In situ XAFS study at the Zr K-edge for SiO₂/ZrO₂ nano-sol

Abstract

The structural characterisation of SiO 2 /ZrO 2 nano-sol particles, prepared by mixing SiO 2 sol and aqueous solution of ZrOCl 2 8H 2 O, has been carried out by in-situ XAS measurement at the Zr K-edge during condensation reaction. The detailed XANES features at the Zr K-edge of the mixed sol of SiO 2 /ZrO 2 are compared with those of other references such as ZrO 2 , ZrOCl 2 8H 2 O, BaZrO 3 , and ZrSiO 4 , and it becomes obvious that the Zr 4+ ions are stabilised in an octahedral symmetry. The EXAFS result also indicates that each Zr atom is coordinated with six oxygen ones as the first nearest neighbour, where two oxygen atoms are from the linkage of (Si-O-Zr) at short distance, and four ones are from water molecules at long distance. As the condensation reaction proceeds, it is found that the number of oxygen atoms due to the formation of (Si-O-Zr) bond at short distance and the second neighbour of silicon atoms increase simultaneously. From the above EXAFS and XANES results, the structural and gelating models could be proposed, which is based on the octahedrally coordinated but distorted zirconium species attaching on the SiO 2 sol surface.

Structural evolution of SiO2–ZrO2 nano-sol intercalated clays upon pillaring reactionElectronic supplementary information (ESI) available: BJH pore size distribution and k3-weighted EXAFS spectra of the SiO2–ZrO2 sol-pillared clay at different calcination temperatures. See http://www.rsc.org/suppdata/jm/b2/b208929g/

“…For the fitting of the third peak, each curve fit was carried out with an oxygen, zirconium, or silicon shell, respectively. Though the curve-fitting with a Zr backscatterer failed to give physically reasonable parameters as previously described, 26 that with two Si neighbors gave rise to a reproducible peak. Finally, we discovered that the addition of new silicon scatterers at around 2.6 A ˚was indispensable to obtaining the most meaningful data and reliable fitting.…”

“…In a previous study on SiO 2 -ZrO 2 sol solutions, only a weak pre-edge peak was observed due to such a quadrupole transition, since the Zr ion was stabilized in a slightly distorted octahedron. 26 In the SiO 2 -ZrO 2 pillared clays described in this report, the pre-edge peak (P) at 17995 eV is found to be more intense than that in the previously studied SiO 2 -ZrO 2 sol, and becomes even stronger upon calcination due to enhanced local distortion. The peak positions of the edge region and edge-top are nearly invariant for all the samples, indicating that the valence state of Zr 41 remains unchanged.…”

The in vitro and in vivo anti-tumor effect of layered double hydroxides nanoparticles as delivery for podophyllotoxin

“…In recent years, LDH has been found to possess promising applications in biomedicine due to their unique anion exchange capability, controlled release and protection of the payload. Many LDH compounds intercalated with bioorganic anions such as DNA (Choy et al, 1999(Choy et al, , 2001Kwak et al, 2004;Hofer et al, 2004), amino acids (Aisawa et al, 2001;Zhang et al, 2004;Hibino and Nishiyama, 2004;Wong et al, 1999;Nakayama et al, 2002), anionic polymers (Wang et al, 2005), pesticides (Zhang et al, 2005(Zhang et al, , 2006, and drugs (Ambrogi et al, 1995;Li et al, 2004;Del Arco et al, 2000;Gutierrez et al, 1995;Qin et al, 2008) have been prepared successfully. Special interests have focused on exploring the possibilities of using LDH-drug delivery systems to deliver anti-inflammatory (Ambrogi et al, 2006) or anti-cancer drugs (Tyner et al, 2004).…”

Two different approaches to synthesizing Mg–Al-layered double hydroxides as folic acid carriers

“…Only in recent years have LDHs speared into the field of biomedicine due to their unique anion-exchange capability. Many LDH constructs with intercalated beneficial organic anions such as DNA [9][10][11][12], amino acids [13][14][15][16][17], anionic polymers [18], pesticides [19,20], or drugs [21][22][23][24] have been prepared successfully. Many investigators have been exploring the possibilities of using LDHs as drug-delivering system to transport anti-inflammatory [25] or anti-cancer drugs [26].…”