Researchers have created a novel optical sensor that simplifies the real-time detection of very low levels of arsenic in water. This innovation could pave the way for at-home arsenic testing, giving individuals the power to check their own water quality.
Researchers have developed a new optical sensor that provides a simple way to achieve real-time detection of extremely low levels of arsenic in water. The technology could enable household testing for arsenic, empowering individuals to monitor their own water quality.
Arsenic pollution presents a significant environmental and health issue, impacting millions globally. This form of contamination happens when natural geological processes release arsenic from soils and rocks into groundwater. Activities like mining, disposal of industrial waste, and the use of arsenic-based pesticides can worsen this issue.
“Drinking water contaminated with arsenic can lead to serious health problems such as arsenic poisoning and various cancers affecting the skin, lungs, kidneys, and bladder,” said Sunil Khijwania, the leading researcher from the Indian Institute of Technology Guwahati. “By developing a sensor that is sensitive, selective, reusable, and affordable, we hope to create an effective and accessible tool for routine monitoring, thereby helping communities mitigate the risks of arsenic exposure.”
In the journal Applied Optics from the Optica Publishing Group, the researchers detail their new sensor, which utilizes an optical fiber and a phenomenon called localized surface plasmon resonance to identify arsenic levels as low as 0.09 parts per billion (ppb)—a level significantly lower than the World Health Organization’s maximum permitted limit of 10 ppb. The sensor demonstrated reliable performance on real drinking water samples taken from various locations and conditions.
“This highly sensitive sensor can analyze results in just 0.5 seconds and shows excellent reusability, stability, and reliability, making it an effective tool for monitoring and ensuring cleaner water quality,” stated Khijwania. “In the future, this technology could simplify the process for individuals to assess their drinking water safety, potentially preventing exposure to harmful arsenic levels and saving lives.”
A user-friendly yet accurate sensor
While conventional spectroscopy methods for arsenic detection are accurate and sensitive, they often require complex, expensive, and cumbersome equipment, which can be difficult to operate. To address this gap, researchers designed an optical fiber sensor that not only achieves low detection levels but is also cost-effective and easy to use for regular arsenic monitoring in drinking water.
To fabricate the new sensor, the researchers coated the inner core of a fiber with gold nanoparticles and a thin layer of a special nanocomposite made of aluminum oxide and graphene oxide, which selectively binds to arsenic ions. A fraction of the light traveling through the core extends into the fiber cladding due to the evanescent wave formed by total internal reflection. By removing the cladding in a small segment of the fiber, the evanescent wave interfaces with the external environment.
As light moves through the optical fiber, the evanescent wave interacts with the gold nanoparticles, prompting localized surface plasmon resonance—where electrons on the nanoparticle’s surface oscillate in response to specific light wavelengths. If arsenic is present, it attaches to the nanocomposite, leading to a measurable change in the surface plasmon resonance wavelength, allowing accurate detection of trace arsenic in water.
Thorough performance assessment
The researchers evaluated the sensor with different arsenic ion solution concentrations and found that it consistently and reliably detected arsenic across the tested ranges. After further optimization, they tested various parameters, showcasing that the sensor delivered consistent results during changes in arsenic concentration and achieved a speedy response time of just 0.5 seconds.
The sensor demonstrated a maximum resolution of ± 0.058 ppb of arsenic and maintained stable results for samples with the same arsenic concentrations analyzed over an 18-day period. The team also compared the sensor’s readings against those taken using inductively coupled plasma mass spectrometry (ICP-MS), a standard method for measuring arsenic. The sensor showed a relative percentage difference of less than 5%, illustrating a strong correlation between the two techniques.
To assess the sensor’s practical effectiveness, researchers tested it on drinking water samples from various locations in Guwahati, India, and found it performed reliably under diverse conditions.
“These studies confirm that the proposed optical fiber sensor offers a highly sensitive, selective, fast, affordable, straightforward, and user-friendly solution for arsenic detection in field settings,” said Khijwania. “In the long run, this new strategy could be adapted to create a series of budget-friendly and accessible environmental monitoring tools.”
The researchers highlighted that while the sensor is prepared for real-world arsenic detection, developing a more affordable and simpler optical source and detector would be essential for broader implementation.
