Institute für Biophysik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany.
Analyst. 2017 Jan 26;142(3):495-502. doi: 10.1039/c6an02278b.
An infrared spectroscopic technique is described that employs a mid-IR broadband (980-1245 cm) tunable quantum cascade laser (QCL) to produce a pump beam, and a detection method based on photothermal deflection, enhanced by total internal reflection. The IR spectra thus obtained are depth-dependent by modulating the pump beam with different frequencies between 10 Hz and 500 Hz. A model system consisting of glucose and a polymer film is used to demonstrate the depth selectivity of this technique. We also apply this photothermal depth profiling method to record in vivo IR spectra of the human epidermis at different depths. This information can be used for a non-invasive glucose monitoring on diabetes patients, which is also demonstrated. Beyond biomedical infrared spectroscopy, there are numerous applications for total internal reflection enhanced photothermal deflection spectroscopy (TIR-PTDS). The high penetration depth of mid-IR light compared to the traditional ATR-FTIR technique and the easy sample access make this technique appropriate for in situ measurements, such as in industrial quality control. The depth selectivity of TIR-PTDS may be a convincing argument for its use in the analysis of multilayered samples or for the analysis of artwork, where the layers of interest are covered by a layer of varnish.
描述了一种红外光谱技术，该技术采用中红外宽带（980-1245cm）可调谐量子级联激光器（QCL）产生泵浦光束，并采用基于全内反射增强的光热偏转检测方法。通过在 10Hz 至 500Hz 之间的不同频率下调制泵浦光束，获得的 IR 光谱具有深度依赖性。我们使用包含葡萄糖和聚合物膜的模型系统来证明该技术的深度选择性。我们还应用这种光热深度剖析方法来记录人体表皮不同深度的活体红外光谱。这些信息可用于对糖尿病患者进行非侵入性血糖监测，我们也进行了相关演示。除了生物医学红外光谱学之外，全内反射增强光热偏转光谱学（TIR-PTDS）还有许多其他应用。与传统的 ATR-FTIR 技术相比，中红外光的穿透深度更高，并且易于获取样品，因此非常适合原位测量，例如在工业质量控制中。TIR-PTDS 的深度选择性可能是其用于分析多层样品或艺术品的有力论据，在这些应用中，感兴趣的层被一层清漆覆盖。
