Fluorescence Spectra Of Dyes Research Articles

PHOTOPHYSICAL PROPERTIES OF INDOTRICARBOCYANINE DYES DURING COMPLEXATION WITH SERUM ALBUMIN

The photophysical properties of indotricarbocyanine dyes upon complexation with serum albumin have been studied, and the technique for controlling their formation using electrophoresis has been optimized. In connection with the degradation of dye molecules under the action of acids, the search for the area of localization of the dye under study on the surface of the gel plate was carried out by recording the fluorescence spectra of the dye before protein fixation and visualization followed by the completion of the protocol for obtaining electrophoregrams. To minimize the possible influence of the luminescence of the gel components, the excitation was carried out by the radiation of a semiconductor laser with a wavelength of 684 nm, which initiates the fluorescence of the studied dyes. It was established that the position of the maxima and the half-width of the fluorescence spectra of dyes with an orthophenylene bridge in the conjugation chain in the regions of the electropherogram corresponding to the localization of albumin coincide with the characteristics of the emission of dyes in initial solutions with albumin, which makes it possible to reveal the formation of covalently bound complexes of dye molecules with albumin.

Replica Symmetry Breaking in Cholesteric Liquid Crystal Bandgap Lasing

AbstractSpin glass theory is an interdisciplinary statistical theory that has been widely used to describe the complex physical systems in diverse fields. In photonic platforms, the characteristic phenomenon of the phase transition between paramagnetic and spin glass state, i.e., replica symmetry breaking (RSB), has been recently observed in random laser (RL) systems via analogies between optical modes and magnetic spins. Here, the RSB phenomenon in cholesteric liquid crystal (CLC) bandgap lasing is reported. The CLC lasing arises from the edge of bandgap when the reflection spectrum edge of CLC spectrally overlaps with the fluorescence spectrum of dye. Different from the RL systems, where the RSB phenomenon is frequently observed, bandgap laser shows weak disorder due to its self‐assembled helical structure. Unexpectedly, based on the statistical study of the lasing spectra, the RSB can still be found when the bandgap laser operates at the threshold point. This RSB phenomenon is robust when the bandgap laser works at different temperatures and wavelengths. These results extend the scope of the feasibility of the spin glass theory in the photonic field, which boost the understanding of the interplay between system disorder and lasing statistical behavior.

Breaking the Brightness Barrier: Design and Characterization of a Selected-Ion Fluorescence Measurement Setup with High Optical Detection Efficiency.

A quadrupole ion trap (QIT) mass spectrometer has been modified and coupled with tunable laser excitation and highly sensitive fluorescence detection systems to perform fluorescence studies on mass-selected ions. Gaseous ions, generated using nanoelectrospray ionization (nano-ESI), are trapped in the QIT that allows optical access for laser irradiation. The emitted fluorescence is collected from a 5.0 mm diameter hole drilled into the ring electrode of the QIT and is directed toward the detection setup. Due to the small inner diameter (7.07 mm) of the ring electrode and a relatively large opening for fluorescence collection, a fluorescence collection efficiency of 2.3% is achieved. After some losses in transmission, around 1.8% of the emitted fluorescence reaches the detectors, more than any other similar instrument reported in the literature. This improved fluorescence collection translates to a much shorter measurement time for a fluorescence signal. Another key feature of this setup is the ability to perform a variety of fluorescence experiments on trapped ions including excitation and emission spectroscopy, lifetime measurement, and ion imaging. The capabilities of the instrument are demonstrated by measuring fluorescence spectra of dyes and biomolecules labeled with dyes in a range of different excitation and emission wavelengths, quantum yields, m/z, and different polarities. A fluorescence lifetime measurement and ion image of trapped rhodamine 6G cations are also shown. With a wide array of functionality and high fluorescence detection performance, this setup provides an opportunity to study biomolecular structures and photophysics of fluorophores in well-controlled environments.

Enhancement of Fluorescence and Photostability Based on Interaction of Fluorescent Dyes with Silver Nanoparticles for Luminescent Solar Concentrators

For luminescent solar concentrators (LSCs), it is important to enhance the fluorescence quantum yield (FQY) and photostability. Our measurements have demonstrated that the addition of silver nanoparticles to dye solution causes broadening of absorption bands, so the spectral range of sunlight absorbed by LSC has increased. Silver nanoparticles (NPs) were characterized by X-ray diffraction (XRD) and UV-Vis absorption spectra. UV-Vis spectrum showed a single peak at 442 nm due to the surface plasmon resonance (SPR). The position of SPR peak exhibited a red shift after the sample was exposed to UV irradiation (unfiltered light). The optical band gap values have a reduction from 2.46 to 2.37 eV after irradiation for 960 minutes. Such reduction in optical band gap may be due to change in particle size calculated using Mie theory. The photostability of organic dyes used was improved after adding silver nanoparticles. The area under fluorescence spectra of dyes with silver NPs increased by 41–31% when compared with identical dye concentrations without silver nanoparticles as a result of interaction of the species with silver NPs.

