Excited-state properties of 6-methoxyflavone in the presence of halide ions in aqueous media

The present work investigated the influence of different halides on the excited state dynamics of 6-methoxyflavone (6MF) in an aqueous solution with steady-state and time-resolved techniques. On successive addition of I¯ and Br¯ ions, the fluorescence (FL) of 6MF quenched significantly, whereas the respective ions do not change the maximum fluorescence band. Fluorescence of 6MF was quenched 66 % by I¯ ions and 34 % by Br¯ ions. In a pure aqueous medium, both the H-bonded: CT and protonated species of 6MF participate in the quenching of FL. The quenching process was categorized by Stern-Volmer (S-V) and Lehrer equations. Quenching parameters such as KSV, KSV-L and kq were higher for I¯ ions than Br¯ ions. The decrease in fluorescence intensity and a reduction in fluorescence lifetime suggested the dynamic nature of quenching by I¯ ions following the electron transfer mechanism. Fluorescence quenching of 6MF has also been observed in the acidic medium in the presence of different halides. Thus, the study reveals that 6MF is responsive towards I¯ ions in a wide range of pH, specifically in a purely aqueous environment (pH~7), hence important for sensing/detection applications.

Selectively probing ferric ions in aqueous environments using protonated and neutral forms of 7-azaindole as a multiparametric chemosensor

7-azaindole (7AI) dimer is a model molecule for DNA study and understanding the mutagenic behavior based on the excited-state proton transfer process in hydrogen-bonded networks. The neutral and protonated forms of 7AI monomer with significant fluorescence (FL) intensity fit the fluorescent sensor strategy to recognize selective metal ions. Out of several metal ions (Fe³⁺, Al³⁺, Fe²⁺, Pb²⁺, Ba²⁺, Ni²⁺, Zn²⁺, Mg²⁺, Ca²⁺, Cu²⁺, Hg²⁺ and Cd²⁺), the absorption, fluorescence and fluorescence lifetime of 7AI in the aqueous medium are selectively sensitive to the ferric (Fe³⁺) ions. The absolute value of absorption intensity increases linearly with concentration of a particular metal ions. FL intensity of both the forms of 7AI decreases gradually with Fe³⁺ ions and trails the linear Stern-Volmer relation. The formation of non-fluorescent complexes was confirmed with Benesi-Hildebrand and Job plots, along with FL and FL decays. The FL lifetime of the protonated form of 7AI, which is 0.83 ± 0.01 ns, is nearly constant with Fe³⁺ ions concentrations, confirming the static quenching mechanism. The limit of detection (LoD) of Fe³⁺ ions over the long range of 16-363 µM for the neutral and protonated forms of 7AI is 0.46 ± 0.02 and 0.49 ± 0.02 µM, respectively, estimated using FL spectra. Additionally, the linear plot of absorbance with Fe³⁺ ions of both the forms of 7AI can also act as a calibration curve with very close LoDs, as obtained by FL spectra. Thus, the multi-parameters-based probe for detecting the Fe³⁺ ions over long-range in real aqueous environments with operational, high sensitivity, fast response (< 5 s), and good selectivity (over 12 metal ions) is undoubtedly a superior approach over other methods.

Spectroscopic Investigation on the Interaction of Direct Yellow-27 with Protein (BSA)

Direct yellow 27 (DY-27) interaction with bovine serum albumin (BSA) was investigated using multi-spectroscopic techniques to understand the toxicity mechanism. Fluorescence quenching of BSA by DY-27 was observed as a result of the formation of a BSA-DY27 complex with a binding constant of 1.19 × 10⁵M^-1and followed a static quenching mechanism with a quenching constant K_svof 7.25 × 10⁴M^-1. The far UV circular dichroism spectra revealed the conformational changes in the secondary structure of BSA in the presence of DY-27. The calculated average lifetime of BSA is 6.04 ns and is nearly constant (5.99 ns) in the presence of dye and supports the proposed quenching mechanism. The change in free energy (ΔG) was calculated to be -28.96 kJ mol^-1and confirmed the spontaneity of the binding process. Further, docking studies have been conducted to gain more insights into the interactions between DY-27 and serum albumin.

