In the present study, chitosan had been utilized as a "green" stabilizing agent for the synthesis of spherical silver nanoparticles in the range of 5-30 nm depending on the percentage of chitosan used (0.1, 0.5, 1.0 and 2.0 wt%) under γ-irradiation. X-ray diffractometer identified the nanoparticles as pure silver having face-centered cubic phase. Ultraviolet-visible spectra exhibited the influence of γ-irradiation total absorbed dose and chitosan concentration on the yield of silver nanoparticles. The antibacterial properties of the silver nanoparticles were tested against Methicillin-resistant Staphylococcus aureus (MRSA) (gram-positive) and Aeromonas hydrophila (gram-negative) bacteria. This work provides a simple and "green" method for the synthesis of highly stable silver nanoparticles in aqueous solution with good antibacterial property.
This study aims to synthesize Fe3O4 nanoparticles from natural iron sand as a starting material. The synthesis process was carried out by the coprecipitation method at a synthesis stirring rate of 270 rpm. Fe3O4 nanoparticle samples’ characterization process was carried out using scanning electron microscopy - energy dispersive X-ray (SEM-EDX), which produced a particle size of 10.76nm, and the Fe content of the sample was 60.96%. Characterization using X-ray diffraction resulted in a crystal size of 12.49 nm and a magnetite phase (Fe3O4) content of 48%. XRD characterization also showed the presence of another phase peak of NH4Cl. NH4Cl contaminants can be degraded by repeated washing using distilled water. This study proves that this synthesis can degrade other elements in natural iron sand to produce Fe3O4 nanoparticles.
Effective storage of biodiesel has proven to be a challenge, which the Indonesian government has invested billions of Indonesian rupiahs (IDR) in to overcome. It is thus important to investigate how different storage methods can affect the quality of biodiesel. The purpose of this study was to determine how storage at room temperature in the dark affects the quality of palm oil biodiesel (POB) and canola oil biodiesel (COB). POB and COB were stored in closed containers at 22 °C in the dark for 12 months. The results showed that POB was more significantly damaged than COB. This study found increases of density (POB by 51.52 kg/m3 and COB by 17.52 kg/m3), kinematic viscosity (POB by 0.67 mm2/s and COB by 0.32 mm2/s), acid value (POB by 0.27 mg-KOH/g and COB by 0.25 mg-KOH/g), total glycerol (POB by 0.58%-mass and COB by 0.60%-mass), and peroxide value (POB by 48 meq-O2/kg and COB by 54 meq-O2/kg), whereas there were decreases in fatty acid methyl esters (POB by 7.11%-mass and COB by 9.36%-mass). Gas chromatography-mass spectrometry results for POB and COB showed decreases in 9-octadecenoic acid methyl ester and 9,12-octadecadienoic acid (Z,Z)-methyl ester, and increases in 9-octadecenoic acid and 9,12-octadecadienoic acid (Z,Z). Fourier transform infrared spectroscopy (FTIR) results revealed the presence of methyl ester functional groups. The storage of biodiesel in a closed container at 22 °C in the dark can minimize biodiesel oxidation, as evidenced by the findings of this study, namely, the insignificant formation of ketone and aldehyde groups in the biodiesel oxidation process during storage, based on the results of FTIR.
Magnetic nanoparticles (Fe3O4) from natural iron sand with PEG-4000 have been successfully synthesized by the co-precipitation method. Natural iron sand was from Kulon Progo beach. Extraction of natural iron sand was separated with a magnet permanent as a precursor. The result of extraction was dissolved by acid chloride (HCl) solution. Precipitation process has been finished after added ammonium hydroxide (NH4OH) solution and added polyethylene glycol (PEG)-4000. This solution was dried until it formed a black precipitate. Magnetic nanoparticles were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), and Fourier Transform Infra-Red (FTIR). The quantitative and qualitative analyzes on XRD were using the Profex 4.2.0 application and Joint Committee Powder on Diffraction Standards (JCPDS) No. 19-0629, respectively. Fe3O4 nanoparticles were successfully formed as indicated by the bonding of Fe-O. The results obtained in this study were the crystalline size of 11-13 nm with lattice parameters of 8.3758 Å for Fe3O4 and 8.3589 Å for Fe3O4 added with PEG. Fe nanoparticles were more dominant with wt% above 65%, which was confirmed by the EDX results. The addition of PEG mass resulted in the smaller crystallite size of the nanoparticles.
This present work was aimed at fabrication of brushite crystals using oil-in-water high internal phase emulsion as a reaction medium. The oil phase of more than 75 wt.% was dispersed in the continuous aqueous phase. Due to the high oil volume fraction, the oil droplets were no longer spherical but were squeezed to take the shape of polyhedral. The morphology of the crystals was influenced by the structure of the emulsion and precursor concentration. The crystals were subjected to cytotoxicity test to ensure their compatibility with synoviocytes, which are cells that line the knee joints of rabbits. The crystals were able to sustain the cells for 5 days, which manifest their potential as osteoconductive coatings.
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