Fluorescence Diagnosis of Damage to Tumor Tissues During Photodynamic Therapy with the Photosensitizer Photolon®

We have studied the feasibility of using an indotricarbocyanine dye as a marker for the efficacy of photodynamic therapy (PDT) of cancers with the photosensitizer Photolon®. We have established that on exposure to laser emission at λ = 667 nm with an exposure dose of 100 J/cm2, we observe that the Photolon® concentration drops by about a factor of two in the exposed part of the tumor, while the concentration of the indotricarbocyanine dye does not change in any region of the tumor node. We have observed a correlation between the change in the shape of the fluorescence spectra of the indotricarbocyanine dye in vivo in the 780–880 nm resulting from a PDT session with the photosensitizer Photolon® and the extent of damage to the tumor tissues. Changes in the shape of the fluorescence spectrum of the dye are interpreted in terms of a model involving the appearance of absorption by different forms of hemoglobin, and changes in their ratio in the exposed part of the tumor due to consumption of molecular oxygen.

Aggregation Control of Hemicyanine Fluorescent Dye by Using of Cucurbit[7]uril and Pillar[6]arene

AbstractThe aggregation of cyanine‐based fluorescent dyes easily results in the fluorescence quenching, which limits the applications in biological science and materials science. So developing an efficient method to adjust the aggregation of cyanine dyes is very significant. In this work, we employ two different macrocyclic hosts pillar[6]arene (DEP[6]) and cucurbit[7]uril (CB[7]) to investigate their effects towards fluorescence spectra of dye 1. The result indicates that both of them can disrupt the aggregation of dye 1, resulting in the enhancement of its fluorescence intensity. Interestingly, investigation on the corresponding titration experiments of 1H NMR and density functional theory calculations shows that CB[7] and DEP[6] play different roles in the process of disaggregation.

Ratiometric CdSe/ZnS Quantum Dot Protein Sensor

We have created a platform for the ratiometric fluorescent sensing of targeted proteins by conjugating conjoined protein binding agent/organic dye ligands to water-soluble, emissive semiconductor quantum dots (QDs). The QD emission is tuned such that it may serve as an energy transfer donor to the dye acceptor. Upon exposure to the target proteins, these analytes bind to the surfaces of the QDs and change the microenvironments of the QD-bound dyes such that the emissive properties of the dyes are perturbed. The resulting alteration in the QD and dye fluorescence spectra creates a readout that is fully quantitative. The advantage of our methodology is that the detection of proteins is very fast as the platform is fully homogeneous, whereas the heterogeneous ELISA assay involves multiple steps with blocking agents and secondary reporters that ultimately complicate the process. The calculated detection limits for the two QD protein-sensing examples reported here are also competitive with the ubiquitous ELISA assay.

Photoactive spherical colloids for opal photonic crystals

The synthesis and characterization of submicrometer‐sized polymer particles, functionalized by different techniques with fluorescent dyes and featuring tunable surface charges, are described. Dyes with a polymerizable moiety were incorporated during emulsifier‐free or seeded emulsion polymerization, whereas non‐polymerizable dyes were included into preformed nanoparticles by a swelling and deswelling process. The particle surface charge was controlled through the choice of suitable initiators. All the nanoparticles were successfully used to grow high optical quality opal photonic crystals by the vertical deposition technique. Optical characterization of such photonic crystals pointed out the presence of the optical stop band and the high‐energy van Hove‐like structures, both scaling with the particle diameter according to the scaling laws of photonic crystals and possessing the expected angular dispersion. These results are indicative of the high size uniformity and of the surface quality of the nanospheres independently on the synthetic method adopted. Preliminary data seem to suggest some effect of the opal photonic band structure on the dye fluorescence spectra. POLYM. COMPOS., 34:1443–1450, 2013. © 2013 Society of Plastics Engineers.

