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Open AccessArticle

Time-Resolved Spectroscopy of Ethanol Evaporation on Free-Standing Porous Silicon Photonic Microcavities

Centro de Investigación en Dispositivos Semiconductores, Instituto de Ciencias (ICUAP), Benemerita Universidad Autonoma de Puebla (BUAP), Ciudad Universitaria, Puebla, Pue. C.P. 72570, Mexico
Faubert Lab, School of Optometry, University of Montreal, Montreal H3T 1P1, QC, Canada
Author to whom correspondence should be addressed.
Materials 2018, 11(6), 894;
Received: 24 March 2018 / Revised: 29 April 2018 / Accepted: 2 May 2018 / Published: 26 May 2018
(This article belongs to the Special Issue Photonic Crystals for Chemical Sensing and Biosensing)
In this work, we have followed ethanol evaporation at two different concentrations using a fiber optic spectrometer and a screen capture application with a resolving capacity of 10 ms. The transmission spectra are measured in the visible-near-infrared range with a resolution of 0.5 nm. Porous Silicon microcavities were fabricated by electrochemistry etching of crystalline silicon. The microcavities were designed to have a localized mode at 472 nm (blue band). Ethanol infiltration produces a redshift of approximately 17 nm. After a few minutes, a phase change from liquid to vapor occurs and the localized wavelength shifts back to the blue band. This process happens in a time window of only 60 ms. Our results indicate a difference between two distinct ethanol concentrations (70% and 35%). For the lower ethanol concentration, the blue shift rate process is slower in the first 30 ms and then it equals the high ethanol concentration blue shift rate. We have repeated the same process, but in an extended mode (750 nm), and have obtained similar results. Our results show that these photonic structures and with the spectroscopic technique used here can be implemented as a sensor with sufficient sensitivity and selectivity. Finally, since the photonic structure is a membrane, it can also be used as a transducer. For instance, by placing this photonic structure on top of a fast photodetector whose photo-response lies within the same bandwidth, the optical response can be transferred to an electrical signal. View Full-Text
Keywords: porous silicon; ethanol evaporation; time window; shift rates porous silicon; ethanol evaporation; time window; shift rates
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Jiménez Vivanco, M.D.R.; García, G.; Doti, R.; Faubert, J.; Lugo Arce, J.E. Time-Resolved Spectroscopy of Ethanol Evaporation on Free-Standing Porous Silicon Photonic Microcavities. Materials 2018, 11, 894.

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