The wonder material graphene — an array of interlinked carbon atoms arranged in a sheet just one atom thick — promised a world of applications, including super-fast electronics, ultra-sensitive sensors and incredibly durable materials. After a few false starts, that promise is close to realization. And a suite of other extremely thin substances is following in its wake.
Graphene got its beginnings in 2003, when scientists at the University of Manchester found they could peel off a gossamer film of the material just by touching a piece of ordinary sticky tape to a block of purified graphite — the solid form of carbon that’s mixed with clay and used as the “lead” in most pencils. Graphene proved stronger than steel but extremely flexible, and electrons could zip through it at high speeds. It earned its discoverers the Nobel Prize in 2010, but researchers spent years struggling to manufacture it on larger scales and figuring out how its remarkable properties could best be used.
They didn’t get it right straight out of the gate, says Todd Krauss, a chemist at the University of Rochester. “Scientists are pretty bad at predicting what’s going to be useful in applications,” he says.
With its atom-thin sheets layered into tiny particles known as quantum dots, graphene was tried as a microscopic medical sensor, but it didn’t perform as desired, Krauss says. With its sheets rolled up into straw-like nanotubes, graphene was built into items like hockey sticks and baseball bats in the hopes that its strength and durability could better existing carbon fiber. But Krauss notes that there has since been a trend away from using nanotubes in consumer products. (Some also worry that long carbon nanotubes could harm the lungs since they have been shown to have some chemical resemblance to asbestos.)
Today graphene is finding its way into different types of products. “Graphene is here,” says Mark Hersam of Northwestern University. Layered over zinc, graphene oxide is actively being developed as a replacement, with higher storage capacity, for the sometimes unreliable graphite now used in battery anodes. And nanotubes were recently used as transistors to build a microprocessor, replacing silicon (unlike flat graphene, nanotubes can be coaxed into acting like a semiconductor). Though the microprocessor was primitive by modern computing standards, akin to the processing level of a Sega Genesis, materials scientists think it could ultimately pave the way for more efficient, faster and smaller carbon components for computer processors.
At the same time, a new generation of two-dimensional materials is emerging. The success of graphene further fueled the ongoing effort to find useful atomically thin materials, working with a range of different chemicals, so as to exploit the physical properties that emerge in such super-thin substances. The newcomers include an insulator more efficient than conventional ones at stopping the movement of electrons, and another that allows electrons to glide across it at a good percent of the speed of light, with little friction. Researchers think some of these may one day replace silicon in computer chips, among other potential uses.
Other materials now in development have even higher aspirations, such as advancing scientists toward one of the most tantalizing goals in chemistry — the creation of high-temperature superconductors.
Speedy electrons
In graphene, carbon atoms link up in an orderly honeycomb pattern, each atom sharing electrons with three neighboring carbon atoms. That structure allows any added electrons to move speedily across its surface. Ordinarily, a single electron might move through a conducting metal like copper at 1.2 inches per minute (given a 12-gauge wire with 10 amps of electricity). But in early experiments on graphene, electrons zipped along at 2.34 billion inches per minute — which could make for electronics that charge in just a few minutes and eventually in a matter of seconds.
