With gold, a tiny test for poison gas

U. PITTSBURGH (US) — Researchers have coaxed gold into nanowires in order to create an inexpensive test for poison in natural gas.

Alexander Star, associate professor of chemistry at the University of Pittsburgh, developed a self-assembly method that uses scaffolds to grow gold nanowires.

Star and his colleagues at the National Energy Technology Laboratory (NETL) report their findings in the Journal of the American Chemical Society.

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“The most common methods to sense gases require bulky and expensive equipment,” says Star. “Chip-based sensors that rely on nanomaterials for detection would be less expensive and more portable as workers could wear them to monitor poisonous gases, such as hydrogen sulfide.”

Star and his research team determined gold nanomaterials would be ideal for detecting hydrogen sulfide because of gold’s high affinity for sulfur and the unique physical properties of nanomaterials.

They experimented with carbon nanotubes and graphene—an atomic-scale chicken wire made of carbon atoms—and used computer modeling, X-ray diffraction, and transmission electron microscopy to study the self-assembly process. They also tested the resulting materials’ responses to hydrogen sulfide.

“To produce the gold nanowires, we suspended nanotubes in water with gold-containing chloroauric acid,” says Star. “As we stirred and heated the mixture, the gold reduced and formed nanoparticles on the outer walls of the tubes. The result was a highly conductive jumble of gold nanowires and carbon nanotubes.”

To test the nanowires’ ability to detect hydrogen sulfide, Star and his colleagues cast a film of the composite material onto a chip patterned with gold electrodes. The team could detect gas at levels as low as 5ppb (parts per billion)—a detection level comparable to that of existing sensing techniques.

Additionally, they could detect the hydrogen sulfide in complex mixtures of gases simulating natural gas. Star says the group will now test the chips’ detection limits using real samples from gas wells.

Funding for the work was provided by NETL.

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