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RISS 인기검색어
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- 저자 : N.Chau (검색결과 39 건)
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Size Controlled Magnetite Nanoparticles and Their Drug Loading Ability
C. V. Thach,N. H. Hai,N. Chau 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Magnetite nanoparticles (MNPs) were synthesized by using coprecipitation method with a reaction between the FeCl₂/FeCl₃ solution and the ammonia water. The size of the MNPs could be controlled from 10.0 to 14.6 nm by changing the concentration of the solutes. The particles were superparamagnetic at room temperature. The saturation magnetization of the MNPs increased with increasing concentration of reactants. The magnetite nanoparticles were coated with a single layer of oleic acid (OA) to have a hydrophobic surface or with a double layer of oleic acid/sodium dodecyl sulfate (OA/SDS) to have hydrophilic surface. The coated particles could be dispersed in n-Hexane or water. The OA/SDS-coated nanoparticles were used to load an antibiotic drug, chloramphenicol (Cm). Three weight percent of Cm could be loaded onto the OA/SDS coated nanoparticles, which is much higher than amount that can be loaded using the traditional drug loading method. Magnetite nanoparticles (MNPs) were synthesized by using coprecipitation method with a reaction between the FeCl₂/FeCl₃ solution and the ammonia water. The size of the MNPs could be controlled from 10.0 to 14.6 nm by changing the concentration of the solutes. The particles were superparamagnetic at room temperature. The saturation magnetization of the MNPs increased with increasing concentration of reactants. The magnetite nanoparticles were coated with a single layer of oleic acid (OA) to have a hydrophobic surface or with a double layer of oleic acid/sodium dodecyl sulfate (OA/SDS) to have hydrophilic surface. The coated particles could be dispersed in n-Hexane or water. The OA/SDS-coated nanoparticles were used to load an antibiotic drug, chloramphenicol (Cm). Three weight percent of Cm could be loaded onto the OA/SDS coated nanoparticles, which is much higher than amount that can be loaded using the traditional drug loading method.
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Long-term anti-cariogenic biofilm activity of glass ionomers related to fluoride release
Chau, N.P.T.,Pandit, S.,Jung, J.E.,Cai, J.N.,Yi, H.K.,Jeon, J.G. Elsevier 2016 Journal of dentistry Vol.47 No.-
<P>Objectives: The aim of this study was to evaluate the difference between anti-cariogenic biofilm activities of glass ionomers (G-Is) during the initial and second fluoride release phases and to define relationships between the anti-biofilm activities and fluoride release. Methods: Fluoride release of three commercially available G-Is in a buffer was evaluated for 770 h, and then 70-h-old Streptococcus mutans UA159 biofilms were formed on the G-Is that had been immersed in the buffer for 0, 100, 200, or 700 h. The dry weight, bacterial cell number, water-insoluble extracellular polysaccharides (EPSs), and accumulated fluoride concentration of the 70-h-old biofilms and fluoride release and acid production rates during biofilm formation were determined. Relationships between the experimental variables and fluoride release rate were also evaluated using linear regression analysis. Results: In this study, fluoride release of the tested G-Is did not exhibit a biphasic pattern during biofilm formation. The release was sustained or did not rapidly decrease even over long immersion periods and was strongly correlated with an increase in accumulated fluoride concentration of the biofilms (R = 0.99, R-2 = 0.98) and reductions in dry weight, water-insoluble EPSs, and acid production rate of the biofilms (R = - 0.99 to - 0.96, R-2 = 0.92-0.98). Conclusions: This study suggests that G-Is can effectively affect acid production, EPS formation, and accumulation of cariogenic biofilms even during the second fluoride release phase, and that the anti-cariogenic biofilm activity is strongly correlated with fluoride release, which may be enhanced by acid production of cariogenic biofilms. (C) 2016 Elsevier Ltd. All rights reserved.</P>
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N. Chau,C. X. Huu,N. D. The,N. Q. Hoa 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2
This article presents our results for the low-field giant magnetocaloric effect (GMCE) around room temperature in a system of Fe-rich amorphous alloys Fe78-xCrxSi4Nb5B12Cu1 (x = 0 -8). The structural examination indicated that the as-cast alloys were fully amorphous. Thermal transition analysis performed on a dierential scanning calorimetry apparatus showed that both the crystallization temperature and the crystallization activation energy of the mentioned amorphous alloys increased with increasing Cr content. Beside the structural stabilizing enhancement, Cr substitution also improved the anti-corrosion of studied alloys. There is a very sharp ferromagnetic-paramagnetic phase transition at at Curie temperature, which is related to high homogeneity of the alloys. Curie temperature, Tc, linearly decreased from 450 K to 297 K with increasing Cr content from x = 0 to x = 8 due to ferromagnetic dilution. The temperature dependence of the magnetic entropy change, |ΔSm|, was studied in magnetic field variations of 13.5 kOe, 10.0 kOe and 5.0 kOe. The results showed that the maximal values of |ΔSm| occurred near Tc and reduced with increasing Cr content. Namely, for x = 0, |ΔSm|max is 11.2 J/kg.K and this value slightly reduces to 8.16 J/kg.K for x = 8. Especially, a giant magnetocaloric effect of 4.1 J/kg.K for x = 8 at 295 K was obtained in a quite low field change of 5.0 kOe. This material is very promising for magnetic refrigerant applications compared with recent typical magnetocaloric materials.
