Photophysical Properties Of Dyes Research Articles

Transient optical properties, laser induced avalanche effect, and all optical switching in molecular aggregates

Organic dyes have attracted expressive research interest in recent years due to their wide range of applications. Self-aggregation occurs in a variety of organic molecules, a phenomenon that changes the photochemical and photophysical properties of dyes. Laser beams with wavelengths of 663 nm and 532 nm were used for thermal modulation of the aggregation states of the methylene blue dye, which led to the discovery of a novel avalanche phenomena in the molecular/supramolecular level and observations of not yet reported material optical behaviors. The obtained experimental data reveals the existence of asymmetric optical responses of aggregated dyes under laser excitation with wavelengths at the monomer or at the dimer absorption bands. The observed optical behaviors, resulting from the laser modulation of the molecular aggregation states, may find applications in the field of organic electronics and devices, such as optical logical gates and optical power limiters. A dual mechanism all optical switching driven by the simultaneous action of the cooperative effects of the laser induced disruption of dimeric dye units and thermal lensing was achieved.

Polymethine Dyes Based on 2,2-Difluoro-1,3,2-dioxaborine: a Minireview

Aim. To summarize and analyze literature data on the polymethine dyes containing the 2,2-difluoro-1,3,2-dioxaborine ring.Results and discussion. Boron difluoride complex of β-diketone (2,2-difluoro-1,3,2-dioxaborine, F2DB) is a unique structural motif endowing organic compounds with prominent physicochemical properties, such as a strong fluorescence and high mo-lar attenuation coefficients. Incorporation of the F2DB core into a polymethine chromophore either as an end-group or as an integral part of the polymethine chain allows obtaining dyes with exceptional characteristics, highly appealing for design of up-to-date functional materials. This review focuses on the synthesis and spectral properties of the F2DB-containing polymethines along with the latest advancement in the synthesis of highly fluorescent polyanionic polymethines. A brief discussion of the effects of the structural modification of the π-conjugated system on the photophysical properties of dyes is included.Conclusions. The literature on the F2DB-containing polymethines demonstrates a high potential of the F2DB core for the development of strongly fluorescent and intensely absorbing dyes.

Enhancing single-molecule sensing and superresolution with DNA nanotech.

In recent years, DNA nanotechnology has matured to enable robust production of complex nanostructures and hybrid materials. We have combined DNA nanotechnology with sensitive optical detection to create functional single-molecule devices that enable new applications in single-molecule biophysics, biosensing and superresolution. To improve the sensitivity of DNA detection assays, we created DNA origami optical antennas for metal enhanced fluorescence. Two gold nanoparticles or nanorods enhance the light-matter interactions of dyes and biomolecular assays placed between them. We first discuss the influence of the metal nanostructure on the photophysical properties of dyes. We then show how single molecules can even be detected on a battery-driven portable smartphone microscope using DNA origami nanoantennas [1]. We further present our work on other biosensing applications of DNA origami as well as the possibility of isotropic nanometric superresolution by combining graphene energy transfer with pMINFLUX and DNA PAINT [2].

Effects of the Surface Charge Density of Clay Minerals on Surface-Fixation Induced Emission of Acridinium Derivatives.

Surface-fixation induced emission is a fluorescence enhancement phenomenon, which is expressed when dye molecules satisfy a specific adsorption condition on the anionic clay surface. The photophysical behaviors of two types of cationic acridinium derivatives [10-methylacridinium perchlorate (Acr+) and 10-methyl-9-phenylacridinium perchlorate (PhAcr+)] on the synthetic saponites with different anionic charge densities were investigated. Under the suitable conditions, the fluorescence quantum yield (Φf) of PhAcr+ was enhanced 22.3 times by the complex formation with saponite compared to that in water without saponite. As the inter-negative charge distance of saponite increased from 1.04 to 1.54 nm, the Φf of PhAcr+ increased 1.25 times. In addition, the increase in the negative charge distance caused the increase in the integral value of the extinction coefficient and the radiative deactivation rate constant (kf) and the decrease in the nonradiative deactivation rate constant. It should be noted that the 2.3 times increase in kf is the highest among the reported values for the effect of clay. From these results, it was concluded that the photophysical properties of dyes can be modulated by changing the charge density of clay minerals.

