Researchers at Macquarie University have developed an innovative method for manufacturing ultraviolet (UV) light sensors. Their approach has the potential to enhance the efficiency and flexibility of wearable devices. The study details how acetic acid vapor, essentially derived from vinegar, can significantly enhance the performance of zinc oxide nanoparticle-based sensors without the need for high-temperature processing.
“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,” said Co-author Professor Shujuan Huang from the School of Engineering at Macquarie University.
Joining zinc oxide nanoparticles together is a crucial step in creating cutting-edge tiny sensors, as it establishes pathways for electron flow. The research team’s groundbreaking vapor method has produced UV detectors that are a staggering 128,000 times more responsive than untreated ones. These sensors maintain their ability to accurately detect UV light without interference, making them incredibly sensitive and dependable.
Associate Professor Noushin Nasiri, the co-author on the paper and head of the Nanotech Laboratory at Macquarie University, says: “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.”
However, the team has discovered a simple chemical process that mimics the effects of the traditional heat treatment. This breakthrough promises to revolutionize the field of sensor technology.
“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’s it – you have a working sensor,” she says.
To create the sensors, the researchers sprayed a zinc solution into a flame, creating a mist of zinc oxide nanoparticles that settled onto platinum electrodes. This resulted in a delicate sponge-like film, which was then exposed to vinegar vapor for five to 20 minutes. The vinegar vapor induced a transformative effect on the arrangement of the tiny particles in the film, facilitating better connectivity among the particles and enabling the flow of electrons through the sensor. Furthermore, the particles retained their small size, enhancing their ability to effectively detect light.
“These sensors are made of many, many tiny particles that need to be connected for the sensor to work,” says Associate Professor Nasiri. “Until we treat them, the particles just sit next to each other, almost as if they have a wall around them, so when the light creates an electrical signal in one particle, it can’t easily travel to the next particle. That’s why an untreated sensor doesn’t give us a good signal.”
The researchers conducted extensive testing of various formulations before discovering the ideal balance in their process.
“Water alone isn’t strong enough to make the particles join. But pure vinegar is too strong and destroys the whole structure,” says Professor Huang. “We had to find just the right mix.”
The study reveals that the best results were achieved when sensors were exposed to the vapor for approximately 15 minutes. Prolonged exposure led to excessive structural changes and decreased 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,” Professor Huang says.
This new room-temperature vapor technique offers numerous advantages over current high-temperature methods. It allows the use of heat-sensitive materials and flexible bases, in addition to being more cost-effective and environmentally friendly. Associate Professor Nasiri emphasized that this process can be easily scaled up for commercial use.
“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.”
The process presents a significant advancement in the development of wearable UV sensors, offering unparalleled flexibility and energy efficiency.
Associate Professor Nasiri emphasizes that this innovative method for UV sensors is poised to revolutionize sensor technology as a whole. By employing straightforward chemical vapor treatments instead of high-temperature sensor processing, it can be applied across diverse functional materials, nanostructures, and substrates, opening doors to a myriad of sensor applications.
Journal reference:
- Jeff Huang, Xiaohu Chen, Shujuan Huang, Noushin Nasiri. Vapor-Tailored Nanojunctions in Ultraporous ZnO Nanoparticle Networks for Superior UV Photodetection. Small, 2024; DOI: 10.1002/smll.202402558