Preparation of Uniform Nano Liposomes Using Focused Ultrasonic Technology.

Liposomes are microspheres produced by placing phospholipids in aqueous solutions. Liposomes have the advantage of being able to encapsulate both hydrophilic and hydrophobic functional substances and are thus important mediators used in cosmetics and pharmaceuticals. It is important for liposomes to have small sizes, uniform particle size distribution, and long-term stability. Previously, liposomes have been prepared using a homo mixer, microfluidizer, and horn and bath types of sonicators. However, it is difficult to produce liposomes with small sizes and uniform particle size distribution using these methods. Therefore, we have developed a focused ultrasound method to produce nano-sized liposomes with better size control. In this study, the liposome solutions were prepared using the focused ultrasound method and conventional methods. The liposome solutions were characterized for their size distribution, stability, and morphology. Results showed that the liposome solution prepared using focused ultrasonic equipment had a uniform particle size distribution with an average size of 113.6 nm and a polydispersity index value of 0.124. Furthermore, the solution showed good stability in dynamic light scattering measurements for 4 d and Turbiscan measurements for 1 week.

Effect of the TiO2 Colloidal Size Distribution on the Degradation of Methylene Blue.

TiO2 is the most commonly used photocatalyst in water treatment. The particle size of TiO2 is an important factor that significantly influences its activity during photocatalytic degradation. In the presence of liquid, the properties of nanopowders composed of exactly the same product clearly differ according to their aggregation size. In this study, TiO2 nanoparticles with a controlled size were fabricated by focused ultrasound dispersion. The high energy generated by this system was used to control the size of TiO2 particles in the suspension. The constant high energy released by cavitation enabled the dispersion of the particles without a surfactant. The activities of the prepared TiO2 photocatalysts for methylene blue (MB) degradation were then compared. The dye degradation effect of the photocatalyst was as high as 61.7% after 10 min when the size of the powder was controlled in the solution, but it was only as high as 41.0% when the aggregation size was not controlled. Furthermore, when the TiO2 concentration exceeded a certain level, the photocatalytic activity of TiO2 decreased. Controlling the size of the aggregated photocatalyst particles is, therefore, essential in water-treatment technologies utilizing TiO2 photocatalytic properties, and adjusting the TiO2 concentration is an important economic factor in this photocatalytic technology. This study contributes to the development of processes for degrading dyes, such as MB, released from wastewater into aquatic environments.

A Comparison of Gelling Agents for Stable, Surfactant-Free Oil-in-Water Emulsions.

Emulsions have a range of applications, for example, in cosmetics, pharmaceuticals, and food. However, the surfactants used to prepare such emulsions can often be toxic to humans and the environment and also affect the oil properties of emulsions. Therefore, interest in surfactant-free emulsions has increased in recent years. One method to enhance emulsion stability without a surfactant is to use a gelling agent to increase the viscosity. Gelling agents are viscous hydrocolloids that gel when dispersed in water, even at low concentrations. In this study, we prepared six oil-in-water emulsions (oil content 20%) with different gelling agents (xanthan gum, Carbopol 981, TR-2, and Ultrez 20) and investigated the effect of the gelling agent concentration. For each sample, particle size and emulsion stability analysis were performed at high temperatures to ensure the stability of the emulsions. We observed that the emulsion prepared using TR-2 (0.25 wt%) did not aggregate at high temperatures for one month. Based on our assessment of the stability of these emulsions under various conditions, we believe that the use of gelling agents for the preparation of surfactant-free emulsions shows great promise for applications requiring long-term stable emulsions, such as cosmetics and medicine.

Preparation of Surfactant-Free Nano Oil Particles in Water Using Ultrasonic System and the Mechanism of Emulsion Stability.

Emulsion technology is widely used in the preparation of cosmetics, pharmaceuticals, drug delivery, and other daily necessities, and surfactants are frequently used to prepare these emulsions because of the lack of reliable surfactant-free emulsification techniques. This is disadvantageous because some surfactants pose health hazards, cause environmental pollution, have costly components, and place limitations on process development. In this paper, an efficient method for surfactant-free nano-emulsification is presented. In addition, we discuss the effects of different operating parameters on the oil particle size, as well as the effect of the particle size on the emulsion stability. Specifically, we compared three surfactant-free ultrasonic emulsification technologies (horn, bath, and focused ultrasonic systems). The focused ultrasonic system, which concentrates sound energy at the center of the dispersion system, showed the best performance, producing emulsions with a particle size distribution of 60-400 nm at 400 kHz. In addition, phase separation did not occur despite the lack of surfactants and thickeners, and the emulsion remained stable for seven days. It is expected to be widely used in eco-friendly emulsification processes.

