The fascinating aspect of excitation dependent fluorescence in carbon nanodots has led to several hypotheses, starting from particle size distribution the presence different emissive states and even sluggish solvent relaxation around nanodot. In this contribution we provide definitive evidence for involvement discrete multiple electronic emission nanodots. types aggregates at very dilute solutions used ensemble spectroscopy, where intensity shows linear dependence with absorbance, is origin...

Despite numerous efforts, there are several fundamental ambiguities regarding the photoluminescence of carbon dots (CDs). Spectral shift measurements display characteristic both π-π* and n-π* transitions for main absorption or excitation band at ∼350 nm, contrary to common assignment exclusive transition. Additionally, generally perceived core-state transition ∼250 involving sp2-networked carbogenic domains shielded from external environments, needs be reassessed because it fails explain...

Solvent polarity and temperature effect on the photophysical properties of two 1,2-benzopyrone dyes, namely, coumarin-152 (C152) coumarin-481 (C481), have been investigated using steady-state time-resolved fluorescence measurements. In nonpolar (NP) solvents (e.g., hexane, cyclohexane, methylcyclohexane, 2-methylpentane, 3-methylpentane), Stokes' shifts (Δν̄) lifetimes (τf) for both dyes are unexpectedly lower. Excluding NP solvents, all other Δν̄ correlates linearly with solvent function,...

The femtosecond fluorescence upconversion technique is used to study the effect of viscosity on excited state relaxation dynamics an amyloid fibril sensor, thioflavin-T, in different solvent media. decay all solvents seen be dependent emission wavelength. From constructed time-resolved spectra, it that present system shows dynamic Stokes' shift as well appreciable increase spectral width with time. These temporal characteristics spectra have been assigned formation a new emissive species...

Photophysical properties of coumarin-120 (C120; 7-amino-4-methyl-1,2-benzopyrone) dye have been investigated in different solvents using steady-state and time-resolved fluorescence picosecond laser flash photolysis (LFP) nanosecond pulse radiolysis (PR) techniques. C120 shows unusual photophysical nonpolar compared to those other moderate higher polarities. Where the Stokes shifts (Δν̄=ν̄abs−ν̄fl), quantum yields (Φf), lifetimes (τf) show more or less linear correlation with solvent polarity...

The fundamental process of bond twisting that is responsible for the fluorescence sensing activity most extensively used amyloid fibril sensor, Thioflavin T, has been revealed using ultrafast time-resolved spectroscopy. From wavelength-dependent decay kinetics and subsequently constructed emission spectra (TRES), dynamic Stokes shift change in spectral width were observed. These results are rationalized on basis proposition that, following photoexcitation, T undergoes to form a twisted...

Photophysical properties and ultrafast excited state torsional dynamics of the protein binding dye, Thioflavin-T, have been investigated in a nanoconfined water pool reverse micelles using both steady-state fluorescence femtosecond upconversion technique. It is seen that due to confined environment micelle, yield Thioflavin-T dramatically enhanced approximately 250-fold as compared bulk water. The decreases nonlinearly with increase size micelles. Fluorescence lifetime also decrease sharply...

Nine complexes of the type [Ru(N−N)2(BPG)]Cl2 1−4, [Ru(N−N)(BPG)2]Cl2 5−8, and [Ru(BPG)3]Cl2 9 where N−N is 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq), dipyrido[3,2-a:2′,3′-c]phenazine (dppz), which incorporates bipyridine−glycoluril (BPG-4b,5,7,7a-tetrahydro-4b,7a-epiminomethanoimino-6H-imidazo[4,5-f][1,10]phenanthroline-6,13-dione) as ancillary ligand, have been synthesized characterized. These with peripheral polypyridyl ligands ability to...

Dynamic Stokes' shift measurements using coumarin 153 as the fluorescence probe have been carried out to study solvation dynamics in two nonionic micelles, viz., triton-X-100 (TX-100) and triton-X-165 (TX-165). In both solvent relaxation is biexponential nature. While fast time tau(s1) seen be almost similar for slow tau(s2) found appreciably smaller TX-165 than TX-100 micelle. light scattering indicate that micelles are substantially size of TX-100. Assuming core expected from chemical...

The temperature effect on solvation dynamics has been investigated in two neutral micelles, namely, Triton X-100 (TX100) and Brij-35 (BJ-35), using dynamic fluorescence Stokes' shift method, to explore the role of micellar size hydration process. In TX-100, C(t) is not only very strong but shows an unusual inversion around 298 K. On contrary, for BJ-35 micelle, that significant. Present results micelles have rationalized basis dependent changes hydration, which are reported be large TX-100...

The influence of confinement in the supramolecular β-cyclodextrin nanocavity on excited state torsional dynamics amyloid fibril sensor, Thioflavin-T, is explored using subpicosecond fluorescence up-conversion spectroscopy. In presence β-cyclodextrin, emission intensity and lifetime Thioflavin-T significantly increases, indicating effect nanocage photophysical behaviour dye. Detailed time-resolved studies show an appreciable dynamic Stokes' shift for dye nanocavity. Analysis area normalized...

