Laser Dye Rhodamine Research Articles

Strong coupling between surface plasmon polariton and laser dye rhodamine 800

We report on strong coupling between surface plasmon polaritons on a thin silver film and laser dye Rhodamine 800. Attenuated total reflection measurements reveal that the pure surface plasmon polaritons interact with the Rhodamine 800 absorption lines exhibiting pronounced anticrossings in the dispersion relation. We show that the corresponding energy gap can be tailored by the concentration of dye molecules in the dielectric matrix between 50 meV and 70 meV. We can well model our data by a classical transfer matrix approach as well as by a quantum mechanical coupled oscillator ansatz.

Adsorption kinetics of a fluorescent dye in a long chain fatty acid matrix

This work reports the adsorption kinetics of a highly fluorescent laser dye rhodamine B (RhB) in a preformed stearic acid (SA) Langmuir monolayer. The reaction kinetics was studied by surface pressure–time ( π– t) curve at constant area and in situ fluorescence imaging microscopy (FIM). Increase in surface pressure (at constant area) with time as well as increase in surface coverage of monolayer film at air–water interface provide direct evidence for the interaction. ATR–FTIR spectra also supported the interaction and consequent complexation in the complex films. UV–vis absorption and Fluorescence spectra of the complex Langmuir–Blodgett (LB) films confirm the presence of RhB molecules in the complex films transferred onto solid substrates. The outcome of this work clearly shows successful incorporation of RhB molecules into SA matrix without changing the photophysical characteristics of the dye, thus making the dye material as LB compatible.

Adsorption of Cationic Laser Dye onto Polymer/Surfactant Complex Film

Fabrication of complex molecular films of organic materials is one of the most important issues in modern nanoscience and nanotechnology. Soft materials with flexible properties have been given much attention and can be obtained through bottom up processing from functional molecules, where self-assembly based on supramolecular chemistry and designed assembly have become crucial processes and technologies. In this work, we report the successful incorporation of cationic laser dye rhodamine 6G abbreviated as R6G into the pre-assembled polyelectrolyte/surfactant complex film onto quartz substrate by electrostatic adsorption technique. Poly(allylamine hydrochloride) (PAH) was used as polycation and sodium dodecyl sulphate (SDS) was used as anionic surfactant. UV-Vis absorption spectroscopic characterization reveals the formation of only H-type aggregates of R6G in their aqueous solution and both H- and J-type aggregates in PAH/SDS/R6G complex layer-by-layber films as well as the adsorption kinetics of R6G onto the complex films. The ratio of the absorbance intensity of two aggregated bands in PAH/SDS/R6G complex films is merely independent of the concentration range of the SDS solution used to fabricate PAH/SDS complex self-assembled films. Atomic force microscopy reveals the formation of R6G aggregates in PAH/SDS/R6G complex films.

Microstructural, Surface Morphological, and Micro-Hardness Analysis and Characterization of Laser Dye Rhodamine (Rh6G) Doped PMMA Polymeric Matrices

Polymer complex samples of laser dye rhodamine (Rh6G) doped polymethyl methacrylate (PMMA) with various compositions (PMMA: Rh6G :: 2 g : 0.005 mg, 2 g : 0.05 mg, 2 g : 0.5 mg) and 2 g pure PMMA were prepared by the solution cast method. The pure and doped polymeric samples were investigated by Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and atomic force microscopy (AFM) techniques. The effect induced by rhodamine (Rh6G) on the strength of polymethyl methacrylate (PMMA) samples was studied by measuring the surface micro-hardness using the Vickers micro-hardness tester. Significant changes were observed in the Vickers micro-hardness number (Hv) and the structural and morphological behavior, which have been correlated.

Spectral properties of rhodamine 6G in smectite dispersions: Effect of the monovalent cations

Montmorillonite monoionic forms with alkali metal and NH4+-cations were prepared by ion exchange. The hydration properties and binding of the ions to montmorillonite surface and the swelling properties of the mineral specimens were analyzed. Whereas Na+- and Li+-ions were fully hydrated over a large range of conditions, large size K+, NH4+, and mainly Rb+ and Cs+ ions were apt to bind directly to the oxygen atoms on the mineral surface. The forms with large ions exhibited reduced hydration and swelling and the absence of macroscopic swelling of the respective aqueous colloids. The interaction of laser dye rhodamine 6G (R6G) in montmorillonite colloids was investigated by absorption and steady-state fluorescence spectroscopies. Significant effects of the properties of both the inorganic ions and swelling properties of colloidal dispersions on R6G molecular aggregation were observed. Large amounts of the molecular aggregates were formed in the colloids of Na+- and Li+-montmorillonites. The aggregates absorbed light at significantly lower wavelengths (∼460nm) with respect to the light absorption by monomers (535nm). Fluorescence spectroscopy provided a key evidence for the assignment of the type of the aggregates: The emission of the aggregates at relatively low energies proved these assemblies are rather a mixed H-/J-type than ideal H-aggregates. The presence of parent inorganic cations of larger size led to a significant lowering of the amount of the R6G aggregates in favor of the monomers. Investigations of the evolution of the dye aggregation with time indicated basic features of dye aggregation reaction: The size of parent inorganic ions did not affect the reaction mechanism, but rather limited the extent of the reaction. Probably the forms with large inorganic ions, such as Rb+ and Cs+, did not provide sufficient surface for the formation of the large size assemblies of the dye. This property can be explained in terms of strong association of the large alkali metal ions to clay mineral surface, as well as to reduced swelling in the colloidal systems of respective forms.

