Earth's 'deadly' element arsenic precisely detected by nanostructure

A team of French researchers has created sensitive silver surfaces with nanostructures that can detect arsenic even at very low concentrations, according to a new study published in the Journal of Applied Physics on February 21. 

Arsenic, an abundant and deadly element in the Earth's crust, is responsible for groundwater contamination in more than 100 nations, including the United States, India, China, and Mexico, and can produce life-threatening illnesses, especially for populations in developing countries. Having no taste or smell, it's particularly dangerous since people could be exposed without realizing it.

Consequently, the new finding might aid in developing the reliable and efficient method for detecting arsenic in soil, food, and water that these situations need.

How can arsenic be detected?

The sensors use surface-enhanced Raman spectroscopy (SERS). As a molecule containing arsenic adheres to the surface, it is also hit with a laser, scattering the laser light and leaving a detectable trace.

"Arsenic exists in water in different forms, so it is important to be able to quantify the species, in addition to the global content," said author Dominique Vouagner in a press release. 

"By using SERS, we can detect and speciate pollutants even at the lowest concentration. This includes arsenic, which should not exceed ten parts per billion (ppb), as per the World Health Organization's recommendations."

The team evaluated the performance of two SERS substrates in terms of speciation and detection. One was created by conventional thermal evaporation, which involves heating the material to the point of vaporization. 

The other was created using an electroless technique, which involves depositing a coating on a material by submerging it in a liquid and instigating a chemical reaction. According to Vouagner, the latter was shown to be considerably more sensitive and is relatively simple and secure to create.

The method differs from the pricey and time-consuming reference methods currently used for trace arsenic speciation. Furthermore, traditional techniques are not well suited for on-site field testing because they also call for sample pre-treatment in a lab.

"Our technique for developing this SERS substrate makes it simple to manufacture because the electroless films can be easily deposited on various substrates," she argued. "Plus, the starting compounds have low environmental toxicity, which is a benefit for detection measurements in natural as well as potable water."

Vouagner also highlighted that the novel technique makes use of a solid substrate to facilitate 'optical interrogation.' She explained that because they're less 'noisy,' optical detection systems are much more sensitive than electronic systems.

"At the same time, they're less sensitive to parasitic electromagnetic fields. Also, the SERS technique allows direct physical-chemical property measurements, whereas electronic systems, and some other optical systems, are indirect," she concluded.