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

Note: These days there has been a rise in questions from biology (rather cell biology in particular).

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 centimeter 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.

Studying small objects

• 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.
• If one wants to perform absorption spectroscopy using visible light, namely, blue, green and red, the wavelengths [of these colours] are about 400 nm, 500 nm and 600 nm, respectively.

What has Indian researchers achieved?

• 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.
• The particles emit electric fields that are analogous to how a tiny magnet would give off magnetic lines of force – this is called a dipole, and the particle is like a tiny mobile phone’s antenna.
• This dipole generates an electromagnetic field depending upon the quantum properties of the erbium dopants in the glass.
• The absorption leaves a gap in the reflected light, which is what is observed and used to analyse the nature of the absorbing material.

Applications of this technology

• There are many potential applications.
• Small molecules almost ten-millionth of an 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 absorption spectroscopy of a single DNA or protein molecule.

Try this

Q.Which of the following statements are correct regarding the general difference between plant and animal cells?

1. Plant cells have cellulose cell walls whilst animal cells do not.
2. Plant cells do not have plasma membranes unlike animal cells which do.
3. Mature plant cell has one large vacuole whilst an animal cell has many small vacuoles.

Select the correct answer using the code given below:

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

Answer this PYQ here:

1

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