Key Points
- This study presented a novel fluorescent sensor, SU-1, that can detect cyanide at an extremely low detection limit of 0.27 nM, which is well below the World Health Organization’s limit for drinking water.
- SU-1 was synthesized using a microwave-assisted method, offering a greener alternative to conventional synthesis while maintaining high purity. The sensor also showed strong selectivity for cyanide over other anions, reducing the risk of false positives in complex environments.
- The SU-1 sensor successfully detected cyanide in real environmental water samples and was used in live-cell imaging of neuronal cells.
In a recent study, a team of researchers, led by Fasil Abebe at Morgan State University, presented a new, sensitive and selective fluorescent sensor for detecting cyanide ions (CN⁻). This study, which was published in the journal Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, highlights how SU-1, a new fluorescent sensor, can be applied in the real world for environmental monitoring (1).
What is cyanide?
Cyanide is a deadly chemical that is highly toxic (2). It comes from some natural substances in foods, such as pits in some common fruits (2). It poses several risks to human health and the environment. Complicating matters is that cyanide is used in several important mining, industrial, and electroplating processes (1). Currently, organizations such as the World Health Organization (WHO) set maximum allowable concentrations of cyanide on several food and beverage products. For example, the WHO set cyanide concentration limits of drinking water at 1.9 μM (1). The current challenge with these limits is that detecting them requires tools that are both practical and precise. The SU-1 sensor addresses this need with an impressive detection limit of 0.27 nM, which is an order of magnitude lower than the WHO threshold (1).
What is the SU-1 sensor?
The SU-1 sensor, which is chemically known as (E)-3-ethyl-2-(2-(2-hydroxynaphthalen-1-yl)vinyl)benzo[d]thiazol-3-ium iodide, was synthesized using a microwave irradiation technique. Normally, when sensors are developed, conventional reflux synthesis techniques are used. However, for the SU-1 sensor, the researchers used microwave-assisted synthesis to be more energy efficient and environmentally friendly (1). The researchers found that this process still resulted in the desired compound with high purity and in a shorter time frame (1).
To characterize the structure of the SU-1 sensor, several analytical techniques were used. In the study, the researchers used the following techniques: ^1H NMR, ^13C NMR, high-resolution mass spectrometry (HRMS), and single-crystal X-ray diffraction (XRD) (1). The researchers further investigated the interaction of SU-1 with cyanide ions using UV-visible absorption, fluorescence spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy.
What was the fluorescence response of the SU-1 probe?
In a DMSO:H₂O (1:1, v/v) matrix, the addition of cyanide ions to SU-1 induces a visible color change from pale yellow to colorless, accompanied by a dramatic red shift (~120 nm) in the absorption spectrum (1). This change results from cyanide-induced deprotonation and a nucleophilic attack on the benzothiazolium double bond (1). Because its fluorescence behavior relies on stopping molecular intramolecular charge transfer, the SU-1 sensor was built with the capability to disrupt the π-conjugation (1).
The SU-1 probe was also specifically designed to improve selectivity for cyanide compared to other anions. The reason why the researchers did this was to avoid false positives. As a result, this sensor is more reliable, which is important when applying it in complex environments (1).
Using Job’s plot analysis, the research team confirmed a 1:1 binding stoichiometry between SU-1 and CN⁻, supported by a calculated stability constant (Ka) of 1.58 × 10⁴ M⁻¹ (1). This strong binding affinity ensures the sensor’s effectiveness even at extremely low analyte concentrations.
What is the practical utility of the SU-1 sensor?
The practical utility of SU-1 extends beyond laboratory settings. The sensor was successfully applied to analyze environmental water samples, detecting trace cyanide levels with high precision (1). In addition, SU-1 demonstrated excellent biocompatibility and was used in fluorescence imaging to visualize intracellular cyanide ions in CAD (Cath.a-differentiated) neuronal cell lines (1).
This dual applicability makes SU-1 particularly valuable for both environmental monitoring and biomedical research. Monitoring cyanide exposure in real time within living cells could provide critical insights into toxicological responses and cellular defense mechanisms (1).
What does this mean for sensor design moving forward?
The study introduces a high-performance sensor but also sets a benchmark for green chemistry in sensor development. SU-1 represents a step toward the development of new sensors that are both efficient and eco-friendly (1).
As cyanide contamination remains a global concern in industrial and environmental contexts, sensors like SU-1 could become vital tools in safeguarding public health and ecological systems (1).
References
- Uota, S.; Hwang, B.-J.; Butcher, R.; et al. A Simple Benzothiazolium-based Sensor for Cyanide Detection: Applications in Environmental Analysis and Bioimaging. Spectrochimica Acta Part A: Mol. Biomol. Spectrosc. 2025, 326, 125155. DOI: 10.1016/j.saa.2024.125155
- Centers for Disease Control, Cyanide. CDC.gov. Available at: https://www.cdc.gov/chemical-emergencies/chemical-fact-sheets/cyanide.html (accessed 2025-07-17).