Effect of halide ions on the fluorescence properties of 3-aminoquinoline in aqueous medium

Fluorescence (FL) quenching of 3-aminoquinoline (3AQ) by halide ions Cl - Br - and I - has been explored in an aqueous acidic medium using the steady-state and time-domain FL measurement techniques. The halide ions showed no significant change in the absorption spectra of 3AQ in an aqueous acidic medium. The FL intensity is strongly quenched by I - ions and the order of FL quenching by halide ions is I - > Br - > Cl - . The decrease in FL lifetime along with a reduction in FL intensity of 3AQ suggested the dynamic nature of quenching. The obtained value of K SV was 328 M - 1 for I - ions and 119 M - 1 for Br - ions and the value k q was around 1.66 × 10 10 M - 1 s - 1 and 6.02 × 10 9 M - 1 s - 1 , respectively. Thus, the observations suggest that the likely governing mechanism for FL quenching should be an electron transfer process and the involvement of the heavy atom effect.

Solvatochromism and estimation of ground and excited state dipole moments of 6-aminoquinoline

The spectral behaviour of 6AQ was investigated using fluorescence spectroscopy in several polar and non-polar solvents. Both the absorption and fluorescence spectra displayed solvatochromism. The Stokes shift increased significantly with increasing solvent polarity and signifies a more polar excited state with possible change in the excited state (ES) geometry. The involvement of π→π^∗ transition was observed. The ground state (GS) and excited state (ES) dipole moments were determined by the solvatochromic shift method using Bilot-Kawaski, Lippert-Mataga, Kawski-Chamma-Viallet, and Reichardt equations. The experimental value of GS dipole moment matches closely with the theoretical value computed using DFT/B3LYP/6-311G(d,p). The ES dipole moment is higher than the GS dipole moment. Besides, the solvatochromic study reveals that the ES of 6AQ is more polarized than the GS due to intramolecular charge transfer (ICT), possibly aided by a change in the geometry of the molecule in the ES. The influence of the non-specific and specific interactions in the photophysical properties of the titled molecule was analyzed using the Catalan scale. The study shows that 6AQ has reasonable band-gap energy and good CIE chromaticity coordinate in the blue region close to the national television standard committee system (NTSC) for the ideal blue CIE coordinate. Therefore, future research into 6AQ as a source of light-emitting diodes and fluorescent sensors may have potential applications in the field of optoelectronics.

Surface plasmon resonance allied applications of silver nanoflowers synthesized from Breynia vitis-idaea leaf extract

An environmentally friendly, green synthesis process has been adopted to synthesize silver nanoparticles (AgNPs) in an aqueous solution from a new remedial plant. Breynia vitis-idaea leaves act like natural capping and reducing agents. The resulting AgNPs were characterized and analyzed using different characterization techniques, such as UV-Vis spectroscopy, X-ray diffraction, zeta potential, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The UV-Vis absorption spectrum showed high stability and a surface plasmon resonance (SPR) peak around 430 nm. The effects of several processing variables, such as reaction time, temperature, concentration and pH, were analyzed. High temperature and alkaline pH intensify the ability to form flower-shaped AgNPs with enhanced properties. AgNPs were investigated for antibacterial activity against Gram-negative E. coli bacterial strains with a 10 mm zone of inhibition. These AgNPs showed dye degradation up to 88% when an aqueous crystal violet dye solution was mixed with AgNPs as the catalyst. Further, AgNPs alone were effectively used in the detection of hydrogen peroxide (H₂O₂) in an aqueous medium with a LOD (limit of detection) of 21 μM, limit of quantification (LOQ) of 64 μM and a decrease in absorption intensity up to 89%. Based on these results, these AgNPs were effectively used in numerous fields, such as biomedical, water purification, antibacterial and sensing of H₂O₂.

