Optical Characterization Instrumentation Laboratory

History:

Optical absorption and emission studies of samples is the most fundamental characterization in material science that is routinely carried out to understand the different optical properties and electronic transitions in a non-destructive way. UV-VIS and FTIR spectra of samples can give a quantitative estimate of the absorption in the samples for wide range of materials and the energy band gaps. These instruments are routinely used for optical characterization of samples. Photoluminescence spectrum gives the emission characteristics of phosphors along with absorption spectra. It also provides information of the impurity levels, band gap, recombination mechanisms and material quality in general. Direct observation of samples is desirable for a quick examination of surface roughness and shape of certain samples (for example single crystals, micro and nanoparticles). An optical microscope is also essential for observing interesting phenomena such as optical trapping, fluorescence from specific regions and biological processes. Some of the instruments were procured under DST-FIST grants and others were purchased from individual project grants from DST-SERB, and CEFIPRA.

Research areas:

Solid state bulk materials such ferrites, intermetallics and transition metal compounds, battery materials, luminescent phosphors, single crystals

Nanomaterials: plasmonic metals such as gold and silver, quantum dots, magnetic nanoparticles

Glasses, liquids, colloidal solutions, luminescent dyes

Thin films of oxides such as TiO₂, ZnO, graphene oxide

Resources and facilities:

• UV-Vis Spectrophotometer-Shimadzu UV-2401PC: 190-900 nm. Up to 0.1 nm resolution, wavelength repeatability of ± 0.1 nm, 50W halogen lamp, transmittance and reflectance mode.
• Fourier Transform Infrared (FTIR) spectrometer- Shimadzu FTIR-8900: 4000-400 cm^-1 range, solid or liquid samples
• Photoluminescence (PL) spectrophotometer
• PTI Quantamaster-500 (Horiba): It features a sensitive, thermo-electrically cooled solid state InGaAs detector covering the range of 500-1700 nm. A Xenon (flash as well as continuous) lamp of 150 W is used for excitation
• Cary-Eclipse (Agilent): 200-900 nm range, Xenon flash lamp, Czerny-Turner type, Wavelength accuracy: ±1.5 nm
• Benchtop configuration with fluorescence, phosphorescence, chemi/bio-luminescence, and time resolved phosphorescence measurements.
• Optical microscopes
• Stereo microscope: Lynx (Lawrence & Mayo), up to 40x zoom
• Inverted optical microscope: Lynx (Lawrence & Mayo), 25x, 40x and 60x objectives
• Inverted optical microscope for imaging Nikon TS2: 10x, 20x, 40x
• Upright optical microscope with photoactivation unit (Nikon Eclipse Ni U): 10x, 40x and 100x oil objective (NA 1.25), darkfield, phase contrast, fluorescence and optical trapping.

Achievements:

UV-Vis and FTIR have been routinely used to characterize the absorption and energy band gap of different variety of materials that has led to numerous publications.

Novel photoluminescent materials have been characterized, for example long -lasting phosphorescence in ZGO:Cr, rare-earth doped compounds and quantum dots.

Optical trapping of quantum dots and bacteria on graphene oxide has been successfully demonstrated.

Observation of single crystals

Faculty-in-charge: Dr. Sudhir Cherukulappurath