Determination of thermodynamic parameters from light intensity signals obtained from oxygen optical sensors

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• 作者：Denis Badocco  ; [Author Vitae] ; Andrea Mondin  ; [Author Vitae] ; Paolo Pastore ; ^{paolo.pastore@unipd.it}  ; [Author Vitae]
• 关键词：Oxygen optical sensors ; Thermodynamic parameter determination
• 刊名：Sensors and Actuators B ; Chemical
• 出版年：2012
• 期刊代码：161_09254005
• 类别：et
• 出版时间：1 March, 2012
• 卷：163
• 期：1
• 页码：165-170
• 文件大小：602 K

摘要

A quite simple and inexpensive experimental set up using a platinum porphine/polysulfone-based oxygen optical sensor was used for determining thermodynamic parameters characterising polymers and luminophores constituting optical sensing membranes. In particular, the activation energies of the non-radiative, 螖E_nr, and diffusion, 螖E_D, processes and the gas solubility enthalpy inside the polymeric layer, 螖E_s, were computed. They were determined by expressing the Stern-Volmer constant, , in terms of luminophore life-time, diffusion coefficient and solubility of the analyte gas. The dependence of the three parameters on temperature ranging between 40 and 90 掳C was accounted for with suitable physical models used to obtain the cited parameters by regression procedures starting from experimental data. The found values are: 螖E_D = 2.8(0.3) kJ/mol, and 螖E_s = 13(3) kJ/mol. These results are in agreement with literature data relative to similar layers. The experimental set-up of the sensor required the sensing membrane supported on optical fibers. Structural information about the membrane was also obtained by monitoring variations with time during the conditioning time, determining how long the polymeric structure takes for reaching equilibrium conditions.