The air is pumped into a chamber in the reader that contains a paper strip, which is embedded with an array of chemical reagents that change color when they come into contact with a specific chemical group. By evaluating the resulting color pattern on the strip, users can determine the nature of any plant disease that may be affecting the plant.
“For this technology to work," says Zheng Li, a postdoctoral researcher at NC State and first author of the paper, "we had to develop reagents that could be embedded in the paper strips. About half of the reagents were off-the-shelf organic dyes, but the other half were gold nanoparticles that we functionalized to respond to specific chemical groups. These functionalized nanoparticles allow us to be more precise in detecting various types of VOCs."
The researchers say they also had to design and build the reader device, since "there is nothing like it on the market."
In proof-of-concept testing, the researchers say they demonstrated the device’s ability to detect and classify 10 plant VOCs down to the parts-per-million (ppm) level. They were able to detect the late blight pathogen that caused the Irish famine two days after tomato plants were inoculated with the pathogen.
The technology was also able to distinguish tomato late blight from two other important fungal pathogens that produce similar symptoms on tomato leaves. In addition, say the researchers, they showed they could detect the pathogen Phytophthora infestans in tomato leaves with greater than 95% accuracy.