Facile Synthesis of Hollow Nickel Submicrometer Spheres

Abstract

tures of these systems may be ideal for biomedical applications in which one desires to deliver cells into the body for a therapeutic purpose (e.g., regeneration of tissues or organs). [25,26] Experimental Sodium alginate (M w = 300 000; Pronova Biopolymers, Norway) was dissolved in 2-(N-morpholino)ethanesulfonic acid (Sigma) buffer (pH 6.5, 0.3 M NaCl) at room temperature, and the peptide was added to the alginate in the presence of N-hydroxysulfosuccinimide (Pierce) and 1-ethyl-3-(dimethylaminopropyl) carbodiimide (Aldrich). The peptide with a sequence of (glycine) 4 ±argi-nine±glycine±aspartic acid±serine±proline (G 4 RGDSP) was synthesized at the University of Michigan Protein and Carbohydrate Structure Core facility. The peptide-modified alginate was purified by extensive dialysis against distilled water for 3 days (molecular weight cut-off, 3500) and activated charcoal-treatment, and sterilized through a 0.22 lm filter. The DS of RGD peptides coupled to the alginate backbone was previously determined using radiolabeled RGD peptides as a tracer molecule [9]. Non-modified alginate (no peptide) was prepared in the same manner as the RGD-modified alginate with the exception that no peptide was added to the reaction.MC3T3-E1 mouse calvarial preosteoblasts were cultured in a-minimum essential media (Hyclone), containing 10 % fetal calf serum (Hyclone) and 100 units mL ±1 penicillin-streptomycin (Gibco). The cells were mixed with alginate solutions using two syringes and a female connector, and incubated at 37 C under 5 % CO 2 atmosphere for 30 min before testing. The final concentration of alginate solutions was fixed at 1 wt.-% and cell concentrations were varied in the range from 0.25 to 1.50 10 8 cells mL ±1 . A controlled stress rheometer (C-VOR 120, Bohlin Instrument) with a coneand-plate (20 mm diameter plate, 4 cone angle) fixture was used to measure the dynamic modulus of alginate solutions in the absence or presence of cells as a function of frequency in the range from 0.01 to 1 Hz. The gap opening at the apex of the cone and plate was set to 150 lm, and the stress amplitude was fixed at 0.05 Pa as it has been found to be well within the linear stress amplitude response regime. The samples and loading apparatus were completely covered with a solvent trap to prevent the evaporation of water during the measurement. Temperature control was achieved within ± 0.1 C, and the strain was 0.1 %.

Anisotropy and magnetization reversal with chains of submicron-sized Co hollow spheres

“…In reduced saturation magnetization, ~ 24% [6] or ~ 38% [7] of the bulk value at 300 K. of the sample is about 0.12 at 50 K, and it goes down to about 0.02 at 380 K. This is much smaller than the theoretically analyzed value, i.e. 0.5, for a system of randomly oriented Stoner-Wohlfarth (SW) particles [14].…”

“…Two stable ground states, the single domain and the vortex curling, have been obtained in theory for this special structure. Experimentally, there are many works concerning the synthesis and magnetic properties of Ni or Co hollow spheres [6][7][8].…”

Morphology-dependent nanocatalysis: metal particles

“…12D) were prepared by reducing NiSO 4 with NaH 2 PO 2 in an emulsion system. 96 When this process is conducted under hydrothermal condition using Ni(DS) 2 (dodecylsulfate) as the precursor, 50-60 nm nickel hollow spheres were obtained.…”

Nanostructured Ni Powder Synthesized from Non-aqueous Bath

“…The exchange coupling effect among the Ni nanoparticles will be reduced due to the isolation effect of the nonmagnetic matter. Meanwhile, the sample exhibits an enhanced coercivity (ie: Hc) value (239 Oe) compared to that of bulk Ni (0.7 Oe) 23 or that of hollow nickel sub-micro spheres (32.3 Oe), 9 hollow Ni nanospheres (102 Oe) 10 and dandelion-like Ni nanostructures (130.3 Oe) 24 at room temperature. Earlier studies in the magnetic nanosystems have shown that the effective anisotropy reins the coercivity, 25,26 which might explain why dendrite Ni possesses much higher coercivity.…”

“…Up to now, there are a variety of techniques used to produce Ni nanoparticles, such as chemical reduction, 4 hydrothermal reduction, 5,6 thermal decomposition of organometals, 7,8 emulsion technique 9,10 and so forth. Generally, most of those wet-chemical methods require the use of highly toxic organometals or reducing agents, which could bring in toxic gases or impurities or a high processes temperature etc., against the development trend of green chemistry and chemical processes.…”