'Nanoworld' Glass Structures Created, Described

Delving into the world of the very, very small, the "nanoworld," scientists have created materials, and viewed them in three dimensions, which may help to solve macro-level problems of technology and the environment.

The cover story of a recent Nature reports the direct three-dimensional imaging of highly structured, porous glass at the nanoscale. This material has potential applications for lasers, optical fibers, coatings for computer chips, containers for the storage and slow release of plant nutrients, packaging to protect and enhance desired biological processes, and various highly sensitive detectors, including sensors for finding biotoxins in the environment.

As intriguing as ice crystals but vastly smaller, the dimensions of these glassy pores, cages, and channels are from one nanometer to 50 nanometers in size. A nanometer is equal to one-thousandth the thickness of a human hair.

How does one see into such a tiny realm? Scientists used an electron microscope that is two stories high, reported coauthor Galen Stucky, professor of chemistry and materials.

Three labs in three different countries cooperated on the research. In addition to Stucky's lab at UCSB, which fabricated the material, researchers at Tohoku University in Sendai, Japan, and the Korea Research Institute of Chemical Technology in Taejon, Korea, worked on the problem. The electron microscope was located at Tohoku University.

"I like to call it three-dimensional etched glass," said Stucky, who with his research group first created the glassy material in 1994 and published the discovery. In 1998, Stucky's group and that of Brad Chmelka (a UCSB colleague in chemical engineering), created and published a better way to make the material.

"Essentially, we take soap (a surfactant or emulsifier) and sand (silica), along with whatever other optical or electronic component that we might wish to incorporate, then we put them together to make materials which are beautifully structured and easily processed," he said.

According to the article, "The three-dimensional structural solution makes clear, at the nanoscale level, the sizes and shapes of the pores and cages, their arrangements, and their connectivity, including sizes of openings."

Imaging and characterizing the material are challenging. Going beyond the usual two-dimensional projected image of a structure seen when using the electron microscope, the researchers developed a new general approach for the direct determination of the three-dimensional structures present in the material. This required several series of mathematical conversions.

With this new knowledge of the material, these "topographic" maps, applications can proceed. "We can make pores as big as any protein," said Stucky. "So we can separate or selectively package biomolecules, such as proteins, or DNA, in a way that makes them readily accessible for use."

The nanotechnology, the chemistry, and the processing make possible many different three-dimensional patterns, shapes, and forms that can be organized at multiple-length scales in numerous ways, said Stucky. "The materials can be used to make all sorts of things--from fibers to films, to lasers and sensors," he added. "They can be used to create nanostructured, highly organized three-dimensional biochemical enzyme factories to sense biotoxins and for the removal of toxic heavy metals from the environment."

Biotechnology applications are being developed with UCSB colleagues Chmelka, molecular geneticist Dan Morse, and biochemist Alison Butler.