Substituted 2-(2-hydroxyphenyl)–3H-quinazolin-4-ones and their difluoroboron complexes: Synthesis and photophysical properties

2-(2-Hydroxyphenyl)–3H-quinazolin-4-ones with diverse substituents at phenol ring and their six-membered difluoroboron complexes have been synthesized via few-stage approach. The photophysical properties of target compounds have been investigated in two solvents as well as in the solid state. The nature of substituents and substitution point in the phenol moiety of ligands and resulting BF2-complexes on the photophysical properties of dyes have been explored. The complex bearing two t-Bu groups proved to be the most emissive in solid state, whereas its 5-methoxy and 4-diethylamino counterparts possess strong emission in toluene solution. The dyes exhibited large Stokes shifts which was attributed to excited state intramolecular proton transfer (ESIPT). Additionally, fluorescence of quinazolinones in the mixture of THF/water was studied. All ligands demonstrated emission enhancement with increase of water fraction which was due to aggregation induced emission.

Explorations into the Effect of meso‐Substituents in Tricarbocyanine Dyes: A Path to Diverse Biomolecular Probes and Materials

AbstractPolymethine cyanine dyes have been widely recognized as promising chemical tools for a range of life science and biomedical applications, such as fluorescent staining of DNA and proteins in gel electrophoresis, fluorescence guided surgery, or as ratiometric probes for probing biochemical pathways. The photophysical properties of such dyes can be tuned through the synthetic modification of the conjugated backbone, for example, by altering aromatic cores or by varying the length of the conjugated polymethine chain. Alternative routes to shaping the absorption, emission, and photostability of dyes of this family are centered around the chemical modifications on the polymethine chain. This Minireview aims to discuss strategies for the introduction of substituents in the meso‐position, their effect on the photophysical properties of these dyes and some structure–activity correlations which could help overcome common limitations in the state of the art in the synthesis.

Explorations into the Effect of meso-Substituents in Tricarbocyanine Dyes: A Path to Diverse Biomolecular Probes and Materials.

Polymethine cyanine dyes have been widely recognized as promising chemical tools for a range of life science and biomedical applications, such as fluorescent staining of DNA and proteins in gel electrophoresis, fluorescence guided surgery, or as ratiometric probes for probing biochemical pathways. The photophysical properties of such dyes can be tuned through the synthetic modification of the conjugated backbone, for example, by altering aromatic cores or by varying the length of the conjugated polymethine chain. Alternative routes to shaping the absorption, emission, and photostability of dyes of this family are centered around the chemical modifications on the polymethine chain. This Minireview aims to discuss strategies for the introduction of substituents in the meso‐position, their effect on the photophysical properties of these dyes and some structure–activity correlations which could help overcome common limitations in the state of the art in the synthesis.

Synthesis and investigation of photophysical, NLO and thermal properties of D-π-A-π-D dyes

A novel coumarin-thiophene based dyes containing azo and dimethine bridges with D-π-A-π-D system were synthesized and investigated their photophysical, nonlinear optical (NLO) and thermal properties. The dyes were characterized by FT-IR, 1H-NMR, 13C-NMR and HRMS. The dyes include dicyanomethylene group as acceptor and different para-substituted alkylamines and carbazole as donor and chlorophenyl as weak acceptor. The photophysical properties of dyes were examined in various solvents with different polarities and they showed absorption in the visible region. The significant bathochromic shifts were observed in the absorption maxima with increasing the electron-donating property of substituents. The second order NLO responses of the compounds are measured by the electric field induced second harmonic (EFISH) generation method and the compounds bearing dialkylamino donor in phenyl moiety were obtained as the larger μβ values 1300 × 10−48 esu, 1850 × 10−48 esu, respectively, than unsubstituted derivative in phenyl ring μβ value 350 × 10−48 esu. The structural and electronic properties of the compounds as well as their NLO properties were studied using DFT calculation. The thermal stabilities obtaining with thermogravimetric analysis (TGA) showed that the dyes have generally a good thermal stability up to 250 °C.

Novel hybrid materials based on alginate-boehmite-riboflavin for photogeneration of reactive oxygen species in aqueous media. Potential environmental implications

In this work, hybrid composites based on beads of alginate, boehmite and riboflavin-5′-phosphate dye (ALG-B-RP) were synthesized in order to obtain novel materials capable to generate reactive oxygen species (ROS). The synthesis was performed by adsorbing the dye RP on boehmite (B) and then alginate (ALG) was added forming a homogeneous suspension. This suspension was dripped on a solution of calcium ions resulting in the formation of bead-shaped yellow hydrogels. Beads with different RP content were synthesized. Confocal laser scanning microscope images indicate that the RP is homogeneously distributed in the ALG polymeric matrix. This microscopy, UV–Vis and fluorescence spectroscopies show that dye photophysical properties are not affected. Uptake oxygen experiments show that these beads have the ability to generate ROS, mainly singlet oxygen O2(1Δg). On top of that mentioned above, these materials are economical, environmentally friendly because are synthesized from non-toxic components and their synthesis does not generate waste and only use water as solvent. On the other hand, these beads are easy to handle and their ability to generate ROS making them promising for water remediation.

