A Vapor Sensor Based on a Porous Silicon Microcavity for the Determination of Solvent Solutions

Abstract

A porous silicon microcavity (PSMC) sensor has been made for vapors of solvent solutions, and a method has been developed in order to obtain simultaneous determination of two volatile substances with different concentrations. In our work, the temperature of the solution and the velocity of the air stream flowing through the solution have been used to control the response of the sensor for ethanol and acetone solutions. We study the dependence of the cavity-resonant wavelength shift on solvent concentration, velocity of the airflow and solution temperature. The wavelength shift depends linearly on concentration and increases with solution temperature and velocity of the airflow. The dependence of the wavelength shift on the solution temperature in the measurement contains properties of the temperature dependence of the solvent vapor pressure, which characterizes each solvent. As a result, the dependence of the wavelength shift on the solution temperature discriminates between solutions of ethanol and acetone with different concentrations. This suggests a possibility for the simultaneous determination of the volatile substances and their concentrations.

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

“…Nonetheless, the mechanism to excite the surface state requires the use of the well-known ATR technique, thus making the sensing mechanism more complicated. Another type of sensor is mentioned in reference [ 25 ], where a porous silicon microcavity is used but it was not lifted off from the silicon substrate. The sensor is used for sensing ethanol and acetone in their vapor phases with different concentrations.…”

Progress in the research and development of photonic structure devices

“…From data in the curves 2 and 3, which were received from the measurement with parameters T and V at 45 °C and 0.84 ml s −1 , and at 30 °C and 1.68 ml s −1 , we obtain the difference of Δλ of about 18.5 nm and 10.0 nm, respectively, between the 0% and 100% ethanol. Whereas having measured with this sensor in the liquid phase in this concentration range, we obtained the Δλ difference of about 5 nm only [20]. Therefore, the sensitivity received from the measurement in the vapor phase with the value of T and V at 45 °C and 0.84 ml s −1 , and at 30 °C and 1.68 ml s −1 increases 3.7 and 2.0 times, respectively, as compared with that in the liquid phase.…”

“…Figure 5 shows the dependence of Δλ on T, Δλ(T), for acetone and ethanol solutions with various concentrations at the airflow velocity of 0.84 ml s −1 [17,20]. The equations (1) and (2) show that we can consider the temperature dependence of Δλ(T) as the temperature dependence of P i (T) modified by multipliers X i if it was assumed that the contribution of water to the solution pressure is small.…”

“…Consequently, a curve describing Δλ(T) characterizes the solution of acetone (or ethanol) at a given concentration. In other words, the dependence of the wavelength shift on the solution temperature discriminates between solutions of ethanol and acetone with various concentrations [20].…”

Nano porous silicon microcavity sensor for determination organic solvents and pesticide in water

“…Consequently, a curve describing Δλ(T) characterizes the solution of acetone (or ethanol) at a given concentration. In other words, the dependence of the wavelength shift on the solution temperature discriminates between solutions of ethanol and acetone with various concentrations [19]. Figure 7 shows the dependence of the resonant wavelength shift Δλ(C) on ethanol concentration, when velocity of the airflow (V) and temperature of the solution (T) work as parameters in the measurements.…”