Laser performance and photostability of Rhodamin B in solid host matrices

Laser dye Rhodamine B was incorporated at different concentrations in GMA polymer, sol–gel glass and organic–inorganic hybrid material synthesized using the sol–gel process. The amplified spontaneous emission (ASE) was studied using Nd-YAG laser of 532 nm. The effect of laser excitation in transfer pumping configuration and the influence of dye concentration on the ASE were studied. Also, the gain and the energy conversion efficiencies were investigated. Relatively high efficiencies (to ∼48%) were obtained with good photostabilities where a decrease to ∼30% of the initial amplified spontaneous emission output energy were observed after pumping by 35000 shots at relatively high repetition rate (10 Hz) and energy (15 mJ). The composition and the properties of the matrix were found that optimize the laser performance and photostability of an investigated dye.

Diphenylhexatrienes as Photoprotective Agents for Ultrasensitive Fluorescence Detection

Given the particular importance of dye photostability for single-molecule investigations, fluorescence fluctuation spectroscopy, and laser-scanning microscopy, refined strategies were explored for enhancing the fluorescence signal by selectively quenching the first excited triplet state of the laser dye Rhodamine 123 (Rh123). The strategy is to quench the T(1) state by Dexter triplet energy transfer, while undesired quenching of the singlet state via Forster or Dexter singlet energy transfer and the generation of free radicals through electron transfer should be avoided. Diphenylhexatrienes (DPHs) were tested in ethanol for their beneficial effects as a novel class of photoprotective agents using fluorescence correlation spectroscopy. A library of DPHs with electron-donating (dimethlyamino) and withdrawing substituents (e.g., trifluormethyl) was synthesized to optimize the electronic properties. Quantum chemical calculations, optical spectroscopy, and cyclic voltammetry were used to determine the electronic properties. The computed T(1) emission energy of Rh123 and the T(1) excitation energies of all DPHs allow for exergonic triplet energy transfer to the quencher. The parent compound quenches the T(1) state of Rh123 nearly diffusion controlled (4.9 x 10(9) M(-1) s(-1)). All electron-deficient DPHs significantly increase (3x) the fluorescence rate of Rh123 by reducing the triplet state population and by avoiding the formation of other long-lived dark radical states. The quenching constants are reduced by more than a factor of 2, if substituents with increasing size or electronegativity are introduced. The beneficial effect of triplet quenching of substituted DPHs is governed by a delicate interplay of steric, electronic, and intermolecular Coulombic effects.

Molecular dynamics simulation of the effect of pH on the adsorption of rhodamine laser dyes on TiO2 hydroxylated surfaces

We have carried out a study of adsorption, on the (1 0 1) surface of anatase TiO2, of two industrially relevant rhodamine molecules [rhodamine 6G (R6G) and rhodamine 800 (R800)] employing molecular dynamics. These theoretical studies have shown that R6G must adsorb on surfaces under basic conditions. Moreover, the adsorption of this molecule shows a strong dependence upon the pH of the system, i.e. under basic conditions the adsorption energy is quite high, under neutral conditions the adsorption energy is lower and under acidic conditions an even lower adsorption energy indicates that there must be very little adsorption under such conditions. By contrast, for R800, there is little dependence of the adsorption energy upon the pH, suggesting that the amount of adsorption of these molecules is little affected by this parameter. These theoretical results are in qualitative agreement with the experimental results consisting of the incorporation of these dye molecules into porous thin films.

Selective mode excitation in dye-doped DNA polyvinyl alcohol thin film

A solid-state laser based on a dye-doped deoxyribonucleic acid (DNA) matrix is described. A thin solid film of DNA has been fabricated by treating with polyvinyl alcohol (PVA) and used as a host for the laser dye Rhodamine 6G. The edge emitted spectrum clearly indicated the existence of laser modes and amplified spontaneous emission. Lasing was obtained by pumping with a frequency-doubled Nd:YAG laser at 532 nm. For a pump energy of 10 mJ/pulse, an intense line with FWHM approximately 0.2 nm was observed at 566 nm due to selective mode excitation.

