Porous silicon Fabry–Pérot interferometer for rapid environmental monitoring of copper

Copper pollution from environmental waters, both industrialized and natural sources, can be hazardous towards the human body. Acute symptoms can include gastrointestinal distress, hematemesis, hypotension and others, while chronic exposure can affect internal organs. Thus, an early and rapid detection of excessive copper contaminations followed by corrective and/or prevention actions can lead to reduction of the overall polluting impact and improve public health. Our study presents a miniaturized optical sensing platform for copper detection in aqueous media. A nanostructured porous silicon, Fabry–Pérot interferometer, is modified with a double layer polyethylenimine cross-linked via glutaraldehyde (PEI-GA-PEI) for enhanced sensitivity. The optical studies reveal high specificity and sensitivity towards copper ions, presenting linear dynamic range of 100 ppb – 5 ppm and low limit of quantification 200 ppb in real samples. Changes in the surface reflected intensity are monitored in real-time by reflective interferometric Fourier transform spectroscopy and correlated to copper concentration in aqueous samples. The specificity and chemical selectivity of the PEI-GA-PEI sensing platform towards copper ions was also tested in the presence of different interfering heavy metals (i.e., ferrous, lead, cadmium, chromium, arsenic cations at 1 ppm). Finally, the performance of the PEI-GA-PEI sensing platform was evaluated in three different real-life water samples. Overall, the presented study offers means for rapid (