Scientists have developed a highly sensitive optical fiber sensor that can detect arsenic contamination in drinking water with unprecedented accuracy.
Study: Localized surface plasmon resonance-based optical fiber arsenic ion sensor employing Al2O3/GO nanocomposite. Image Credit: rahmi ayu/Shutterstock.com
Published in Applied Optics, the study presents a sensor based on localized surface plasmon resonance (LSPR) technology, featuring a nanocomposite film of aluminum oxide (Al2O3) and graphene oxide (GO). The new sensor is designed for real-time monitoring, offering a rapid and selective method for detecting arsenic ions (As3+) at levels far below the World Health Organization’s (WHO) recommended limit of 10 parts per billion (ppb). With arsenic contamination posing a significant health risk worldwide, this innovation could be a game-changer for water safety.
Background
While surface plasmon resonance (SPR) and LSPR technologies have been widely used for arsenic detection, they come with significant limitations. Many existing sensors struggle to meet the stringent 10 ppb detection limit set by the WHO, often exhibiting slow response times, poor selectivity, or limited reusability.
Although prior studies have reported detection limits as low as 0.47 to 1 ppb, these sensors frequently show inconsistent or non-linear responses across different arsenic concentrations. To address these challenges, this research presents an advanced optical fiber sensor designed for greater precision, faster detection, and real-time monitoring.
The Study’s Approach
The optical fiber sensor is built using a plastic-clad-silica (PCS) multimode optical fiber with a core diameter of 600 μm. The fabrication process begins with preparing a 40 cm fiber, polishing both ends for optimal light transmission.
The sensing region is created by stripping the cladding from a 2.5 cm section at the fiber’s center. This section is treated with chromic acid and functionalized with 3-amino-propyltrimethoxysilane (APTMS) to introduce amine groups that enhance the adhesion of gold nanoparticles (AuNPs). The AuNPs are then deposited onto the fiber by immersing it in a nanoparticle solution.
The Al2O3/GO nanocomposite plays a crucial role in the sensor’s functionality. GO is chosen for its superior adsorption capacity for heavy metals, while aluminum oxide enhances sensitivity due to its oxygen content. The sensor’s characterization involves control experiments to assess responses to refractive index variations before testing with As3+ ions. The LSPR technique enables real-time monitoring by detecting shifts in wavelength caused by changes in the surrounding refractive index when As3+ ions bind to the sensing film.
Key Findings
The sensor demonstrates impressive performance across several critical parameters. It offers a linear detection range for As3+ concentrations from 0 to 20 ppb, with an outstanding detection limit of just 0.09 ppb—significantly below WHO’s threshold.
The sensor achieves a maximum sensitivity of 0.217 nm/ppb, making it a strong candidate for real-world applications. Additionally, it boasts a rapid response time of just 0.5 seconds, allowing for near-instantaneous detection. The sensor also exhibits high selectivity for As3+ ions, effectively distinguishing them even in the presence of other heavy metals.
The stability of the sensor is rigorously tested over an 18-day period, showing minimal variation in readings (less than 0.004 %), demonstrating excellent repeatability and reliability. Short-term stability tests further confirm the sensor’s robustness.
To validate its effectiveness in real-world conditions, the researchers tested drinking water samples from various locations in Guwahati, Assam. The sensor’s results closely matched those obtained through inductively coupled plasma mass spectrometry (ICPMS), reinforcing its accuracy and practical viability.
Conclusion
This study highlights a significant advancement in arsenic detection technology. The LSPR-based optical fiber sensor, enhanced by the Al2O3/GO nanocomposite, delivers exceptional sensitivity, ultra-low detection limits, and rapid response times while maintaining high selectivity. These attributes make it a promising tool for real-time monitoring of arsenic contamination in drinking water, addressing a crucial public health concern.
The successful validation of the sensor against ICPMS results further supports its potential for widespread application. Future research could focus on optimizing the sensor for broader environmental monitoring, expanding its role in ensuring water safety.
Journal Reference
Banoo F., & Khijwania S. K. (2025). Localized surface plasmon resonance-based optical fiber arsenic ion sensor employing Al₂O₃/GO nanocomposite. Applied Optics 64(4), 1019-1027. DOI: 10.1364/AO.544358, https://opg.optica.org/ao/fulltext.cfm?uri=ao-64-4-1019&id=567506