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Research

TCSPC set-up.

Rounded Rectangle: Techniques Use:

We use mainly UV-vis spectrophotometer, steady state fluorescence spectrometer, time-resolved fluorescence spectrometer. All the instruments are available in IISER, Pune. In time-resovled fluorescence, we have time correlated single photon counting (TCSPC) instrument as well as femtosecond fluorescence up-conversion instrument with us.

Mai-Tai Coupled Femtosecond up-conversion and TCSPC set-up.

Femtosecond up-conversion set-up.

Femtosecond up-conversion set-up.

Present Research Interests

 

Spectroscopy of Materials:

 

v Exploring Lyotropic Liquid Crystalline Systems:

 

Lipid based lyotropic liquid crystalline (LLC) materials based on 1-linoleoyl-rac-glycerol (ML)/glycerol monooleate (GML) have been utilized in a wide range of applications due to their excellent topological feature, high biocompatibility, and outstanding phase behaviour. we plan to probe the stability and photophysical properties of guest molecules (drugs and biologically important molecules/fluorophores) inside these LLC phases rather than the stability of host (LLC phases), which has been primarily focused in the literature. Conformational transition of different biomolecules, like, protein, DNA etc. will also be probed inside the water nano-channels of these bio-mimicking systems owing to the several biological applications of these LLC phases. Additionally, due to the confined and restricted environment of these water nano-channels inside the LLC phases, we will try to stabilize the other forms of DNA like, i-motif DNA, A-DNA, Z-DNA, poly (A) or poly (dA), which are usually unstable in physiological pH at normal condition.

 

v Design, Synthesis and Photophyiscs of novel Thermally Activated Delayed Fluorescence (TADF) and Mechanochromic Fluorescent Luminogens:

 

In the field of organic light-emitting diodes (OLEDs), thermally activated delayed fluorescence (TADF) emitters have been emerged as a potential candidate for efficient harvesting of triplet excitons from the lowest triplet (T1) excited state to the lowest singlet (S1) excited state via reverse intersystem crossing (RISC), induced by thermal activation. In spite of multiple reports on TADF molecules in the last decade, the development and design of efficient TADF emitters still remain as a challenge. The main reason for this is, simultaneous achievement of smaller value along with a larger fluorescence radiative decay rate in one molecule is inherently difficult through molecular designing. In this project, we plan to carry out the synthesis, charcaterizations followed by photophysical studies of some novel thermally activated delayed fluorescence (TADF), which will exhibit nearly 100% internal luminescence quantum efficiency.

 

v Self-assembly Mediated Broadband Emission Tunability of Luminescent Copper Nano-clusters:

 

Organic ligand protected metal nanoclusters comprised of a few metal atoms establish a connection between single metal atom and plasmonic metal nanoparticles where they behave like neither of these two, rather, the electronic structure of the metal nanoclusters become discrete in nature and photoluminescence properties start emerging. Ultra-small size, greater photo-stability, and tunable fluorescence make these materials excellent alternatives to quantum dots and organic dyes for various applications. Structural and conformational diversity in the protecting ligands makes the metal nanoclusters suitable for being self-assembled with additional properties and enhanced functionalities. Self-assembled metal nanoclusters have numerous applications in different fields such as, biomedicine, drug delivery, bio-imaging, sensing, optoelectronic utilizations and catalytic applications. These additional properties and functionalities can not only be incorporated by non-covalent interactions through sel-assembly but also, by forming multiple covalent bonds between metal nanoclusters. These covalent nanocluster superstructures will be much more stable compared to self-assembled one. Our primary motive is to synthesize the single metal nanoclusters at first and after that we use those single cluster particles as a building block to form nanocluster superstructures with additional properties and enhanced functionalities for further catalytic applications.

