Creating a high-performance composite optical pH sensor

What is it about?

pH sensors are devices that measure the acidity or basicity of water. Commercial pH sensors use light-based sensing as it is highly sensitive to changes in pH. In this process, a pH-sensitive dye is excited with light and its fluorescence is then detected. But optical pH sensors have many drawbacks. The indicator dye is, in general, hydrophobic, and its fluorescence decreases when it comes in contact with water. It can undergo a process called "photobleaching," which makes it unable to fluoresce. The dye can leak out from pores in the senor material. But if there are fewer pores, the pH detection takes longer. In this paper, the authors develop a new optical pH sensor. It consists of a polymer with nanometer-sized particles buried in it. The polymer contains a pH-responsive dye, while the nanoparticles are coated with a reference dye. In this design, the nanoparticles act as pockets that shield the hydrophobic reference dye from water. This ensures that the fluorescence does not decrease inside water. In addition, the design is stable at high temperatures. This makes the dye stable against photobleaching. The design stops the pH-sensitive dye from leaking out and helps the target material move fast through the polymer pores. Further, the new design shows excellent sensing performance. Based on this, it could have promising applications in the industry.

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Photo by Pawel Czerwinski on Unsplash

Photo by Pawel Czerwinski on Unsplash

Why is it important?

pH values can indicate important chemical changes, such as the presence of pollutants in water. As a result, it can have many industrial applications. Optical sensors are highly sensitive to pH changes. But they suffer from downsides that limit their usefulness. This study pioneers a new kind of optical sensor that is free of such problems. It could, therefore, make for large-scale applications of optical pH sensors. KEY TAKEAWAY: A new optical pH sensor made using fluorescent dye-coated nanoparticles and a polymer solves all the issues of existing pH sensors.