European JRC report on global deployment of more than 200 kW fuel cells

Near-infrared dyes are useful to monitor nanocarriers in vitro and in vivo and can serve as photosensitizers in cancer photodynamic therapy. However, strategies need to be developed to guarantee that the dye photophysical properties and loading within the drug delivery system remain stable for reliable tracking within biological systems. This work reports the facile chemical conjugation of the carbocyanine heptamethine near-infrared dye IR780 to polylactide for stable fluorescent labeling of biodegradable polyester nanocarriers. “Clickable” polylactide was synthesized via organocatalyzed ring opening polymerization of D,L-lactide with a cyclooctyne initiator. IR780 was derivatized and conjugated to polylactide via a one-pot copper-free azide-alkyne cycloaddition reaction. The synthetic strategy developed was effective to promote conjugation of the near-infrared fluorescent dye to polylactide, as confirmed by high performance liquid chromatography. Nanoparticles containing the dye–polymer conjugate were prepared by nanoprecipitation and characterized. Asymmetric flow field-flow fractionation with light scattering and fluorescence detection revealed that the near-infrared fluorescence of the nanoparticles remained stable and was not transferred to serum proteins. In contrast, significant transfer of the dye to serum proteins was evidenced when the dye was merely encapsulated in similar nanoparticles through physical entrapment. Confocal microscopy and fluorescence tomography imaging showed that the polymer-dye conjugate confers fluorescence properties to the NP suitable for further in vitro and in vivo pre-clinical studies.

IR780-polymer conjugates for stable near-infrared labeling of biodegradable polyester-based nanocarriers

Near-infrared dyes are useful to monitor nanocarriers in vitro and in vivo and can serve as photosensitizers in cancer photodynamic therapy. However, strategies need to be developed to guarantee that the dye photophysical properties and loading within the drug delivery system remain stable for reliable tracking within biological systems. This work reports the facile chemical conjugation of the carbocyanine heptamethine near-infrared dye IR780 to polylactide for stable fluorescent labeling of biodegradable polyester nanocarriers. “Clickable” polylactide was synthesized via organocatalyzed ring opening polymerization of D,L-lactide with a cyclooctyne initiator. IR780 was derivatized and conjugated to polylactide via a one-pot copper-free azide-alkyne cycloaddition reaction. The synthetic strategy developed was effective to promote conjugation of the near-infrared fluorescent dye to polylactide, as confirmed by high performance liquid chromatography. Nanoparticles containing the dye–polymer conjugate were prepared by nanoprecipitation and characterized. Asymmetric flow field-flow fractionation with light scattering and fluorescence detection revealed that the near-infrared fluorescence of the nanoparticles remained stable and was not transferred to serum proteins. In contrast, significant transfer of the dye to serum proteins was evidenced when the dye was merely encapsulated in similar nanoparticles through physical entrapment. Confocal microscopy and fluorescence tomography imaging showed that the polymer-dye conjugate confers fluorescence properties to the NP suitable for further in vitro and in vivo pre-clinical studies.

Accurate Determination of Human CPR Conformational Equilibrium by smFRET Using Dual Orthogonal Noncanonical Amino Acid Labeling.

Conjugation of fluorescent dyes to proteins-a prerequisite for the study of conformational dynamics by single-molecule (sm) FRET-can lead to substantial changes in a dye's photophysical properties, ultimately biasing the determination of inter-dye distances. In particular, cyanine dyes and their derivatives, the most commonly used dyes in smFRET experiments, exhibit such behavior. To overcome this, we developed a general strategy to equip proteins site-specifically with FRET pairs through chemoselective reactions with two distinct noncanonical amino acids simultaneously incorporated through genetic code expansion in Escherichia coli. Application of this technique to human NADPH-cytochrome P450 reductase (CPR) demonstrated the importance of homogenously labeled samples for accurate determination of FRET efficiencies and unveiled the effect of NADP+ on the ionic-strength-dependent modulation of the conformational equilibrium of CPR. Thanks to its generality and accuracy, the presented methodology establishes a new benchmark for deciphering of complex molecular dynamics in single molecules.

