Abstract
Copper and zinc are elements commonly used in industrial applications as aqueous solutions. Before the solutions can be discharged into civil or native waterways, waste treatment processes must be undertaken to ensure compliance with government guidelines restricting the concentration of ions discharged in solution. While currently there are methods of analysis available to monitor these solutions, each method has disadvantages, be it high costs, inaccuracy, and/or being time-consuming. In this work, a new optical fiber-based platform capable of providing fast and accurate results when performing solution analysis for these metals is described. Fluorescent compounds that exhibit a high sensitivity and selectivity for either zinc or copper have been employed for fabricating the sensors. These sensors demonstrated sub-part-per-million detection limits, 30-second response times, and the ability to analyze samples with an average error of under 10%. The inclusion of a fluorescent compound as a reference material to compensate for fluctuations from pulsed excitation sources has further increased the reliability and accuracy of each sensor. Finally, after developing sensors capable of monitoring zinc and copper individually, these sensors are combined to form a single optical fiber sensor array capable of simultaneously monitoring concentration changes in zinc and copper in aqueous environments.
Highlights
The use of optical fibers as a means for sensing a target analyte has wide ranging applications.Optical fiber sensors have been employed to monitor physical characteristics such as strain or temperature changes [1,2]
Our crossed-fiber design allows for fabrication of sensor arrays capable of analyzing aqueous environments for metal ions and for spatially resolved readout of these arrays with optical time of flight spectroscopy (OTOFS) [11]
The discharge limit set by the EPA, which states that a manufacturing facility may discharge up to an average of 1.48 mg/L of zinc per day over a 30-day period, falls within this range
Summary
The use of optical fibers as a means for sensing a target analyte has wide ranging applications.Optical fiber sensors have been employed to monitor physical characteristics such as strain or temperature changes [1,2]. Of greater pertinence to this research is the work that has been done in the past to detect the presence and determine the concentrations of various chemicals or biomolecules [3,4]. Analytes such as pH [5], dissolved oxygen [6], and carbon dioxide [7] have been well studied and a variety of sensors have been developed which are able to quantitatively analyze solutions for these parameters. A category of analytes which has not received as much attention for detection with optical fiber-based sensors, are transition metal ions. Our crossed-fiber design allows for fabrication of sensor arrays capable of analyzing aqueous environments for metal ions (here copper and zinc) and for spatially resolved readout of these arrays with optical time of flight spectroscopy (OTOFS) [11]
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