Fluorescence Spectra Of Solutions Research Articles

Absorption and fluorescence spectra of new pyrrolo[3,4‐b]quinolizines in condensed phases: A joint experimental and computational study

AbstractNewly synthesized pyrrolo[3,4‐b]quinolizines, blue‐green to orange‐red in fluorescent dye in solutions and yellow to red fluorescent dyes in solid states, were experimentally and computationally investigated for the electronic and fluorescence spectra in solution as well as in solid state. The solvent effects on the absorption and emission spectra were theoretically investigated by the snapshots‐averaged spectra obtained by the first principle molecular dynamics combined with polarizable continuum model (PCM). Alternatively, the solute–solvent interaction effect on the spectra was examined by fragment molecular orbital‐time dependent density functional theory (FMO‐TDDFT) which considered the explicit solute–solvent interactions. The results indicate that the quantitative prediction limitations of PCM and that the solvatochromic shifts in dichloromethane and ethanol were correctly reproduced by FMO‐TDDFT. The luminescence quantum yields of the compounds were analyzed on the excited state potential surface via the S0/S1‐conical intersections.

Franck‐Condon factors within damped displacement harmonic oscillators: Solvent‐enhanced absorption and fluorescence spectra

AbstractDamped harmonic oscillators that take into account local‐mode nuclear vibrations interacting with solvent molecules are developed into Franck‐Condon factors within displaced harmonic oscillator approximation. This is practically done by scaling an unperturbed Hessian matrix that represents local modes of force constants for molecules in a gaseous phase, and then by diagonalizing the perturbed Hessian matrix it results in direct modification of Huang–Rhys factors which represent normal modes of solute molecule perturbed by solvent environment. For highly symmetric polycyclic aromatic hydrocarbon molecules in which hydrogen atom vibrations in a solution can be scaled equally, one‐set scaling parameters constructed into damped Franck‐Condon factors can reproduce solvent‐enhanced absorption and fluorescence spectra in solution. However, for low symmetry molecules with atoms other than hydrogen and carbon atoms, multi‐set scaling parameters constructed into damped Franck‐Condon factors can also reproduce solvent‐enhanced absorption and fluorescence spectra in solution. Examples for high symmetry perylene in benzene solution with one‐set scaling parameters and for low symmetry carbazole in n‐hexane solution with multi‐set scaling parameters are given, in both cases, the present damped Franck‐Condon simulation can reproduce solvent‐enhanced absorption and fluorescence spectra in solution.

Tris(trifluoromethyl)germyl biphenyl conjugated molecular system with ferrocenyl substituent: Confirmation of photoinduced intramolecular charge transfer to the germanium center

Unsymmetrical 4,4′-biphenyl derivative with tris(trifluoromethyl)germylethynyl ‒CC‒Ge(CF3)3 and ferrocenylethynyl Fc‒CC‒ substitutes have been prepared (21), its properties have been studied and compared with those full non-fluorinated analogue of trimethylgermylethynyl ‒CC‒Ge(CH3)3 compound (20). UV-visible, absorption, steady state, and time-resolved fluorescence spectra in solution for these germanium and a number of similar compounds (15-17, 22) have been investigated. The process of photoinduced electron transfer from the π-conjugated system to the germanium center is confirmed for 21, as well as for the first time discovered earlier [19] in the 4-biphenyl ‒CC‒Ge(CF3)3 molecule (9). It was found that the lifetime of the radical-ion pair 21 in the excited state (kCR2 = 1.2 × 105 s-1) is approximately an order of magnitude longer than for 9, which can be explained by the stabilizing effect of the electron donor Fc‒CC‒ group. Density-functional theory (DFT) computations was used to calculate the optimized geometry of 21 in excited state, and two main bands in the emission spectrum at laser excitation (340 and 386 nm) an excellent fit to the experimental data. An additional data on the nature of the (CF3)3Ge group, including geometry, electronegativity, and contributions 4d AOs of germanium into lowest unoccupied molecular orbital (LUMO) in a wide range of fluorinated and non-fluorinated compounds were also calculated. The molecular structure of compound 21 was determined by X-ray structural analysis. In the crystal lattice of 21, numerous intermolecular F‧‧‧F interactions shortened in comparison with the van der Waals radii were detected, which leads to the formation of quasi-two-dimensional fluorinated layers in crystals.

