Present study aims at development of thin films of sol–gel Ta2O5 with tunable refractive index that could be used as an active medium for volatile organic compound (VOCs) optical detection. In order to tune the refractive index, mesoporosity is introduced through soft templating approach where series of co-polymers (Pluronics) are utilized as structure-directing agents. Thin films are prepared by spin-coating method using tantalum sol synthesized from TaCl5 as a precursor and ethanol as a solvent. The temperature annealing at 320 °C finalizes the tantalum oxide lattice formation and decomposes the template being used. The morphology and elemental composition of the films are studied by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy in STEM, respectively, and the amorphous status of the films is confirmed by selected area electron diffraction. Non-linear curve fitting method and non-destructive UV–Vis reflectance measurements are used for determination of optical parameters of the films. The free volume fraction in the films is estimated through modeling of refractive index by Bruggeman effective medium approximation. The films are exposed to acetone vapors as a commonly studied VOC. The reaction of the film due to vapors’ exposure is recorded as a change in the reflection spectra of the film and the adsorbed acetone quantity is estimated. The influence of template composition on optical and sensing properties of Ta2O5 films is revealed and discussed.

中文翻译：

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用于光学传感应用的具有可调折射率的溶胶-凝胶五氧化二钽薄膜

本研究旨在开发具有可调折射率的溶胶-凝胶 Ta2O5 薄膜，该薄膜可用作挥发性有机化合物 (VOC) 光学检测的活性介质。为了调整折射率，通过软模板方法引入中孔率，其中使用一系列共聚物（Pluronics）作为结构导向剂。以TaCl5为前驱体，乙醇为溶剂合成钽溶胶，通过旋涂法制备薄膜。在 320 °C 的温度退火完成氧化钽晶格的形成并分解所使用的模板。分别通过透射电子显微镜 (TEM) 和 STEM 中的能量色散 X 射线光谱研究薄膜的形貌和元素组成，通过选区电子衍射确认薄膜的非晶态。非线性曲线拟合方法和非破坏性紫外-可见反射率测量用于确定薄膜的光学参数。薄膜中的自由体积分数是通过 Bruggeman 有效介质近似的折射率建模来估计的。薄膜暴露于丙酮蒸气中，作为一种普遍研究的 VOC。由于暴露于蒸气而导致的薄膜反应被记录为薄膜反射光谱的变化，并估算吸附的丙酮量。揭示并讨论了模板组成对 Ta2O5 薄膜光学和传感性能的影响。非线性曲线拟合方法和非破坏性紫外-可见反射率测量用于确定薄膜的光学参数。薄膜中的自由体积分数是通过 Bruggeman 有效介质近似的折射率建模来估计的。薄膜暴露于丙酮蒸气中，作为一种普遍研究的 VOC。由于暴露于蒸气而导致的薄膜反应被记录为薄膜反射光谱的变化，并估算吸附的丙酮量。揭示并讨论了模板组成对 Ta2O5 薄膜光学和传感性能的影响。非线性曲线拟合方法和非破坏性紫外-可见反射率测量用于确定薄膜的光学参数。薄膜中的自由体积分数是通过 Bruggeman 有效介质近似的折射率建模来估计的。薄膜暴露于丙酮蒸气中，作为一种普遍研究的 VOC。由于暴露于蒸气而导致的薄膜反应被记录为薄膜反射光谱的变化，并估算吸附的丙酮量。揭示并讨论了模板组成对 Ta2O5 薄膜光学和传感性能的影响。由于暴露于蒸气而导致的薄膜反应被记录为薄膜反射光谱的变化，并估算吸附的丙酮量。揭示并讨论了模板组成对 Ta2O5 薄膜光学和传感性能的影响。由于暴露于蒸气而导致的薄膜反应被记录为薄膜反射光谱的变化，并估算吸附的丙酮量。揭示并讨论了模板组成对 Ta2O5 薄膜光学和传感性能的影响。