Optical microfluidic system based on ionophore modified gold nanoparticles for the continuous monitoring of mercuric ion

• Simple, portable and automatic analyzer for continuous monitoring of mercuric ion.
• Microfluidics as easy and reproducible tool for reactions handling based on NPs.
• Ionophore-modified gold nanoparticles used as recognition/detection method.
• New thiourea derivative highly selective to mercury.
• Improvement of sensitivity and detection limit by means of microfluidics.

An optical microfluidic system based on the use of modified gold nanoparticles for monitoring Hg(II) is presented. The system is based on the specific recognition of the heavy metal by a new synthesized ionophore based on a modified thiourea, which is attached to the gold nanoparticles. This interaction generates a change on the gold Surface Plasmon Resonance (SPR) band. The sensitivity and selectivity of the procedure is firstly studied in batch. The obtained results demonstrate the mercury selective response over the different tested ions that can be found in environmental water samples. Due to the remarkable unusual rapid signal change observed during the interaction of the metal and the modified gold nanoparticles, the reaction can be easily performed in a microfluidic system. Results obtained by using the microfluidic system revealed improved analytical features compared to batch experiments such as a lower detection limit (11 ppb), higher sensitivity and faster analysis time, all this with an easy and automated procedure. Therefore, the approach has shown great potential for designing low cost instrumentation for automatic in-field discrete or continuous measurements of Hg(II).