Jan 19 2011
Crystals are typical examples for high-order structures which are able to build up on their own.
In a similar way also tiny silica channels can grow and coalesce. These structures play an important role for many applications of nanotechnology. The single channels have a diameter of only about 3 nanometers. Scientists of the Nanosystems Initiative Munich (NIM) have now developed a method, which allows watching the growth of these structures despite their diminutiveness (Nature Nanotechnoloy, Online January 10, 2011).
In their experiment, the scientists used elongate fluorescent dye molecules that were embedded lengthwise in the nanochannels. Using polarisation fluorescence microscopy, they were able to detect the dye molecules with a specific confocal laser scanning microscope which allows concluding the orientation of the silicate canals. The size of such sections and their stacking were determined with an atomic force microscope.
Particularly interesting, however, is the fact that the researchers were able to watch the formation of the channels and how the structure expands - basically in real time. They could observe that the temperature and the moisture have a strong influence on the growth.This method also enabled the researchers to watch the steps from the initial state, the so-called lamellar structures, consisting of two-dimensional silicate nanochannels to the three-dimensional silica nanochannels in a so-called hexagonal structure.
This made them realise, that the restructuring takes place wherever the hexagonal channel structure meets the already existing lamellar structures.
Nanochannel structures are relevant for a number of potential applications. For example, they can be enhanced with specific active substances and used as implants in medicine. Also they can be used in laboratories to undo complex molecule mixtures or to catalyse chemical reactions. Also, the embedding of specific molecules in the nanochannels causes specific optical effects that can be of use for the field of nanooptics.
Source: http://www.en.uni-muenchen.de/