Ultrafast Spectroscopy Laboratory
Ultrafast Excited State Dynamics
This research area involves the optical excitation of molecular systems in a time scale of few femtoseconds, followed by tracing the events which occur in the excited state or states of these molecular systems. Femtosecond pulses from Ti-Sapphire laser take the molecules from ground to excited state and once the molecule reaches the locally excited Franck-Condon state, it starts relaxing towards the local minima in the excited state potential energy surface. The dynamical events commencing from the Frack-Condon state till its return back to the ground state are traced and the mechanistic details of each and every step are formulated to get to know all radiative and non-radiative decays channels which deplete the excited state to ground state. Such kind of study not only answers the very fundamentals questions about the excited states, but can also have lot other implications in many ways.
Bio-Physical Chemistry/ Single Molecule Spectroscopy
We are interested in elucidating the structure-function-dynamics
relationship of proteins using bulk and single molecular level
spectroscopic studies. Our main directions are:
Spectroscopic Studies of Perovskite Materials
Recently our group takes interest in contemplating various dynamical processes in the perovskite materials that has made it one of the most efficient energy converting material. Lead based perovskite nanocrystals with high photoluminescence quantum yield are in the top of interest in the scientific world due to its tunable photoluminescence properties in visible range which makes them potential candidates in the field of optoelectronics. Doping of different cations in the B-site of lead based perovskite nanocrystals results some interesting properties in the photoluminescence behavior as well as in carrier dynamics. The primary interest of our research is to find out the effect of doping in carrier dynamics using ultrafast studies in lead based perovskite nanocrystals. We are also interested in study that how capping ligand behaves in the nanocrystal solution. Beside these our group is also interested in exploring the new ways of preparations for perovskite materials both in quantum dot and in bulk level.
Microscopic Structure of Binary Solvent Mixtures and Deep eutectic solvents (DES)
The main objective of our research is to understand various interactions present in binary solvent mixtures. The interactive solvents develops a micro heterogeneous environment in solution phase via specific interaction e.g. hydrogen bonding or by nonspecific such as dipole-dipole, dipole-induced dipole interaction or hydrophobic interactions leading to a unique property. We have observed synergetic solvation behavior in MeOH-CHCl3 and MeOH-DCM binary solvent mixture and has been studied by spectroscopic techniques and modeling. It has been concluded that the week hydrogen bonded network between hydrogen bond accepting (MeOH) and donating (CHCl3, DCM) solvent is mainly responsible for the obserbed synergism leading to an extended H-bonded network. Recently our main focus is to understand various interactions in the Deep Eutactic solvents (DES) by combining femtosecond transient absorption spectroscopy, picosecond salvation dynamics and microsecond level fluctuation using FCS.
Study of Interfaces
This area of research is dedicated to the study of non-centrosymmetric surfaces by Second Harmonic Generation. This method enables us to distinguish the surface properties from the bulk by the estimates of second order polarisation term. The development of the instrument is underway. A mode-locked Ti-Sapphire laser will illuminate the sample and the frequency doubled light will be collected by high performance photodiode. This apparatus will be used to study the orientational configurations and interactions of a molecule on a solid or liquid surface.
|Pratik Sen Group, February 2021|