Optical nanomaterials, silica

The size of silica nanoparticles affects their physical, chemical, electronic, and optical properties. Proper size of silica nanoparticles is crucial for design of silica-based nanomaterials. In Stober methods, the size of silica nanoparticles is adjusted by changing the type of organic solvent, the amount of silicon alkoxide, and the... 

The optical properties of a DDSN are mainly determined by the properties of dye molecules. Since silica nanomaterials are effectively transparent they are unlikely to absorb light in the near-infrared, visible or ultraviolet regions, which allows the dye molecules inside the silica matrix to keep their original optical properties [64]. Meanwhile, the presence of the silica matrix provides a new environment for dye molecules and affects dye fluorescence properties. 

Why optical (photoabsorption and PL) properties of Si02 and Ge02 nanomaterials can dramatically differ from the properties of bulk silica... 

What is the role of point defects in optical properties of silica and germania nanomaterials ... 

Discuss common features and differences in optical properties of analogous point defects in silica and germania nanomaterials. 

Chiral nematic mesoporous films of Eu " doped Zr02 have been produced via a hard-templating approach using nanoctystalline cellulose-templated silica (Fig. 11). It was found that these chiral nematic nanostructures are capable of modulating the spontaneous emission of the Eu ions. The emission lines of the Eu " at 596 nm, 613 and 625 nm were significantly suppressed, and an increase in the luminescence lifetime is observed. It was suggested that these new chiral luminescent nanomaterials could find potential applications in sensing and new optical nanodevices. 

Carbothermal route provides a general method for preparing crystaUine nanowires of oxides such as ZnO, Al Oj and Ga Oj, nitrides such as AIN and SijN, and carbides such as SiC [3], The set-up employed for the synthesis of oxide nanomaterials is shown in Figure 3.1. The method has enabled the synthesis of crystalhne nanowires of both silica and sihcon. In the case of GaN, it has been possible to dope it with Mn, Mg and Si to bestow useful optical and magnetic properties. Carbothermal reaction involving Ga Oj powder mixed with activated carbon or carbon nanotubes carried out at 1100 °C in flowing Ar yields nanowires, nanorods as well as novel nanostructures... 

A third type of measurement is aimed at characterizing the optical properties of the nanomaterials, and for this both conventional optical microscopy and transmission UV-visible spectroscopy are applicable. Another method-circular dichroism-can be used to study the heUcity of silica nanomaterials, while Raman spectroscopy has also been used for their characterization. 

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