A new tripodal 8-hydroxyquinoline as a high sensitivity fluorescence sensor for Zn(II) in ethanol and its two morphology in solid

New tripodal ligand form two different dinuclear Zn 2+ complex in solid, but identical in solution. The strong chelate significantly increased fluorescence sensitivity toward Zn 2+ in ethanol solution. • New tripodal ligands (HL) were synthesized from 8-hydroxyquinoline and bis(pyridin-2-ylmethyl)amine. • HL forms stable Zn(II) complexes which has very strong fluorescence in ethanol. The LOD for Zn(II) fluorescence is 2.3 nM. • Symmetric/asymmetric dinuclear Zn(II) complexes with identical formulae can be isolated from CH 3 CN solution, but they are identical in solution. A new tripodal chelate HL was synthesized from tridentate chelate bis(pyridin-2-ylmethyl)amine (BPA) and 8-hydroxyquinoline (8-HQ) to increase interaction between HL and Zn 2+ and improve fluorescence sensitivity. Asymmetric and symmetric dinuclear Zn(II) complex in rod and block shape were formed in CH 3 CN with identical formula, 1 H NMR and fluorescence spectra in solution, but different IR, TG, and PXRD in solid. The fluorescence quantum yields are 0.0145 and 0.602 for HL and [ZnL] 2 2+ in ethanol respectively. LOD reached 2.3 nM Zn 2+ , which is the highest sensitivity. The 7-position functionalization of 8-HQ is critical to the strong coordination and high fluorescence sensitivity.

The Influence of Iron Ions on Optical Brighteners and Their Application to Cotton Fabrics.

The influence of iron ions at concentrations of 0.2, 0.5, and 1.0 g/L on optical brighteners of the groups stilbene and biphenyl in solution and on cotton fabric was investigated. Both groups of optical brighteners are intended for detergent formulations. The influence of iron ions was studied by absorption and fluorescence spectra in solution and by whiteness degree, identifying color differences using CIEL*a*b* coordinates and Ultraviolet Protection Factor (UPF) of cotton fabrics. The obtained results in solutions and cotton fabrics showed different behavior of optical brighteners stilbene and biphenyl in the presence of iron. Stilbene compounds with metal ions produced new species capable of absorbing in the UV-B region of the spectrum. A biphenyl compound in combination with iron had no effect on the absorption properties. Both optical brighteners were influenced by iron ions in the sense of fluorescence quenching. The influence of iron ions in single- and two-bath treatments of cotton fabrics after one cycle on whiteness degree and UPF was negligible.

Characterization of tracers for two-color laser-induced fluorescence thermometry of liquid-phase temperature in ethanol, 2-ethylhexanoic-acid/ethanol mixtures, 1-butanol, and o-xylene.

The fluorescence spectra of dye solutions change their spectral signature with temperature. This effect is frequently used for temperature imaging in liquids and sprays based on two-color laser-induced fluorescence (2cLIF) measurements by simultaneously detecting the fluorescence intensity in two separate wavelength channels resulting in a temperature-sensitive ratio. In this work, we recorded temperature-dependent absorption and fluorescence spectra of solutions of five laser dyes (coumarin 152, coumarin 153, rhodamine B, pyrromethene 597, and DCM) dissolved in ethanol, a 35/65 vol.% mixture of ethanol/2-ethylhexanoic acid, ethanol/hexamethylsiloxane, o-xylene, and 1-butanol to investigate their potential as temperature tracers in evaporating and burning sprays. The dissolved tracers were excited at either 266, 355, and 532 nm (depending on the tracer) for temperatures between 296 and 393 K (depending on the solvent) and for concentrations ranging between 0.1 and 10 mg/l. Absorption and fluorescence spectra of the tracers were investigated for their temperature dependence, the magnitude of signal re-absorption, the impact of different solvents, and varying two-component solvent compositions. Based on the measured fluorescence spectra, the tracers were analyzed for their 2cLIF temperature sensitivity in the respective solvents. Coumarin 152 showed for single-component solvents the overall best spectroscopic properties for our specific measurement situation related to temperature imaging measurements in spray-flame synthesis of nanoparticles as demonstrated previously in ethanol spray flames [Exp. Fluids61, 77 (2020)10.1007/s00348-020-2909-9].

