Sol-gel synthesis and characterisation of nano-scale hydroxyapatite

Sol–gel synthesis route was suggested to prepare calcium hydroxyapatite (Ca10(PO4)6(OH)2, CHA) thin films on quartz substrates. CHA thin films were obtained using dip-coating and spin-coating techniques by coating the substrates 1, 5, 15 and 30 times. In the sol–gel process, the ethylenediaminetetraacetic acid and 1,2-ethandiol as complexing agents were used. Moreover, triethanolamine and polyvinyl alcohol were used as gel network forming materials. After each coating procedure the films were annealed at 1,000 °C. The results obtained from dip-coating and spin-coating techniques were compared in this study. It was demonstrated, that the formation of calcium hydroxyapatite depends on dipping (or spinning) time and annealing duration.

Sol–gel synthesis of calcium hydroxyapatite thin films …

T1 - Synthesis of strontium-doped hydroxyapatite powder via sol-gel method

Comparison of Hydrothermal and Sol-Gel Synthesis of …

Abstract:
The current interest of our research group is largely focused on the development and understanding of precipitated crystalline organometallic compounds. We are placing a strong emphasis in the study of the synthetic procedures, the morphology, and on the structural determination of such compounds. Special importance is engaged in the preparation coordination polymers crystallized from solutions of supercritical CO2, (scCO2), where the use of a co-solvent is occasionally employed depending on reagents solubility [1-3]. The correct selection of experimental conditions in the scCO2 reactive crystallization technique, allows a precipitation known from other methodologies, as well as new crystalline phases. This procedure leads to the crystallization of stable hierarchical nanoestructures involving micro and mesoporosity. As the preparation of the crystalline materials is carried out in scCO2, these obtained with microporous structures were recovered activated, i.e., with open volume, since the removal of any guest molecules from the framework is carried out by simple depressurization. This method is expected to have many potential applications in the development of green crystallization techniques for coordination polymers synthesis.

Experimental Procedure Sol–Gel Synthesis The composites of ..

Abstract:
Inorganic fertilizers along with high yielding varieties have contributed immensely for success of green revolution. Increasing pressure towards food production globally demands unconscientious fertilizer usage in future as well. Nitrogenous fertilizers are the extensively used fertilizers but also suffer huge losses from agriculture ecosystem due to faster rate of release which is not synchronized with crop demand. Thus resulting in low nitrogen use efficiency. In order to have a sustained release of nitrogen from fertilizer, nanoparticle coated with urea is an effective option. We report urea coated hydroxyapatite based nanofertilizer and its performance on aerobic paddy. In this study hydroxyapatite (HA) nanoparticles were synthesized by adding orthophosphoric acid to calcium hydroxide solution under constant vigorous stirring. Saturated urea solution was added to the HA particle suspension and was stirred continuously for 12 hours for surface modification. The urea modified HA particles were washed and dried at 65ºC. Hydroxyapatite nanoparticles (HA) and urea coated hydroxyapatite nanoparticles (UHA) were characterized using Dynamic Light Scattering (DLS), Scanning Electron Microscope (SEM), Powder X-ray Diffraction (PXRD) and Fourier Transform Infrared (FTIR) Spectroscopy. Nitrogen content of UHA was analyzed using Kjeldahl method. Nitrogen content of UHA particles was found to be 36% and Zeta potential was 165.0 mV indicating stable nanodispersion. PXRD pattern of UHA particles indicated the presence of peaks due to hydroxyapatite and urea. SEM images of UHA particles exhibited oblong structures resembling rice grains with diameter less than 90 nm. FTIR spectroscopy showed prominent peaks around γmax/cm–1 1041 indicating phosphate group in hydroxyapatite and γmax/cm–1 3336 and 3432 indicating presence of urea. Synthesized nanofertilizer was evaluated on aerobic paddy under completely randomized design and was compared with recommended dose of conventional urea (100kgN/ha) in aerobic paddy. Nanofertilizer at 25% of recommended dose recorded highest grain yield. Nanofertilizer@ 50% dose showed similar performace to 100% dose of conventional urea. The results indicate amount of fertilizer application into soil can be reduced than regular dosage with nanofertilizer without affecting the yield. This will reduce environmental pollution of water and soil without compromising agricultural production.