Fluorescent carbazole based pyridone dyes – Synthesis, solvatochromism, linear and nonlinear optical properties

Carbazole based pyridone dyes are investigated for their non-linear optical (NLO) properties. They exhibit positive solvatochromism and charge transfer character with a high fluorescence quantum yield which encouraged us to study their NLO characteristics. Photophysical properties of dyes in different solvents are evaluated and correlated with computational optical absorption and fluorescence emission using global hybrid (B3LYP) and long range separated functional (CAM-B3LYP) with 6–31G(d) basic set. Frontier Molecular Orbital analysis and Generalised Mulliken Hush analysis reveal a strong intramolecular molecular charge transfer character in these dyes. DFT and TD-DFT are performed to understand the electronic and photophysical properties of dyes. The resultant decrease in the HOMO-LUMO energy gap is responsible for bathochromic shift. Large enhancement in the non-linear optical properties are seen for these dyes than urea confirming their use in non-linear optical materials. The MEP analysis reveals the sites for electrophilic and nucleophilic attack in the dye. The experimental data are in good agreement with those obtained by computation (DFT) method. Fundamental limiting values of β, γ for dyes are observed within the estimated limits.

The Effect of Fluorophore Conjugation on Antibody Affinity and the Photophysical Properties of Dyes

Because the degree of labeling (DOL) of cell-bound antibodies, often required in quantitative fluorescence measurements, is largely unknown, we investigated the effect of labeling with two different fluorophores (AlexaFluor546, AlexaFluor647) in a systematic way using antibody stock solutions with different DOLs. Here, we show that the mean DOL of the cell-bound antibody fraction is lower than that of the stock using single molecule fluorescence measurements. The effect is so pronounced that the mean DOL levels off at approximately two fluorophores/IgG for some antibodies. We developed a method for comparing the average DOL of antibody stocks to that of the isolated, cell-bound fraction based on fluorescence anisotropy measurements confirming the aforementioned conclusions. We created a model in which individual antibody species with different DOLs, present in an antibody stock solution, were assumed to have distinct affinities and quantum yields. The model calculations confirmed that a calibration curve constructed from the anisotropy of antibody stocks can be used for determining the DOL of the bound fraction. The fluorescence intensity of the cell-bound antibody fractions and of the antibody stocks exhibited distinctly different dependence on the DOL. The behavior of the two dyes was systematically different in this respect. Fitting of the model to these data revealed that labeling with each dye affects quantum yield and antibody affinity differentially. These measurements also implied that fluorophores in multiply labeled antibodies exhibit self-quenching and lead to decreased antibody affinity, conclusions directly confirmed by steady-state intensity measurements and competitive binding assays. Although the fluorescence lifetime of antibodies labeled with multiple fluorophores decreased, the magnitude of this change was not sufficient to account for self-quenching indicating that both dynamic and static quenching processes occur involving H-aggregate formation. Our results reveal multiple effects of fluorophore conjugation, which must not be overlooked in quantitative cell biological measurements.

Electronic and Functional Scope of Boronic Acid Derived Salicylidenehydrazone (BASHY) Complexes as Fluorescent Dyes.

A series of boronic acid derived salicylidenehydrazone (BASHY) complexes was prepared and photophysically characterized. The dye platform can be modified by (a) electronic tuning along the cyanine-type axis via modification of the donor-acceptor pair and (b) functional tuning via the boronic acid residue. On the one hand, approach (a) allows the control of photophysical parameters such as Stokes shift, emission color, and two-photon-absorption (2PA) cross section. The resulting dyes show emission light-up behavior in nonpolar media and are characterized by high fluorescence quantum yields (ca. 0.5-0.7) and brightness (ca. 35000-40000 M-1 cm-1). Moreover, the 2PA cross sections reach values in the order of 200-300 GM. On the other hand, the variation of the dye structure through the boronic acid derived moiety (approach (b)) enables the functionalization of the BASHY platform for a broad spectrum of potential applications, ranging from biorelevant contexts to optoelectronic materials. Importantly, this functionalization is generally electronically orthogonal with respect to the dye's photophysical properties, which are only determined by the electronic structure of the cyanine-type backbone (approach (a)). Rare exceptions to this generalization are the presence of redox-active residues (such a triphenylamine or pyrene). Finally, the advantageous photophysics is complemented by a significant photostability.

Rose bengal in poly(2-hydroxyethyl methacrylate) thin films: self-quenching by photoactive energy traps