A New Fluorometric Dosimetry for Low-medium Gamma Radiation Doses.

In this study, for the first-time, solutions of a Schiff base was evaluated as a possible chemical dosimeter for gamma-rays at low-medium dose ranges. The solutions of N-N'-bis(salicylidene)-1,3-propanediamine (LH2) were prepared at different ethanol/water compositions and the effect of various irradiation doses on the fluorometric response of these solutions were investigated. Fluorescence spectra of non-irradiated and irradiated solutions showed that fluorescence intensity of LH2 (λex = 375 nm, λem = 498 nm) decreased as the radiation dose increased. This decrease was observed over a wider dose range for the solutions that contain 40-60 % water. In order to increase the sensitivity of the method, LH2-Zn complexes were formed by adding Zn (II) to non-irradiated and irradiated LH2 solutions. After that, analytical parameters such as linearity, LOD, LOQ, repeatability and reproducibility were determined by measuring fluorescence spectra of these solutions (λex = 350 nm, λem = 444 nm). The performance characteristics of the chemical dosimetry system suggest that LH2 can be used as a dosimeter in dose range 0.04-5kGy. The proposed method is simple, sensitive, reproducible and cost-effective, and can be useful in measuring doses in food irradiation.

The Plasmon Effects of AgNPs on Wave Guide Consisting of Polymers Mixed with Rhodamine Dyes

In this research, the optical properties refractive index, absorption spectrum, and fluorescence spectrum of solutions of different concentrations have been studied in order to prepare thin films to obtain an efficient waveguide. A wave guide consisting of three layers has been prepared in which the middle layer has a relatively higher refractive index than the upper and lower layers. This optical wave guide was prepared by using different solutions of two concentrations of poly vinyl pyrrolidone (PVP) & poly vinyl alcohol (PVA) polymers. Different concentrations of the rhodamine pigments RhB & Rh6G were prepared. It is added to the middle layer of the optical wave guide in order to raise its refractive index first and to obtain a laser profit. The practical results have proven that there are specific concentrations of polymers and dyes that can be used to obtain wave guides that have the ability to transmit and amplify the input signal and operate within certain wavelengths. The PVA + RhB(10-4M) model showed the best laser emission performance and the PVA + Rh6G (10-5M) model showed the best signal transmission performance. Finally, the plasmon effect is clearly appears when we added the AgNPs on our samples it’s effecting on threshold pumping and increase the efficiency of wave guide.

7-Alkoxy-appended coumarin derivatives: synthesis, photo-physical properties, aggregation behaviours and current-voltage (I-V) characteristic studies on thin films.

In this study, we designed and synthesised a series of coumarin derivatives appended with a long alkoxy chain on the seventh position of the coumarin-3-carboxylate/carboxylic acid core to make thin film materials. Synthesised compounds were characterized by their UV and fluorescence spectra in solutions as well as their films prepared by both LB and spin-coated methods. The surface morphology and electrical behaviour of thin films were judged by AFM, SEM and I–V characteristic mapping respectively. Isotherm, UV-Vis absorption and fluorescence spectroscopic investigations revealed the formation of aggregates on thin films. The result of SEM and AFM images provides the information about the length and height of aggregates on the thin films of coumarin derivatives. From I–V characteristics, it was found that at room temperature, the spin-coated films of coumarin derivatives containing an ester functional group exhibited a threshold switching behaviour, whereas derivatives containing the carboxylic acid functional group showed both threshold and bipolar switching behaviours. We also noticed that the I–V characteristic features of synthesized materials depended on the length of the alkyl chain of individual series.

