Researchers Develop Color-changing Sensor for Fluoride

Researchers at Florida State University (FSU) have developed a molecular sensor that changes color when it comes into contact with fluoride. Sourav Saha, PhD, an assistant professor in the university's department of chemistry and biochemistry, and a team of graduate students and postdoctoral researcher, developed the sensor based on naphthalene diimide (NDI), which belongs to a family of neutral aromatic compounds that are colorless unless fluoride is added.

Their research, published in the Journal of American Chemical Society, explains how this sensor differs from other fluoride sensors in that it can not only detect the level of fluoride present, but also differentiate fluoride from other anions. According to the report, this technology could fill an important need in the scientific community to determine the level of fluoride in water, consumer products or in the human body.

Saha stated in an FSU report, “A small amount of fluoride will quickly turn the sample orange, while a larger amount will turn it pink." In addition to its other benefits, the sensor reportedly is one of the most sensitive fluoride sensors to date, detecting approx. 1/10,000 mg of fluoride in a liter of water.

The sensor relies on an electron transfer event from a fluoride ion to the NDI receptor to generate a color change. According to Saha, the electron transfer process can be reversed, and the sensor can be regenerated and reused.

Saha has filed for a US patent on the fluoride-sensing process and the researchers plan to license the discovery to an outside company that could test it for commercial potential. Since fluoride is a material used in oral care products, perhaps the sensor could be used to test fluoride content in them to ensure product safety and optimize formulations.

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