Rapid optical sensor for recognition of explosive 2,4,6-TNP traces in water through fluorescent ZnSe quantum dots

In this report, blue fluorescent zinc selenide quantum dots (ZnSe QDs) were synthesized using 3-mercaptopropionic acid through a direct aqueous route at a lower temperature of 70 °C. The photoluminescence (PL) characteristics of ZnSe QDs have been employed to recognize nitroaromatic compounds, i.e., traces of 2,4,6-TNP (picric acid) in water. The sensing of nitroaromatic compounds was performed via fluorescence techniques. The PL band of ZnSe QDs observed at 490 nm is selectively quenched with an increasing concentration of picric acid in DI water and river water. For the proposed sensing probe, the Stern-Volmer (S-V) plot shows linearity over the range of 2.0 µM-0.25 mM with the detection limit of 12.4 × 10^-6 M without any interference effect of other nitroaromatic compounds. The plausible mechanism of PL quenching is considered as the inner filter effect, based on absorption, PL and PL lifetimes.

Reinvestigation of the photophysics of 3-aminobenzoic acid in neat and mixed binary solvents

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.

Wavefunction Engineering of Type-I/Type-II Excitons of CdSe/CdS Core-Shell Quantum Dots

Nanostructured semiconductors have the unique shape/size-dependent band gap tunability, which has various applications. The quantum confinement effect allows controlling the spatial distribution of the charge carriers in the core-shell quantum dots (QDs). Upon increasing shell thickness (e.g., from 0.25-3.25 nm) of core-shell QDs, the radial distribution function (RDF) of hole shifts towards the shell suggesting the confinement region switched from Type-I to Type-II excitons. As a result, there is a jump in the transition energy towards the higher side (blue shift). However, an intermediate state appeared as pseudo Type II excitons, in which holes are co-localized in the shell as well core whereas electrons are confined in core only, resulting in a dual absorption band (excitation energy), carried out by the analysis of the overlap percentage using the Hartree-Fock method. The findings are a close approximation to the experimental evidences. Thus, the understanding of the motion of e-h in core-shell QDs is essential for photovoltaic, LEDs, etc.

Luminescence properties and exciton dynamics of core–multi-shell semiconductor quantum dots leading to QLEDs

Carrier relaxation processes in CdSe core QDs and core–multi-shell QDs under excitation at 450 nm.

A2B corroles: Fluorescence signaling systems for sensing fluoride ions

Four free base corroles, 1-4, A₂B, (where A = nitrophenyl, and B = pentafluorophenyl, 2, 6-difluoro, 3, 4, 5-trifluoro and 4-carboxymethylphenyl group) have been synthesized, characterized and demonstrated as excellent chemosensor for the detection of fluoride ions selectively in toluene solution. The reported corroles shows highest quantum yield in free base form of porphyrinoid systems so far. All these corrole, 1-4, have the excellent ability to sense fluoride ion. Cumulative effect of static and dynamic factors is responsible for the quenching of fluorescence which indicates the detection of fluoride ion in solution.

Facile Synthesis of Semiconducting Ultrathin Layer of Molybdenum Disulfide

In this paper, we have reported a simple and efficient method for the synthesis of uniform, highly conducting single or few layer molybdenum disulfide (MoS2) on large scale. Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) have been used for the confirmation of mono or few layered nature of the as-synthesized MoS2 sheets. X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD) and Raman Spectroscopy have also been used to study the elemental, phase, and molecular composition of the sample. Optical properties of as-synthesized sample have been probed by measuring absorption and photoluminescence spectra which also compliment the formation of mono and few layers MoS2 Current-voltage (I-V ) characteristics of as-synthesized sample in the pellet form reveal that MoS2 sheets have an ohmic character and found to be highly conducting. Besides characterizing the as-synthesized sample, we have also proposed the mechanism and factors which play a decisive role in formation of high quality MoS2 sheets.

Probing Charge-Transfer and Short-Lived Triplet States of a Biosensitive Molecule, 2,6-ANS: Transient Absorption and Time-Resolved Spectroscopy

We report the existence of a short-lived triplet electronic state of 2,6-ANS (2-anilinonaphthalene-6-sulfonic acid), which, together with nonplanar (NP) and planar [charge-transfer (CT)] states, is produced following photoexcitation; these results are based on nanosecond transient absorption and time-resolved decays. The short-lived triplet state has a lifetime of ∼126 ns and is observed via triplet-triplet (T-T) transitions after exciting 2,6-ANS with a pump laser pulse of 355 nm (probe wavelength range of 360-500 nm). Moreover, the CT state, which is very close to the NP state produced from the locally excited state/NP state, emits active fluorescence with a lifetime of ∼11 ns. The solvent plays a major role in the rotation of the phenylamino group during the conversion of the NP state to the CT state, and vice versa. Intersystem crossing occurs from the CT state. Thus, investigating the triplet state together with the CT/NP states of 2,6-ANS, a commonly used probe for sensing proteins and other biomolecules, is highly relevant and helps reveal its photoexcitation dynamics.

