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With pollution levels rising, the need to quickly check water quality has become more urgent than ever. Traditional monitoring systems often rely on expensive bulky equipment with operational difficulty, making them impractical in remote areas or in places with limited resources.

In a significant advancement, researchers at Institute of Science Tokyo (Science Tokyo), Japan, have built a self-powered device that detects toxic amines in water using electrochemiluminescence (ECL). The technology works by producing light during a chemical reaction. The brightness of the light indicates whether pollutants are present, allowing for the detection of contamination on the spot.

The ECL process relies on two key molecules: a chromophore, which serves as the light emitter; and a coreactant, which is a sacrificial species. These molecules undergo redox reactions that push the chromophore into an excited state.

As the chromophore relaxes back to its ground state, it emits light, indicating the presence of the target compound. Traditionally, ECL required an external power supply to drive these reactions. The new device, however, needs no power source at all. Instead, it taps into the voltage generated when liquid flows through the system.

The research team was led by Professor Shinsuke Inagi from the Department of Chemical Science and Engineering at Science Tokyo, along with Dr. Elena Villani (then a specially appointed Assistant Professor) and Mr. Rintaro Suzuki (then a graduate student). The features and working of the device have been published in the journal on September 8, 2025.

"Since this ECL technique does not require a power supply, it opens new possibilities for applications such as pollutant detection in rivers or pipelines using natural flow energy. This concept can be extended for the ECL detection of a large pool of analytes, beyond environmental monitoring, such as for food and water testing, and biowarfare agents," says Inagi.

The team designed a microfluidic device with two chambers containing platinum wire electrodes, connected by a channel filled with porous material. The electrodes are connected by an ammeter, forming a split bipolar electrode system. When liquid is pushed through the channel, even with a simple hand-operated syringe, it generates a streaming potential of up to 2–3 volts, enough to trigger redox reactions at the electrodes.

For the chromophore, the researchers deposited benzothiadiazole-triphenylamine (BTD-TPA) on the anode, while tri-n-propylamine (TPrA) was used as the coreactant. The researchers chose to detect amines as they are widely used in industrial processes and are known to be toxic, carcinogenic, and cause genetic mutations.

When a solution containing TPrA flowed through the device, the streaming potential drove the oxidation of both the amine and the chromophore at the anode, initiating a series of reactions that produced visible light. The electroluminescence was strong enough to be captured by a digital camera, with detectable signals generated at voltages as low as 2.3 volts.

In addition to TPrA, the device was able to detect other amines, such as 2-(dibutylamino)ethanol and triethanolamine, although with reduced efficiency. It also successfully detected trace concentrations of amines in both distilled and tap water, with a detection limit as low as 0.01 millimolar for TPrA. The implications are significant. Since the system requires no external power supply, it could be deployed for real-time pollutant monitoring, especially during emergency scenarios when electricity is unavailable.

"We believe that our prototype may represent an innovative class of low-cost and portable analytical electrochemical devices that can be employed by using the electrical power of nature. Our vision for the future is that, once this technology has advanced and become more robust, a continuous natural water flow, for example, in a river, could be exploited to provide the necessary electrical energy to run the device," says Inagi.