optical emission spectrometry, and photoluminescence spectroscopy. The resulting HAp-coated NPs were successfully tested by a cell-culture-based viability assay with respect to a later application as a luminescent marker for biomedical applications.
authors: Fraunhofer Institute for Silicate Research ISC, Neunerplatz 2, 97082 Würzburg, Germany. sofia.dembski@isc.fraunhofer.de
authors: Sofia
authors: S
authors: Dembski
authors: Moritz
authors: M
authors: Milde
authors: Marcel
authors: M
authors: Dyrba
authors: Stefan
authors: S
authors: Schweizer
authors: Carsten
authors: C
authors: Gellermann
authors: Torsten
authors: T
authors: Klockenbring
mesh_terms: D000818:Animals; D002130:Calcium Phosphates / Q000737:chemistry*; D002478:Cells, Cultured; D005063:Europium / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D049449:Luminescence; D051379:Mice; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D002130:Calcium Phosphates; D005063:Europium; D012822:Silicon Dioxide; C020243:calcium phosphate