ABSTRACT In chips with nanometer-sized channels, photothermal lens microscopy (TLM) suffers quite low detection sensitivity, due to the ultrashort optical path length and the heat loss to the substrate. For a given optical path length, one feasible way to enhance the sensitivity of TLM is to control the heat (i.e., the photothermal effect) in nanospace. In this article, I show that by introducing two coatings with favorable thermophysical properties into a chip, the detection sensitivity can be enhanced from a few times to over 100 times for different optical path lengths from ~10 nm to ~1 µm. A detailed theoretical investigation on the periodic heat transfer and related photothermal effect in such a chip structure was presented. This photothermal effect strengthening method was experimentally demonstrated on a TiO2-coated cell with an optical path length of, for example, 300 nm, on which a sensitivity enhancement of 18 times was achieved in comparison with a cell without coatings and an absorption detection limit down to 2.5 × 10–2 cm−1 can be expected. This work illuminates the importance of heat control to the sensitivity enhancement of photothermal microscopy in nanospaces.

中文翻译：

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控制纳米通道芯片中的热传递，大大提高光热检测灵敏度

摘要 在具有纳米级通道的芯片中，光热透镜显微镜 (TLM) 的检测灵敏度非常低，这是由于超短光程长度和基板的热损失。对于给定的光路长度，提高 TLM 灵敏度的一种可行方法是控制纳米空间中的热量（即光热效应）。在本文中，我展示了通过在芯片中引入两种具有良好热物理特性的涂层，对于从 ~10 nm 到 ~1 µm 的不同光程长度，检测灵敏度可以从几倍提高到 100 倍以上。对这种芯片结构中的周期性热传递和相关光热效应进行了详细的理论研究。这种光热效应增强方法在光路长度为 300 nm 的 TiO2 涂层电池上进行了实验证明，与没有涂层的电池相比，其灵敏度提高了 18 倍，并且吸收检测限降低了到 2.5 × 10–2 cm−1 是可以预期的。这项工作阐明了热控制对纳米空间中光热显微镜灵敏度增强的重要性。