Gold-coated nanowires provide low-cost gas detection method

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Researchers at Pittsburgh University have coaxed gold into nanowires as a way of creating an inexpensive material for detecting poisonous gases found in natural gas.

Along with colleagues at the National Energy Technology Laboratory (NETL), Alexander Star, associate professor of chemistry in Pittsburgh University’s Kenneth P Dietrich School of Arts and Sciences and principal investigator of the research project, developed a self-assembly method that uses scaffolds to grow gold nanowires.

The team’s findings, entitled ‘Welding of Gold Nanoparticles on Graphitic Templates for Chemical Sensing’, were published in the Journal of the American Chemical Society.

‘The most common methods to sense gases require bulky and expensive equipment,’ said 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 sulphide.’

According to a statement, Star and his research team determined that gold nanomaterials would be ideal for detecting hydrogen sulphide owing to gold’s high affinity for sulphur and the unique physical properties of nanomaterials.

They experimented with carbon nanotubes and graphene and used computer modelling, X-ray diffraction and transmission electron microscopy to study the self-assembly process. They also tested the resulting materials’ responses to hydrogen sulphide.

‘To produce the gold nanowires, we suspended nanotubes in water with gold-containing chloroauric acid,’ said 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 sulphide, 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 — a detection level said to be comparable to that of existing sensing techniques.

Additionally, they could detect the hydrogen sulphide in complex mixtures of gases simulating natural gas.

Star said the group will now test the chips’ detection limits using real samples from gas wells.