Fluorescence of a photosensitizer based on an indotricarbocyanine dye in photochemotherapy

We present the results for studies of the spectral luminescence properties of a symmetric indotricarbocyanine dye (PD1) in HeLa tumor cells and animal tissues in vivo during a photochemotherapy session and after the end of the session. We have established that when the dye is exposed to light in tumor tissues, changes occur in the position and half-width of the dye fluorescence spectra, while in a culture of HeLa cells its spectral characteristics are constant. Based on analysis of the effect of overlap between the absorption spectra of endogenous biomolecules and the fluorescence spectra of the dye plus comparison of the experimental data with numerical modeling results, we have concluded that the observed changes in the fluorescence spectra of PD1 in vivo are due to a change in the ratio of the different forms of hemoglobin in the tumor tissue. We have shown that the spectral characteristics of PD1, fluorescing in the near IR range, correlate with the depth of tumor tissue necrosis achieved on exposure to light. We have established that tumor tissue necrosis occurs down to a depth of 2 cm in the case of all strains studied: S-45, SM-1, and W-256, where as a result of exposure to light, we observe an increase in the half-width and a short-wavelength shift of the fluorescence spectrum of the dye PD1, and also the intensity of its fluorescence does not recover.

Spectral luminescence properties of indotricarbocyanine dye in biological tissues

We have established that the shape and position of the maximum in the fluorescence spectrum of an indotricarbocyanine dye in tumor and normal tissues in vivo change over time after intravenous injection of the dye. Based on analysis of the spectral properties of the dye in vivo and in blood plasma, the dependence of the properties on the time since injection has shown that in the living body, the environment of the dye molecule changes as the photosensitizer goes from the skin into the tissue. We have established that in tissues in vivo, the dye molecules are localized in a region with low dielectric constant of the medium. We have shown that the change in the ratio of the concentrations of the different forms of hemoglobin in the blood has an effect on the absorption and shape of the fluorescence spectrum of the dye in tissues in vivo.

Low Threshold Lasing in Cholesteric Liquid Crystals

Cholesteric liquid crystals, due to their periodic structure and large birefringence, are 1-d photonic band-gap materials. Circularly polarized light of the same handedness as the cholesteric structure cannot propagate in the reflection band. We have studied the effects of this band-gap structure on the fluorescence spectrum of dyes dissolved in the cholesteric liquid crystal, as well as on the fluorescence spectrum of the liquid crystal itself. We have found that emission is enhanced at the band edges, and, above a certain pump threshold, lasing occurs both in dye-doped and in pure liquid crystals. Extremely low lasing thresholds and high efficiencies were observed in dye-doped systems. The results suggest an active energy transfer mechanism between the LC host and the fluorescent dye molecules.

51.3: Lasing in Cholesteric Liquid Crystals

AbstractWe have observed mirrorless lasing in dye‐doped and pure cholesteric liquid crystals. The periodic structure and large birefringence gives rise to photonic band‐gap behavior in these materials. We have studied the effects of this band‐gap structure on the fluorescence spectrum of dyes dissolved in the cholesteric liquid crystal as well as on the emission characteristics of the liquid crystal itself. Enhancement of fluorescence at the band edges, and, above a certain pump threshold, lasing both in dye‐doped and in pure liquid crystals was observed. Extremely low lasing thresholds and high efficiencies were obtained in dye‐doped systems. Experimental results suggest an active energy transfer mechanism between the LC host and the fluorescent dye molecules.

Light sources inside photonic crystals

We have measured the optical fluorescence spectra of dye incorporated in high-quality photonic crystals made from colloids. The spectra reveal a stopgap that is due to Bragg reflection with strikingly reduced attenuation compared with plane-wave transmission. The modified attenuation is independent of the position of the sources in the sample and is brought about by diffuse scattering from defects near the surface. In the presence of a photonic bandgap, the diffuse component would disappear. Thus we have found a simple, unambiguous probe for the presence of photonic bandgaps.

Luminescence properties of anodic aluminum oxide films with organic luminophores embedded into pores

Luminescence properties of porous anodic aluminum oxide films formed in a 0.6 M solution of citric acid and luminescence of paraterphenyl, perylene, coumarin 7, and rhodamine 6G dyes adsorbed by the films are investigated. The nature of emitting centers in anodic aluminum oxide is revealed. Intense photoluminescence of all tested dyes embedded into pores of anodic aluminum oxide has been found. A redshift of fluorescence spectra of dyes adsorbed by the matrix and emergence of an additional longwave band have been detected. Data obtained can be used in developing new thin-film luminescent coatings for future applications in optoelectronics and molecular electronics.

