Aggregation Of Rhodamine Research Articles

Characterizing Counterion-Dependent Aggregation of Rhodamine B by Classical Molecular Dynamics Simulations.

The aggregation in a solution of charged dyes such as Rhodamine B (RB) is significantly affected by the type of counterion, which can determine the self-assembled structure that in turn modulates the optical properties. RB aggregation can be boosted by hydrophobic and bulky fluorinated tetraphenylborate counterions, such as F5TPB, with the formation of nanoparticles whose fluorescence quantum yield (FQY) is affected by the degree of fluorination. Here, we developed a classical force field (FF) based on the standard generalized Amber parameters that allows modeling the self-assembling process of RB/F5TPB systems in water, consistent with experimental evidence. Namely, the classical MD simulations employing the re-parametrized FF reproduce the formation of nanoparticles in the RB/F5TPB system, while in the presence of iodide counterions, only RB dimeric species can be formed. Within the large, self-assembled RB/F5TPB aggregates, the occurrence of an H-type RB-RB dimer can be observed, a species that is expected to quench RB fluorescence, in agreement with the experimental data of FQY. The outcome provides atomistic details on the role of the bulky F5TPB counterion as a spacer, with the developed classical FF representing a step towards reliable modeling of dye aggregation in RB-based materials.

Improvement of light stability of DHR123 radio fluorogenic nano clay gel dosimeter by incorporating a new dispersant

A tissue-equivalent three-dimensional dosimeter is being developed to verify dose distributions for radiotherapy. Recently, we have reported a nanocomposite fluorescent gel (NC-RFG) dosimeter that enables readout by the fluorometry, which is more sensitive than absorption method in principle. However, irradiating by an excitation light for a dose information readout also produces fluorescent dyes and is not negligible in the low-dose irradiation range under 1 Gy. In this study, we investigate new additives to improve the NC-RFG’s light stability. We successfully suppressed the light-sensitive property of the NC-RFG to at least 10% of normal conditions by adding either N-vinylpyrrolidone or pyridine as a new dispersant that is presumed to break up aggregation of rhodamine 123 (RD123) and dihydrorhodamine 123 (DHR123) to stop photoexcited RD123 from oxidizing the adjacent DHR123. We also provide a detailed study of sensitivity characteristics such as dose rate dependence for fluorescent gel dosimeters.

Diltiazem Potentiation of Doxorubicin Cytotoxicity and Cellular Uptake in Human Breast Cancer Cells

Aim: Breast cancer is the most common cancer among Arab women and also around the world. Chronic cardiotoxicity and multidrug resistance are potential limiting factors of doxorubicin (DOX), a known anthracycline antibiotic. Materials & methods: DOX cytotoxicity was evaluated by the sulforhodamine method. DOX cellular uptake, detection of P-glycoprotein activity and the photomicrograph of MCF-7 cells were also determined. Results: Diltiazem (DIL) treatment improved DOX cytotoxic activity and increased the cellular uptake of DOX significantly and aggregation of rhodamine 123, reflecting inhibition of P-glycoprotein pump. Cytopathological investigation of MCF-7 cells revealed marked cytotoxic activity of DOX in the presence of DIL. Conclusion: DIL treatment enhanced DOX cytotoxic effect and reduced multidrug resistance, which increased the drug accumulation intracellularly.

Reaction kinetics of molecular aggregation of rhodamine 123 in colloids with synthetic saponite nanoparticles

The reaction kinetics of the molecular aggregation of rhodamine 123 in the colloids of synthetic saponite (Sumecton, Kunimine, Japan) was measured using a UV–Vis spectrophotometer equipped with a diode array detector with fast sampling and combined with a thermostatic stopped-flow device. The colloids exhibited a very small tendency to produce dye molecular aggregates, which can be explained by the low layer charge of saponite. Nevertheless chemometric methods, including principal component analysis and multivariate curve resolution, were able to sensitively identify spectral components. The reaction kinetics of dye aggregation followed the model, which was mathematically described by two-phase exponential functions, which indicated the presence of two parallel first-order reactions. Oblique aggregates were formed, characterized by approximate right angles between interacting transition moments. Another reaction, which was assigned to the structural changes of the aggregates, was detected after longer reaction times. The total span of the reaction was relatively low (~5%). The reaction was relatively fast, giving half-lives in the range 8–10s. Reaction kinetics parameters can be useful for the characterization of similar reactions occurring in dye/clay mineral colloidal systems.

