Solvent and Rotational Relaxation of Coumarin 153 in a Protic Ionic Liquid Dimethylethanolammonium Formate

The solvent relaxation and orientational dynamics of coumarin 153 (C-153) was investigated in N,N-dimethylethanolammonium formate (DAF) with a variation of temperature. DAF is a protic room-temperature ionic liquid, comprised of nonaromatic cations. Both solvent relaxation and orientational dynamics of C-153 in DAF are linearly well-correlated with the bulk viscosity at different temperatures. We optimized the geometry of DAF using quantum chemical calculations using density functional theory methods. The optimized structure of DAF shows a nonbonded interaction between cation and anion, which suggests that a hydrogen bond is formed between hydrogen atoms attached to the nitrogen atom of the cation with the oxygen atom of the anion in DAF

Tribute to Professor Kankan Bhattacharyya

Tribute to Professor Kankan Bhattacharyy

Interaction of Ionic Liquid with Water in Ternary Microemulsions (Triton X-100/Water/1-Butyl-3-methylimidazolium Hexafluorophosphate) Probed by Solvent and Rotational Relaxation of Coumarin 153 and Coumarin 151

The interaction of ionic liquid with water in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6])/Triton X-100 (TX-100)/H2O ternary microemulsions, i.e., “[bmim][PF6]-in-water” microregions of the microemulsions, has been studied by the dynamics of solvent and rotational relaxation of coumarin 153 (C-153) and coumarin 151 (C-151). The variation of the time constants of solvent relaxation of C-153 is very small with an increase in the [bmim][PF6]/TX-100 ratio (R). The rotational relaxation time of C-153 also remains unchanged in all micremulsions of different R values. The invariance of solvation and rotational relaxation times of C-153 indicates that the position of C-153 remains unaltered with an increase in R and probably the probe is located at the interfacial region of [bmim][PF6] and TX-100 in the microemulsions. On the other hand, in the case of C-151, with an increase in R the fast component of the solvation time gradually increases and the slow component gradually decreases, although the change in solvation time is small in comparison to that of microemulsions containing common polar solvents such as water, methanol, acetonitrile, etc. The rotational relaxation time of C-151 increases with an increase in R. This indicates that with an increase in the [bmim][PF6] content the number of C-151 molecules in the core of the microemulsions gradually increases. In general, the solvent relaxation time is retarded in this room temperature ionic liquid/water-containing microemulsion compared to that of a neat solvent, although retardation is very small compared to that of the solvent relaxation time of the conventional solvent in the core of the microemulsions

Arginine-Based Ionic Liquid in a Water–DMSO Binary Mixture for Highly Efficient CO₂ Capture from Open Air

Carbon dioxide (CO2) absorption in the open air is essential for reducing the atmospheric CO2 concentration and averting global climate change. The high CO2 absorption capacity of amino acid-based ionic liquids (AAILs) makes them a more plausible carbon capture system than conventional amine solutions. We synthesized an ionic liquid derived from arginine, triethylmethylammonium argininate ([N2221][Arg]), and utilized it to capture pure CO2 and CO2 from the open air. Although AAILs have some notable advantages for CO2 capture, like low toxicity, biocompatibility, and superior stability, they also have important drawbacks, such as high viscosity and low mass transfer. Now, in order to resolve these problems, we blended [N2221][Arg] with a binary mixture of water and dimethyl sulfoxide (DMSO) with a variable volume ratio. On increasing the volume of DMSO in water–DMSO binary mixtures, the CO2 uptake gradually decreased, reaching a minimum in a pure DMSO medium and the maximum in an aqueous solution, which was obtained from the vapor–liquid equilibrium (VLE) experiment. We applied this [N2221][Arg] ionic liquid in the aqueous medium to absorb CO2 from direct air. The open-air CO2 uptake value was approximately 1.01 mol/mol in the aqueous solution of arginine-based ionic liquid; to the best of our knowledge, this is the first report of such an ionic liquid system having high CO2 absorption efficiency under ambient air. We believe that our system will be advantageous for removing CO2 from highly polluted air

Comparative Fluorescence Resonance Energy-Transfer Study in Pluronic Triblock Copolymer Micelle and Niosome Composed of Biological Component Cholesterol: An Investigation of Effect of Cholesterol and Sucrose on the FRET Parameters

The formation of pluronic triblock copolymer (F127)–cholesterol-based niosome and its interaction with sugar (sucrose) molecules have been investigated. The morphology of F127–cholesterol -based niosome in the presence of sucrose has been successfully demonstrated using dynamic light scattering (DLS) and transmission electron microscopic (TEM) techniques. The DLS profiles and TEM images clearly suggest that the size of the niosome aggregates increases significantly in the presence of sucrose. In addition to structural characterization, a detailed comparative fluorescence resonance energy transfer (FRET) study has been carried out in these F127-containing aggregates, involving coumarin 153 (C153) as donor (D) and rhodamine 6G (R6G) as an acceptor (A) to monitor the dynamic heterogeneity of the systems. Besides, time-resolved anisotropy and fluorescence correlation spectroscopy measurements have been carried out to monitor the rotational and lateral diffusion motion in these F127–cholesterol-based aggregates using C153 and R6G, respectively. During the course of FRET study, we have observed multiple time constants of FRET inside the F127–cholesterol-based niosomes in contrast with the F127 micelle. This corresponds to the presence of more than one preferential donor–acceptor (D–A) distance in niosomes than in F127 micelle. FRET has also been successfully used to probe the effect of sucrose on the morphology of F127–cholesterol-based niosome. In the presence of sucrose, the time constant of FRET further increases as the D–A distances increase in sucrose-decorated niosome. Finally, the excitation-wavelength-dependent FRET studies have indicated that as the excitation of donor molecules varies from 408 to 440 nm the contribution of the faster rise component of the acceptor enhances considerably, which clearly establishes the dynamics heterogeneity of both systems. Our findings also indicate that FRET is completely intravesicular in nature in these block copolymer-cholesterol-based aggregates