Investigation of biocompatible and protein sensitive highly luminescent quantum dots/nanocrystals of CdSe, CdSe/ZnS and CdSe/CdS

The size and shape dependent semiconductor quantum dots (0D nanoparticles) with color tunability demonstrating significant influence in a biological system and considered as ideal probes. Here, a non-coordinated colloidal approach was used for the synthesis of CdSe, CdSe/ZnS and CdSe/CdS core-shell quantum dots (QDs) of 3-4nm. The synthesized nanocrystals show a high crystallinity, examined by X-ray diffraction (XRD) and high-resolution electron microscopy (HRTEM). The core-shell semiconductor QDs exhibit stronger photoluminescence (PL) as compared to the core QDs. The strong PL with small full-width half maximum (FWHM) indicates that the prepared QDs have a nearly uniform size distribution and well dispersibility. The quantum yield (QY) of core-shell QDs increases due to the surface passivation. Further, the PL of BSA is quenched strongly by the presence of core-shell QDs and follows the well-known Stern-Volmer (S-V) relation, whereas the PL lifetime does not follow the S-V relation, demonstrating that the observed quenching is predominantly static in nature. Among CdSe core, CdSe/ZnS and CdSe/CdS core-shell QDs, the CdSe/ZnS QDs shows the least cytotoxicity and most biocompatibility. Thus, the prepared core-shell QDs are biocompatible and exhibit strong sensing ability.

Synthesis, characterization and fluorescence turn-on behavior of new porphyrin analogue: meta-benziporphodimethenes

New fluorescence switch-on meso-substituted free base meta-benziporphodimethenes were synthesized, characterized via acid catalyzed condensation reaction and metallated with Zn(2+). Their photophysical properties were also studied. The fluorescence spectra analysis demonstrates substituent's independent behaviour on emitting λmax. The average Stokes shift of 33nm was observed. Crystal structure of 8 was obtained and gave expected perturbed geometry.

Experimental and theoretical study of hydroxyquinolines: hydroxyl group position dependent dipole moment and charge-separation in the photoexcited state leading to fluorescence

Optical absorption and fluorescence (FL) spectra of 2-, 6-, 7-, 8-hydroxyquinolines (2-,6-,7- and 8-HQs) have been measured at room temperature in the wide range of solvents of different polarities, dielectric constant and refractive index. The ground state dipole moment (µ _g) and excited state dipole moment (µ _e) of 2-, 6-, 7- and 8-HQs were obtained using solvatochromic shift (SS) methods and microscopic solvent polarity parameters (MSPP). Change in the dipole moment (Δµ) between the ground and photo-excited states was estimated from SS and MSPP methods. DFT and TDDFT based theoretical calculations were performed for the ground and excited states dipole moments, and for vertical transitions. A significant enhancement in the excited state dipole moment was observed following photo-excitation. The large value of Δµ clearly indicates to the charge-separation in the photo-excited states, which in turn depends on the position of the hydroxyl group in the ring.

Affinity of Smectite and Divalent Metal Ions (Mg(2+), Ca(2+), Cu(2+)) with L-leucine: An Experimental and Theoretical Approach Relevant to Astrobiology