Tunable wavelength light emission and amplification in Rhodamine 6G aggregates

In this work, the authors present experimental results of tunable amplified spontaneous emission (ASE) and random lasing (RL) emission wavelength, which mechanism is based on Rhodamine 6G (Rh6G) aggregates formation. Dye concentration controlled light amplification has been applied for RL and ASE on Rhodamine-doped biopolymeric layers like modified deoxyribonucleic acid (DNA) or starch. Additionally, measurements of ASE from water suspension with and without phosphatidylcholine (PC) lipids, confirmed Rhodamine aggregates role on different wavelength emission of ASE and RL. There have been acquired wide tuning of lasing equal to 35 nm observed for different studied biological systems.

Fluorinated counterion-enhanced emission of rhodamine aggregates: ultrabright nanoparticles for bioimaging and light-harvesting.

The key to ultrabright fluorescent nanomaterials is the control of dye emission in the aggregated state. Here, lipophilic rhodamine B derivatives are assembled into nanoparticles (NPs) using tetraphenylborate counterions with varied fluorination levels that should tune the short-range dye ordering. Counterion fluorination is found to drastically enhance the emission characteristics of these NPs. Highly fluorinated counterions produce 10-20 nm NPs containing >300 rhodamine dyes with a fluorescence quantum yield of 40-60% and a remarkably narrow emission band (34 nm), whereas, for other counterions, aggregation caused quenching with a weak broad-band emission is observed. NPs with the most fluorinated counterion (48 fluorines) are ∼40-fold brighter than quantum dots (QD585 at 532 nm excitation) in single-molecule microscopy, showing improved photostability and suppressed blinking. Due to exciton diffusion, revealed by fluorescence anisotropy, these NPs are efficient FRET donors to single cyanine-5 acceptors with a light-harvesting antenna effect reaching 200. Finally, NPs with the most fluorinated counterion are rather stable after entry into living cells, in contrast to their less fluorinated analogue. Thus, the present work shows the crucial role of counterion fluorination in achieving high fluorescence brightness and photostability, narrow-band emission, efficient energy transfer and high intracellular stability of nanomaterials for light harvesting and bioimaging applications.

Spectroscopic properties of Rhodamine B entrapped in hybrid porous nanolayers at high dye concentration

The preparation procedure and characterization of Rhodamine B entrapped in zirconia, silica and mixed silica–zirconia nanolayers is described. The nanolayers were produced by the sol–gel spin-coating technique. The pronounced effect of the dye concentration on the absorption and fluorescence spectra as well as on time-resolved fluorescence spectra was found. The results show that the aggregation of Rhodamine B is stronger in silica based matrices compared to zirconia nanolayers. Time-resolved emission spectra at highest Rhodamine B concentration show that the dye aggregates are fluorescent.

Dewetting-Assisted Formation of Novel Dequenched Aggregates of Rhodamines: Comparison with J- and H-Aggregates

Self-organized rhodamine aggregates prepared by wetting/dewetting process of an ethanol solution on a hydrophilic glass surface consistently exhibited fluorescence without quenching. Upon annealing, the aggregates exhibited an irreversible transition to quenched state, similar to H-aggregate, whereas the fluorescence spectrum was unchanged. The as grown highly fluorescent aggregate is a novel aggregate, neither a J-aggregate nor an H-aggregate, showing a blue-shifted excitation spectrum whereas the emission spectrum is similar to that of molecularly dispersed solution. This fluorescent aggregate was only realized in nonequilibrium by the rapid dewetting process.