Spectroscopic investigations of the potential-sensitive membrane probe RH421

The absorbance spectra, fluorescence emission and excitation spectra, and fluorescence anisotropy of the potential-sensitive styryl dye RH421 have been investigated in aqueous solution and bound to the lipid membrane. The potential-sensitive response of the dye has been studied using a preparation of membrane fragments containing a high density of Na +, K 1-ATPase molecules. In aqueous solution the dye is sensitive both to changes in pH and ionic strength. Evidence has been found that the dye readily aggregates in aqueous solution. Aggregation is enhanced by an increase in ionic strength. The aggregates formed display a low fluorescence intensity. At high pH values (above approx. 8) changes in the dye's fluorescence spectra are observed, which may be due to a reaction of the dye with hydroxide ions. When bound to the membrane the dye also exhibits concentration-dependent fluorescence changes. The potential-sensitive response of the dye in Na +, K +-ATPase membrane fragments after addition of MgATP in the presence of Na + ions cannot be explained by a purely electrochromic mechanism. The results are consistent with either a potential-dependent equilibrium between membrane-bound dye monomers and membrane-bound dimers. similar to that previously proposed for the dye merocyanine 540, or with a field-induced structural change of the membrane.

FLUORESCENCE ENHANCEMENT OR QUENCHING OF MOLECULE AT SERS ACTIVE SURFACES

Molecular fluorescence spectra of dye adsorbed on silver colliod and silver mirror were studied. Acriding Orange was used as sample in the experiment. We have found that the enhancement or quenching are depend on the competition of two processes, i.e., local field enhancement and non-radiation energy transfer from the molecule to metal surface. The fluorescence is enhanced when enhanced absorption and enhanced emission conditions are achieved. However, molecular fluorescence is far less enhanced then Raman. Theoretical calculation shows that peak enhencement of fluorescence intensity will be 10-102. It agrees with the experimental value for Acriding Orenge adsorbed on silver mirror.

Effects of human serum albumin on absorption and fluorescence spectra of dyes related to Chrome Azurol S.

Effects of human serum albumin on absorption and fluorescence spectra of dyes related to Chrome Azurol S.

On the nanosecond mobility in proteins. Edge excitation fluorescence red shift of protein-bound 2-(p-toluidinylnaphthalene)-6-sulfonate.

The fluorescence of 2-(p-toluidinylnaphthalene)-6-sulfonate associated with beta-lactoglobulin, beta-casein, and bovine and human serum albumins are shown to depend on excitation wavelength. A long-wave shift of the spectra is observed at the long-wave edge excitation, reaching 10 nm and above. A similar phenomenon is found in glucose glass and in glycerol at +1 degrees C, i.e., in systems with delayed dipolar solvent relaxation, but not in liquid solutions. This phenomenon is proposed to be based on relaxation processes in the excited state. There exists a distribution of chromophore microstates with different interactions with surrounding groups which results in heterogeneous broadening of the electronic spectra and allows photoselection of a part of this distribution, being characterized by a low transition energy. The fast structural relaxation results in an altered distribution and, if this is the case, the effect of edge excitation of fluorescence spectra is not observed. If the structural relaxation during the excited state lifetime is absent, this effect is maximal. This interpretation is in agreement with results on the influence of red edge excitation on the low-temperature fluorescence spectra of dyes and with the data on time-resolved nanosecond fluorescence spectroscopy. The results of this work strongly support the significant dye fluorescence spectral shifts on protein binding, being determined not only by polarity changes in their environment, but also by relaxation properties of protein groups in this environment. These results also indicate that on the nanosecond time scale, the structural relaxation around the excited chromophore in proteins may be incomplete.

Fluorescence and absorption spectra of Rose-Bengal dye in the presence of surfactants

The fluorescence and absorption spectra of Rose Bengal dye in aqueous solution have been studied in the presence of various nonionic, anionic and cationic surfactants. With cationic and nonionic surfactants, shifts occur in the absorption and emission peaks of the dye solution, with a large enhancement in the absorption and fluorescence intensity at the shifted λ max. No appreciable change in the absorption and fluorescence spectra of the dye has been observed on the addition of anionic surfactants. All the changes observed in the absorption and fluorescence spectra of the dye solution with surfactants may be attributed, to binding of the surfactant with dye molecules and the disaggregation of the dye multimer forms into the monomeric form.