Immobilization of dipyrenylphosphinic acid to boehmite: Fluorescent hybrid with weakened pyrene-aggregation

Ethyldipyrenylphosphate (DPyPOOEt) was designed and synthesized by utilizing ethyldichlorophosphate as the core and 1-bromopyrene as substituting groups, and afterwards dipyrenylphosphinic acid (DPyPOOH) was synthesized by the hydrolysis reaction of DPyPOOEt by using bromotrimethylsilane (TMSBr). Fluorescent hybrid was finally prepared by the dehydration condensation between DPyPOOH and hydroxyl groups on the surface of boehmite. The chemical structure of DPyPOOEt and DPyPOOH were characterized by 1H NMR and 13C NMR. Crystal structure, chemical structure and microtopography of hybrid were characterized by X-ray diffraction spectra (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), respectively. The results demonstrate that the incorporation of two pyrene substituent groups into phosphine oxide can be successfully immobilized on the surface without any change of crystal structure of boehmite. Fluorescence spectra in solution and powder further demonstrated the occurrence of shape-changed and red-shifted emission peaks of DPyPOOEt and DPyPOOH than that of pyrene. In particular, compared to DPyPOOEt and DPyPOOH in solid, the hybrid shows blue-shifted fluorescence. Optimized molecular conformation, ground electronic structure of DPyPOOEt has been investigated in detail by quantum chemistry method. The introduction of phosphine oxide tunes the conjugated structure of pyrene-ring and spatial conformation between the pyrene-ring. In addition, intramolecular V-shanped conformation when DPyPOOH confined to boehmite surface reduce π-π aggregation between pyrene rings. Therefore, these results indicate that the hybrid is expected to highly efficient blue light-emitting material.

Application of SERS and SEF Spectroscopy for Detection of Water-Soluble Fullerene–Chlorin Dyads and Chlorin e6

Free fluorescence spectra in solution and surface-enhanced Raman scattering (SERS) and surface enhanced fluorescence (SEF) spectra of chlorin e6 and water-soluble covalent fullerene–chlorin dyads have been studied. It has been demonstrated that chlorin e6 and covalent fullerene–chlorin dyads have similar characteristic SERS spectra. The fullerene–chlorin dyads show a pronounced SEF signal, while native chlorin e6 has no fluorescence on surface, which is consistent with the theory predicting an inverse dependence of the SEF intensity on the free fluorescence quantum yield. The concentration dependence of the SEF intensity is linear for the dyads in the range 0.1–2.0 μmol/L. These effects allow one to determine, with high sensitivity, the content of fullerene–chlorin dyads with a low quantum yield of free fluorescence in solutions, which opens wide opportunities for study of biological properties of fullerene–chlorin dyads and their applications in medicine.

Indenopyrans - synthesis and photoluminescence properties.

New indeno[1,2-c]pyran-3-ones bearing different substituents at the pyran moiety were synthesized and their photophysical properties were investigated. In solution all compounds were found to be blue emitters and the trans isomers exhibited significantly higher fluorescence quantum yields (relative to 9,10-diphenylanthracene) as compared to the corresponding cis isomers. The solid-state fluorescence spectra revealed an important red shift of λmax due to intermolecular interactions in the lattice, along with an emission-band broadening, as compared to the solution fluorescence spectra.

Tris(trifluoromethyl)germylethynyl derivatives of biphenyl and anthracene: Synthesis, structure, and evidence of the intramolecular charge transfer on the germanium center

Symmetrical and unsymmetrical 4,4′-biphenyl, and 9,10-anthracene derivatives with tris(trifluoromethyl)germylethynyl –CC–Ge(CF3)3 substitutes have been prepared, their properties have been studied and compared with those of dimethyl(phenyl)silylethynyl –CC–Si(Ph)Me2 compounds. UV–visible absorption, steady-state, and time-resolved fluorescence spectra in solution for this germanium and silicon compounds have been investigated. The process of photoinduced electron-transfer from the aromatic group to the germanium center has been found in the unsymmetrical 4-biphenyl –CC–Ge(CF3)3 molecule. Anthracene derivatives with –CC–Ge(CF3)3 substitutes have been characterized crystallographically.

