Synthesis of α-calcium sulfate hemihydrate submicron-rods in water/n-hexanol/CTAB reverse microemulsion

Rapid Micelle-Mediated Size-Controlled Fabrication of Calcium Sulfate Nanorods Using Silver Nanoparticles

Calcium sulfate nanorods (CS-NRs) are valuable materials utilized in various applications, particularly in the medical field. In this work, the size-controlled synthesis of CS-NRs was carried out on the basis of the micelle-mediated phase separation phenomenon. A nonionic surfactant, Triton X-114, was employed for the thermoresponsive phase separation of a homogeneous solution to a surfactant-rich phase. Whereas each specific ion, Ca²⁺ and SO₄^2-, was difficult to individually extract when present at concentrations less than their equilibrium concentration (solubility product constant, K_sp), the synthesized CS microrods (CS-μRs) were extracted into the surfactant-rich phase (enrichment factor = ca. 50). The presence of nitric acid increased the size of the materials up to 6707 ± 3488 nm on the long side and 87 ± 37 nm on the short side. The addition of silver nanoparticles (Ag-NPs) to the reaction mixture led to the formation of much smaller products, i.e., uniform CS-NRs whose sizes were in the range of 89 ± 15 nm (long side) and 25 ± 4 nm (short side). The size of the extracted Ag-NPs and CS-NRs decreased with an increase in added Ag-NP concentration until their microscopic observation became difficult. The factors (such as additive concentration, pH, temperature) affecting size control were evaluated.

Effect of calcium sulphate nanorods on mechanical properties of chitosan-hydroxyethyl methacrylate (HEMA) copolymer nanocomposites

Copolymers of chitosan and hydroxyetheyl methacrylate (HEMA) were successfully synthesized using ceric ammonium nitrate (CAN) as an initiator, via in situ polymerization method, followed by efficacious preparation of their nanocomposites by incorporating calcium sulphate nanorods via solution blending process. Hydrophilicity studies confirmed that grafting of HEMA in the backbone of the hydrophobic chitosan chains induced the improvement in hydrophilicity of chitosan, while mechanical properties of the nanocomposites were also enhanced significantly up to 20%, due to availability of enlarged surface area and higher aspect ratio of CaSO₄ nanorods. This was supported by FE-SEM and XRD analysis in terms of proper distribution of nanofiller through the copolymer matrix and corresponding rise in percentage crystallanity respectively. Results obtained from biodegradation studies proved the efficiency of CaSO₄ nanofillers to improve biomechanical strength of chitosan nanocomposites, without affecting their normal degradation profile that renders the products to be applicable for biomedical applications.

Ultrasonication assisted and surfactant mediated synergistic approach for synthesis of calcium sulfate nano-dendrites

Calcium sulfate (CaSO4) nano-dendrimers were fabricated successfully via ultrasonic irradiation method using calcium chloride [CaCl2] and ammonium per sulfate [(NH4)2SO4] as precursors in aqueous solution by using cetyl trimethyl ammonium bromide (CTAB) as chemical surfactants. Diffusion-induced branching growth mechanism (DIBGM), influenced with the action of head-group and hydrocarbon chain effect of cationic surfactants, was the backbone in the formation of CaSO4 nano-dendrites. Fourier Transform Infra-red Spectroscopy (FTIR), X-Ray powder Diffraction (XRD), Atomic Emission Spectroscopy (AES), Selected Area Electron Diffraction (SAED), Field-Emission Scanning Electron Microscopy (FE-SEM), Energy-Dispersive Spectroscopy (EDS), Dynamic Light Spectroscopy (DLS) and BET surface area analyzer were used to characterize the products. Results obtained were compared with conventional stirring method that proved the superiority of sonication method to obtain well-crystalline nanostructures. Also, surfactant concentration, sonication frequency and time were noticed as the critical factors to generate such absolute morphologies at nano-crystalline size.

Ultrasound-assisted/biosurfactant-templated size-tunable synthesis of nano-calcium sulfate with controllable crystal morphology

Nano-sized crystals of alpha calcium sulfate hemihydrate (α-HH) with considerable morphology-dependent properties find promising applications in the clinical fields as a cementitious material. Towards this end, ultrasound-assisted rhamnolipid and surfactin biosurfactant-template route is explored to control the morphology and aspect ratio of nano-CaSO4 by adjusting the mass ratio of rhamnolipid/H2O, surfactin/H2O and rhamnolipid/surfactin. The change in the molar ratio of [SO4(2-)]:[Ca(2+)] results in modification in variable morphology and size of nano-CaSO4 including long, short rods and nanoplates. With increase in the rhamnolipid/H2O ratio from 1.3 to 4.5, the crystal length decreases from 3 μm to 600 nm with the corresponding aspect ratio reduced sharply from 10 to 3. Similarly, the crystal morphology gradually changes from submicrometer-sized long rod to hexagonal plate, and then plate-like appearance with increase in surfactin concentration. The preferential adsorption of rhamnolipid on the side facets and surfactin on the top facets contributes to the morphology control. The process using 50% amplitude with a power input of 45.5 W was found to be the most ideal as observed from the high yields and lower average l/w aspect ratio, leading to more than 94% energy savings as compared to that utilized by the conventional process. As a morphology and crystal habit modifier, effects of Mg(2+) and K(+) ions on α-HH growth were investigated to find an optimal composition of solution for α-HH preparation. Mg(2+) ions apparently show an accelerating effect on the α-HH growth; however, the nucleation of α-HH is probably retarded by K(+) ions. Thus, the present work is a simple, versatile, highly efficient approach to controlling the morphology of α-HH and thereby, offers more opportunities for α-HH multiple applications.