Direct Observation of Solvation Dynamics in an Aqueous Reverse Micellar System Containing Silver Nanoparticles in the Reverse Micellar Core

In this work we have reported the synthesis of silver nanoparticles in aqueous AOT (dioctylsulfosuccinate, sodium salt) n-heptane reverse micelles and then carried out the study of solvation dynamics keeping the system unaltered, i.e., inside the reverse micelles containing silver nanoparticles. Solvation dynamics and anisotropy studies showed that they were highly affected and became slower in reverse micelles containing silver nanoparticle in comparison to the pure reverse micellar system

Probing the Interaction of 1-Ethyl-3-methylimidazolium Ethyl Sulfate ([Emim][EtSO₄]) with Alcohols and Water by Solvent and Rotational Relaxation

The effect of the addition of cosolvents in the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium ethyl sulfate ([Emim][EtSO4]) was probed by the solvent and rotational relaxation studies of coumarin 153 in neat ionic liquid [Emim][EtSO4] and [Emim][EtSO4]−cosolvent mixtures by using steady-state and time-resolved fluorescence spectroscopy. With gradual addition of cosolvents in the RTIL, both the average solvation time and rotational relaxation times gradually decrease. Addition of cosolvents in the IL decreases the viscosity of the medium. We have optimized the geometry of [Emim][EtSO4] and [Emim][EtSO4]−cosolvent mixtures by using quantum chemical calculations using density functional theory methods, which show the formation of hydrogen bond between cosolvents with [Emim][EtSO4]. With addition of the same amount of alcohols in neat [Emim][EtSO4], the rotational relaxation time decreases more compared to the addition of the same amount of water

Unveiling the Interaction of Duplex DNA with Graphene Oxide in the Presence of Two Diverse Binders: A Detailed Photophysical Study

Coupling of biomolecules with nanomaterials has drawn immense attraction because of the improved synergistic properties, functions, and biocompatible nature. Thus, this process manifests its important role and fascinating potential in various nanobiotechnogical, biomedical, biosensing, and imaging applications. In this work, fundamental understanding of the interfacial properties and the interaction of double-stranded DNA (dsDNA) with graphene oxide (GO) has been systematically investigated by employing two different DNA-binding probes. Our results suggest that the unusual adsorption of duplex DNA onto the GO surface has been facilitated due to the partial deformation of the helical structure of DNA as evident from circular dichroism (CD) spectroscopy. Depending on the location of the probes inside the DNA helix, the photophysical properties of the dye-bound DNA in the presence of GO have been changed. Interestingly, the translational diffusion and rotational motion of the minor groove-binding probe, 4'-6-diamidino-2-phenylindole (DAPI) bound DNA, have been significantly altered with the addition of GO. In contrast, efficient electron transfer may occur from the DNA-intercalated ethidium bromide (EB) to GO with a time constant of ∼300 fs as evident from the ultrafast time-resolved measurement. Conclusively, a basic understanding of the interaction mechanism and dynamics of two different probes inside DNA and at the DNA-GO interface opens up new windows for the future development of various nano/bio applications

Nanocavity Effect On Photophysical Properties Of Colchicine: A Proof by Circular Dichroism Study and Picosecond Time-Resolved Analysis in Various Reverse Micellar Assemblies

In August 2009, colchicine won Food and Drug Administration (FDA) approval in the United States as a stand-alone drug for the treatment of acute flares of gout and familial Mediterranean fever. Recently, it is now the center of attraction in medicinal research. In this present paper, we have employed two other analogues of colchicine for exploring the photophysical properties inside nanocavity environment in details. Here we have a series of interesting results that have interesting similarity with the colchinoid–tubulin interaction. To monitor fluorescence properties of colchinoids, we have used absorption, emission, and time-resolved spectroscopy and to monitor structural properties we have measured circular dichroism. Steady-state anisotropy and dynamic light scattering results give an idea about the microenvironment sensed by the colchinoids molecules. A sharp increment for colchicine, very small increment for isocolchicine and no increment for colcemid in fluorescence and different circular dichroism (CD) spectra of all of these colchinoids upon embedment inside nanocavity of reverse micelle made a supposition that all these changes of fluorescence properties and CD results of colchinoids is not solely due to viscosity effect but also the constraint, that is, very narrow space to spread over, given by the nanocavity of reverse micelle. Moreover, we have noticed that the B ring of the colchinoids also have a pronounced effect on the interaction nature as well as on conformational change of these compounds after entrapment