Synthesis and Characterization of Soluble Silyl End‐capped Arene‐Thiophene Co‐Oligomers

Soluble dimethyl‐n‐octylsilyl end‐capped arene‐thiophene oligomers with the central unit including phenyl, biphenyl, fluorine, and naphthalene were synthesized by Stille reaction. The optical, electrochemical, and thermal properties of the oligomers were then measured. The absorption maxima of the arene‐thiophene oligomers in dilute solutions were close to that obtained for DSi‐4T (λabs = 403 nm). They exhibited well‐resolved fluorescence spectra in solution with emission maxima at 445, 446, 448, and 450 nm for DSi‐TTPTT , DSi‐TTPPTT , DSi‐TTFTT , and DSi‐TTNTT , respectively. The highest occupied molecular orbital (HOMO) energy levels were determined to be −5.29, −5.33, −5.27 and −5.29 eV, respectively; therefore all co‐oligomers displayed a lower HOMO energy level than the −5.14 eV of DSi‐6T . The thermal stability of the arene‐thiophene oligomers was investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Except for DSi‐TTPTT , the TGA results showed a 5% weight loss at around 400 °C, which indicates high thermal stability. Dimethyl‐n‐octylsilyl end substituents allowed solution processability due to their high solubility. Overall, the electrochemical analysis of arene‐thiophene oligomers indicated superior oxidative stability to DSi‐6T .

Treatment of Humic Acid in Drinking Water by Combining Potassium Manganate (Mn(VI)), Ferrous Sulfate, and Magnetic Ion Exchange

This article summarizes a preliminary investigation of the treatment of humic acid (HA) in drinking water by a novel combination of potassium manganate, ferrous sulfate, and magnetic ion exchange (MIEX) resin. Manganate (MnO42−) is a stronger oxidant than permanganate, which has received little attention to date as a water treatment chemical, but in combination with ferrous sulfate (FeMnO) can offer a potentially advantageous and more economical means of achieving preoxidation objectives and in-situ coagulation by Fe(III) species. To enhance removal of organic substances, particularly low-molecular-weight and more hydrophilic compounds, subsequent treatment by MIEX was included as part of the overall process. Using model HA solutions of 5 mg/L dissolved organic carbon (DOC), a solution pH of 6.5, and a constant Fe:Mn molar ratio (2:1), the optimal FeMnO dose for organics (DOC) removal was 0.06 mM (as K2MnO4). At this optimal dose, and with 10 mL/L of MIEX, the DOC remaining after treatment was only 0.4 mg/L, representing an overall organics removal of 92%. Synchronous fluorescence spectra of solutions during the treatment stages showed a corresponding major reduction in fluorophore peaks with a near complete removal of fluorophore compounds in the ranges, 360 nm<λex<420 nm and λex>420 nm.

Design, synthesis and photoswitching of broad-spectrum fluorescent hexaarylbiimidazoles

A series of novel hexaarylbiimidazole (HABI)-containing fluorophores with broad-spectrum emissions ranging from blue, green and red emissions, have been designed and synthesized. Their photochromism and fluorescence switching properties are investigated by UV-Vis absorption and fluorescence spectra in solutions and PMMA films. By connecting carbazole (Cz), naphthalimide (NI) and perylene-mono-imide (PMI) to HABI with a spacer, three molecular photoswitches with broad-spectrum fluorescence varying from deep blue (Cz–O–HABI, λem = 390 nm, ΦF = 0.27), green (NI–O–HABI, λem = 490 nm, ΦF = 0.25) to far red (PMI–O–HABI, λem = 650 nm, ΦF = 0.25) have been obtained. The “ON”/“OFF” ratios are calculated to be about 8.9, 8.0 and 3.7 (calculated from FL spectra) for Cz–O–HABI, NI–O–HABI and PMI–O–HABI, respectively. Such a series of photoswitchable fluorophores constitute prototypes of a photochromic molecular library in which fluorescence resonance energy transfer can be reversibly modulated by an external stimulus, namely, UV light.

