Highly dispersive strontium carbonate (SrCO3) nanostructures with uniform dumbbell, ellipsoid, and rod-like morphologies were synthesized in methanol solution without any additives. These SrCO3 were characterized by X-ray diffraction, field emission scanning electron microscopy, and N2 adsorption-desorption. The results showed that the reaction temperature and the methanol/water ratio had important effects on the morphologies of SrCO3 particles. The dumbbell-like SrCO3 exhibited a Broader-Emmett-Teller surface area of 14.9 m2 g-1 and an average pore size of about 32 nm with narrow pore size distribution. The formation mechanism of the SrCO3 crystal was preliminary presented.
Directed nucleation and growth by balancing local supersaturation and substrate/nucleus lattice mismatch
- Proceedings of the National Academy of Sciences of the United States of America
- Published 2 months ago
Controlling nucleation and growth is crucial in biological and artificial mineralization and self-assembly processes. The nucleation barrier is determined by the chemistry of the interfaces at which crystallization occurs and local supersaturation. Although chemically tailored substrates and lattice mismatches are routinely used to modify energy landscape at the substrate/nucleus interface and thereby steer heterogeneous nucleation, strategies to combine this with control over local supersaturations have remained virtually unexplored. Here we demonstrate simultaneous control over both parameters to direct the positioning and growth direction of mineralizing compounds on preselected polymorphic substrates. We exploit the polymorphic nature of calcium carbonate (CaCO3) to locally manipulate the carbonate concentration and lattice mismatch between the nucleus and substrate, such that barium carbonate (BaCO3) and strontium carbonate (SrCO3) nucleate only on specific CaCO3polymorphs. Based on this approach we position different materials and shapes on predetermined CaCO3polymorphs in sequential steps, and guide the growth direction using locally created supersaturations. These results shed light on nature’s remarkable mineralization capabilities and outline fabrication strategies for advanced materials, such as ceramics, photonic structures, and semiconductors.
The defined origin of food products is nowadays often seen as a marker of quality. Sr isotope ratio determination can be used to verify the origin of such food products and it has thus become an important technique. Wine samples in particular are often investigated using this technique. Sr isotopic ratio measurements are often disturbed by isobaric Rb interference, making a separation procedure necessary. In this investigation a very simple and effective procedure for the separation of Rb(+) and Sr(2+) ions for Sr isotope ratio determination in mineral water and wine samples was developed.
Radioactive strontium ((90)Sr) leaked into saline environments, including the ocean, from the Fukushima Daiichi Nuclear Power Plant after a nuclear accident. Since the removal of (90)Sr using general adsorbents (e.g., zeolite) is not efficient at high salinity, a suitable alternative immobilization method is necessary. Therefore, we incorporated soluble Sr into biogenic carbonate minerals generated by urease-producing microorganisms from a saline solution. An isolate, Bacillus sp. strain TK2d, from marine sediment removed > 99% Sr after contact for four days in a saline solution (1.0 × 10(-3) mol L(-1) Sr, 10% marine broth, and 3 weight% NaCl). Transmission electron microscopy and Energy-dispersive X-ray spectroscopy showed Sr and Ca were accumulated as phosphate minerals inside the cells and adsorbed at the cell surface at two days of cultivation, and then carbonate minerals containing Sr and Ca developed outside the cells after two days. Energy dispersive spectroscopy revealed that Sr, but not Mg, was present in the carbonate minerals even after eight days. X-ray absorption fine structure analyses showed that a portion of the soluble Sr changed its chemical state to strontianite (SrCO3) in biogenic carbonate minerals. These results indicated that soluble Sr was selectively solidified into biogenic carbonate minerals by the TK2d strain in highly saline environments.ImportanceRadioactive nuclides, (134, 137)Cs and (90)Sr leaked into saline environments, including the ocean, by the Fukushima Daiichi Nuclear Power Plant accident. Since the removal of (90)Sr using general adsorbents, such as zeolite, is not efficient at high salinity, a suitable alternative immobilization method is necessary. Utilizing the known concept that radioactive (90)Sr is incorporated into bones by biomineralization, we got the idea of removing (90)Sr into biominerals. In this study, we revealed the Sr removal ability of the isolated ureolytic bacteria under highly salinity condition and the mechanism of Sr incorporation into a biogenic calcium carbonate over a longer duration. These findings indicated the mechanism of the biomineralization by urease-producing bacterium and the possibility of the biomineralization application for a new purification method for (90)Sr in highly saline environments.
