Experimental setup for the detection of lead ions in water. **University of California, San Diego.
Engineers at the University of California, San Diego, USA, have developed an ultrasensitive sensor made of graphene that can detect very low concentrations of lead ions in water. The device detects lead down to femtomolar levels and is 1 million times more sensitive than previous sensing technologies. The study** was recently published in Nano Letters.
Studies have shown that lead concentrations in drinking water at levels of a few parts per million can lead to harmful consequences, such as stunting human growth and development.
The new inspection equipment consists of a single layer of graphene mounted on a silicon wafer. Graphene's superior electrical conductivity and surface-to-volume ratio provide an ideal platform for sensing applications. The researchers enhanced graphene's sensing capabilities by attaching a linker molecule to the graphene's surface. This linker acts as an anchor for ion acceptors and ultimately as an anchor for lead ions.
Researchers use aptamers, a short, single-stranded DNA or RNA, as ion acceptors. These receptor molecules are selective for specific ions. By tweaking the receptor's DNA or RNA sequence, the researchers further enhanced the receptor's affinity for lead ions, ensuring that the sensor was only triggered when it bound to lead ions.
The researchers analyzed the system's thermodynamic parameters, such as binding energy, capacitance variation, and molecular conformation, and found that they played a key role in optimizing sensor performance. By optimizing these thermodynamic parameters, as well as the design of the entire system, the researchers created a sensor that can detect lead ions with unprecedented sensitivity and specificity, achieving the detection limit at the femtomolar level.
While the technology is still in the proof-of-concept phase, the researchers hope to use it for real-world testing in the future, with the ultimate goal of "detecting even the presence of only one lead ion in water." (Reporter Zhang Jiaxin).