Department of Chemical Engineering, Texas Tech University, Lubbock, Texas 79409, United States.
J Phys Chem B. 2011 Nov 17;115(45):13287-91. doi: 10.1021/jp2076963. Epub 2011 Oct 26.
Accurate thermodynamic parameters of thin films of materials are crucial in understanding their behavior in the nanometer scale. A new and simple method for determining the vapor pressure and thermodynamic properties of nanometer thick films of materials was developed based on UV-absorbance spectroscopy. Well-characterized benzoic acid was used to calibrate the spectrometer and the experimental conditions. The thermodynamic properties of pentaerythritol tetranitrate (PETN) were determined to validate the use of this new method. The estimated values of the thermodynamic parameters of PETN are in excellent agreement with the values reported using the most widely used Knudsen effusion method for determining vapor pressure lower than 1 pascal. The elegance of this method is its simplicity. The results indicate that UV-absorbance spectroscopy is a model-free and powerful technique in determining thermodynamic parameters in the nanoscale.
准确的材料薄膜热力学参数对于理解它们在纳米尺度下的行为至关重要。本研究提出了一种新的、简单的基于紫外吸收光谱法来测定纳米厚度材料薄膜蒸气压和热力学性质的方法。使用经过良好表征的苯甲酸来校准光谱仪和实验条件。并利用该方法测定了季戊四醇四硝酸酯（PETN）的热力学性质，验证了该方法的适用性。所测定的 PETN 热力学参数值与使用最广泛的用于低于 1 帕斯卡蒸气压的克努森扩散法测定蒸气压的报告值非常吻合。该方法的优点是简单。结果表明，紫外吸收光谱法是一种在纳米尺度下确定热力学参数的无模型、强大的技术。