 

 

Biophysics:

 

v Designing of Novel Fluorophores for Probing Amyloid Fibril:

 

Misfolding of amyloidogenic protein results the deposition of protein agglomerates in different part of human body, and are believed to be involved in the pathology of amyloidosis, such as Alzheimer disease, Parkinson disease, Prion diseases, type II diabetes etc. Several small organic molecules have been designed for the optical imaging of amyloid fibrils. Most of the cases the detection is based on the enhancement of fluorescence intensity of the probes. However, such intensity-based or fluorescent turn on probes are always susceptible to self-quenching at higher concentrations, making the fluorophores unsuitable for quantitative analysis. Moreover, using such fluorescent turn on probe, it is hard to investigate the detail mechanism of fibril formation as they only reports on the formation of final fibrillar state, and does not reveal the presence of oligomers or other types of aggregates. Thus, instead of monitoring the fibrillation by a single intensity-based, it would be very simple and effective if one can monitor this fibril formation process directly by the switch in the fluorescence color of the probes. In continuation of this effort, here we are going to introduce a series of donor acceptor-based charge transfer probe molecules, which forms AIE dots in buffer, and able to sense insulin amyloid fibrils in terms of disaggregation induced fluorescence switching and fluorescence enhancement.

 

v Conformational Transition and Stabilization of Non-canonical Forms of DNA, i.e., G- quadruplex, i-motif:

 

The primary motivation of the works is to control and detect the conformational transition between different secondary structures of DNA, which will be advantageous in terms of their participation in different biologically important processes. Structural characteristics of these different DNA forms will be utilized to modulate their conformational transitions by some external stimuli, which will give us an excellent opportunity to understand the molecular mechanism behind the formation and stabilization of these different DNA structures.

 

 

The present study shows that a special class of ionic liquid (Gua-IL) can act as a stabilizer of telomeric GQ-DNA exerting minimal effect towards the duplex structure and thereby can be considered as a potential telomerase inhibitor. Phys. Chem. Chem. Phys., 2016, 18, 29740-29746.

Dual fluorescence property of an eminent anticancer drug, ellipticine, has been explored to directly monitor its efficient loading into MCM-41 and subsequent release to DNA. Nanoscale, 2016, 8, 18436-18445.

Investigation of Photopyrolytic Processes of an Anticancer Drug Topotecan inside Biocompatible Lyotropic Liquid Crystalline Systems. Langmuir, 2016, 32, 3057-3065.

An antimalerial/anticancer drug, Cryptolepine is encapsulated inside the nano-cavity of cucurbit[7]uril, and its subsequent release to DNA is monitored using an external stimulus, acetylcholine chloride. ChemPhysChem, 2016, 17, 506-515.

Solvation dynamics has been investigated in different Phases of lyotropic liquid crystalline systems. J. Phys. Chem. B, 2015, 119, 11721-11731.

Femtosecond Up-conversion Studies of [2,2-Bipyridyl]-3,3-diol in Octyl-β-D-glucoside and Other Micellar Aggregates. J. Phys. Chem. A, 2015, 119, 12715-12721.

Fluorescence Switching of Sanguinarine in Micellar Environments. Phys. Chem. Chem. Phys. 2015, 17, 20725-20732.

An ionic liquid induced Green Solvent Induced DNA Package. Scientific Reports, 2015, 5, Article number: 9137.

Important Published Works

Biophysical aspects of binding interactions between anticancer drug, Proflavine and human telomeric DNA have been monitored with different spectroscopic techniques. We have observed that Proflavine instigates and stabilizes the G-quadruplex DNA.J. Phys. Chem. B, 2014, 118, 11090-11099

Prototropical and photophysical properties of an anti-cancer drug, EPT are explored inside the inclusion complexes formed by cyclodextrins and cucurbit[n]urils using spectroscopic and computational studies.

J. Phys. Chem. B, 2013, 117, 14099-14107.

The effect of physical nanocavity on double proton transfer dynamics of BP(OH)2 is studied from femtosecond to nanosecond regime using TCSPC and fluorescence upconversion techniques. Phys. Chem. Chem. Phys. 2014, 16 (3), 933 - 939.

Prototropical and photophysical properties of an anticancer drug, ellipticine are explored inside the octyl-b-D-glucoside micelles using steady state and time resolved spectroscopic techniques. Phys. Chem. Chem. Phys. 2014, 16, 14953-14960.

Urea Induced Unfolding dynamics of Flavin Adenine Dinucleotide (FAD): Spectroscopic And Molecular Dynamics Simulation Studies from Femto-second to Nano-second regime. J. Phys. Chem. B, 2014, 118, 1881-1890.

A clearly visible emission color switching of an anti-cancer drug, ellipticine in presence of protein (blue),

DNA (green) and protein-DNA system (sea green) promotes a novel technique to probe protein-DNA interaction. Phys. Chem. Chem. Phys. 2014, 16, 3914-3917.