Photoinduced electron transfer (ET) between coumarin dyes and aromatic amines has been investigated in Triton-X-100 micellar solutions the results have compared with those observed earlier homogeneous medium. Significant static quenching of fluorescence due to presence high concentration around fluorophore micelles steady-state studies. Time-resolved studies nanosecond resolutions mostly show dynamic part for excited by amine quenchers. A correlation rate constants, estimated from...

Photophysical studies on coumarin-7 (C7) dye in different protic solvents reveal interesting changes the properties of increasing solvent polarity (Deltaf; Lippert-Mataga parameter) beyond a critical value. Up to Deltaf approximately 0.31, photophysical follow good linear correlations with Deltaf. For > however, properties, especially fluorescence quantum yields (Phi(f)), lifetimes (tau(f)) and nonradiative rate constants (k(nr)), undergo large deviations from above linearity, suggesting an...

An ultrafast intramolecular bond twisting process is known to be the responsible mechanism for sensing activity of extensively used amyloid fibril sensor thioflavin T (ThT). However, it not yet which one two possible single bonds in ThT actually involved process. To resolve this fundamental issue, derivatives have been designed and synthesized subsequently their photophysical properties studied different solvents. It understood from present study that rotation around central C-C bond, C-N...

Fluorescence readouts for an amyloid fibril sensor critically depend on its molecular interaction and local environment offered by the available structural motifs. Here we employ polarized points accumulation imaging in nanoscale topography with intramolecular charge transfer probes transiently bound to fibrils investigate organization of nanostructures probe binding configurations. Besides in-plane (θ ≈ 90°) mode surface parallel long axis, also observed a sizable population over 60%...

Molecular-level interactions among lipids, cholesterol, and water dictate the nanoscale membrane organization of lipid bilayers into liquid-ordered (Lo) liquid-disordered (Ld) phases, characterized by different polarities orders. Generally, solvatochromic dyes easily discriminate polarity difference between Lo Ld whereas molecular flippers rotors show distinct photophysics depending on order. Despite progress in single-molecule spectral imaging orientation mapping, direct experimental proof...

Photoinduced intermolecular electron transfer interaction between coumarin dyes and aromatic amines has been investigated in sodium dodecyl sulphate micellar solutions using steady-state time-resolved fluorescence quenching measurements. Steady-state of the by amine quenchers always shows a positive deviation from linear Stern–Volmer relationship, which arises due to localized high quencher concentrations at Stern layer. In measurements, analysis decays following kinetics model assuming...

The salt induced sphere-to-rod growth in the micelles of PEO-PPO triblock copolymers, Pluronic P123 (EO(20)PO(70)PEO(20)) and P103 (EO(16)PO(61)PEO(16)), has been studied by dynamic light scattering (DLS), viscometry, small angle neutron (SANS) techniques. observed micellar growths are found to be time dependent have a strong variation their rate with changing anion type copolymer composition. increases rather significantly an increase water structure making abilities anions along Hofmeister...

Interaction of cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), with pluronics F88 (EO(103)-PO(39)-EO(103)) and P105 (EO(37)-PO(56)-EO(37)) micelles its effect on modulating the location an anionic solute in mixed have been investigated using time-resolved fluorescence small angle neutron scattering (SANS) studies. SANS results indicate formation pluronic-CTAB supramolecular assemblies, which hydrophobic chains CTAB occupy core pluronic micelle while positively charged head...

The sphere-to-rod growth behavior of the triblock copolymer EO(20)PO(70)EO(20) (P123) micelles has been studied in an aqueous medium by dynamic light scattering (DLS), viscometry, and small angle neutron (SANS) techniques. Unlike other pluronic systems, P123 solutions show a time dependent micellar on approaching their cloud points. rate increases with increase temperature, but quite interestingly, it improves rather dramatically when are subjected to heat cycling, i.e., heating them phase...

Fluorescence correlation spectroscopy (FCS) of photoinduced electron transfer (PET) between the dye Atto-655 and amino acid tryptophan has been extensively used for studying fast conformational dynamics small disordered peptides proteins. However, a precise understanding quenching mechanism its exact rates that would explain ensemble as well single-molecule results is still lacking. In this contribution, general unified model intermolecular PET developed, which involves ground-state complex...

Dynamic Stokes' shift and fluorescence anisotropy measurements using coumarin-153 (C153) coumarin-151 (C151) as the probes have been carried out in aqueous poly(ethylene oxide)20-poly(propylene oxide)70-poly(ethylene oxide)20 (P123) oxide)100-poly(propylene oxide)100 (F127) block copolymer micelles with an aim to understand water structures dynamics micellar corona region. It has established that reside is indicated regions of P123 F127 are relatively less hydrated than Palisade layers...