Living Systems Institute, Faculty of Health and Life Sciences, University of Exeter, Stocker Road, Exeter, Devon, EX4 4QJ, UK.
Automation Department, Faculty of Electrical Engineering and Computer Science, Transilvania University of Brasov, 500036 Brasov, Romania.
Analyst. 2023 Apr 11;148(8):1797-1804. doi: 10.1039/d3an00143a.
Absorption spectroscopy is a widely used analytical technique due to its label-free nature, however its application to small liquid samples is hampered by the associated short absorption pathlengths, which limit sensitivity. A novel concept for the development of an ultrasensitive broadband absorption spectrometer optimised for thin liquid films is presented here. To enhance sensitivity of the absorbance measurements an optical cavity is implemented on a fibre-based absorption spectrometer (CEASpec). Light is circulated multiple times through the sample of interest to increase sensitivity. The bandwidth of the instrument is chosen by the choice of the dielectric mirrors forming the optical cavity spectra and, in this implementation, has been set to be 200 nm wide (250-450 nm). The sensing volume of the spectroscope is prescribed by the choice of optical fibres employed to deliver light to the sample, and in this implementation fibres of 400 μm in diameter were employed, giving a sensing volume of 630 picolitres for a thin film of 5 μm in thickness. Amphotericin B, a broad light absorber in the 280-450 nm region of the spectrum, was used here to prove the capabilities of the proposed cavity enhanced absorption spectroscope. Cavity enhancement factors, the equivalent pathlength increase over classical absorption spectroscopy, in the range of 200× have been achieved across a broad wavelength range.
吸收光谱学是一种广泛应用的分析技术，由于其无需标记的特性，但由于相关的短吸收光程限制了其灵敏度，因此其在小液体样本中的应用受到阻碍。本文提出了一种用于优化薄液膜的超灵敏宽带吸收光谱仪的新概念。为了提高吸收测量的灵敏度，在基于光纤的吸收光谱仪（CEASpec）上实现了光学腔。光通过感兴趣的样品多次循环，以提高灵敏度。仪器的带宽由形成光学腔谱的介电反射镜的选择决定，在这种实现方式中，将其设置为 200nm 宽（250-450nm）。光谱仪的传感体积由用于将光传输到样品的光纤选择决定，在这种实现方式中，使用了直径为 400μm 的光纤，对于厚度为 5μm 的薄膜，传感体积为 630 皮升。两性霉素 B 是光谱 280-450nm 区域的广谱光吸收剂，这里用于证明所提出的腔增强吸收光谱仪的性能。在宽波长范围内，实现了 200×范围内的腔增强因子，即等效光程相对于经典吸收光谱学的增加。
