Single Drop of Ethanol to Revolutionize Nanosensor Production

Macquarie University, Sydney, Australia

Schematic of a) Flame Spray Pyrolysis (FSP) and b) the evolution of DNC upon the ongoing deposition time and the correspondingly deposited DNC film. c) The cross-sectional SEM image of deposited DNC film after spraying for 100 s at the HAB of 12 cm. d–g) Illustrations of the key morphological transformation process from the DNCs to NMACs with frozen frames of the actual morphology under the video metrological investigation. All scale bars are 10 μm. (Image: onlinelibrary.wiley.com/doi/10.1002/adfm.202302808)

Macquarie University engineers have developed a new technique to make the manufacturing of nanosensors far less carbon-intensive, much cheaper, more efficient, and more versatile — substantially improving a key process in this trillion-dollar global industry.

The team found a way to treat each sensor using a single drop of ethanol, as opposed to the conventional process that involves heating materials to high temperatures.

“Nanosensors are usually made up of billions of nanoparticles deposited onto a small sensor surface — but most of these sensors don't work when first fabricated,” said corresponding author Associate Professor Noushin Nasiri.

The nanoparticles assemble themselves into a network held together by weak natural bonds which can leave so many gaps between nanoparticles that they fail to transmit electrical signals, so the sensor won't function.

The team uncovered the finding while working to improve ultraviolet light sensors, the key technology behind Sun-watch, which saw Nasiri become a 2023 Eureka Prize finalist.

Nanosensors have 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. Many materials can't currently be used to make sensors because they can't withstand heat,” said Nasiri.

“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 to join to each other,” added Nasiri. “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, Jayden (Xiaohu) Chen, accidentally splashed some ethanol onto a sensor while washing a crucible — an incident that would usually destroy these sensitive devices.

“I thought the sensor was destroyed, but later realized that the sample was outperforming every other sample we've ever made,” said Chen.

“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,” said Nasiri. “It was like Goldilocks — three microliters was too little and did nothing effective, 10 microliters was too much and wiped the sensing layer out, five microliters was just right!"

The team has patents pending for the discovery, which has the potential to make a very big splash in the nanosensor world, and Nasiri has already been approached by companies in Australia and internationally who are keen to work with her 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,” said Nasiri.

For more information, contact Fran Molloy at This email address is being protected from spambots. You need JavaScript enabled to view it..