A Lossy Mode Resonance optical sensor using silver nanoparticles-loaded films for monitoring human breathing

• Published in: Sensors and actuators. B, Chemical Chemical, 2013-10, Vol.187, p.40-44
• Main Authors: Rivero, Pedro J., Urrutia, A., Goicoechea, J., Matias, I.R., Arregui, F.J.
• Format: Article
• Language: English
• Subjects: atomic force microscopy; Breathing; cations; Coating; coatings; dimethylamine; energy; energy-dispersive X-ray analysis; Human; humans; Humidity sensing; Lossy Mode Resonances (LMR); monitoring; nanosilver; Reduction; refractive index; Self assembly; Sensors; Silver; Silver nanoparticles (Ag-NPs); spectroscopy; Synthesis; X-radiation
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2012.09.022

This work is focused on the fabrication of a human breathing sensor based on the in situ synthesis of silver nanoparticles (Ag-NPs) inside a polymeric coating previously deposited on an optical fiber core by means of the Layer-by-Layer self-assembly. The Ag-NPs were created using a synthesis protocol consisting of a loading step of the Ag+ cations into the polymeric film and a further reduction step using dimethylamine borane (DMAB). The morphology and distribution of the Ag-NPs inside the polymeric coating have been studied using atomic force microscopy (AFM). Furthermore, UV–VIS spectroscopy and energy dispersive X-ray (EDX) were also used to confirm the synthesis of the Ag-NPs within the resultant coating. The amount of Ag-NPs increases when the number of loading/reduction cycles is higher. Therefore the incorporation of the Ag-NPs affects the refractive index of the overlay promoting the observation of a resonant attenuation band in the infrared region (NIR), known as Lossy Mode Resonance (LMR), which can be used as a sensing signal to monitor the human breathing. The quality of the device has been experimentally tested with good sensitivity (0.455nm per RH%) and fast response time (692ms and 839ms for rise/fall).