Earth is the only known planet bestowed with life. Several attempts have been made to explore the pathways of the origin of life on planet Earth. The search for the chemistry which gave rise to life has given answers related to the formation of biomonomers, and their adsorption on solid surfaces has gained much attention for the catalysis and stabilization processes related to the abiotic chemical evolution of the complex molecules of life. In this communication, surface interactions of L-leucine (Leu) on smectite (SMT) group of clay (viz. bentonite and montmorillonite) and their divalent metal ion (Mg(2+), Ca(2+) and Cu(2+)) incorporated on SMT has been studied to find the optimal conditions of time, pH, and concentration at ambient temperature (298 K). The progress of adsorption was followed spectrophotometrically and further characterized by FTIR, SEM/EDS and XRD. Leu, a neutral/non polar amino acid, was found to have more affinity in its zwitterionic form towards Cu(2+)- exchanged SMT and minimal affinity for Mg(2+)- exchanged SMT. The vibrational frequency shifts of -NH3 (+) and -COO(-) favor Van der Waal's forces during the course of surface interaction. Quantum calculations using density functional theory (DFT) have been applied to investigate the absolute value of metal ion affinities of Leu (Leu-M(2+) complex, M = Mg(2+), Ca(2+), Cu(2+)) with the help of their physico-chemical parameters. The hydration effect on the relative stability and geometry of the individual species of Leu-M(2+) × (H2O)n, (n =2 and 4) has also been evaluated within the supermolecule approach. Evidence gathered from investigations of surface interactions, divalent metal ions affinities and hydration effects with biomolecules may be important for better understanding of chemical evolution, the stabilization of biomolecules on solid surfaces and biomolecular-metal interactions. These results may have implications for understanding the origin of life and the preservation of biomarkers.

Spin mixed charge transfer states of iridium complex Ir(ppy)3: transient absorption and time-resolved photoluminescence

Transient absorption and time-resolved PL together with quantum chemistry calculations demonstrated the existence of multiple low-lying metal-to-ligand charge transfer states of Ir(ppy)₃.

Correction: Spin mixed charge transfer states of iridium complex Ir(ppy)3: transient absorption and time-resolved photoluminescence

Correction for ‘Spin mixed charge transfer states of iridium complex Ir(ppy)₃: transient absorption and time-resolved photoluminescence’ by Mohan Singh Mehata et al., RSC Adv., 2015, 5, 34094–34099.

TDDFT study of the polarity controlled ion-pair separation in an excited-state proton transfer reaction

6-Hydroxyquinoline (6HQ) is an ideal photoacid system for exploring excited-state proton transfer (ESPT) reactions. We have previously (Mahata et al. (2002)) shown that the ESPT reaction between 6HQ and trimethylamine (TMA) leads to an "unusual" emission in the 440-450 nm range, containing two decay components (∼5 ns and ∼12 ns). The observed results suggest the presence of a contact ion-pair and a solvent separated ion-pair. In this work, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) have been employed to study the nature of the contact ion-pair formed between 6HQ and TMA and to determine why the decay component ∼12 ns is absent in a non-polar solvent. Calculations of the hydrogen-bonded complexes formed between 6HQ and TMA and its ESPT reaction product, namely 6HQ-TMA and 6HQ-TMA-PT, respectively, have been carried out, both in the electronic ground and excited states. Moreover, by using the CPCM model, different dielectric constants have been introduced into the calculations. On increasing the dielectric constant, the hydrogen bond in 6HQ-TMA-PT becomes weaker and the hydrogen bond length becomes larger; this effectively facilitates the proton transfer reaction and formation of separated ion-pair. Thus, the separation and diffusion of the contact ion-pair can be controlled by changing the polarity of the surroundings.

Surface interaction of L-alanine on hematite: an astrobiological implication

In the present work, surface interaction of L-alanine (L-ala) has been investigated on hematite (α-Fe2O3), an abundant mineral on Mars, as a function of time (5 min-48 h), pH (4.0 and 6.20 ± 0.10) and concentration (1 × 10(-3) M-10 × 10(-3) M) with optical absorbance and energy-dispersive spectroscopy (EDS). Adsorption parameters (XM and KL) were calculated from Langmuir adsorption isotherms. L-alanine has maximum affinity (65.31 %) in its zwitterionic form at pH 6.20, while it is only 29.86 % adsorbed at pH 4.0. Possible astrobiological implications are discussed.

