Preparation of Nano-TiO2 by a Surfactant-Free Microemulsion-Hydrothermal Method and Its Photocatalytic Activity.

The TiO2 nanoparticles with high photocatalytic activity were prepared by the surfactant-free microemulsion (SFME)-hydrothermal method at lower temperatures using oil-in-water SFME systems as templates. The phase diagram of the SFME ethyl acetate (EA)/propan-2-ol/water was determined by electrical conductivity and UV-visible spectroscopy. The synthesized TiO2 nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, and N2 adsorption-desorption techniques. They were all assigned to the anatase phase and showed type IV adsorption-desorption isotherms with type H2 hysteresis loops. As the EA content (fO) of the SFME decreases, the Brunauer-Emmett-Teller (BET) specific surface area (SBET) of the TiO2 nanoparticles increases. This results in an increase in the photocatalytic activity of the TiO2 nanoparticles. With an increase in temperature, the photocatalytic activity of the TiO2 nanoparticles increases significantly, whereas the SBET values decrease and the crystal size increases. Under the same conditions, the degradation rate of the TiO2 prepared at 190 °C reaches 97%, which is significantly higher than that of Degussa P-25 (66%). This may be due to the use of the SFME system to synthesize the TiO2 nanoparticles, which avoids the blocking effects of surfactant molecules on the active sites of the nanoparticles.

The physiological response of oriental river prawn Macrobrachium nipponense to starvation-induced stress.

Environmental stresses play critical roles in the physiology of crustaceans. Food deprivation is an important environmental factor and a regular occurrence in both natural aquatic habitats and artificial ponds. However, the underlying physiological response mechanisms to starvation-caused stress in crustaceans are yet to be established. In the present study, the hepatopancreas tissue of Macrobrachium nipponense was transcriptome analyzed and examined for starvation effects on oxidative stress, DNA damage, autophagy, and apoptosis across four fasting stages (0 (control group), 7, 14, and 21 days). These results indicated that a ROS-mediated regulatory mechanism is critical to the entire fasting process. At the initial stage of starvation (fasting 0 d ~ 7 d), ROS concentration increased gradually, activating antioxidant enzymes to protect the cellular machinery from the detrimental effects of oxidative stress triggered by starvation-induced stress. ROS content production (hydrogen peroxide and superoxide anion) then rose continuously with prolonged starvation (fasting 7 d ~ 14 d), reaching peak levels and resulting in autophagy in hepatopancreas cells. During the final stages of starvation (fasting 14 d ~ 21 d), excessive ROS induced DNA damage and cell apoptosis. Furthermore, autophagolysosomes and apoptosis body were further identified with transmission electron microscopy. These findings lay a foundation for further scrutiny of the molecular mechanisms combating starvation-generated stress in M. nipponense and provide fishermen with the theoretical guidance for adopting fasting strategies in M. nipponense aquaculture.

A surfactant-free microemulsion consisting of water, ethanol, and dichloromethane and its template effect for silica synthesis.

A new type of surfactant-free microemulsion (SFME) containing water/ethanol/dichloromethane was constructed, and three microregions water-in-dichloromethane (W/O), bicontinuous (B.C.) and dichloromethane-in-water (O/W) regions were identified. The polarity environment of the SFME was investigated. Solid silica nanoparticle (SSN) was selected as a model nanomaterial to investigate the feasibility of the water/ethanol/dichloromethane SFME for the preparation of nanomaterials. In the O/W SFME region of the microemulsions, uniform spherical solid silica nanoparticles (SSNs) were synthesized. Under the same experimental conditions, they are of smaller particle size and have narrower range of diameter distribution, than the SSNs synthesized from ethanol and water mixture. The effects of tetraethylorthosilicate concentration (CTEOS), ammonia hydroxide concentration ( [Formula: see text] ) and dichloromethane content on the size and morphology of the SSNs were investigated. The average diameters of the SSNs increased with increasing CTEOS and [Formula: see text] . However, the effect of increasing [Formula: see text] on the particle size is more significant. The time evolution of the morphology and diameter of the SSNs were also investigated to elucidate the growth mechanism for the SSNs synthesized in the O/W SFMEs.