Myers Tanya L, Bernacki Bruce E, Wilhelm Michael J, Jensen Karissa L, Johnson Timothy J, Primera-Pedrozo Oliva M, Tonkyn Russell G, Smith Steven C, Burton Sarah D, Bradley Ashley M
Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
Phys Chem Chem Phys. 2022 Sep 21;24(36):22206-22221. doi: 10.1039/d2cp02920k.
This paper investigates the accuracy of deriving the composite optical constants of binary mixtures from only the complex indices of refraction of the neat materials. These optical constants enable the reflectance spectra of the binary mixtures to be modeled for multiple scenarios (, different substrates, thicknesses, volume ratios), which is important for contact and standoff chemical detection. Using volume fractions, each mixture's complex index of refraction was approximated three different mixing rules. To explore the impact of intermolecular interactions, these predictions are tested by experimental measurements for two representative sets of binary mixtures: (1) tributyl phosphate combined with -dodecane, a non-polar medium, to represent mixtures which primarily interact dispersion forces and (2) tributyl phosphate and 1-butanol to represent mixtures with polar functional groups that can also interact dipole-dipole interactions, including hydrogen bonding. The residuals and the root-mean-square error between the experimental and calculated index values are computed and demonstrate that for miscible liquids in which the average geometry of the cross-interactions can be considered isotropic (, dispersion), the refractive indices of the mixtures can be modeled using composite and values derived from volume fractions of the neat liquids. Conversely, in spectral regions where the geometry of the cross-interactions is more restricted and anisotropic (, hydrogen bonding), the calculated and values vary from the measured values. The impact of these interactions on the reflectance spectra are then compared by modeling a thin film of the binary mixtures on an aluminum substrate using both the measured and the mathematically computed indices of refraction.
本文研究了仅从纯物质的复折射率推导二元混合物复合光学常数的准确性。这些光学常数能够针对多种情况（如不同的基底、厚度、体积比）对二元混合物的反射光谱进行建模，这对于接触式和远距离化学检测非常重要。利用体积分数，通过三种不同的混合规则对每种混合物的复折射率进行了近似。为了探究分子间相互作用的影响，针对两组代表性的二元混合物通过实验测量对这些预测进行了检验：（1）磷酸三丁酯与作为非极性介质的正十二烷混合，以代表主要通过色散力相互作用的混合物；（2）磷酸三丁酯与1 - 丁醇混合，以代表具有极性官能团且还能通过偶极 - 偶极相互作用（包括氢键）相互作用的混合物。计算了实验值与计算得到的折射率值之间的残差和均方根误差，结果表明，对于可混溶液体，在交叉相互作用的平均几何形状可被视为各向同性的情况下（如色散），混合物的折射率可以使用由纯液体体积分数得出的复合实部和虚部值进行建模。相反，在交叉相互作用的几何形状更受限且各向异性的光谱区域（如氢键），计算得到的实部和虚部值与测量值不同。然后，通过使用测量的和数学计算得到的折射率对铝基底上的二元混合物薄膜进行建模，比较了这些相互作用对反射光谱的影响。
