Photothermal spectroscopy

Hello,
last week I was assigned to do research on the method that was used to measure the glucose level in the blood (non-invasive). This method is called (Photothermal Spectroscopy).


Photothermal spectroscopy is a high sensitivity of detecting the changes in the spectra that are produced from the emission of the electromagnetic radiation of the matter. the basics of these techniques are measuring the absorbance of the radiations that were caused by the thermal characteristics of a sample. the changes in the thermal characters are caused by the light that is directed to the sample. When there is no loss of light by the emission, the temperature of the sample will rise therefore it will affect the thermodynamic properties of the sample. Measurement of the temperature, pressure, or density changes that occur due to optical absorption is ultimately the basis for the photothermal spectroscopic measurements.

photothermal spectroscopy is an indirect method for measuring optical absorption because it's not based on the light measurement directly which is involved in the absorption. in other words, photothermal methods measure the absorption directly, and not finding it by calculating it from the transmission as is the case of more usual spectroscopic techniques. that is the reason for these methods being highly sensitive because, in the transmission techniques, it calculates the lights absorbance where we find the difference between the light that is transmitted and the impinged on and from the sample, an inaccuracy will be present in this measurement because it will deal with large numbers but small differences, when the absorption is small. In photothermal spectroscopies, instead, the signal is essentially proportional to the absorption and is zero when there is zero true absorption, even in the presence of reflection or scattering. In photothermal spectroscopies, instead, the signal is essentially proportional to the absorption and is zero when there is zero true absorption, even in the presence of reflection or scattering.
photothermal spectroscopy uses various techniques and methods. These methods and techniques are named according to the specific physical effect measured:
  • Photothermal lens spectroscopy (PTS or TLS),
  • Photothermal deflection spectroscopy (PDS),
  • Photothermal diffraction
  • Photothermal emission
  • Photothermal single-particle microscopy


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