Abstract
Highly sensitive plasmonic optical fiber platforms combined with receptors have been recently used to obtain selective sensors. A low-cost configuration can be obtained exploiting a D-shaped plastic optical fiber covered with a multilayer sensing surface. The multilayer consists of a gold film, functionalized with a specific receptor, where the surface plasmon resonance (SPR) occurs. The signal is produced by the refractive index variation occurring as a consequence of the receptor-to analyte binding. In this work, a selective sensor for copper(II) detection in drinking water, exploiting a self-assembled monolayer (SAM) of d,l-penicillamine as the sensing layer, has been developed and tested. Different concentrations of copper(II) in NaCl 0.1 M solutions at different pH values and in a real matrix (drinking water) have been considered. The results show that the sensor is able to sense copper(II) at concentrations ranging from 4 × 10−6 M to 2 × 10−4 M. The use of this optical chemical sensor is a very attractive perspective for fast, in situ and low-cost detection of Cu(II) in drinking water for human health concerns. Furthermore, the possibility of remote control is feasible as well, because optical fibers are employed.
Highlights
Copper(II) is an essential element for human health since it is a cofactor of many enzymes involved in chemical redox reactions, with antioxidant activity
We have recently developed a very convenient experimental setup for surface plasmon resonance (SPR) sensing of metal ions, based on a multimode plastic optical fiber (POF) [15]
When molecules are immobilized on the gold surface, even as a thin layer as a self-assembled monolayer (SAM), an increase of the refractive index occurs, determining a shift of the resonance wavelength to higher values
Summary
Copper(II) is an essential element for human health since it is a cofactor of many enzymes involved in chemical redox reactions, with antioxidant activity. It can be of concern for human health when present at high concentration, as it is able to induce oxidative stress by different mechanisms [1]. It appears to be involved in neurological disorders of high social concern as Parkinson and Alzheimer disease [2,3]. For the above reasons copper(II) is usually present at low concentration in natural waters, but it can be at relatively high concentrations in drinking water at the tap. Copper(II) concentration in drinking water may increase during distribution, especially in waters with an acid pH or with a high carbonate content at Sensors 2019, 19, 5246; doi:10.3390/s19235246 www.mdpi.com/journal/sensors
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