Direct white light photoluminescent nanoparticles with one fluorophore

Aggregation of Rhodamine B (RhB) fluorophore in confined nanoscale domains changes thephotoluminescence behavior of RhB in core–shell silica/PGMA–RhB nanoparticles. Underan excitation at 365 nm, silica/PGMA–RhB nanoparticles exhibit a two-band emission ofyellow and blue in a tetrahydrofuran (THF) solution, compared to the yellow emission ofRhB in a THF solution. The yellow and blue emissions of silica/PGMA–RhBnanoparticles are of approximately equal intensity, and mix together to showwhite light emission from the core–shell nanoparticles. Removal of the silica corefrom the core–shell nanoparticles does not alter its photoluminescence behavior.Therefore, the white light emission of RhB in the nanoparticles originates from theaggregation of RhB molecules in a nanoscale domain. This finding provides a new andconvenient approach to the preparation of white light photoluminescent materials.

Selective formation of dequenched aggregates of rhodamines: comparison with J‐ and H‐aggregates

AbstractSelf‐organized rhodamine aggregates prepared by wetting / dewetting process of an ethanol solution on a hydrophilic glass surface consistently exhibited fluorescence without quenching. Upon annealing, the aggregates exhibited an irreversible transition to quenched state, similar to H‐aggregate, whereas the fluorescence spectrum was unchanged. The as grown highly fluorescent aggregate is a novel aggregate, neither a J‐aggregate nor an H‐aggregate, showing a blue‐shifted excitation spectrum whereas the emission spectrum is similar to that of molecularly dispersed solution. This fluorescent aggregate was only realized in nonequilibrium by the rapid dewetting process. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Selective Formation of a Novel Dequenched Aggregates of Rhodamines: Comparison with J- and H-Aggregates

Self-organized rhodamine aggregates prepared by wetting/dewetting process of an ethanol solution on a hydrophilic glass surface consistently exhibited fluorescence without quenching. Upon annealing, the aggregates exhibited an irreversible transition to quenched state, like H-aggregate, whereas the fluorescence spectrum was unchanged. The as grown fluorescent aggregate is a novel aggregate, neither a J-aggregate nor an H-aggregate, showing a blue-shifted excitation spectrum whereas the emission spectrum is similar to that of molecularly dispersed solution. This fluorescent aggregate was only realized in nonequilibrium by the rapid dewetting process. [DOI: 10.1380/ejssnt.2009.89]

Aggregation of Rhodamine B in Water

Protolytic and associative equilibria in aqueous solutions of rhodamine B were studied. The curves of potentiometric titration with NaOH solution of the dye hydrochloride within the 5 ×10-4-3 ×10-2 M range and at an ionic strength of 0.1 M (NaCl or KCl) were treated by chemometric methods of successive modification of the equilibrium system models with regard to spectrophotometric data. The most probable value of the equilibrium constants of the reaction iH+ + jR ⇄ H i R j i+ were determined.

Resonant Second Harmonic Spectroscopy of Rhodamine B Adsorbed onto Fused Silica.

A measurement system for resonant second harmonic(RSH) spectroscopy using an optical arrangement of total internal reflection was developed as an analytical method for investigating molecules adsorbed on substrate surfaces. RSH spectra were measured for the rhodamine B molecules adsorbed on a fused quartz substrate with different coverages. It was demonstrated for the first time by the polarization measurements that aggregation of rhodamine B occurred on a fused quartz, and that both of the dimeric and monomeric species coexisted on the surface.

On the aggregation of rhodamine B in ethanol

The dimer and the trimer aggregation constants of the cationic form of rhodamine B are determined in very concentrated ethanolic solutions of the dye. The absorption spectrum, the geometrical structure and the association bonding of the aggregates are discussed and compared with those previously obtained in aqueous solution.