Controlled synthesis of monodisperse α-calcium sulfate hemihydrate nanoellipsoids with a porous structure

Abstract

We report a facile and green chemical solution approach to synthesize monodisperse α-calcium sulfate hemihydrate (α-HH) nanoellipsoids with a length of 600 nm and a width of 300 nm by simply mixing Ca(2+) and SO4(2-) glycerol-water precursor solutions in the presence of Na2EDTA. The α-HH nanoellipsoid is formed through a Na2EDTA-mediated self-assembly of small primary building blocks (α-HH domains: ∼14 nm). The study on the morphological evolution of α-HH reveals that the controlled synergy of supersaturation (precursor concentration) and Na2EDTA is crucial for the development of α-HH into nanoellipsoids. Further thermal annealing of the nanoellipsoid could make the α-HH domains transit into calcium sulfate anhydrites and grow up, generating the gaps between them and resulting in a porous structure. This work paves a new way for preparing high-quality α-HH nanoellipsoids with a monodisperse nanosize and a porous structure, promising their future application in many fields such as biomedicine.

A facile method to control the structure and morphology of α-calcium sulfate hemihydrate

“…The crystal lattice of α-HH consists of -Ca-SO 4 -Ca-SO 4 -Ca-chains with repeating, ionically bonded Ca and SO 4 ions, which forms a framework with continuous channels parallel to the c axis and favors the preferential 1D growth along the c axis. 15 In general, as the Na 2 EDTA concentration is raised, the monodispersity and smoothness of α-HH polycrystalline microspheres get better and then deteriorate. The crystallization process changes upon the addition of Na 2 EDTA.…”

“…4,11 The structure, morphology and size of α-HH often determine its properties and functionalities. 13,14 On the other hand, micro-scale α-HH single crystals are mainly used as ceramic molds, building materials and bone-substitute materials, while the nano-scale α-HH polycrystals can promisingly serve as drug carriers and find other medical applications, 15 thus highlighting the importance of structure and morphology control of α-HH. 12 In comparison, α-HH particles with a low aspect ratio or spherical shape possess better injectability and mechanical properties after hydration, and are preferable for use as bone cements.…”

Aspect ratio-controlled preparation of α-CaSO4·0.5H2O from phosphogypsum in potassium tartrate aqueous solution

“…5b, three adsorption peaks at 1584 cm À1 , 1404 cm À1 and 1385 cm À1 in the FT-IR spectrum of the obtained a-CaSO 4 $0.5H 2 O crystals (blue curve in Fig. 5b) should be assigned to the asymmetric and symmetric stretching vibrations of -COO-, 44,48 and the three peaks were all shied to lower wavenumbers as compared with those in the FT-IR spectrum of PT. This result indicated that tartrate ions from PT were absorbed on the surface of the obtained a-CaSO 4 $0.5H 2 O crystals.…”

“…2b) of the crystal showed that the observed d-spacing were 0.598 nm and 0.344 nm, closing to that for (002) and (020) facets of a-CaSO 4 $0.5H 2 O, respectively. 44 The XRD pattern of the as-prepared rod-shaped crystals was shown in Fig. 2c, and the main diffraction peaks at 14.91 , 25.61 , 26.82 , 29.77 and 31.52 were assigned to (200), (020), (À121), (400) and (204) facets of CaSO 4 $0.5H 2 O crystals (JCPDS 41-0224), respectively.…”

“…42 To control the aspect ratio of 1D a-CaSO 4 $0.5H 2 O crystals, various crystallization (synthetic) methods have been proposed. 43,44 The a-CaSO 4 -$0.5H 2 O whiskers can be obtained by autoclave hydrothermal method in the presence of Mg 2+ , but its aspect ratio cannot be efficiently controlled and the reaction temperature up to 150 C. 9,18 Rod-shaped a-CaSO 4 $0.5H 2 O crystals were successfully produced from ue gas desulfurization in Ca(NO 3 ) 2 solution and its size could be signicantly controlled via adjusting the Ca(NO 3 ) 2 concentration. 42 However, regardless of the size of the rod-shaped a-CaSO 4 $0.5H 2 O crystals, its aspect ratio remained unchanged.…”