Fabrication of Controlled Nanostructures

• 27 May 2020

Why in News

Recently, the researchers at the Institute of Nano Science and Technology (INST) Mohali have found a route to fabricate precisely controlled nanostructures of desired geometry and location on 2D materials, through a rapid one-step low power laser writing process.

• INST, Mohali is an autonomous institute under the Department of Science and Technology (DST).

Key Points

• INST developed a hybrid Surface-Enhanced Raman Spectroscopy (SERS) platform of Molybdenum disulfide (MoS2, an inorganic compound) nanostructure decorated with gold NanoParticles (AuNPs).
  
  • SERS is a commonly used sensing technique in which inelastic light scattering by molecules is greatly enhanced when the molecules are adsorbed onto corrugated metal surfaces such as silver or gold nanoparticles (NPs).
  • It enhances the Raman scattering light from molecules, thus leading to effective analysis of the molecules.
• Direct laser writing (3D printing for microscopic world) was used to engineer the artificial edges on the surface of MoS₂ which created localized hotspots with precision and control.
  
  • A focused laser beam of meagre power of a conventional Raman spectrometer was used which enables the superior deposition of AuNPs along the artificial edges.
  • Nanostructuring was done on the 2D MoS₂ sheet.
• The hybrid SERS platform offers controlled formation of localized hotspots for ultrasensitive and reproducible detection of analytes (substances whose chemical constituents are being identified and measured).
• Significance:
  
  • This research will open a new avenue for the development of commercialized SERS substrates (a silicon wafer coated with a metal like gold or silver) with a localized detection capability of analytes.
    
    • SERS detection has been emerging as a powerful tool for the detection of a variety of analytes due to its very high sensitivity and fingerprinting recognition capabilities.
  • This will also shed new light in the SERS sensing of biological and chemical molecules.
  • The technology can be used in combination with an antibody for the spectroscopic detection of various biomarkers (an objective measure that captures what is happening in a cell or an organism at a given moment).

Raman Effect

• It is a phenomenon in spectroscopy discovered by the eminent physicist Sir Chandrasekhara Venkata Raman on 28^th February 1928.
  
  • In his honour, 28^th February is celebrated as National Science Day in India.
• In 1930, he got a Nobel Prize for this remarkable discovery and this was the first Nobel Prize for India in the field of Science.
• Raman effect is the inelastic scattering of a photon by molecules which are excited to higher vibrational or rotational energy levels. It is also called Raman scattering.
  
  • In simpler words, it is a change in the wavelength of light that occurs when a light beam is deflected by molecules.
  • When a beam of light traverses a dust-free, transparent sample of a chemical compound, a small fraction of the light emerges in directions other than that of the incident (incoming) beam.
  • Most of this scattered light is of unchanged wavelength. A small part, however, has wavelengths different from that of the incident light and its presence is a result of the Raman Effect.
• The Raman effect forms the basis for Raman spectroscopy which is used by chemists and physicists to gain information about materials.
  
  • Spectroscopy is the study of the interaction between matter and electromagnetic radiation.

Source: PIB