Photophysical Chemistry, Fluorescence Spectroscopy
Development of innovative photophysical concepts, instrumentation and fluorimetry applications.
Development of novel fluorescent molecular probes as well as probe concepts, and their applications for the understanding of micro- and nano-scale heterogeneous systems like lipid bilayer membranes, hydrogels, dendrimers and aggregates.
Understanding of fundamental photophysics of various excited state intra- and inter-molecular processes.
Among the most noteworthy contributions from Dr Mishra’s laboratory in recent years, the following are highlighted.
Dr. Mishra has also contributed in areas like electrical engineering (monitoring transformer oil degradation), chemical engineering (glass-transition temperature of nylon polymer blends), analytical biochemistry (estimation of total lipids in fungal systems), and environmental science (characterization of soil-humus).
Dr. Mishra’s work in the area of fundamental photophysics is significant. To mention a few:
Introduction of a noteworthy procedure for quick approximate estimation of all the dynamical parameters concerning exciplex formation and decay, using minimal fluorescence lifetime data and certain valid approximations.
Recent work of Dr. Mishra brings out the significance of diacetylene moiety in the photophysics of diyne bridged extended aromatic systems, a class of molecules of high current interest with exciting potentials in areas like optoelectronics and Raman imaging.
Very recently, Förster resonance energy transfer (FRET) was utilized to generate white light emission from a cocktail of common vegetable extracts, which has pH sensing ability.
Dr. Mishra’s research on lipid bilayer membrane using fluorescence spectroscopy has resulted in significant innovative contributions to the area. To name a few:
Introduction of ‘Excited State Prototropism (ESPT) as a molecular probe concept for lipid bilayer membranes’ – sensitive response of fluorescence lifetime parameters to membrane property changes, opening new avenues towards research on lipid bilayer membranes.
Fluorescence of various ESPT probes such as 1-naphthol and fisetin has been found to show sensitive response to phase transition in membranes, membrane property changes by cholesterol, drug, peptides, bile salts, and bilayer interdigitation.
Very recently, the interaction of capsaicin (an ingredient of a wide variety of red peppers) with dimyristoylphosphatidylcholine (DMPC) lipid bilayer membrane has been investigated by monitoring various photophysical parameters using capsaicin’s intrinsic fluorescence, which could have potential implications in cancer therapy and drug delivery. This work appeared in ACS Press Release (http://www.acs.org/content/acs/en/pressroom/presspacs/2015/acs-presspac-september-9-2015.html).
Dr. Mishra has introduced several new fluorescent molecular probes such as N,N-dimethylaniline containing ethynyl pyrene, conjugated fluorophores such as coumarin-cholesterol, pyrene-lactose and N-acylated dansylamides for studying various heterogeneous and organized systems. Some other work includes studies on fluorescent dendrimers, hydrogels, peptide-membrane interactions, bile salt organizations and their interactions with drugs, membranes and thermoreversible gels.
Dr. Mishra has made some major innovative contributions to analytical fluorimetry, especially in the area of analyzing complex multifluorophoric systems. Some of them include:
Introduction of a novel concept for analyzing multifluorophoric systems using synchronous fluorescence spectroscopy (SFS) by a modification of Beer-Lambert’s Law. This research provides a conceptual foundation for understanding ‘concentration dependent red shift’ observed in Synchronous Fluorescence (SF) Spectroscopy based analysis of complex multifluorophoric systems and also introduces a protocol for SF analysis.
Introduction of ‘Total Synchronous Fluorescence Spectroscopy’ (TSFS) as an attractive alternative to the existing Excitation-Emission Matrix Spectroscopy, and a procedure for theapplication of PARAFAC (a chemometric technique) to TSFS data enabling automation of data processing.
Introduction of a facile measurement technique for luminescence quantum yield , by designing an optical spectrometer that uses the same light source and detector for both the electronic absorption and luminescence spectral measurements.
Introduction of a new fluorescence data collection concept, ‘White Light Excitation Fluorescence’ and showcasing its application potential.
Introduction of miniaturized fiber-optic compatible fluorimeter configurations and probe-heads.
Introduction of a new parameter called ‘total fluorescence quantum yield’ relating to the volume under the 3D EEMF plots and the method of ‘excitation emission matrix spectral subtraction fluorescence’ .
Innovative optimization of fluorescence data acquisition techniques and various chemometric methods towards developing practical applications like petroleum fuel adulteration analysis , petroleum fuel-biofuel blend composition estimation , monitoring of transformer oil degradation , analysis of polycyclic aromatic compounds in water, classification of Ayurvedic preparations and oral cancer diagnosis.