Precursor and Solvent Effects in the Nonhydrolytic Synthesis of Complex Oxide Nanoparticles for Bioimaging Applications by the Ether Elimination (Bradley) Reaction

Abstract

Investigation of the solvent and alkoxide precursor effect on the nonhydrolytic sol-gel synthesis of oxide nanoparticles by means of an ether elimination (Bradley) reaction indicates that the best crystallinity of the resulting oxide particles is achieved on application of aprotic ketone solvents, such as acetophenone, and of smallest possible alkoxide groups. The size of the produced primary particles is always about 5 nm caused by intrinsic mechanisms of their formation. The produced particles, possessing the composition of natural highly insoluble minerals, are biocompatible. Optical characteristics of the perovskite complex oxide nanoparticles can easily be controlled through doping with rare earth cations; for example, by Eu(3+). They can be targeted through surface modification by anchoring the directing biomolecules through a phosphate or phosphonate moiety. Testing of the distribution of Eu-doped BaTiO(3) particles, modified with ethylphosphonic acid, demonstrates their facile uptake by the plants with active fluid transport, resulting finally in their enhanced concentration within the cell membranes.

The Power of Non-Hydrolytic Sol-Gel Chemistry: A Review

“…These were studied already by Bradley in the 1950s and were used only in few cases (mainly with alkoxides of Mo VI , W VI , and Nb V ) [55]. A new application was recently found in the synthesis of mixed metal oxide nanoparticles [56,57].…”

“…This reaction principle was later utilized for the synthesis of other oxide-alkoxide molecular species (Ti, Ba-Mo, Na-W, Na-Mo, etc.) [158][159][160], polyoxovanadate and molybdate clusters [161] and finally for the preparation of metal oxide nanoparticles [56,162,163]. The synthesis was often performed in alcoholic solutions as the protic solvent facilitates the condensation [56].…”

“…[158][159][160], polyoxovanadate and molybdate clusters [161] and finally for the preparation of metal oxide nanoparticles [56,162,163]. The synthesis was often performed in alcoholic solutions as the protic solvent facilitates the condensation [56]. A part of this research area therefore coincides with the benzyl alcohol route of metal oxide nanoparticles synthesis [56].…”

Novel solvothermal approach to hydrophilic nanoparticles of late transition elements and its evaluation by nanoparticle tracking analysis

“…This results from easy nucleation of both oxides (Pazik 2009) and noble metal particles (Wilkinson 2011) emerging in the form of single crystals of the corresponding phase. It has been thus observed that among the late transition metals the solvothermal synthesis starting from Ni(acac) 2 yields in the absence of reducing agents solely Ni(II) derivatives (Pazik 2013), while Pd(acac) 2 produces the reduced phase of Pd(s), the so called H-Pd (Wilkinson 2011).…”

“…Bradley reaction, the solvothermal decomposition of metal alkoxides and alcohol solvates of salts at low temperatures through ether elimination and beta-hydrogen elimination has been reported recently as a route to highly crystalline oxide nanoparticles of a broad variety of compositions (Pazik 2009, Pazik 2013, involving in particular late transition metals. Even the synthesis of highly uniform in size palladium nanoparticles by this approach in acetophenone as solvent has been demonstrated (Wilkinson 2011).…”