The effect of dye concentration on the fluorescence,ΦF, and singlet molecular oxygen,ΦΔ, quantum yields of rose bengal loaded poly(2-hydroxyethyl methacrylate) thin films (∼200 nm thick) was investigated, with the aim of understanding the effect of molecular interactions on the photophysical properties of dyes in crowded constrained environments. Films were characterized by absorption and fluorescence spectroscopy, singlet molecular oxygen (1O2) production was quantified using a chemical monitor, and the triplet decay was determined by laser flash-photolysis. For the monomeric dilute dye, ΦF = 0.05 ± 0.01 and ΦΔ = 0.76 ± 0.14. The effect of humidity and the photostability of the dye were also investigated. Spectral changes in absorption and fluorescence in excess of 0.05 M and concentration self-quenching after 0.01 M are interpreted in the context of a quenching radius model. Calculations of energy migration and trapping rates were performed assuming random distribution of the dye. Best fits of fluorescence quantum yields with concentration are obtained in the whole concentration range with a quenching radius rQ = 1.5 nm, in the order of molecular dimensions. Agreement is obtained only if dimeric traps are considered photoactive, with an observed fluorescence quantum yield ratio ΦF,trap/ΦF,monomer ≈ 0.35. Fluorescent traps are capable of yielding triplet states and 1O2. Results show that the excited state generation efficiency, calculated as the product between the absorption factor and the fluorescence quantum yield, is maximized at around 0.15 M, a very high concentration for random dye distributions. Relevant information for the design of photoactive dyed coatings is provided.

Charge Transfer Enhancement in the D-π-A Type Porphyrin Dyes: A Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) Study.

The electronic geometries and optical properties of two D-π-A type zinc porphyrin dyes (NCH3-YD2 and TPhe-YD) were systematically investigated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) to reveal the origin of significantly altered charge transfer enhancement by changing the electron donor of the famous porphyrin-based sensitizer YD2-o-C8. The molecular geometries and photophysical properties of dyes before and after binding to the TiO2 cluster were fully investigated. From the analyses of natural bond orbital (NBO), extended charge decomposition analysis (ECDA), and electron density variations (Δρ) between the excited state and ground state, it was found that the introduction of N(CH3)2 and 1,1,2-triphenylethene groups enhanced the intramolecular charge-transfer (ICT) character compared to YD2-o-C8. The absorption wavelength and transition possess character were significantly influenced by N(CH3)2 and 1,1,2-triphenylethene groups. NCH3-YD2 with N(CH3)2 groups in the donor part is an effective way to improve the interactions between the dyes and TiO2 surface, light having efficiency (LHE), and free energy change (ΔGinject), which is expected to be an efficient dye for use in dye-sensitized solar cells (DSSCs).

Synthesis and photophysical properties of a new BODIPY-based siloxane dye

A fluorescent dye comprising four BODIPY derivatives conjugated to a cyclotetrasiloxane core was synthesized by consecutive hydrosilylation and esterification reactions. Photophysical properties of the dye in various organic solvents were investigated. It was shown that due to a fourfold extinction coefficient increase and a moderate quantum yield decrease the brightness of the tetra-BODIPY dye in low-polarity solvents, calculated per molecule, increased 3 times when compared to mono-BODIPY. By contrast, in polar solvents there was a dramatic drop in brightness apparently associated with intramolecular interactions of the low-polar BODIPY chromophores.

The effect of the number, position, and shape of methoxy groups in triphenylamine donors on the performance of dye-sensitized solar cells

Four new organic photosensitizers (SH-11∼14) that introduced methoxy groups as an additional donor were synthesized, and used in dye-sensitized solar cells. The dyes were designed in order to investigate the effects on the dye photophysical properties and the cell photovoltaic performance, by the number, position, and shape of methoxy groups introduced at the para-/ortho- and para-/meta- and para-(open or closed ring shape) positions on the triphenylamine donor. The introduction of methoxy groups led to bathochromic shift of the absorption spectrum, and enhancement of the molar extinction coefficient of the dyes. Their introduction decreased the amount of dye adsorbed on TiO2 surface, due to the increased steric hindrance. As their number increased, an open-circuit voltage value decreased. All things considered, the dye (SH-14) with closed ring shape shows the best conversion efficiency of 6.01% under AM 1.5G conditions (N719 dye's 7.59% under the same conditions).

Synthesis of novel carbazole based styryl: rational approach for photophysical properties and TD-DFT.

The synthesis and solvatochromic behavior of four novel carbazole based fluorescent styryl dyes were explained. In chlorinated solvents such as DCM and chloroform, these dyes show bathochromic shift in their absorption as well as emission. The styryl dyes 6b and 6c show solid state yellow fluorescence. DFT and TD-DFT computations were performed to study structural, molecular, electronic and photophysical properties of these dyes. The computed absorption and emission wavelength values are found to be in good agreement with the experimental results. The photophysical properties of these 1-styryl carbazole dyes are also compared with the recently reported 3-styrl carbazole dyes. The unique behavior of dye 6d is well explained by its optimized geometry found in the excited state. Ratio of ground to excited state dipole moment of the synthesized novel styryl compounds were calculated by Bakhshiev and Bilot-Kawski correlations.