2001 and the advances in nanochemistry

In March, Yuji Okawa and Masazaku Aono, from Japan, managed to create conjugated polymer nanowires using the probe tip of a scanning tunneling microscope (STM), an important feat because their technique takes molecular nanoelectronics into a realm beyond current silicon-based technology, where device fabrication using lithography and pattern transfer is practical only to the 100 nm level.

A subject that has already been touched here: "Carbon nanotubes are now the top candidate to replace silicon when current chip features just can´t be made any smaller", in the words of Phaedon Avouris, from IBM, who created from single-wall nanotubes an array of fiel-effect transistors (FETs) - the first array of transistors made from nanotubes (see more about FETs below). Chemical and Engineering News says that Avouris and coworkers also used carbon nanotubes to construct the first single-molecule logic gates.

Another promising research was made by Eric W. Kaler (University of Delaware) and Orlin D. Velev (North Carolina State University), with coworkers, who created a technology to build microwires which could be used in wet electronic and bioelectronic circuits, including chemical sensors. This feature reminds us that such microwires could be used with neurons, with striking consequences.

Particularly active this year was chemistry Professor Charles M. Lieber, from Harvard University. He and coworkers developed nanowire-based electrical components: probably the smallest light-emitting diode (LED) ever made, in which light is emitted where two doped semiconductors nanowires that received a voltage cross. Also they made sensitive and selective sensors using boron-doped silicon nanowires of three types: a pH sensor, a device that senses protein binding, and a calcium ion sensor. Chemistry and Engineering News says that nanowire-based sensors could be useful for sensing single molecules and detecting cancer marker proteins at physiologically relevant levels. In November they published an article in Science which described how they used semiconductors nanowires to build field-effect transistors (FETs), and they performed basic digital computations using logic devices built from nanowire-based FET logic gates.

Professor Cees Dekker, from the Netherlands, led a team that built a multi-transistor logic circuit using carbon nanotube FETs. These are individually controllable and can be integrated on a single chip. Prior to this study, nanotube FETs couldn´t be turned on and off individually.

These are a just a few conquests of nanochemistry in 2001.

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