Researchers from Macquarie University have used vinegar vapor to dramatically improve ultraviolet (UV) sensors in a low-cost, room-temperature operated process. The aim is to create better wearable devices.
Wearable sensors are evolving from watches and electrodes to bendable devices that provide far more precise biometric measurements and comfort. The new development is focused on improving the capabilities of the sensor.
The study shows how acetic acid vapour — essentially vinegar fumes — can rapidly improve the performance of zinc oxide nanoparticle-based sensors without using high-temperatures for processing.
Co-author Professor Shujuan Huang, from the School of Engineering at Macquarie University, says: “We found by briefly exposing the sensor to vinegar vapour, adjoining particles of zinc oxide on the sensor’s surface would merge together, forming a bridge that could conduct energy.”
Joining zinc oxide nanoparticles together is a critical part of building tiny sensors, as it creates channels for electrons to flow through.
The research team found that their vapour method could make UV detectors 128,000 more responsive than untreated ones, and the sensors could still accurately detect UV light without interference, making them highly sensitive and reliable.
Typically, such sensors are processed in an oven, heated at high temperature for 12 hours or so, before they can operate or transmit any signal. As an alternative, the scientists found a simple chemical way to copy the effects of the heat process.
This involves exposing a sensor to vinegar vapour for five minutes to produce a working sensor.
To create the sensors, the researchers sprayed a zinc solution into a flame, producing a fine mist of zinc oxide nanoparticles that settled onto platinum electrodes. This formed a thin sponge-like film, which they then exposed to vinegar vapour for five to 20 minutes.
The vinegar vapour changed how the tiny particles in the film were arranged, helping the particles connect to each other, so electrons could flow through the sensor. At the same time, the particles stayed small enough to detect light effectively.
The sensors are made of many, many tiny particles that need to be connected for the sensor to work. Until they are treated, particles just sit next to each other, almost as if they have a wall around them. If the sensors are exposed to the vapour for around 15 minutes, this is optimal for performance.
The research appears in the science journal Small, with the paper titled “Vapor‐Tailored Nanojunctions in Ultraporous ZnO Nanoparticle Networks for Superior UV Photodetection.”
