IIT Guwahati Develops Fluorescent Sensor To Detect Cyanide In Water and Human Cells

Guwahati: The Indian Institute of Technology (IIT) Guwahati researchers have developed a highly responsive fluorescent sensor capable of detecting cyanide in both water and human cells by using only a UV light source.

The team of research scholars led by Prof. G. Krishnamoorthy from the Department of Chemistry said that the sensor changes colour and emits bright fluorescence when exposed to cyanide, offering a powerful tool for environmental safety, medical diagnostics, and forensic investigations. It has been successfully tested on real-world samples, including river water and breast cancer cells, and is also compatible with portable paper strip-based testing.

Cyanide is a highly toxic chemical commonly used in various industrial processes such as synthetic fibre production, metal cleaning, plastics, electroplating, and gold mining. Improper disposal of cyanide can lead to environmental contamination, particularly of water bodies and soil. Even minimal exposure to cyanide can severely disrupt the body’s oxygen supply, resulting in serious health issues or death. Detecting even trace amounts of cyanide is therefore critical in safeguarding both environmental and human health.

Fluorescent chemosensors, which emit light when they interact with specific target molecules, are popular due to their simplicity, affordability, high sensitivity, and utility in biological systems. While many existing sensors detect harmful substances by reducing fluorescence—a “turn-off” mechanism—a “turn-on” approach, where the signal brightens in the presence of a target, offers better clarity and reduces the likelihood of false negatives.

The IIT Guwahati team has developed a “turn-on” chemosensor based on a compound named 2-(4′-diethylamino-2′-hydroxyphenyl)-1H-imidazo-[4,5-b]pyridine, which emits a faint blue fluorescence under UV light. In the presence of cyanide, the fluorescence intensifies and shifts to a cyan colour, indicating a chemical transformation in the sensor molecule. This reaction is highly specific to cyanide, especially in a carefully selected water-based solvent system. The sensor achieved a detection limit of 0.2 μM in aqueous samples, which is significantly lower than the World Health Organization’s permissible limit of 1.9 μM for cyanide in drinking water and Indian cuisine.

To validate the mechanism behind this detection, the researchers employed a combination of laboratory experiments and computational techniques known as Density Functional Theory (DFT) calculations. According to Prof. Krishnamoorthy, an expert in molecular fluorescence and spectroscopy, “What sets this sensor apart is its versatility. The sensor works not only in lab-prepared solutions but also in real water samples such as river and tap water, with an accuracy of 75 to 93 percent. It can be embedded into paper strips for easy, portable testing and has shown excellent performance in live cell imaging. In fact, we were able to detect cyanide within biological cells, demonstrating its strong potential for applications in environmental and forensic fields.”

The researchers also discovered that the molecular sensor could mimic the function of a basic logic gate, which is a foundational component in digital electronic circuits. This indicates the possibility of integrating such sensors into smart, sensor-based devices capable of real-time detection of hazardous substances like cyanide.