Ethanol enables more efficient nanosensor manufacture

Macquarie University engineers have developed a new technique to make the manufacture of nanosensors less carbon-intensive, less expensive, more efficient and more versatile, by treating each sensor using a single drop of ethanol instead of the conventional process that involves heating materials to high temperatures. Their research has been published in the journal Advanced Functional Materials.

Nanosensors have a huge surface-to-volume ratio made up of layers of nanoparticles, making them highly sensitive to the substance they are designed to detect. But most nanosensors don’t work effectively until heated in a time-consuming and energy-intensive 12-hour process using high temperatures to fuse layers of nanoparticles, creating channels that allow electrons to pass through layers so the sensor will function.

“The furnace destroys most polymer-based sensors, and nanosensors containing tiny electrodes, like those in a nanoelectronic device, can melt,” said corresponding author Associate Professor Noushin Nasiri, Head of Macquarie University’s NanoTech Laboratory. “Many materials can’t currently be used to make sensors because they can’t withstand heat.”

The new technique discovered by the Macquarie team bypasses this heat-intensive process, allowing nanosensors to be made from a much broader range of materials. Nasiri explained, “Adding one droplet of ethanol onto the sensing layer, without putting it into the oven, will help the atoms on the surface of the nanoparticles move around, and the gaps between nanoparticles disappear as the particles join to each other.

“We showed that ethanol greatly improved the efficiency and responsiveness of our sensors, beyond what you would get after heating them for 12 hours.”

The new method was discovered after the study’s lead author, postgraduate student Jayden (Xiaohu) Chen, accidentally splashed some ethanol onto a sensor while washing a crucible, in an incident that would usually destroy these sensitive devices. Chen said, “I thought the sensor was destroyed, but later realised that the sample was outperforming every other sample we’ve ever made.”

According to Nasiri, the method’s effectiveness depended on painstaking work to identify the exact volume of ethanol used. She explained, “When Jayden found this result, we went back very carefully trying different quantities of ethanol. He was testing over and over again to find what worked.”

“It was like Goldilocks — three microlitres was too little and did nothing effective; 10 microlitres was too much and wiped the sensing layer out; five microlitres was just right!”

The team currently has patents pending for the discovery, and Nasiri has already been approached by companies in Australia and internationally who are keen to put the technique into practice.

“We have developed a recipe for making nanosensors work and we have tested it with UV light sensors, and also with nanosensors that detect carbon dioxide, methane, hydrogen and more — the effect is the same,” Nasiri said

“After one correctly measured droplet of ethanol, the sensor is activated in around a minute. This turns a slow, highly energy-intensive process into something far more efficient.”

Image credit: iStock.com/Kittisak Kaewchalun