A method for preparation of a composite comprising an anthocyanidin (aglycone of anthocyanin) dye and HMS-type mesoporous silica under neutral conditions was developed and the colorant properties of the composite as a red pigment were investigated. HMS containing a small amount of Al in the synthesis step (Al-HMS) effectively adsorbed anthocyanidin dye to generate a red composite. However, the color of the composite shifted from red to purple as the Al content of Al-HMS increased. This phenomenon was not observed for the composite comprising Al and MCM-41-type mesoporous silica (Al-MCM-41) synthesized under strongly basic conditions. Washing with dilute NaOH(aq) was effective for resolving this issue. Superficial Al species external to the silica framework were removed, and the resulting composite exhibited a vivid red color, even when the Al concentration was high. Minimal elution of the dye from the Al-HMS composite was observed in water and the composite exhibited higher photo-stability than the Al-MCM-41 composite.
Direct thermal printing is a data recording system based on the thermal reaction of fluoran dyes and color developers. This printing technology is widely used in our daily lives because of its simplicity as well as portable device characteristics. In the coloration process of fluoran dyes, the developers act as a proton donor. They play significant roles in the improvement of the performance of thermal paper, such as sensitivity and image stability. Herein, we present an overview of recent studies which focus on the relationship between molecular structure and the development ability of the developers using single crystal X-ray structure analysis.
Luminescence comprises two types of circularly polarized luminescence (CPL): left-handed and right-handed CPL. The properties of CPL are different from those of the linearly polarized light, which is often used in present-day liquid crystals and is expected to have applications in various other fields. The present paper describes the distinguishing properties of CPL used in our laboratory and the control of its nonclassical properties by using an axially chiral binaphthyl compound as a luminescent material.
Zinc phosphate and chromate, typical chemical conversion coatings, have been applied from long ago to automobile bodies and zinc-plated steel plate for household appliances. Against the background of recent advances in global environmental protection, the use of these technologies is restricted, and new environmental technologies have been developed and commercialized. In addition to the conventional technologies, zinc phosphate and chromate, the alternative non-phosphorus-based conversion coating and chromium-free coatings are outlined.
Colour, in addition to being a physical feature of objects and an optical feature of light, is a psychological phenomenon called ‘sensation’. Perceived colour often differs from that expected from light physics, which shows that our perceptual mechanisms work in a very intellectual manner rather than simply being mistaken. Instances that are caused in the retinal level, mid-level and higher level of our neurophysiological processes are given in order to show how our colour perception is shaped by our brains complex and plastic mechanisms. These instances, in what is a very advanced field, show us the relationships between the neural mechanism of vision and psychological phenomena of colour.