Experimental setup of the device detecting lead ions in a drop of water. Credit: Bandaru Lab/UC San Diego
Key points:
- An ultra-sensitive detector uses graphene and an aptamer to hone in on lead ions at an unprecedented level.
- The device achieves a record limit of detection of lead down to the femtomolar range, which is 1 million times more sensitive than previous sensing technologies.
- The proof-of-concept device also overcomes cost issues, as it is meant to be deployed in homes, given its relative ease of manufacture.
Engineers at the University of California San Diego have developed an ultra-sensitive sensor made with graphene that can detect extraordinarily low concentrations of lead ions in water. The device achieves a record limit of detection of lead down to the femtomolar range, which is 1 million times more sensitive than previous sensing technologies.
The device comprises a single layer of graphene mounted on a silicon wafer. But the sensing capabilities of the graphene layer are enhanced due to a linker molecule attached to its surface. This linker serves as the anchor for an ion receptor and, ultimately, the lead ions.
As detailed in a paper published in Nano Letters, the researchers used an aptamer as the ion receptor. These receptor molecules are known for their inherent selectivity toward specific ions—including lead. The researchers further enhanced the receptor’s binding affinity for lead ions by tailoring its DNA or RNA sequence. This ensured that the sensor would only be triggered upon binding to lead ions.
Achieving the femtomolar limit of detection was made possible by studying in detail the molecular events occurring on the graphene sensor’s surface. The researchers analyzed thermodynamic parameters of the system such as binding energies, changes in capacitance, and molecular conformations and found that they played critical roles in optimizing the sensor’s performance. By optimizing each of these thermodynamic parameters, along with the design of the entire system, from the electronics and materials all the way down to the ion receptor, the researchers created a sensor that can detect lead ions with unprecedented sensitivity and specificity.
While the technology is currently at the proof-of-concept stage, the UC San Diego team hopes to one day implement it in real-world settings.
“The technology that we developed aims to overcome issues of cost as well as reliability,” said study author Prabhakar Bandaru, professor at the UC San Diego Jacobs School of Engineering. “Our goal is for it to be eventually deployed in homes, given its relative ease of manufacture.”
Next steps include scaling up the production for commercial use, which will necessitate collaboration with industry partners.