The Center of Excellence at the Australian Research Council for TMOS or Transformative Meta-Optical Systems, has announced the development of a new type of sensor. This is a minuscule sensor made for detecting nitrogen dioxide. They claim it can protect the environment from pollutants that vehicles typically release. These pollutants can cause acid rain and lung cancer.

According to the researchers, the sensor consists of an array of nanowires. The array occupies a square of only a fifth of a millimeter on each side. That means a silicon chip can easily incorporate the sensor.

The researchers have published their findings in the latest issue of Advanced Materials. They have described their sensor as not requiring any power source, as it has a built-in solar-powered generator to run it.

According to the researchers, by incorporating the new sensor into a network benefits the Internet of Things technology, as the sensor has low power consumption, low system size, and is inexpensive. They claim that it is possible to install the sensor into a vehicle. If the sensor were to detect dangerous levels of nitrogen dioxide from exhaust emissions, it will sound an alarm and send an alert to the owner’s phone.

The researchers feel this device is only a beginning, as they can adapt the sensor for the detection of other gases like acetone, which can lead to the design of a ketosis breath tester. Such a non-invasive tester can help to detect diabetic ketosis, saving countless lives.

This is an important development, as existing detectors require a trained operator and are bulky and slow. The new device, in contrast, detects gases instantly, measuring less than one part per billion of the gas. The prototype from TMOS even has a USB interface, allowing it to connect to a computer.

Belonging to the NOx category of pollutants, Nitrogen dioxide is highly dangerous to humans even when present in very small concentrations. Moreover, it contributes to acid rain, cars generate it commonly as a pollutant, and gas stoves can also generate it indoors.

Common to the fundamental construction of a solar cell, the nanowire sensor also consists of a PN junction, but in the shape of a nanowire. Sitting on a base, the nanowire is a small hexagonal pillar that has a diameter of about 100 nanometers. The complete sensor has a thousand of these nanowires in an ordered array, with the spacing between them measuring 600 nanometers.

Made from Indium Phosphide, the sensor has its base doped with zinc, forming the P part, while the tip of the nanowires forms the N section, as the researchers have doped it with silicon. Separating the P and N sections, the middle part of each of the nanowires remains undoped, constituting the intrinsic section.

As in the case of a solar cell, any light falling on the device causes the flow of a small current between the N and P sections. If nitrogen dioxide is present and touches the intrinsic middle section, there will be a dip in the current. This is due to nitrogen dioxide being a strong oxidizer that removes electrons.