Effect of Particle Size on the Mechanical Properties of TiO2-Epoxy Nanocomposites.

This study investigated the effects of the packing density and particle size distribution of TiO2 nanoparticles on the mechanical properties of TiO2-epoxy nanocomposites (NCs). The uniform dispersion and good interfacial bonding of TiO2 in the epoxy resin resulted in improved mechanical properties with the addition of nanoparticles. Reinforcement nano-TiO2 particles dispersed in deionized water produced by three different ultrasonic dispersion methods were used; the ultrasonication effects were then compared. The nano-TiO2 suspension was added at 0.5-5.0 wt.%, and the mechanical and thermal properties of TiO2-epoxy NCs were compared using a universal testing machine, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC). The tensile strength of the NCs was improved by the dispersion strengthening effect of the TiO2 nanoparticles, and focused sonication improved the tensile strength the most when nano-TiO2 suspensions with a particle size of 100 nm or smaller were used. Thus, the reinforcing effect of TiO2 nanoparticles on the epoxy resin was observed, and the nano-TiO2 suspension produced by focused sonication showed a more distinct reinforcing effect.

Novel Surfactant-Free Water Dispersion Technique of TiO2 NPs Using Focused Ultrasound System.

Titanium dioxide (TiO2) nanoparticles are used in a wide variety of products, such as renewable energy resources, cosmetics, foods, packaging materials, and inks. However, large quantities of surfactants are used to prepare waterborne TiO2 nanoparticles with long-term dispersion stability, and very few studies have investigated the development of pure water dispersion technology without the use of surfactants and synthetic auxiliaries. This study investigated the use of focused ultrasound to prepare surfactant-free waterborne TiO2 nanoparticles to determine the optimal conditions for dispersion of TiO2 nanoparticles in water. Under 395-400 kHz and 100-105 W conditions, 1 wt% TiO2 colloids were prepared. Even in the absence of a surfactant, in the water dispersion state, the nanoparticles were dispersed with a particle size distribution of ≤100 nm and did not re-agglomerate for up to 30 days, demonstrating their excellent dispersion stability.

Influence of Piezoelectric Properties on the Ultrasonic Dispersion of TiO2 Nanoparticles in Aqueous Suspension.

In this study, the soft-type and hard-type lead zirconate titanate (PZT) ceramics were compared in order to create an optimal system for ultrasonic dispersion of nanoparticles, and sound pressure energy for each PZT ceramic was analyzed and closely examined with ultrasonic energy. TiO2 was water-dispersed using the soft-type and hard-type PZT transducer, possessing different characteristics, and its suspension particle size and distribution, polydispersity index (PDI), zeta potential, and dispersion were evaluated for 180 days. Furthermore, it was confirmed that the particles dispersed using the hard-type PZT transducer were smaller than the particles dispersed using the soft-type PZT by 15 nm or more. Because the hard-type PZT transducer had a lower PDI, uniform particle size distribution was also confirmed. In addition, by measuring the zeta potential over time, it was found that the hard-type PZT transducer has higher dispersion safety. In addition, it was confirmed that the ultrasonically dispersed TiO2 suspension using a hard-type PZT transducer maintained constant particle size distribution for 180 days, whereas the suspension from the soft-type PZT aggregated 30 days later. Therefore, the hard-type PZT is more suitable for ultrasonic dispersion of nanoparticles.

Performance Improvement of Ring-Type PZT Ceramics for Ultrasonic Dispersion System.

This study has been based on the examination of the characterization of ring-type lead zirconate titanate (PZT) ceramics for high-intensity focused ultrasonic dispersion system. The ring-type PZT ceramics were fabricated by the powder molding method. The mechanical properties, dielectric constant, and microstructure of the ceramics were investigated. Consequently, the density of the ceramics was increased with increasing forming pressure while the density of ceramics that were sintered at 1350 °C was decreased due to over-sintering. Furthermore, the mechanical properties were excellent at the higher forming pressure. The dielectric property of the ring-type PZT ceramics was not clearly influenced by the manufacturing and sintering conditions. The abnormal grain growth of the ceramics, however, could be prevented by a lower heating rate in addition to reducing the porosity.