Single-phase mixed aluminates-titanates Nd1-x Sr x Al1-x Ti x O3 (x = 0.3 ÷ 0.9) were prepared from stoichiometric amounts of constituent oxides Nd2O3, Al2O3, TiO2 and strontium carbonate SrCO3 by solid-state reaction technique in air at 1773 K. Crystal structure parameters of Nd1-x Sr x Al1-x Ti x O3 were refined by full-profile Rietveld refinement in space groups R [Formula: see text] c (x = 0.3, 0.5, 0.7 and 0.8) and Pm [Formula: see text] m (x = 0.9). Comparison of the obtained structural parameters with the literature data for the end members of the system NdAlO3 and SrTiO3 revealed formation of two kinds of solid solutions Nd1-xSrxAl1-xTixO3 with the cubic and rhombohedral perovskite structure. Morphotropic rhombohedral-to-cubic phase transition in Nd1-xSrxAl1-xTixO3 series occurs at x = 0.84. Based on the results obtained as well as the literature data for the parent compounds, the tentative phase diagram of the NdAlO3-SrTiO3 pseudo-binary system have been constructed.
Metal orthopedic implants still face challenges in some compromised conditions, partly due to bio-inertness. The present study aimed to functionalize metallic implants with organic-inorganic nanocomposite (strontium-containing chitosan/gelatin) coatings through a simple single-step electrophoretic deposition under mild conditions. The surface characterization and in vitro cellular response were studied and compared with chitosan/gelatin (CS/G) coatings. SEM images suggested the inorganic nanoparticles may be encapsulated within or mixed with organic polymers. The XRD patterns showed that strontium carbonate was generated in the coatings. The TEM images revealed strontium-containing nanoparticles were released from the coatings in PBS. The continuous release after the initial burst release ensured the enduring effects of the functionalized surface. The tensile bond strength of the coatings to the substrates increased after the addition of strontium. In vitro cellular study confirmed that strontium-containing coatings supported the proliferation of MC3T3-E1 cells and exhibited excellent ability to enhance the differentiation of such pre-osteoblasts. Therefore, such organic-inorganic nanocomposite coatings are a promising candidate to functionalize orthopedic implant surfaces.
We report the interfacial reaction-driven formation of micro/nanostructured strontium carbonate (SrCO3) biomorphs with subcelluar topographical features on strontium zinc silicate (Sr2ZnSi2O7) biomedical coatings, and explore their potential use in bone tissue engineering. The resulting SrCO3 crystals build a well-integrated scaffold surface that not only prevents burst release of ions from the coating but also presents a nanotopographic feature similar to cellular filopodia. The surface with biomorphic crystals enhances osteoblast adhesion, upregulates ALP activity and increases collagen production, highlighting the potential of the silica-carbonate biomorphs for tissue regeneration.
Aim of this study was to evaluate two different approaches to obtain strontium-modified calcium phosphate bone cements (SrCPC) without elaborate synthesis of Sr-containing calcium phosphate species as cement precursors that could release biologically effective doses of Sr(2+) and thus could improve the healing of osteoporotic bone defects. Using strontium carbonate as strontium(II) source, it was introduced into a hydroxyapatite forming cement by either the addition of SrCO3 to an α-tricalcium phosphate-based cement precursor mixture (A-type) or by substitution of CaCO3 by SrCO3 during precursor composition (S-type). The cements, obtained after setting in a water-saturated atmosphere contained up to 2.2at-% strontium in different distribution patterns as determined by time of flight secondary ion mass spectrometry (ToF-SIMS) and energy dispersive X-ray spectroscopy (EDX). Setting time of CPC and A-type cements was in the range of 6.5-7.5 min and increased for substitution-type cements (12.5-13.0 min). Set cements had an open porosity between 26 and 42%. Compressive strength was found to increase from 29 MPa up to 90% in substituted S-type cements (58 MPa). SrCPC samples released between 0.45 and 1.53mgg(-1) Sr(2+) within 21days and showed increased radiopacity. Based on these findings, the SrCPC developed in this study could be beneficial for the treatment of defects of systemically impaired (e.g. osteoporotic) bone.