Excited-state proton transfer via hydrogen-bonded acetic acid (AcOH) wire for 6-hydroxyquinoline

Spectroscopic studies on excited-state proton transfer (ESPT) of hydroxyquinoline (6HQ) have been performed in a previous paper. And a hydrogen-bonded network formed between 6HQ and acetic acid (AcOH) in nonpolar solvents has been characterized. In this work, a time-dependent density functional theory (TDDFT) method at the def-TZVP/B3LYP level was employed to investigate the excited-state proton transfer via hydrogen-bonded AcOH wire for 6HQ. A hydrogen-bonded wire containing three AcOH molecules at least for connecting the phenolic and quinolinic -N- group in 6HQ has been confirmed. The excited-state proton transfer via a hydrogen-bonded wire could result in a keto tautomer of 6HQ and lead to a large Stokes shift in the emission spectra. According to the results of calculated potential energy (PE) curves along different coordinates, a stepwise excited-state proton transfer has been proposed with two steps: first, an anionic hydrogen-bonded wire is generated by the protonation of -N- group in 6HQ upon excitation to the S(1) state, which increases the proton-capture ability of the AcOH wire; then, the proton of the phenolic group transfers via the anionic hydrogen-bonded wire, by an overall "concerted" process. Additionally, the formation of the anionic hydrogen-bonded wire as a preliminary step has been confirmed by the hydrogen-bonded parameters analysis of the ESPT process of 6HQ in several protic solvents. Therefore, the formation of anionic hydrogen-bonded wire due to the protonation of the -N- group is essential to strengthen the hydrogen bonding acceptance ability and capture the phenolic proton in the 6HQ chromophore.

Electroabsorption Spectroscopy of 6-Hydroxyquinoline Doped in Polymer Films: Stark Shifts and Orientational Effects

Stark absorption spectroscopy was applied to 6-hydroxyquinoline (6-HQ) doped in polymer films of poly(methyl methacrylate) (PMMA) and poly(vinyl alcohol) (PVA) at temperatures of 50-300 K. The electroabsorption (E-A) spectrum of 6-HQ markedly depends on temperature in a PMMA film. The polarization dependence as well as the temperature dependence of the E-A spectra reveals that 6-HQ is oriented along the direction of the applied electric field at room temperature in a PMMA film. As the temperature becomes lower, the field-induced orientation of 6-HQ is restricted, and only the Stark shift induced by a change in electric dipole moment and in molecular polarizability is observed. On the other hand, E-A spectra of 6-HQ doped in a PVA film are essentially independent of temperature, suggesting that 6-HQ is not oriented along the electric field even at room temperature in PVA. These results show that the molecular motion of 6-HQ in a polymer film is very sensitive to the microenvironment of the surrounding matrix.

Fluorescence characteristics of protonated form of 6-hydroxyquinoline in Nafion film

Fluorescence characteristics of 6-hydroxyquinoline (6-HQ) have been studied at room temperature in Nafion(R) film by steady state and nano-second time-resolved fluorescence spectroscopy. The fluorescence spectrum exhibits single emission band corresponding to the protonated form of 6-HQ in this matrix. However, the decay fits with two or three exponential functions depending on the emission wavelength monitored. At blue edge of the emission, the decay fits to three-exponential function, whereas at longer wavelengths, the decay fits to bi-exponential function. Two tentative mechanisms have been proposed to explain the experimental data, viz. a closely lying charge transfer state (CT) or an excited state proton transfer (ESPT) process. The photophysical parameters appear to be sensitive to the change in microstructure due to swelling of the membrane by the solvents.

Steady state and time-resolved spectroscopic studies of 7-hydroxyquinoline in various polymeric matrices

The photophysical behavior of 7-hydroxyquinoline (7HQ) is studied in four polymer matrices, viz. polymethyl methacrylate (PMMA), cellulose acetate (CA), polyvinyl alcohol (PVA) and Nafion-117, at ambient temperature using both steady state and time-domain measurements. The study reveals both ground as well as excited state tautomerization in the case of PVA. In PMMA and CA, the intermolecular hydrogen bond to the host polymer results in proton transfer. Edge excitation red shift (EERS) and excitation and emission wavelength dependent decays are observed for normal emission in PMMA and CA matrices. These results are attributed to the trapping of a normal molecule in different geometries. In Nafion, the results show the presence of 7HQ cationic species trapped in the polymer.