TTOOCC.TIF

Dual fluorescence property of an eminent anticancer drug, ellipticine, has been explored to directly monitor its efficient loading onto graphene oxide and subsequent release to biomolecules like DNA/RNA. Nanoscale, 2014, 6, 2937-2944.

A fluorescence switch from ultraviolet (UV) to visible (cyan) is observed as a consequence of upward pKa shift of milrinone inside the CB7 nano-cavity. Phys. Chem. Chem. Phys. 2014, 16(7), 2823-2826.

Inside the nano-cavity of CB7, ESPT of TPT is inhibited and fluorescence switches from green to blue (see picture). When NaCl is introduced into the TPT-CB7 solution, the blue colour switches back to green. ChemPhysChem, 2013, 14 3375-3383.

ESPT dynamics of a potential anti-cancer drug, Topotecan has been explored in aqueous reverse micelle using steady-state and time-resolved fluorescence measurements. J. Phys. Chem. B, 2015, 119, 2363-2371.

Cucurbit[7]uril (C7U) assists the pKa shift of an anticancer drug, 20(S)-camptothecin (CPT) by forming 2:1 (C7U:CPT) inclusion complex. However, the protonation does not take place when it is encased by β-cyclodextrin cavity. ChemPhysChem 2013, 14, 532.

The modulation over excimer formation drift of a molecular motor, called DCVJ, have been probed inside various cavity sizes of cyclodextrins host. Phys. Chem. Chem. Phys. 2013, 15, 330

The binding interactions of flavins (riboflavin (RF), flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN)) with HSA have been monitored with the help of steady state and time-resolved fluorescence spectroscopy, isothermal titration calorimetry, circular dichroism studies, and supported by docking and molecular dynamics (MD) simulations studies. ChemPhysChem. 2012, 13, 2142-2153.

In this work the urea dynamics inside AOT reverse micelle has been monitored without intervention of water using time resolved fluorescence techniques from picosecond to nanosecond time regime. Urea dynamics inside the reverse micelle is severely hindered compared to dry as well as water RM due to the formation of highly networked molecular cluster of urea. J. Phys. Chem. A, 2011, 115, 10398-10407.

We have studied the solvation dynamics and rotational relaxation of Coumarin 153 (C-153) in SDS dispersed two different types of single walled carbon nanotubes (SWNTs), namely metallic and semiconducting, using picosecond fluorescence spectroscopy. Chem. Phys. Lett., 2010, 501, 33-38.

Welcome to Dr. Partha Hazra Group

Professor in Chemistry

 

Hydrogen Bonding Abilities of LLC Water Molecules and their Effects on Intramolecular Hydrogen Bonds of Target Probe Molecules. PCCP, 2020, Accepted.

Impact of Topology on the Characteristics of Water inside Cubic Lyotropic Liquid Crystalline Systems. J. Phys. Chem. B, 2019, 123, 18, 4118-4128.

A new approach has been explored to detect i-motif DNA structures based on the hemi-protonated cytosine-cytosine (C+-C) base pairing recognition instead of conventional loop detection of i-motif DNA. Along with its selectivity towards i-motif DNA over its complimentary GQ DNA, this approach shows its versatility by detecting different kind of i-motif structures with different chain lengths, molecularity and sizes etc. Organic & Biomolecular Chemistry (OBC) 2019, 17, 5392-5399.

Strategy to Mechanical Activation of Centro-Symmetrically Packed Organic Luminogens. J. Phys. Chem. C, 2019, 123, 3848-3854.

Ultrafast Fluorescence Dynamics of Highly Stable Copper Nanoclusters Synthesized inside the Aqueous Nano-pool of Reverse Micelles.

J. Phys. Chem. C2018, 122, 5742-5752 .

Developing Structure-Property Relationship to Design Solid State Multi-stimuli Responsive Materials and Their Potential Applications in Different Fields. Chemical Science2018, 9, 3592-3606.

A new approach has been explored to instigate the formation and stabilization of i-motif DNA at neutral and alkaline medium by means of incorporating into mesoporous silica nano-channels (MCM-41). Additionally, this i-motif DNA formation has been controlled using positively charged lysozyme protein which drags the DNA from the nano-pore followed by protein-DNA complex formation.

Chemical Communications2018, 54 (51), 7054-7057 .