Boon Hoong Ong

Palm olein-in-water Pickering emulsion stabilized by Fe3O4-cellulose nanocrystal nanocomposites and their responses to pH

We studied the formation of palm olein-in-water (O/W) Pickering emulsion stabilized by Fe3O4-cellulose nanocrystals (MCNC) nanocomposites obtained by ultrasound assisted in-situ co-precipitation method. The synthesized MCNC nanocomposites successfully stabilized Pickering emulsion with dual responses. The magnetic tests revealed a direct-relation between attractability of MCNC-stabilized Pickering emulsions and the emulsion droplet diameter. The Pickering emulsions were stable under pH ranging from 3 to 6. The stability substantially reduced around pH 8-10, and regained slowly when approaching pH 13. From microscopic and mastersizer analysis, monodisperse emulsion droplets were noticed at pH 3-6, and 13, while polydisperse emulsion were obtained at pH 8-12. The Pickering emulsions prepared at pH 6 are stable up to 14 days, while Pickering emulsions at pH 8 experienced coalescence. In this study, the dual stimuli-responsive Pickering emulsion stabilized by MCNC may hold potentials for biomedical and drug delivery as new generation of smart nanotherapeutic carrier.

Hematite Nanoparticles-Modified Electrode Based Electrochemical Sensing Platform for Dopamine

Hematite (α-Fe2O3) nanoparticles were synthesized by the solid transformation of ferrous hydroxide and ferrihydrite in hydrothermal condition. The as-prepared α-Fe2O3 nanoparticles were characterized by UV-vis, PL, XRD, Raman, TEM, AFM, FESEM, and EDX analysis. The experimental results indicated the formation of uniform hematite nanoparticles with an average size of 45 nm and perfect crystallinity. The electrochemical behavior of a GC/α-Fe2O3 electrode was studied using CV and EIS techniques with an electrochemical probe, [Fe(CN)6]3−/4− redox couple. The electrocatalytic activity was investigated toward DA oxidation in a phosphate buffer solution (pH 6.8) by varying different experimental parameters. The chronoamperometric study showed a linear response in the range of 0–2 μM with LoD of 1.6 μM for DA. Square wave voltammetry showed a linear response in the range of 0–35 μM with LoD of 236 nM for DA.

Synthesis of silver nanoparticles prepared in aqueous solutions using helium dc microplasma jet

Silver nanoparticles (AgNPs) were synthesized in aqueous solutions by reduction of silver nitrate (AgNO3) assisted by a helium dc microplasma jet at atmospheric pressure without additional chemical reducing agents. Surfactant-free AgNPs were obtained at low initial AgNO3 precursor concentrations ≤0.5 mM. A surface plasmon resonance peak at approximately 400 nm confirmed the presence of AgNPs. At higher concentrations, sucrose was used to prevent agglomeration and cap the growth of nanoparticles. The effects of the molar ratio of sucrose/AgNO3 on the size distribution and morphologies of AgNPs were investigated. The average sizes of AgNPs synthesized at molar ratios of 20, 50, and 60% were 11.2 ± 0.4, 10.0 ± 0.2, and 6.2 ± 0.1 nm, respectively.

Characterization of Chemically Prepared Magnetite Nanoparticles

Magnetite (Fe3O4) nanoparticles are being extensively researched as potential building blocks for nanoscaled structures, devices and systems. They exhibit many unique properties due to their dimension that lies in the mesoscopic scale (in between atomic scale and microscopic scale). In addition, it is possible to fine tune the properties of magnetite particles prepared by wet chemical techniques simply by varying the synthesis parameters. Thus, they are widely considered for various applications in fields such as electronics, optoelectronics, biomedicine and medical diagnostics. However, in order to be widely utilized for biomedical and commercial applications, these particles have to be produced at a large scale with low cost, high yield and high reproducibility. Moreover, the particles have to possess uniform properties and narrow size distribution. In this paper, Fe3O4 nanoparticles are prepared under non‐oxidized environment using co‐precipitation of Fe2+ and Fe3+ with an alkaline base. The effect of preparation variables, such as the stirring rate, stirring period and reaction temperature, on the properties of the nanoparticles are compared using TEM, VSM and XRD.

Dispersion stability, magnetivity and wettability of cellulose nanocrystal (CNC)-dispersed superparamagnetic Fe3O4 nanoparticles: impact of CNC concentration

This study investigates the effects of cellulose nanocrystals (CNCs) on the dispersion and colloidal stability of Fe3O4–cellulose nanocrystal nanocomposites (MCNCs). The hybrid composites were prepared using an ultrasound assisted in situ co-precipitation technique in the presence of cellulose nanocrystals (CNCs) as the dispersant. The microscopy analysis showed that the dispersion of MNPs improved greatly with CNC as dispersant. STEM images showed that the mean particle size of Fe3O4 nanoparticle (MNPs) on all CNC samples was found to be less than 20 nm. However, the MNPs aggregated in the sample with 0.01 wt% of CNC. The colloidal stability improved substantially in the presence of 0.05 wt% CNC, and increasing the CNC concentration any more made no difference to the dispersive properties. The surface charges of MCNCs decreased drastically from −14.6 to −59.7 mV as CNC concentration increase from 0.00 to 1.00 wt%. The amount of MNPs deposited on CNC template decreased considerably as CNC concentration increased. Higher amount of MNPs deposited on the CNC surface gave rise to a higher surface wettability and magnetivity. All MCNC samples exhibited superparamagnetic properties and the saturation magnetization (Ms) of MCNC composites was reduced from 30.798 to 1.625 emu g−1 with increasing CNC content from 0.01 to 1.00 wt%. Overall, the results of the study showed that the incorporation CNC led to an improvement of the MNP dispersion and colloidal stability. The as-prepared MCNCs can be used to stabilize palm olein-based emulsions, suggesting their potential usefulness as nanocarriers in food and drug delivery applications.