T1 - Preparation of aluminum oxide-hybridized hydroxyapatite powder by the sol-gel method
Synthesis of Titanium Dioxide by Ultrasound Assisted Sol-gel Technique Effect of Calcination Time

Sol-gel synthesis of calcium hydroxyapatite thin ..

Abstract:
Heterogeneous photo-catalysis is an advanced oxidation process (PAO), which has been the subject of numerous studies and applications, particularly using the commercial oxide of TiO2 (P25, Evonik). Zinc oxide (ZnO) has often been considered a valid alternative to TiO2 due to its good opto-electronic, catalytic and photochemical characteristics along with its low cost. In order to improve the photocatalytic performance of ZnO for practical applications, various types of synthetic approaches have been developed, including, among others, the hydrothermal / solvothermal growth method, sol-gel method, ultrasonic assisted method, deposition chemistry in vapor phase, etc. with the aim of preparing ZnO particles with different sizes and morphologies. However, all of these methods require relatively severe reaction conditions such as high temperature, sophisticated techniques, high purity of gases, adjustable gas flow, expensive raw materials, etc. Therefore, it is important to find a simple and cost-effective method for the synthesis of crystalline nano-particles of ZnO. For this reason, in the present work, the ZnO has been synthesized by three different procedures: conventional aqueous precipitation method, hydrothermal method (H) and microwave assisted method (MW). In all three processes, the same material is obtained, hydrocincite [Zn5(CO3) 2(OH)6], which evolves to crystalline ZnO after calcination thermal treatments. We investigated the effect of the calcination temperature, at the same time (2 h), on the optical, textural and structural properties. Photo-catalytic studies were performed using two selected substrates, Methyl Orange and Phenol, as toxic model substrates (one colorant and the other transparent). The catalysts prepared were characterized by several techniques: DRX, SBET, FE-SEM, TEM and UV-Vis (in diffuse reflectance mode).From the results of XRD, it has been possible to establish that a minimum difference between the relative intensities of exposed faces (I100 and I002) is a crucial factor to obtain good photocatalytic properties. This minimum difference is achieved, in our cases by thermal treatments of calcination at 400ºC, 2 h. When this temperature is chosen, there is no appreciable variation between the photocatalytic activities of the oxides of zinc obtained by the three processes, and there are small differences depending on the nature of the substrate chosen, which can be attributed to the textural differences between the oxides. In any case, the obtained zinc oxides show, for each substrate, photo-catalytic activities in the UV that are superior to those presented by the widely used commercial oxide TiO2 (P25) used as reference.

AICAM 2005: Particle Size Control in Sol-Gel Synthesis of Nano Hydroxyapatite

Sol-gel synthesis of nanostructured hydroxyapatite …

Nanoscale hydroxyapatite (HA) is an optimal candidate biomaterial for bone tissue engineering because of its bioactive and osteoconductive properties. In this study, micro- and nanoscale HA particles with rod- and wirelike morphology were synthesized by a novel sol–gel–hydrothermal process. Sol–gel chemistry was used to produce a dry gel containing amorphous calcium phosphate (ACP), which was used as a precursor material in a hydrothermal process. The sol–gel–hydrothermal products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to determine particle morphology, crystal structure, and the presence of chemical functional groups. A pure HA crystal was synthesized, which underwent both one- and three-dimensional growth, resulting in tunable microrod and nanorod, and wire morphologies. The effects of solution pH and reaction time on particle diameter and length were assessed. Particle diameter ranged from 25 to 800 nm and decreased with an increase in solution pH, whereas both particle length and diameter increased as the hydrothermal process was prolonged. Nanowire HA powders (10–50 wt %) were mixed with poly(ε-caprolactone) (PCL) to produce PCL/HA composites. Fracture surfaces of PCL/HA composites showed a well-dispersed and homogeneous distribution of HA nanowires within the PCL matrix. Mechanical testing revealed a significant (

Preparation of aluminum oxide-hybridized hydroxyapatite powder by the sol-gel ..

Green Synthesis of Metallic Nanoparticles via ..

Processing design in terms of time and temperature for both hydrolysisand ageing steps of the sol-gel synthesis was thoroughly investigatedand successfully optimized for phase-pure HAp formation.