2 research outputs found
Photo Induced Membrane Separation for Water Purification and Desalination Using Azobenzene Modified Anodized Alumina Membranes
Water purification and desalination to produce end-use water are important agendas in 21st century, because the global water shortage is becoming increasingly serious. Those processes using light energy, especially solar energy, without the consumption of fossil fuels are desired for creating sustainable society. For these earth-friendly water treatments, nanoporous materials and membranes are expected to provide new technologies. We have reported before that the repetitive photo isomerization of azobenzene groups between the trans and cis isomers induced by the simultaneous irradiation of UV and visible lights accelerates the molecular movement of nearby molecules in nanoporous materials. After further studies, we recently found that the permeation of water through azobenzene modified anodized alumina membranes as a photo responsive nanoporous membrane was achieved by the simultaneous irradiation of UV and visible lights, while no water penetration occurred under no light, only single UV or visible light. The photo induced permeation of water was promoted by the vaporization of water with the repetitive photo isomerization of azobenzene. This membrane permeation achieved the purification of water solutions, because dye molecules and a protein dissolved in aqueous solutions were not involved in the photo induced penetrated water. When 3.5% of sodium chloride solution as model seawater was employed for this membrane separation, the salt content of the permeated water was less than 0.01% to accomplish the complete desalination of seawater
Temperature Control of Light Transmission Using Mixed System of Silica Hollow Particles with Nanoparticle Shell and Organic Components
We
reported before that a silica hollow particle whose shell consists
of silica nanoparticle (<b>SHP-NP</b>) has a high light reflection
ability to prevent light transmission through the particle, which
is caused from the intensive light diffusion by the hollow structure
and the nanoparticle of the shell. Since the difference in the refractive
indices between silica and air is responsible for the strong light
reflection, the mixing of the particle with organic components having
refractive indices close to that of silica such as tetradecane produced
transparent mixtures by suppression of the light reflection. The transparency
of the mixtures thus prepared could be controlled by temperature variation.
For example, the mixture of the particle <b>SHP-NP</b> with
tetradecane was transparent at 20 °C and opaque at 70 °C,
while the mixture with <i>n</i>-hexyl cyclohexane was opaque
at 20 °C and transparent at 70 °C. As the refractive indices
of organic components changed with temperature more than 10 times
wider than that of silica, the temperature alternation produced a
significant change in the difference of the refractive indices between
them to achieve complete control of the transparency of the mixtures.
This simple control of the light transmission that can automatically
regulate sunlight into the room with temperature alteration is expected
to be suitable for smart glass technology for energy conservation