Absorption spectroscopy: New technique to study ultrasmall particles in cells


  • Researchers from IIT Madras and IISER Kolkata have developed a method to detect minute quantities of chemicals in solution.

  • They use a variation of absorption spectroscopy that surpasses the systemic limits imposed by conventional absorption spectroscopy.

  • With this technique, they can, in principle, illuminate the insides of cells and detect minuscule quantities of substances present there. 

About the absorption spectroscopy

  • Absorption spectroscopy is a tool to detect the presence of elements in a medium.
  • Light is shone on the sample, and after it passes through the sample is examined using a spectroscope.
  • Dark lines are seen in the observed spectrum of the light passed through the substance, which correspond to the wavelengths of light absorbed by the intervening substance and are characteristic of the elements present in it.
  • In usual methods, about a cubic centimetre of the sample is needed to do this experiment.
  • In the method developed here, minute amounts of dissolved substances can be detected easily.
  • Usually in absorption spectroscopy, the principle used is that light because of its wavelike nature, shows diffraction patterns, that is, dark and light fringes, when it scatters off any object. A related concept called the Abbe criterion sets a natural limit on the size of the object being studied. According to this criterion, the size of the observed object has to be at least of the order of the wavelength of the light being shone on it. 
  • In the method used by the researchers here, tiny, nano-sized particles that can absorb light being shone on them and re-emit red, blue and green light were employed.

Inside living cells

  • There are many potential applications. “We are ourselves going to put these particles inside living cells, and the emission can be used as a tiny flash lamp to look for absorption from individual molecules in the close proximity to the particle,”.
  • This is way in which small molecules almost ten-millionth of a mm in diameter can be detected while these pass the emission region of the glass particle… The future is to use it to measure individual molecules, see an absorption spectroscopy of a single DNA or protein molecule.

Source: The Hindu

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