First-principle computation of absorption and fluorescence spectra in solution accounting for vibronic structure, temperature effects and solvent inhomogenous broadening

We compute the line shape of absorption and emission electronic spectra of two different dyes, Coumarin C153 and N-methyl-6-Quinolinium betaine accounting for the vibronic structure, temperature effects and polar solvent inhomogeneous broadening, without using any phenomenological parameter. We exploit a number of recent developments including a time-dependent (TD) approach to the computation of vibronic spectra that provides fully converged line shapes at finite temperature accounting for both Duschinsky and Herzberg–Teller effects, and the state-specific (SS) implementation of Polarizable Continuum Model (PCM). This latter is adopted to compute the solvent reorganization energy connected to inhomogenoeus broadening. We compute the absorption and fluorescence spectra in the gas-phase, non-polar and polar solvents analyzing the relative importance of different sources of broadening. To this end we investigate the performance of TD Density Functional Theory, Complete Active Space Self Consistent Field (CASSCF) and Complete Active Space second-order Perturbation Theory (CASPT2) methods in the computation of inhomogeneous broadening.

Study and Characterization of the Antioxidant Activity of the Inclusion Complex of Apigenin with beta-Cyclodextrin and HP-beta-Cyclodextrin in solution

The formation of the complexes of Apigenin with β-Cyclodextrin (β-CD) and HP-β-Cyclodextrin (HP-β-CD) were studied by fluorescence spectra in solution. The formation constants (Ks) of complexes were determined by fluorescence method and Phase-solubility measurements. The results showed that the inclusion ability of β-Cyclodextrin and its derivative were the order: HP-β-CD> β-CD. In addition, the experimental resulted confirmed the existence of 1:1 inclusion complex of Apigenin with Cyclodextrins. Kinetic studies of Scavenging of DPPH free radical with Apigenin and Cyclodextrins complexes were done. The results obtained indicated that the Apigenin/HP-β-CD complex was the most reactive form, then was β-CD complex, and last was free Apigenin.

Synthesis, photophysical and electrochemical properties of aza-boron-diquinomethene complexes

A series of aza-boron-diquinomethene (aza-BODIQU) complexes with different aryl-substituents (B1–B6) were synthesized and characterized. Their photophysical properties were investigated systematically via spectroscopic and theoretical methods. All complexes exhibit strong 1π–π* absorption bands and intense fluorescent emission bands in the visible spectral region at room temperature. The fluorescence spectra in solution show the mirror image features of the S0→S1 absorption bands, which can be assigned to the 1π–π*/1ICT (intramolecular charge transfer) emitting states. Except for B6, all complexes exhibit high photoluminescence quantum yields (ΦPL = 0.47–0.93). The spectroscopic studies and theoretical calculations indicate that the photophysical properties of these aza-BODIQUs can be tuned by the appended aryl-substituents, which would be useful for rational design of boron–fluorine complexes with high emission quantum yield for organic light-emitting applications.

Fluorescence Spectral Changes of Perylene in Polymer Matrices during the Solvent Evaporation Process

This work examined concentration-dependent variations in the fluorescence spectra of solutions of perylene and PMMA in toluene during the process of evaporation, using fluorescence microscopy. At low perylene concentrations, the fluorescence spectra of the resulting perylene/PMMA films exhibited a structural band originating from monomeric perylene. Increasing the concentration resulted in the appearance of new, broader bands due to the formation of two excimer species. An estimation of variations in the fluorescence excitation spectra of these same films with changing concentration and excitation wavelength indicated the formation from monomer to fully overlapped excimer via partially overlapped excimer in terms of the kinetic situation. These species are believed to consist of either ground state aggregates or α-crystals resulting from phase separation within the PMMA films. Dynamic fluorescence changes during solvent evaporation were monitored by fluorescence spectroscopy and CCD photography. Fluorescence emission changed from blue to green with the formation of α-crystals, a pattern which was also observed when increasing perylene concentrations in PMMA films during static trials. The concentration distribution around α-crystals was attributed to the crystal growth process and could be followed by observing the fluorescence color gradient radiating from the crystal. Studying concentration-dependent fluorescence spectral changes during solvent evaporation not only provides insight into the molecular dynamics of the casting process and the compatibility between the dispersed material and the polymer matrix but also provides information concerning molecular assembly and the nucleation and growth of crystals of the fluorescent organic molecules.