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Mössbauer Investigation of γ-Fe2O3 Nanocrystals in Silica Matrix Prepared by the Sol-gel Method

“…In the sample B the ratio between the BM and the max of the ZFC susceptibility is much smaller than that predicted by the Neèl theory for non-interacting particles (ratio in the range 2-7) [20], pointing out the presence of strong interactions between nanoparticles. These results agree with TEM observations, which showed the formation of nanoparticle agglomerates along with the presence of isolated particles [19].…”

“…The zero field cooled (ZFC) d. c. susceptibility of the sample B has been measured with a SQUID (superconducting quantum interference device) magnetometer [19]; the temperature max is 93 K [19]. For noninteracting superparamagnetic particles, the difference of BM and max is explained by the different time of measurement of the different techniques; the Mössbauer spectroscopy has a measurement time m 10 8 s, which is much shorter than m 100 s of the SQUID.…”

GELATION OF N3P3[NH(CH2)3Si(OEt)3]6-n [X]n X = NH(CH2)3Si(OEt)3, NCH3(CH2)3CN AND OC6H4(CH2)CN, n = 0 or 3 at the LIQUID/AIR/INTERFACE

“…Solid state 29 Si MAS NMR measurements provide information about the silicon environment and the structure of the gels 2 . Thus, 29 Si NMR signals in the range of 50-60 ppm show the T structures corresponding to the presence of R-Si(OH)(OSi) 2 (T 2 ) and R-Si(OSi) 3 (T 3 ) moieties in the structure of the (1), (2) and (3) gels.…”

“…For 13 C experiments spectral frequency was 100.577 MHz and the NMR chemical shifts are externally referenced to adamantane (major peak positioned at 38.6 ppm). For 29 Si experiments spectral frequency was 79.46 MHz and the NMR chemical shifts are externally referenced to DSS. For 31 P experiments spectral frequency was 161.923 MHz and the NMR chemical shifts are externally referenced to ADP.…”

“…Solid state Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) spectra were obtained using an Oxford wide bore 9.4 T magnet equipped with a Bruker Avance II console and employing a 4 mm H/X-CPMAS probe. For all samples, 1 H-X Cross Polarization (CP) experiments were acquired using a CP mixing time of 2ms (X being 13 C, 29 Si and 31 P). A strong 1 H decoupling during acquisition time was applied by using the two-pulse phase modulation (TPPM) scheme .…”