caa a22 4500 463228049 CHVBK 20180405153233.0 cr unu---uuuuu 170326e20071201xx s 000 0 eng 10.1007/s10853-007-1980-4 doi (NATIONALLICENCE)springer-10.1007/s10853-007-1980-4 Paramagnetic silica-coated gold nanoparticles [Elektronische Daten] [Corneliu Ghica, Petre Ionita] Water soluble gold nanoparticles, obtained by the reduction of the gold (III) chloride with sodium borohydride in the presence of citric acid or thioctic acid, were covered with a paramagnetic silica layer using the Stober method, yielding a hybrid metallic-inorganic nanomaterial (gold nanoparticles, with an average size of 5nm, embedded into silica nanoparticles, with an average size of 100nm). The paramagnetic silica layer was formed by copolymerization of a paramagnetic silica precursor (derived from 3-aminopropyltrimethoxysilane) with tetramethyorthosilicate. The paramagnetic silica precursor was obtained by coupling 3-aminopropyltrimethoxysilane with 3-carboxy-proxyl free radical. TEM pictures show that each silica nanoparticle of about 100nm in size embedded about 10 gold nanoparticles. These hybrid nanoparticles are quite stable and exhibit the expected paramagnetic characteristics, as seen by electron paramagnetic resonance. The accessibility of methanol through the silica layer was also studied. Depending on the capping ligands of the gold nanoparticles (citric or thioctic acid), different silica networks are formed, as seen by the mobility of the spin-label inside the silica layer. The EPR spectra showed that the paramagnetic silica layer is very robust and the mobility of the spin-probe inside the silica layer is very little affected by methanol. However, if spin-labeled thioctic acid protected gold nanoparticles were used in the material synthesis, the mobility of the spins attached to the gold surface is quite high in the presence of methanol, while the spins embedded into the silica layer remains immobilized. Springer Science+Business Media, LLC, 2007 Ghica Corneliu National Institute for Materials Physics, PO Box MG-7, 077125, Bucharest-Magurele, Romania aut Ionita Petre Institute of Physical Chemistry, 202 Spl. Independentei, 060021, Bucharest, Romania aut Journal of Materials Science Springer US; http://www.springer-ny.com 42/24(2007-12-01), 10058-10064 0022-2461 42:24<10058 2007 42 10853 https://doi.org/10.1007/s10853-007-1980-4 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10853-007-1980-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ghica Corneliu National Institute for Materials Physics, PO Box MG-7, 077125, Bucharest-Magurele, Romania aut NATIONALLICENCE 700 1- Ionita Petre Institute of Physical Chemistry, 202 Spl. Independentei, 060021, Bucharest, Romania aut NATIONALLICENCE 773 0- Journal of Materials Science Springer US; http://www.springer-ny.com 42/24(2007-12-01), 10058-10064 0022-2461 42:24<10058 2007 42 10853 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer