Hirdyesh Mishra - Academia.edu (original) (raw)
Papers by Hirdyesh Mishra
Density functional theory calculations in electronic structure studies of n-Bu2SnL2 (where L is t... more Density functional theory calculations in electronic structure studies of n-Bu2SnL2 (where L is the monoanion of chlordiazepoxide (LH), a benzodiazepine derivative with hypnotic action) have been reported using the Gaussian09 software. The molecular geometries of LH and tetrahedral n-Bu2SnL2 have been optimized at B3LYP/6-31G(d,p) and B3LYP/ 6-31G(d,p)/Def2-SVP(Sn) level of theory, respectively. Harmonic vibrational frequencies are computed at the same level of theory to find the true potential energy surface minima. The effect of functional, basis set and computational cost is analyzed. The various geometrical and thermochemical parameters have been obtained in gas phase and in the solvent. The atomic charges at all the atoms are calculated using Mulliken population analysis, Hirshfeld population analysis and natural population analysis. The charge distribution within the studied complex is explained on the basis of molecular electrostatic potential maps, and conceptual-DFT based g...
Journal of Photochemistry and Photobiology A: Chemistry, 2018
Serotonin (5-HT) is an important monoamine neurotransmitter that plays a vital role in the regula... more Serotonin (5-HT) is an important monoamine neurotransmitter that plays a vital role in the regulation of various cognitive and behavioural functions including sleep, mood, pain, depression, anxiety, aggression, learning etc. From the nanotoxicity and neurotoxicity point of view, interaction studies between serotonin and nanoparticles are highly essential to develop an indispensable understanding on the effect of nanoparticles on monoamine neurotransmitters. In the present work, steady-state and time-domain fluorescence measurements were carried out along with binding energy measurements through X-ray photoelectron spectroscopic (XPS) technique to understand the interaction of 5-HT with silver nanoparticles (AgNPs). The emergence of a week red absorption band and quenching of fluorescence intensity along with decrease in full width half maximum, but not the excited state decay time of 5-HT in the addition of AgNPs suggest the formation of a non-fluorescent complex in the ground state that indicates static quenching along with radiative energy transfer among them. This is also confirmed by the low energy shift of Ag transition in 3 d 3/2 and 3 d 5/2 in XPS measurements and a coupling of L b transition with the surface plasmons of AgNPs in the excitation spectra. The obtained thermodynamic parameters from the fluorescence quenching reveal the nature of interaction between 5-HT and AgNPs is hydrophobic. The increase in binding constant with increasing temperature suggested an enhancement in the strength of this interaction due to rise in the mobility of the molecules and hence increases the sensitivity and association of 5-HT with AgNPs.
Chemical Physics, 2008
Molecular orbital calculations reveal that the keto tautomer of HOCHCHNHNCHz, unlike the enol, do... more Molecular orbital calculations reveal that the keto tautomer of HOCHCHNHNCHz, unlike the enol, does not represent a minimum in the ground state proton transfer potential. Excitation to the first excited singlet or triplet state leads to a rapid and barrierless transfer to the keto which becomes strongly preferred. Similar conclusions apply to a larger system with a full aromatic ring appended.
Optical Materials, 2021
This work reports the green to red color tunable upconversion emission in a newly synthesized Ho3... more This work reports the green to red color tunable upconversion emission in a newly synthesized Ho3+/Yb3+ codoped YV0.75Ta0.25O4 phosphor, prepared by solid-state reaction (SSR) method. The crystal phase formation has been confirmed by X-Ray diffraction analysis. The Fourier transform infrared (FTIR) spectrum show bands at different frequencies due to V-O and Ta-O, and found to play a vital role in relaxation (radiative and non-radiative) processes. The synthesized phosphor sample show intense upconversion (UC) emission in green (∼539 nm), red (∼659 nm) and in near infrared (NIR∼ 754 nm) regions on 980 nm laser excitation. These bands appear as a result of (5F4+5S2→5I8), (5F5→5I8) and (5F4+5S2→5I7) transitions of Ho3+ ion, respectively. The tunability in color from green to orange-red is observed on varying the pump power of NIR laser (980 nm excitation). The intrinsic optical bistability is observed in both, green & red upconversion bands with the increase and decrease in power of NI...
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2021
The present study elucidates the reinvestigation of the photophysical behavior of 3-aminobenzoic ... more The present study elucidates the reinvestigation of the photophysical behavior of 3-aminobenzoic acid (3ABA) in solvents of different polarities using the steady-state spectroscopic techniques. Kamlet-Taft and Catalan solvatochromic models have been used to analyze the solvatochromic changes in neat solvents. The hydrogen bond donating ability of the solvent was found to be the main parameter affecting the spectral behavior of 3ABA. The solvatochromic characteristics of 3ABA have also been examined in binary solvent mixtures viz. acetonitrile (ACN)-methanol (MeOH) and benzene (BEN)-MeOH using the concept of preferential solvation. The preferential solvation of 3ABA shows unusual behavior for BEN-MeOH binary mixture and described unnoticed sigmoidal behavior in the ground state and synergistic impact in the excited state. Besides, the 3ABA was studied theoretically by quantum chemical calculations using (HF) Hartree-Fock and (DFT/B3LYP) density functional theories and its electronic absorption bands have been assigned by time-dependent density functional theory (TD-DFT). The effect of solvents on 3ABA was considered using a IEF-PCM-TDDFT (integral equation formalism of the polarizable continuum model- TDDFT) method. Thus, the theoretical results were found to be closer to the experimental results.
The Journal of Physical Chemistry C, 2021
The Molybdenum disulfide nanosheets (MoS2-NSs) thin films has received increasing attention recen... more The Molybdenum disulfide nanosheets (MoS2-NSs) thin films has received increasing attention recently due to their versatile multi functionality including catalytic properties, photoluminescence and flexibility, which suggests their future, uses for biomedical applications. However, there are no studies in detail related with biocompatibility of MoS2 thin sheets. Here, weevaluated the dose-dependent effects of MoS2-NSs on cell viability (MTT assay) and release of lactate dehydrogenase (LDH) into culture media using MG-63 cells, as well as haemolysis, hematological, serum biochemical, antioxidants and histopathological parameters in Swiss albino mice. The MoS2-NSs was synthesized via facile hydrothermal method and characterized using XRD, Raman, SEM, TEM and HRTEM. The in vitro study results suggest that at lower concentration MoS2-NSs does not causes any toxicity. The lethal dose (LD50) was evaluated by intraperitoneal administration with different concentrations and estimated as ~1....
Ceramics International, 2020
Abstract The multimodal [Upconversion (UC), Downshifting (DS) and Quantum cutting (QC)] behaviour... more Abstract The multimodal [Upconversion (UC), Downshifting (DS) and Quantum cutting (QC)] behaviour of Tm3+/Yb3+ co-doped YTaO4 ceramic material is investigated extensively. The samples are prepared by solid-state reaction method at two different temperatures (at 1573 and 1723 K) and their structural and optical properties are compared with each other. The effect of synthesis temperature as well as doping, on crystal phase was analysed via X-ray diffraction measurements. Particles shape and size are investigated through scanning electron microscopy images. The structural behaviour is further verified through vibrational structural study of material via FTIR measurements. This shows similar structural changes as observed in XRD patterns of the samples prepared at two different temperatures. The optical band gap of YTaO4 is nearly 4.8 eV at both the temperatures. Intense blue (476 nm), red (648 nm) and NIR (802 nm) peaks are observed in UC emission spectra of Tm3+/Yb3+ co-doped YTaO4 ceramic on excitation with 980 nm. The blue UC emission is suitable for display devices. The UC emission intensity increases significantly when sample is prepared at higher temperature (1723 K). Addition of Bi3+ ion further enhances the overall UC emission intensity due to change in environment around the activator ion. On excitation with UV radiation (λExc = 284 nm), YTaO4: 1 Tm3+ produces intense DS emission at 454 nm (blue region) due to energy transfer from charge transfer band of [TaO4]3- to Tm3+ ion. The sample synthesized at 1723 K shows better DS emission. One interesting result is that addition of Bi3+ ion enhances the DS emission due to formation of metal-metal charge transfer band. We have also observed the quantum cutting phenomenon in which self-activated blue photon is converted into two or more NIR photons. The efficiency of quantum cutting emission increases significantly in presence of Bi3+ ion and shows strong, intense NIR emission through CET. Thus, the multimodal behaviour of Tm3+/Yb3+/Bi3+ doped YTaO4 makes them a suitable candidate for a spectral converter that can be used in display and solar cell devices.
![Research paper thumbnail of Excitation Energy Transfer/Migration between Tris(8-hydroxyquinoline) Aluminum and Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] in Chloroform](https://attachments.academia-assets.com/88515900/thumbnails/1.jpg)
](The Journal of Physical Chemistry C, 2020
Excitation energy transfer/migration between fluorescent electron transport molecule: Tris-(8hydr... more Excitation energy transfer/migration between fluorescent electron transport molecule: Tris-(8hydroxyquinoline) aluminium (AlQ3, donor) and fluorescent hole transport polymer: Poly [2methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV, acceptor) were studied in chloroform solution at room temperature using steady-state and time-domain fluorescence measurements. The blend of this pair widely used in the fabrication of organic light-emitting diode. The considerable overlap integral between the emission spectrum of donor and absorption spectrum of acceptor indicates high donor-acceptor interaction and the effective enhancement of the acceptor fluorescence along with a decrease in fluorescence intensity of donor by exciting the donor states characterized the excitation energy transfer between them. Relatively faster decay of
Dyes and Pigments, 2020
A new class of D-A type intramolecular charge transfer (ICT) fluorescent probe, ICU has been desi... more A new class of D-A type intramolecular charge transfer (ICT) fluorescent probe, ICU has been designed and synthesized. The solvatochromic behavior, anion interaction and morphological features of the probe have been studied in detail. The molecular probe upon interaction with different class of anions showed good sensitivity for F and CN anions in organic medium with high detection limit and rapid response time. The time dependent fluorescence studies suggested about the dynamic and static fluorescence quenching with F and CN anions. The scanning electron microscopy (SEM) and diffraction light scattering (DLS) experiments have been performed to understand the morphological behavior and particle size of the probe to distinguish both anions. Upon interaction with F and CN the morphology of probe reveals a clear shape reconstruction from the initial aggregated spherical ball shape to fine leaf like and dumbbell like structures, respectively by disaggregation to form minimum energy structures. The photophysical and theoretical (DFT) studies all together suggested about the charge transfer process from imidazole (donor, D) to coumarin (acceptor, A) unit. The probe has been also utilized to detect the anions on test paper strips. The mechanism of interaction between probe and both the anions has been confirmed by 1 HNMR and HRMS spectral data analysis.
ACS Omega, 2019
The present study demonstrates the near-field effect of silver nanostructure island films (SNIFs)... more The present study demonstrates the near-field effect of silver nanostructure island films (SNIFs) on the photophysics and exited-state dynamics of quinine sulphate (QS) and its di-cation (QSD), doped in polyvinyl alcohol (PVA) films. The results indicate a nearly 3.8-fold enhancement in absorption and 4000-fold enhancement in fluorescence in SNIF-coated QS-doped PVA films, whereas only twofold enhancement in absorption and sevenfold enhancement in fluorescence intensity are found in SNIF-coated QSD-doped PVA films. However, an increase in photostability and a decrease in decay time have been observed in both the SNIF-coated films as compared to their uncoated forms. Further, a decrease in the magnitude of the edge excitation red shift in emission spectra along with a red shift in the L a band and a rise in the intensity of the L b band of excitation is observed in SNIF-coated QSD films because of strong coupling of the L b band with the surface plasmons of silver nanoparticles. Moreover, X-ray photoelectron spectroscopic measurement of silver nanoparticle-coated QS−PVA films shows no change in 3d 3/2 and 3d 5/2 transitions of silver, whereas the decrease in energy in these silver transitions in the QSD−PVA system is observed as compared to silver nanoparticle-coated PVA films. These results indicate the formation of a field-governed radiating plasmon and plasmon-coupled unified fluorophore system, respectively. This affects the photophysics of both of the molecules by plasmonic coupling of the Frank−Condon state, solvent relaxation state, and charge-transfer state by different orders of magnitude.
Applied Organometallic Chemistry, 2018
A new series of triorganotin(IV) complexes of sparfloxacin (HL) having general formula R 3 SnL (w... more A new series of triorganotin(IV) complexes of sparfloxacin (HL) having general formula R 3 SnL (where L is the monoanion of sparfloxacin (HL) and R = Me (1)/n-Bu (2)/Ph (3)/Cy (4)) have been synthesized and characterized by elemental analysis, IR, NMR (1 H, 13 C, 119 Sn), 2D-HETCOR, ESI-MS and UV-Vis studies. These investigations suggest that, in these 1:1 monomeric derivatives the sparfloxacin ligand acts as monoanionic bidentate coordinating through the O carboxylate and O pyridone , and the polyhedron around tin is intermediate between pseudotetrahedral and cis-trigonal bipyramidal, with O pyridone and two organic groups in equatorial plane and the carboxylate oxygen and the third organic group in axial positions. The proposed structures have been validated by density functional theory (DFT) based quantum chemical calculations at B3LYP/6-31G(d,p)/Def2-SVP(Sn) level of theory. A detailed electronic structure calculations were performed at this level of theory to calculate atomic charges at the selected atoms, molecular electrostatic potential (MEP) map to assign sites on the surface of the molecules, the selected conceptual-DFT based global reactivity descriptors to obtain an insight into the structure and reactivity behaviour, and the frontier molecular orbital analysis to analyze the nature of frontier orbitals. All the complexes were screened for their in vitro antibacterial activity against two Gram-positive and five Gram-negative bacterial strains. All the complexes exhibited promising antibacterial activity as compared to sparfloxacin against all the chosen strains.
Biosensors & bioelectronics, Jan 15, 2018
Highly fluorescent nitrogen doped carbon quantum dots (NCQDs) were synthesized using microwave as... more Highly fluorescent nitrogen doped carbon quantum dots (NCQDs) were synthesized using microwave assisted green method. It was characterized by Transmission Electron Microscopy (TEM), FTIR, UV-Visible absorption and Photoluminiscence (PL) techniques. The NCQDs were immobilized with an enzyme named quinolinate phoshphoribosyl transferase (QPRTase). The NCQDs immobilized by QPRTase was used as a fluorescent bioprobe for the selective detection of endogenous neurotoxin quinolinic acid (QA) whose elevated level in serum is marker of many neurological disorders such as Alzheimer's, Huntington's and HIV associated dementia (HAD) as well as deficiency of vitamin B6. Steady state PL studies were carried out to measure the PL response of the fabricated fluorescent bioprobe as a function of QA concentrations in human serum samples. This probe was found applicable in linear range [3.22-51µM] with the limit of detection ~ 6.51µM. It has desirable sensitivity ~ (0.02340±0.0001) µM-1, excel...
Sensors and Actuators B: Chemical, 2017
Main Group Metal Chemistry, 2016
The quantum-chemical calculations based on density functional theory (DFT) have been performed on... more The quantum-chemical calculations based on density functional theory (DFT) have been performed on the diphenyltin(IV) derivative of glycyl-phenylalanine (H
Journal of Chemical Sciences, 2015
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 5, 2016
Study of copper complex of creatinine and urea is very important in life science and medicine. In... more Study of copper complex of creatinine and urea is very important in life science and medicine. In this paper, spectroscopic and structural study of a newly synthesized heteroligand complex of copper with creatinine and urea has been discussed. Structural studies have been carried out using DFT calculations and spectroscopic analyses were carried out by FT-IR, Raman, UV-vis absorption and fluorescence techniques. The copper complex of creatinine and the heteroligand complex were found to have much increased water solubility as compared to pure creatinine. The analysis of FT-IR and Raman spectra helps to understand the coordination properties of the two ligands and to determine the probable structure of the heteroligand complex. The LIBS spectra of the heteroligand complex reveal that the complex is free from other metal impurities. UV-visible absorption spectra and the fluorescence emission spectra of the aqueous solution of Cu-Crn-urea heteroligand complex at different solute concen...
Nanoscale, 2015
Coupling of nano-structure metal surface plasmons with organic molecule excitons can improve the ... more Coupling of nano-structure metal surface plasmons with organic molecule excitons can improve the spectral and charge transport properties of electro-luminescent devices.
The Journal of Physical Chemistry C, 2011
Density functional theory calculations in electronic structure studies of n-Bu2SnL2 (where L is t... more Density functional theory calculations in electronic structure studies of n-Bu2SnL2 (where L is the monoanion of chlordiazepoxide (LH), a benzodiazepine derivative with hypnotic action) have been reported using the Gaussian09 software. The molecular geometries of LH and tetrahedral n-Bu2SnL2 have been optimized at B3LYP/6-31G(d,p) and B3LYP/ 6-31G(d,p)/Def2-SVP(Sn) level of theory, respectively. Harmonic vibrational frequencies are computed at the same level of theory to find the true potential energy surface minima. The effect of functional, basis set and computational cost is analyzed. The various geometrical and thermochemical parameters have been obtained in gas phase and in the solvent. The atomic charges at all the atoms are calculated using Mulliken population analysis, Hirshfeld population analysis and natural population analysis. The charge distribution within the studied complex is explained on the basis of molecular electrostatic potential maps, and conceptual-DFT based g...
Journal of Photochemistry and Photobiology A: Chemistry, 2018
Serotonin (5-HT) is an important monoamine neurotransmitter that plays a vital role in the regula... more Serotonin (5-HT) is an important monoamine neurotransmitter that plays a vital role in the regulation of various cognitive and behavioural functions including sleep, mood, pain, depression, anxiety, aggression, learning etc. From the nanotoxicity and neurotoxicity point of view, interaction studies between serotonin and nanoparticles are highly essential to develop an indispensable understanding on the effect of nanoparticles on monoamine neurotransmitters. In the present work, steady-state and time-domain fluorescence measurements were carried out along with binding energy measurements through X-ray photoelectron spectroscopic (XPS) technique to understand the interaction of 5-HT with silver nanoparticles (AgNPs). The emergence of a week red absorption band and quenching of fluorescence intensity along with decrease in full width half maximum, but not the excited state decay time of 5-HT in the addition of AgNPs suggest the formation of a non-fluorescent complex in the ground state that indicates static quenching along with radiative energy transfer among them. This is also confirmed by the low energy shift of Ag transition in 3 d 3/2 and 3 d 5/2 in XPS measurements and a coupling of L b transition with the surface plasmons of AgNPs in the excitation spectra. The obtained thermodynamic parameters from the fluorescence quenching reveal the nature of interaction between 5-HT and AgNPs is hydrophobic. The increase in binding constant with increasing temperature suggested an enhancement in the strength of this interaction due to rise in the mobility of the molecules and hence increases the sensitivity and association of 5-HT with AgNPs.
Chemical Physics, 2008
Molecular orbital calculations reveal that the keto tautomer of HOCHCHNHNCHz, unlike the enol, do... more Molecular orbital calculations reveal that the keto tautomer of HOCHCHNHNCHz, unlike the enol, does not represent a minimum in the ground state proton transfer potential. Excitation to the first excited singlet or triplet state leads to a rapid and barrierless transfer to the keto which becomes strongly preferred. Similar conclusions apply to a larger system with a full aromatic ring appended.
Optical Materials, 2021
This work reports the green to red color tunable upconversion emission in a newly synthesized Ho3... more This work reports the green to red color tunable upconversion emission in a newly synthesized Ho3+/Yb3+ codoped YV0.75Ta0.25O4 phosphor, prepared by solid-state reaction (SSR) method. The crystal phase formation has been confirmed by X-Ray diffraction analysis. The Fourier transform infrared (FTIR) spectrum show bands at different frequencies due to V-O and Ta-O, and found to play a vital role in relaxation (radiative and non-radiative) processes. The synthesized phosphor sample show intense upconversion (UC) emission in green (∼539 nm), red (∼659 nm) and in near infrared (NIR∼ 754 nm) regions on 980 nm laser excitation. These bands appear as a result of (5F4+5S2→5I8), (5F5→5I8) and (5F4+5S2→5I7) transitions of Ho3+ ion, respectively. The tunability in color from green to orange-red is observed on varying the pump power of NIR laser (980 nm excitation). The intrinsic optical bistability is observed in both, green & red upconversion bands with the increase and decrease in power of NI...
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2021
The present study elucidates the reinvestigation of the photophysical behavior of 3-aminobenzoic ... more The present study elucidates the reinvestigation of the photophysical behavior of 3-aminobenzoic acid (3ABA) in solvents of different polarities using the steady-state spectroscopic techniques. Kamlet-Taft and Catalan solvatochromic models have been used to analyze the solvatochromic changes in neat solvents. The hydrogen bond donating ability of the solvent was found to be the main parameter affecting the spectral behavior of 3ABA. The solvatochromic characteristics of 3ABA have also been examined in binary solvent mixtures viz. acetonitrile (ACN)-methanol (MeOH) and benzene (BEN)-MeOH using the concept of preferential solvation. The preferential solvation of 3ABA shows unusual behavior for BEN-MeOH binary mixture and described unnoticed sigmoidal behavior in the ground state and synergistic impact in the excited state. Besides, the 3ABA was studied theoretically by quantum chemical calculations using (HF) Hartree-Fock and (DFT/B3LYP) density functional theories and its electronic absorption bands have been assigned by time-dependent density functional theory (TD-DFT). The effect of solvents on 3ABA was considered using a IEF-PCM-TDDFT (integral equation formalism of the polarizable continuum model- TDDFT) method. Thus, the theoretical results were found to be closer to the experimental results.
The Journal of Physical Chemistry C, 2021
The Molybdenum disulfide nanosheets (MoS2-NSs) thin films has received increasing attention recen... more The Molybdenum disulfide nanosheets (MoS2-NSs) thin films has received increasing attention recently due to their versatile multi functionality including catalytic properties, photoluminescence and flexibility, which suggests their future, uses for biomedical applications. However, there are no studies in detail related with biocompatibility of MoS2 thin sheets. Here, weevaluated the dose-dependent effects of MoS2-NSs on cell viability (MTT assay) and release of lactate dehydrogenase (LDH) into culture media using MG-63 cells, as well as haemolysis, hematological, serum biochemical, antioxidants and histopathological parameters in Swiss albino mice. The MoS2-NSs was synthesized via facile hydrothermal method and characterized using XRD, Raman, SEM, TEM and HRTEM. The in vitro study results suggest that at lower concentration MoS2-NSs does not causes any toxicity. The lethal dose (LD50) was evaluated by intraperitoneal administration with different concentrations and estimated as ~1....
Ceramics International, 2020
Abstract The multimodal [Upconversion (UC), Downshifting (DS) and Quantum cutting (QC)] behaviour... more Abstract The multimodal [Upconversion (UC), Downshifting (DS) and Quantum cutting (QC)] behaviour of Tm3+/Yb3+ co-doped YTaO4 ceramic material is investigated extensively. The samples are prepared by solid-state reaction method at two different temperatures (at 1573 and 1723 K) and their structural and optical properties are compared with each other. The effect of synthesis temperature as well as doping, on crystal phase was analysed via X-ray diffraction measurements. Particles shape and size are investigated through scanning electron microscopy images. The structural behaviour is further verified through vibrational structural study of material via FTIR measurements. This shows similar structural changes as observed in XRD patterns of the samples prepared at two different temperatures. The optical band gap of YTaO4 is nearly 4.8 eV at both the temperatures. Intense blue (476 nm), red (648 nm) and NIR (802 nm) peaks are observed in UC emission spectra of Tm3+/Yb3+ co-doped YTaO4 ceramic on excitation with 980 nm. The blue UC emission is suitable for display devices. The UC emission intensity increases significantly when sample is prepared at higher temperature (1723 K). Addition of Bi3+ ion further enhances the overall UC emission intensity due to change in environment around the activator ion. On excitation with UV radiation (λExc = 284 nm), YTaO4: 1 Tm3+ produces intense DS emission at 454 nm (blue region) due to energy transfer from charge transfer band of [TaO4]3- to Tm3+ ion. The sample synthesized at 1723 K shows better DS emission. One interesting result is that addition of Bi3+ ion enhances the DS emission due to formation of metal-metal charge transfer band. We have also observed the quantum cutting phenomenon in which self-activated blue photon is converted into two or more NIR photons. The efficiency of quantum cutting emission increases significantly in presence of Bi3+ ion and shows strong, intense NIR emission through CET. Thus, the multimodal behaviour of Tm3+/Yb3+/Bi3+ doped YTaO4 makes them a suitable candidate for a spectral converter that can be used in display and solar cell devices.
The Journal of Physical Chemistry C, 2020
Excitation energy transfer/migration between fluorescent electron transport molecule: Tris-(8hydr... more Excitation energy transfer/migration between fluorescent electron transport molecule: Tris-(8hydroxyquinoline) aluminium (AlQ3, donor) and fluorescent hole transport polymer: Poly [2methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV, acceptor) were studied in chloroform solution at room temperature using steady-state and time-domain fluorescence measurements. The blend of this pair widely used in the fabrication of organic light-emitting diode. The considerable overlap integral between the emission spectrum of donor and absorption spectrum of acceptor indicates high donor-acceptor interaction and the effective enhancement of the acceptor fluorescence along with a decrease in fluorescence intensity of donor by exciting the donor states characterized the excitation energy transfer between them. Relatively faster decay of
Dyes and Pigments, 2020
A new class of D-A type intramolecular charge transfer (ICT) fluorescent probe, ICU has been desi... more A new class of D-A type intramolecular charge transfer (ICT) fluorescent probe, ICU has been designed and synthesized. The solvatochromic behavior, anion interaction and morphological features of the probe have been studied in detail. The molecular probe upon interaction with different class of anions showed good sensitivity for F and CN anions in organic medium with high detection limit and rapid response time. The time dependent fluorescence studies suggested about the dynamic and static fluorescence quenching with F and CN anions. The scanning electron microscopy (SEM) and diffraction light scattering (DLS) experiments have been performed to understand the morphological behavior and particle size of the probe to distinguish both anions. Upon interaction with F and CN the morphology of probe reveals a clear shape reconstruction from the initial aggregated spherical ball shape to fine leaf like and dumbbell like structures, respectively by disaggregation to form minimum energy structures. The photophysical and theoretical (DFT) studies all together suggested about the charge transfer process from imidazole (donor, D) to coumarin (acceptor, A) unit. The probe has been also utilized to detect the anions on test paper strips. The mechanism of interaction between probe and both the anions has been confirmed by 1 HNMR and HRMS spectral data analysis.
ACS Omega, 2019
The present study demonstrates the near-field effect of silver nanostructure island films (SNIFs)... more The present study demonstrates the near-field effect of silver nanostructure island films (SNIFs) on the photophysics and exited-state dynamics of quinine sulphate (QS) and its di-cation (QSD), doped in polyvinyl alcohol (PVA) films. The results indicate a nearly 3.8-fold enhancement in absorption and 4000-fold enhancement in fluorescence in SNIF-coated QS-doped PVA films, whereas only twofold enhancement in absorption and sevenfold enhancement in fluorescence intensity are found in SNIF-coated QSD-doped PVA films. However, an increase in photostability and a decrease in decay time have been observed in both the SNIF-coated films as compared to their uncoated forms. Further, a decrease in the magnitude of the edge excitation red shift in emission spectra along with a red shift in the L a band and a rise in the intensity of the L b band of excitation is observed in SNIF-coated QSD films because of strong coupling of the L b band with the surface plasmons of silver nanoparticles. Moreover, X-ray photoelectron spectroscopic measurement of silver nanoparticle-coated QS−PVA films shows no change in 3d 3/2 and 3d 5/2 transitions of silver, whereas the decrease in energy in these silver transitions in the QSD−PVA system is observed as compared to silver nanoparticle-coated PVA films. These results indicate the formation of a field-governed radiating plasmon and plasmon-coupled unified fluorophore system, respectively. This affects the photophysics of both of the molecules by plasmonic coupling of the Frank−Condon state, solvent relaxation state, and charge-transfer state by different orders of magnitude.
Applied Organometallic Chemistry, 2018
A new series of triorganotin(IV) complexes of sparfloxacin (HL) having general formula R 3 SnL (w... more A new series of triorganotin(IV) complexes of sparfloxacin (HL) having general formula R 3 SnL (where L is the monoanion of sparfloxacin (HL) and R = Me (1)/n-Bu (2)/Ph (3)/Cy (4)) have been synthesized and characterized by elemental analysis, IR, NMR (1 H, 13 C, 119 Sn), 2D-HETCOR, ESI-MS and UV-Vis studies. These investigations suggest that, in these 1:1 monomeric derivatives the sparfloxacin ligand acts as monoanionic bidentate coordinating through the O carboxylate and O pyridone , and the polyhedron around tin is intermediate between pseudotetrahedral and cis-trigonal bipyramidal, with O pyridone and two organic groups in equatorial plane and the carboxylate oxygen and the third organic group in axial positions. The proposed structures have been validated by density functional theory (DFT) based quantum chemical calculations at B3LYP/6-31G(d,p)/Def2-SVP(Sn) level of theory. A detailed electronic structure calculations were performed at this level of theory to calculate atomic charges at the selected atoms, molecular electrostatic potential (MEP) map to assign sites on the surface of the molecules, the selected conceptual-DFT based global reactivity descriptors to obtain an insight into the structure and reactivity behaviour, and the frontier molecular orbital analysis to analyze the nature of frontier orbitals. All the complexes were screened for their in vitro antibacterial activity against two Gram-positive and five Gram-negative bacterial strains. All the complexes exhibited promising antibacterial activity as compared to sparfloxacin against all the chosen strains.
Biosensors & bioelectronics, Jan 15, 2018
Highly fluorescent nitrogen doped carbon quantum dots (NCQDs) were synthesized using microwave as... more Highly fluorescent nitrogen doped carbon quantum dots (NCQDs) were synthesized using microwave assisted green method. It was characterized by Transmission Electron Microscopy (TEM), FTIR, UV-Visible absorption and Photoluminiscence (PL) techniques. The NCQDs were immobilized with an enzyme named quinolinate phoshphoribosyl transferase (QPRTase). The NCQDs immobilized by QPRTase was used as a fluorescent bioprobe for the selective detection of endogenous neurotoxin quinolinic acid (QA) whose elevated level in serum is marker of many neurological disorders such as Alzheimer's, Huntington's and HIV associated dementia (HAD) as well as deficiency of vitamin B6. Steady state PL studies were carried out to measure the PL response of the fabricated fluorescent bioprobe as a function of QA concentrations in human serum samples. This probe was found applicable in linear range [3.22-51µM] with the limit of detection ~ 6.51µM. It has desirable sensitivity ~ (0.02340±0.0001) µM-1, excel...
Sensors and Actuators B: Chemical, 2017
Main Group Metal Chemistry, 2016
The quantum-chemical calculations based on density functional theory (DFT) have been performed on... more The quantum-chemical calculations based on density functional theory (DFT) have been performed on the diphenyltin(IV) derivative of glycyl-phenylalanine (H
Journal of Chemical Sciences, 2015
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, Jan 5, 2016
Study of copper complex of creatinine and urea is very important in life science and medicine. In... more Study of copper complex of creatinine and urea is very important in life science and medicine. In this paper, spectroscopic and structural study of a newly synthesized heteroligand complex of copper with creatinine and urea has been discussed. Structural studies have been carried out using DFT calculations and spectroscopic analyses were carried out by FT-IR, Raman, UV-vis absorption and fluorescence techniques. The copper complex of creatinine and the heteroligand complex were found to have much increased water solubility as compared to pure creatinine. The analysis of FT-IR and Raman spectra helps to understand the coordination properties of the two ligands and to determine the probable structure of the heteroligand complex. The LIBS spectra of the heteroligand complex reveal that the complex is free from other metal impurities. UV-visible absorption spectra and the fluorescence emission spectra of the aqueous solution of Cu-Crn-urea heteroligand complex at different solute concen...
Nanoscale, 2015
Coupling of nano-structure metal surface plasmons with organic molecule excitons can improve the ... more Coupling of nano-structure metal surface plasmons with organic molecule excitons can improve the spectral and charge transport properties of electro-luminescent devices.
The Journal of Physical Chemistry C, 2011