Showing papers by "Pham Thanh Phong published in 2018"

Size-controlled heating ability of CoFe 2 O 4 nanoparticles for hyperthermia applications

Abstract: The magnetic properties and heating capacity of cobalt ferrite (CoFe2O4) nanoparticles 13–24 nm in size were studied. Results showed that the specific absorption rate of the nanoparticles strongly depended on their magnetic properties and particle size. Specific absorption rate values decreased with increased particle size, and the smallest CoFe2O4 nanoparticles (13.5 nm) exhibited the highest specific absorption rate. The mechanism underlying the decrease in specific absorption rate of the CoFe2O4 nanoparticles with increased particle size was also discussed.

Polymer-coated cobalt ferrite nanoparticles: synthesis, characterization, and toxicity for hyperthermia applications

Abstract: Monodispersed CoFe2O4 nanoparticles were synthesized by the thermal decomposition of Co and Fe acetylacetonate in octadecene, which contained oleic acid (OA) and oleylamine (OLA). The hydrophobicity of the CoFe2O4 nanoparticles was alleviated such that they were water dispersible by encapsulating them with poly(maleic anhydride-alt-1-octadecene) (PMAO). The heating ability of these magnetic fluids was assessed by calorimetry measurement of specific absorption rate under an alternating magnetic field of 300 Oe within the frequency interval of 290–450 kHz. The highest value of the specific absorption rate was 297.4 W g−1 for a sample concentration of 1 mg mL−1 under an applied field of 300 Oe and frequency of 450 kHz. Linear response theory was used to explain the results. The high specific absorption rate of the nanofluid based on PMAO-encapsulated CoFe2O4@OA/OLA showed that it may meet the requirements for practical applications in tumor-targeted hyperthermia treatment. In vitro cytotoxicity analysis was also performed on Sarcoma 180 cancer cells, and the results showed that these nanoparticles were nontoxic to cells.

Enhanced Photocatalytic Performance of Nitrogen-Doped TiO2 Nanotube Arrays Using a Simple Annealing Process

Abstract: Nitrogen-doped TiO2 nanotube arrays (N-TNAs) were successfully fabricated by a simple thermal annealing process in ambient N2 gas at 450 °C for 3 h. TNAs with modified morphologies were prepared by a two-step anodization using an aqueous NH4F/ethylene glycol solution. The N-doping concentration (0–9.47 at %) can be varied by controlling N2 gas flow rates between 0 and 500 cc/min during the annealing process. Photocatalytic performance of as-prepared TNAs and N-TNAs was studied by monitoring the methylene blue degradation under visible light (λ ≥ 400 nm) illumination at 120 mW·cm−2. N-TNAs exhibited appreciably enhanced photocatalytic activity as compared to TNAs. The reaction rate constant for N-TNAs (9.47 at % N) reached 0.26 h−1, which was a 125% improvement over that of TNAs (0.115 h−1). The significant enhanced photocatalytic activity of N-TNAs over TNAs is attributed to the synergistic effects of (1) a reduced band gap associated with the introduction of N-doping states to serve as carrier reservoir, and (2) a reduced electron‒hole recombination rate.

Biocompatible nanoclusters of O-carboxymethyl chitosan-coated Fe3O4 nanoparticles: synthesis, characterization and magnetic heating efficiency

Abstract: In this work, we developed a polymer encapsulation of Fe3O4 nanoparticles as a core–shell nanocluster with different sizes to investigate the cluster structure effect on their magnetic properties and magnetic heating behavior. Well-dispersed nanoclusters of O-carboxymethyl chitosan-coated Fe3O4 nanoparticles were synthesized by microwave-assisted co-precipitation. The cluster sizes were tunable by varying the concentration of polymers used during synthesis. Nanoclusters present superparamagnetic behavior at room temperature with a reduction in saturation magnetization as a consequence of coating layer. The shift of blocking temperature to the higher value with increasing clusters size shows the stronger magnetic interaction in larger magnetic clusters. In a low alternating magnetic field with frequency of 178 Hz and amplitude of 103 Oe, nanoclusters offer a high heating efficiency. A maximum specific absorption rate of 204 W/g is observed in the sample with hydrodynamic size of 53 nm. In vitro cytotoxicity analysis performed on HeLa cells verified that nanoclusters show a good biocompatibility and can be an excellent candidate for applications in hyperthermia cancer treatment.

Effect of zinc on structure, optical and magnetic properties and magnetic heating efficiency of Mn1-xZnxFe2O4 nanoparticles

Abstract: Mn1-xZnxFe2O4 (0 ≤ x ≤ 0.7) nanoparticles were synthesised by a hydrothermal process. X-ray diffraction patterns reveal that all samples have spinel crystalline structures. Scanning electron microscopy and X-ray diffraction patterns show that nanoparticles are near-spherical in morphology and their average size is 13–45 nm. The elemental analysis was carried out by energy dispersive X-ray analysis technique. The optical direct band gap of Mn1-xZnxFe2O4 nanoparticle decreases from 2.38 to 1.88 eV as the Zn content increases. Moreover, the saturation magnetisation at room temperature tends to decrease with increasing Zn content. The specific absorption rate (SAR) values were measured at a fixed frequency of 178 kHz with magnetic field amplitude of 80 Oe. The SAR initially decreases with the sample concentration and its decrease is attributed to the enhancement of dipolar interaction and agglomeration of the particles. The intrinsic loss power (ILP) value varies between 6.5 and 15 nHm2kg−1 in the biologically safe experimental limit of 1.13 × 109Am−1s−1. The high value of ILP makes these nanoparticles possible for potential candidates for treating magnetic hyperthermia.

Critical Phenomena and Estimation of Spontaneous Magnetization by Magnetic Entropy Analysis of La 0.7 Sr 0.3 Mn 0.94 Cu 0.06 O 3

Abstract: This paper presents a detailed study on the structural, magnetic, and critical behavior and magnetocaloric effect of La0.7Sr0.3Mn0.94Cu0.06O3 prepared by solid-state reaction method. X-ray diffraction patterns indicate that Cu-doped manganite crystallizes to a single phase with a rhombohedral structure. Critical components β, γ, and δ were determined by using modified Arrott plot, Kouvel–Fisher method, and critical isotherm analyses. These components are consistent with their corresponding values and were validated by Widom scaling law and scaling theory. The deduced critical exponents (β = 0.456, γ = 0.9912, and δ = 3.206) are also close to their corresponding theoretical values predicted by mean-field model, indicating that long-range interaction dominates the critical behavior of the LSMCO system. Spontaneous magnetization was determined by two methods. One method is based on magnetic entropy change under different magnetic fields, and the other method is based on classical extrapolation from the Arrott plot. The two methods are in excellent agreement, confirming the validity of the deduction of spontaneous magnetization using the magnetic entropy change.