Yield Control of Chemically‐Synthesized Magnetite Nanoparticles

Magnetic Fe3O4 nanoparticles have generated a vast amount of interest as they bridge the gap between the atomic and microscopic world. Below a certain size (<15 nm), these particles display a novel phenomenon known as superparamagnetism in which they can be magnetized and demagnetized rapidly with the aid of an external magnetic field. Thus, they have potential applications such as targeted drug delivery, hyperthermia, etc. in the biomedical field. Yield control is essential if these particles are to be used for diverse applications on a large scale. In this study, Fe3O4 have been prepared using the standard co‐precipitation of Fe2+ and Fe3+ with an alkaline base. Three synthesis parameters, namely the stirring rate, stirring period and the reaction temperature were varied to study their effects on the yield of the nanoparticles.

Synthesis and characterization of nickel ferrite magnetic nanoparticles by co-precipitation method

Magnetic nickel ferrite (NiFe2O4) nanoparticles have been synthesized via co-precipitation method by varying the metal precursors ratio. Four different precursors ratio (Fe:Ni) are varied at 40:60, 50:50, 60:40 and 80:20. The size of the nanoparticles is found to increase with increasing iron (Fe) content. In addition, the morphology of the particles are observed to change from spherical to a shape similar to a nanooctahedral particle when the Fe content in the initial precursors ratio increases. The X-ray Diffraction (XRD) patterns have proved the presence of nickel ferrite nanoparticles. The magnetic properties characterized by Vibrating Sample Magnetometer (VSM) at room temperature proved that the assynthesized nickel ferrite nanoparticles are ferromagnetic and the saturation magnetization (Ms) increases with the content of Fe in the sample.

Investigations of field instability of ferrofluid in hypergravity and microgravity

The field instability of the free surface of ferrofluid was investigated under microgravity and hypergravity environments conducted by parabolic flight. It is observed that the perturbation was suppressed under hypergravity, whereas at the microgravity condition, it appeared to have only slight increase in the amplitude of the perturbation peaks compared to the case of ground condition. Besides, an observation of peak-trough distance showed that not only the peak, but the trough was also very much dependent on the applied magnetic field. The difference of magnetic pole (north and south) had shown to be a factor to the perturbation as well.

Thermal stability of magnetite (Fe3O4) nanoparticles

Magnetite (Fe 3 O 4 ) nanoparticles are prime candidates for biomedical applications due to their biocompatibility and good magnetic properties. However, magnetite is highly susceptible to oxidation when exposed to the atmosphere. In order to preserve their properties, it is important for the particles to maintain their magnetite phase. In this study, magnetite nanoparticles were prepared using the conventional co3precipitation of ferrous (Fe 2+ ) and ferric (Fe 3+ ) chloride salt solutions with sodium hydroxide (NaOH). Thermogravimetric analysis (TGA) was subsequently carried out to identify the transition temperatures. Energy Dispersive X3Ray (EDX) spectrum shows the presence of impurities, such as sodium (Na) and chloride (Cl) ions in the as3synthesized magnetite nanoparticles. The as3synthesized samples were then calcined in a chamber furnace according to TGA data. The calcined samples were next characterised by X3ray Powder Diffraction (XRD), Transmission Electron Microscopy (TEM) and Vibrating Sample Magnetometer (VSM) to determine the changes in phase and magnetic properties of the nanoparticles as a function of different calcination temperatures.

Microscopic Characterization and Analysis of Electrospun TiO2-PVP and TiO2-PVDF Fibers

Titanium dioxide (TiO2) is a suitable material to be used in the field of photocatalytic water treatment. In this research, TiO2 membrane fibers were synthesized using a combination of non-aqueous sol gel method and electrospinning technique. Titanium isopropoxide (TTIP) was used as the precursor for the TiO2 filler of the fibers. Both polyvinylpyrrolidone (PVP) and polyvinylidene fluoride (PVDF) were used as the polymer base to obtain the respective membrane fibers. The effects of weight concentration of TTIP as well as the type and molecular weight of the polymer on the morphology of the fibers were studied. Microscopic characterization using field-emission scanning electron microscopy (FESEM) and Energy Dispersive X-Ray (EDX) analysis was performed to obtain the morphology and elemental composition of the fibers. Sub-micron range fibers with a continuous network were generally obtained. Fibers that are subjected to post-electrospinning calcination have a lower fiber diameter. Polymer decomposition is shown to occur during calcination which yielded higher purity TiO2 fibers. The use of higher molecular weight polymers can produce a stronger fibre network for membranes.