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Magnetic Properties and Magnetic Viscosity of Pr4Fe76Co10B6Nb3Cu1 Nanocomposite Magnet
N. D. The,N. H. Hai,C. X. Huu,H. D. Anh,L. V. Vu,N. Chau,V. V. Hiep 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
The nanocomposite magnet Pr4Fe76Co10B6Nb3Cu1 has been obtainedbynanocrystallizationofa rapidly-quenchedamorphous ake. Thein uenceoftheannealingprocessonthestructuralandthe magnetic properties are investigated. High magnetic hardness was reached with of large coercivity of Hc = 3.65 kOe, a remanent induction of Mr = 12.0 kG, Mr=Ms = 0.79 and maximum energy product (BH)max = 17.6 MGOe at optimal annealing conditions. The multiphase structures of Fe3B as soft phases and of Pr2Fe14B as hard phase were conrmed by X-ray diraction data. The magneticviscosityasafunctionofthereverseeldwasevaluatedforallspecimen. Theresultsshow thatthemagneticviscositycoecientpeaksatacriticalnucleationeld,atwhichthemagnetization reversal of the specimens becomes irreversible.
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Magnetic Properties of (FePt)100-xCux Thin Films
N. T. T. Van,N. H. Hai,N. H. Luong,V. V. Hiep,N. Chau 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
A series of (FePt)100-xCux (x = 0, 5, 8 and 11) thin films have been prepared by RF sputtering. The as-deposited films are nanocrystalline with fine particles. Upon annealing, the films transfer to the ordered fct FePt phase, which is hard magnetic. The influences of the Cu content, as well as the heat treatment conditions, on the magnetic properties of the films have been studied. Addition of 5 -- 8 at.% Cu lowers the optimum annealing temperature and improves the magnetic squareness and convexity of the hysteresis loop. Addition of a higher Cu content weakens the hard magnetic properties of the films. The dependence of the hard phase formation on the annealing conditions is investigated. A series of (FePt)100-xCux (x = 0, 5, 8 and 11) thin films have been prepared by RF sputtering. The as-deposited films are nanocrystalline with fine particles. Upon annealing, the films transfer to the ordered fct FePt phase, which is hard magnetic. The influences of the Cu content, as well as the heat treatment conditions, on the magnetic properties of the films have been studied. Addition of 5 -- 8 at.% Cu lowers the optimum annealing temperature and improves the magnetic squareness and convexity of the hysteresis loop. Addition of a higher Cu content weakens the hard magnetic properties of the films. The dependence of the hard phase formation on the annealing conditions is investigated.
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Mechanism for Sustainable Magnetic Nanoparticles under Ambient Conditions
N. H. Hai,N. D. Phu,N. H. Luong,N. Chau,H. D. Chinh,L. H. Hoang,D. L. Leslie-Pelecky 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Iron-based magnetic fluids are widely used in physical applications. Recently, they have been extended to many biological applications due to their magnetic and biocompatible properties. However, their stability under an ambient environment still has not been systematically investigated. In this report, we present the oxidation process of magnetic fluids. The oxidation process depends on the materials that make the nanoparticles, the diffusion of oxygen atoms from the environment to the magnetic nanoparticles, which mainly depends on the viscosity of the solution and the surfactant that coats the nanoparticles. We suggest three ways to protect nanoparticles from oxidation: (a) using highly viscous carrier liquid (b) using relevant surfactants and (c) substitution of Ni²+ and Co²+ for Fe²+ in magnetite. Methods (a) and (b) are general, so they can be applied for many environmentally sensitive magnetic fluids. Method (c) is specific for a magnetite fluid. Iron-based magnetic fluids are widely used in physical applications. Recently, they have been extended to many biological applications due to their magnetic and biocompatible properties. However, their stability under an ambient environment still has not been systematically investigated. In this report, we present the oxidation process of magnetic fluids. The oxidation process depends on the materials that make the nanoparticles, the diffusion of oxygen atoms from the environment to the magnetic nanoparticles, which mainly depends on the viscosity of the solution and the surfactant that coats the nanoparticles. We suggest three ways to protect nanoparticles from oxidation: (a) using highly viscous carrier liquid (b) using relevant surfactants and (c) substitution of Ni²+ and Co²+ for Fe²+ in magnetite. Methods (a) and (b) are general, so they can be applied for many environmentally sensitive magnetic fluids. Method (c) is specific for a magnetite fluid.
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