Sm doped mesoporous CeO₂ nanocrystals: aqueous solution-based surfactant assisted low temperature synthesis, characterization and their improved autocatalytic activity

Abstract

Mesoporous Sm(3+) doped CeO2 (Ce-Sm) with a nanocrystalline framework, a high content of Ce(3+) and surface area (184 m(2) g(-1)), have been synthesized through a facile aqueous solution-based surfactant assisted route by using inorganic precursors and sodium dodecyl sulphate as a template. The XRD results indicate that the calcined Ce-Sm and even the as-prepared material have a cubic fluorite structure of CeO2 with no crystalline impurity phase. XRD studies along with HRTEM results confirmed the formation of mesoporous nanocrystalline CeO2 at a lower temperature as low as 100 °C. A detailed analysis revealed that Sm(3+) doping in CeO2 has increased the lattice volume, surface area, mesopore volume and engineered the surface defects. Higher concentrations of Ce(3+) and oxygen vacancies of Ce-Sm resulted in lowering of the band gap. It is evident from the H2-TPR results that Sm(3+) doping in CeO2 strongly modified the reduction behavior of CeO2 by shifting the bulk reduction at a much lower temperature, indicating increased oxygen mobility in the sample which enables enhanced oxygen diffusion at lower temperatures, thus promoting reducibility, i.e., the process of Ce(4+)→ Ce(3+). UV-visible transmission studies revealed improved autocatalytic performance due to easier Ce(4+)/Ce(3+) recycling in the Sm(3+) doped CeO2 nanoparticles. From the in vitro cytotoxicity of both pure CeO2 and Sm(3+) doped CeO2 calcined at 500 °C in a concentration as high as 100 μg mL(-1) (even after 120 h) on MG-63 cells, no obvious decrease in cell viability is observed, confirming their excellent biocompatibility. The presence of an increased amount of surface hydroxyl groups, mesoporosity, and surface defects have contributed towards an improved autocatalytic activity of mesoporous Ce-Sm, which appear to be a potential candidate for biomedical (antioxidant) applications.

Magnetic Properties of Rare Earth Doped SnO2, TiO2 and CeO2 Nanoparticles

“…Finally we will calculate the magnetization M of a Sm doped CeO 2 NP. The radius of the doping ion Sm 3+ (1.17 Å) is larger compared to that of Ce 4+ (0.97 Å) and leads to increasing of the lattice what is in qualitative agreement with the experimental data of many authors . The grain size decreases with increasing Sm concentration .…”

“…Swatsitang et al reported a maximum in the lattice parameter values and in the magnetization M at small Sm concentration, . The cited above experimental data are for 0.2–0.25. We have calculated also M in Sm doped SnO 2 and TiO 2 NPs taking the lattice parameter values from Ref.…”

Electronic Structure and Room Temperature Ferromagnetism in Gd‐doped Cerium Oxide Nanoparticles for Hydrogen Generation via Photocatalytic Water Splitting

“…For higher doping concentrations ( x = 0.08 and 0.10) peak is again shifted toward lower angle side. This shifting of (111) peak toward lower and higher angle side is attributed to the lattice expansion and reduction, respectively, which is induced by incorporation of Gd 3+ ions in CeO 2 NPs . Furthermore, it can be seen in Figure a, diffraction peaks become broader after doping and broadness of peaks are also observed to change with fluency of Gd 3+ ions in CeO 2 NPs, indicating that crystal size and crystallinity of the samples are affected with the fluencies of Gd 3+ ions.…”

“…Since, the larger ionic radii Gd 3+ (0.1053 nm) ions are substituted for the smaller ionic radii Ce 4+ (0.097 nm) ions and created the larger radii Ce 3+ ions (0.114 nm) . Furthermore, for maintaining charge neutrality in CeO 2 lattice, Gd 3+ and Ce 3+ ions are collectively creating oxygen vacancies in the CeO 2 lattice, which causes further lattice expansion …”

“…On Account of spin–orbit coupling, these deconvoluted Ce 3d core‐level spectra are resolved into ten peaks, which include six and four structures arise from Ce 4+ and Ce 3+ ions, respectively. These series of peaks are labeled as “ u ” and “ v ,” which are due to 3d 3/2 and 3d 5/2 spin–orbit states, respectively . The four peaks labeled with v o , v ′, u o , and u ′ are characteristic peaks of Ce 3+ , whereas, the peaks labeled with v , v″ , v‴ , u , u″ , and u‴ are characteristic peaks of Ce 4+ (shown in Figure ) .…”