Optical fiber sensing devices based on organic vapor indicators towards sensor array implementation

A family of vapochromic complexes has been used to develop optical fiber sensor transducers; these materials show reversible changes in their optical properties in presence of some solvents, so they can be used to detect volatile organic compounds (VOCs). The materials' common chemical structure is described by the formula [Au₂Ag₂(C₆F₅)₄L₂]_n, where L is a ligand molecule that varies for each material, and determines its sensitivity to specific organic vapors. The optical architecture used as transducer was a doped nanocavity built onto a cleaved ended fiber by Electrostatic Self-Assembly (ESA) method. These sensor transducers were used in a reflexive set-up, and their response was characterized in terms of reflected optical power at 850 nm and absorbance spectra. Up to 4 different sensors were built following this procedure. Absorbance spectra were measured to confirm the response of all the sensors in a qualitative way; additionally, it was studied quantitatively exposing them to different solvents, showing a linear relationship between reflected power and the vapor concentration for each VOC. Finally, the four sensors were exposed to three different beverages, registering in each case different absorbance spectras. This highlights the potential use of these sensors in an array system to identify aromatic alcoholic beverages.