Reviewed by Lexie CornerAug 30 2024
Macquarie University researchers have discovered a novel method for creating ultraviolet (UV) light sensors, which could result in more adaptable and efficient wearable technology. The study, published in the journal Small, demonstrates how zinc oxide nanoparticle-based sensors may be quickly enhanced in performance by acetic acid vapor or vinegar fumes without the need for high processing temperatures.
We found by briefly exposing the sensor to vinegar vapor, adjoining particles of zinc oxide on the sensor’s surface would merge together, forming a bridge that could conduct energy.
Shujuan Huang, Study Co-Author and Professor, School of Engineering, Macquarie University
Joining zinc oxide nanoparticles is essential for building tiny sensors, as it creates pathways for efficient electron flow.
The researchers found that their vapor-based approach could enhance the responsiveness of UV detectors by up to 128,000 times compared to untreated ones. Furthermore, the sensors maintained high sensitivity and reliability, enabling them to detect UV radiation without interference.
Usually, these sensors are processed in an oven, heated at high temperature for 12 hours or so, before they can operate or transmit any signal.
Noushin Nasiri, Study Co-Author, Associate Professor and Head, Nanotech Laboratory, Macquarie University
Instead, the group discovered a straightforward chemical method to mimic the effects of the heat process.
“We found a way to process these sensors at room temperature with a very cheap ingredient - vinegar. You just expose the sensor to vinegar vapor for five minutes, and that is it - you have a working sensor,” she said.
The scientists created the sensors by pouring a zinc solution into a flame. This produced a thin mist of zinc oxide nanoparticles that settled onto platinum electrodes, forming a thin, sponge-like coating on the sensors.
They then exposed the coating to vinegar vapor for 5 to 20 minutes. The vinegar vapor altered the microscopic arrangement of the particles, enhancing their conductivity and allowing electrons to flow more easily through the sensor. Despite these changes, the particles remained small enough to effectively detect light.
These sensors are made of many, many tiny particles that need to be connected for the sensor to work. Until we treat them, the particles just sit next to each other, almost as if they have a wall around them, so when light creates an electrical signal in one particle, it cannot easily travel to the next particle. That is why an untreated sensor does not give us a good signal.
Noushin Nasiri, Study Co-Author, Associate Professor and Head, Nanotech Laboratory, Macquarie University
The researchers thoroughly tested a number of formulas before determining the ideal balance for their procedure.
Professor Huang said, “Water alone is not strong enough to make the particles join. But pure vinegar is too strong and destroys the whole structure. We had to find just the right mix.”
Their study found that sensors exposed to the vapor for approximately 15 minutes produced the best results. Longer exposure times caused excessive structural changes and diminished performance.
“The unique structure of these highly porous nanofilms enables oxygen to penetrate deeply so that the entire film is part of the sensing mechanism,” said Professor Huang.
Compared to the existing high-temperature approaches, the new room-temperature vapor technology offers numerous advantages. It is less expensive and more environmentally friendly, and it permits the use of flexible bases and heat-sensitive materials.
The researchers meticulously tested various formulas before identifying the optimal balance for their process.
"Water alone isn't strong enough to make the particles join, but pure vinegar is too strong and destroys the entire structure. We had to find just the right mix," explained Professor Huang.
Their study found that sensors exposed to the vapor for approximately 15 minutes produced the best results. Longer exposure times caused excessive structural changes and diminished performance.
"The unique structure of these highly porous nanofilms allows oxygen to penetrate deeply, making the entire film part of the sensing mechanism," Professor Huang added.
The new room-temperature vapor technology offers several advantages over traditional high-temperature methods. It is less expensive, more environmentally friendly, and compatible with flexible bases and heat-sensitive materials.
According to Associate Professor Nasiri, scaling the method for commercial production is straightforward.
Professor Nasiri adds, “The sensor materials could be laid out on a rolling plate, passing through an enclosed environment with vinegar vapors, and be ready to use in less than 20 minutes.
This method is particularly useful for developing wearable UV sensors, which need to be highly flexible and energy-efficient.
Associate Professor Nasiri also highlighted that this technique could be applied to other types of sensors by using simple chemical vapor treatments instead of high-temperature processing on various bases, substrates, functional materials, and nanostructures.
Journal Reference:
Huang, J., et al. (2024) Vapor‐Tailored Nanojunctions in Ultraporous ZnO Nanoparticle Networks for Superior UV Photodetection. Small. doi.org/10.1002/smll.202402558.