Effect of Host Medium on the Fluorescence Emission Intensity of Rhodamine B in Liquid and Solid Phase

In this work, we study the effect of concentration, host medium, PH and phase states on the fluorescence emission from the laser dye Rhodamine B pumped by UV laser as exited source. The polymethylmethacrylate PMMA is used as a host medium in case of solid phase samples while, ethanol and Tetrahydrofuran (THF) are used in case of a liquid one. Laser Induced Fluorescence (LIF) technique was used to study the fluorescence properties of both cases of liquid and thin film solid-state samples. In addition, the Dual Thermal Lens (DTL) technique was used to study the quantum yield of these samples. The concentrations of Rhodamine B in ethanol as solvent between 2 x 10(-2) M and 5 x 10(-6) M were studied. The maximum fluorescence emission is observed at concentration of Rhodamine B C = 3 x 10(-4) M. Comparison studies were investigated for different host medium such as ethanol, THF, PMMA in liquid phase state and PMMA in solid phase state. The measurements revealed that, the behavior of both phases state was analogous. Rhodamine B/PMMA thin film sample by ratio of 4:1 and thickness 0.12 mm was found to have the best photostability sample with a quantum yield about approximately 0.82.

Using random laser emission to investigate the bonding energy of laser dye dimers

We report on a new method, based on random laser emission, to investigate the formation of dimers in laser dye solutions. The single peak spectrum observed at low dye concentration evolves to a double peak spectrum as the concentration increases, and a simple analysis allow us to directly investigate the dimers bonding energy. Our samples were prepared with rhodamine laser dyes dissolved in ethanol, containing TiO 2 nanoparticle scatterers. The laser dyes used in this experiment were Rhodamine 590, Rhodamine 610, Kiton Red 620, and Rhodamine 640. Our results are corroborated by theoretical and experimental data in the literature.

Complexation between Rhodamine 101 and Single-Walled Carbon Nanotubes Indicative of Solvent−Nanotube Interaction Strength

Single walled carbon nanotubes (SWNT) have excellent mechanical, electrical, and thermal properties but their manipulation is hampered since they do not readily dissolve in most organic solvents. In particular, the interaction of nanotubes and organics is not universally understood. Using UV−vis absorption and visible fluorescence spectroscopy we show that, in chloroform, the laser dye Rhodamine 101 (R101) forms ground-state complexes with CoMoCAT SWNT, but that in N,N-dimethylacetamide (DMA), no such complexes exist. We suggest a strong interaction between zwitterionic R101 and nanotube in chloroform where the interaction between nanotube and solvent is weak. We describe how this interaction is solvent specific and how R101 and its analogs may be used as an indicator of strength of interaction of solvent. We also suggest that charge transfer/dipole stabilization should be investigated further in the search for more stable and long lasting SWNT dispersions for improved nanotube manipulation.

Structural, morphological and microhardness characterization in polymer complex of laser dye rhodamine (Rh6G) doped polymethyl methacrylate

Polymer systems have various contents of rhodamine (Rh6G) doped Polymethyl methacrylate (PMMA) prepared by solution cast method. The structural and morphological properties were studied by Differential Scanning calorimetry (DSC), Fourier Transform Infrared spectroscopy (FTIR) Scanning Electron Microscopy (SEM) and X-ray diffraction methods. The induced effect on the strength of rhodamine (Rh6G) doped Polymethyl methacrylate (PMMA) samples were studied by measuring the surface microhardness using the Vicker’s microhardness tester. Significant changes were observed in the Vickers microhardness number (Hv)

Laser properties of a conjugate polymer (MEH-PPV) in the liquid-excimeric state

We have studied the amplified spontaneous-emission characteristics (ASE) of conjugated poly[2-methoxy-5-(2-ethylhexyloxy)1,4-phenylenevinylene] MEH-PPV in a few organic solutions. The ASE of MEH-PPV appears to arise from its excimeric state. This is perhaps the first report, to the best of our knowledge, on an excimeric-liquid state laser. MEH-PPV in solutions of benzene or tetrahydrofuran (THF) was pumped by the second and third harmonics of an Nd:YAG (532 and 355 nm) for different pump-pulse energies. The ASE of MEH-PPV was compared with the conventional laser dyes Rhodamine B (Rh B) and Rhodamine 6G (Rh 6G). The most important and distinguishing features are: (a) MEH-PPV has a four-times better photochemical stability than Rh B or Rh 6G; (b) the threshold and concentration for the laser action in MEH-PPV is far less than Rh B or Rh 6G.

Dynamics of Rhodamine 6G Sorption into a Porous Tri-block Copolymer Thin Film

The dynamics of sorption of the laser dye rhodamine 6G (R6G+) into a thin ion-exchange polymer film was measured by spectroscopic ellipsometry. The system under study consisted of a nanometer-sized polymer film in direct contact with a liquid phase. A thin film of a partially sulfonated tri-block copolymer preconcentrated the dye from dilute solutions (10-5 M) driven by ion-exchange to a film concentration of about 0.1 M. Spectroscopic ellipsometry was used to simultaneously measure the dynamics of the film physical (thickness) and optical changes (refractive index n(λ) and extinction coefficient k(λ)). The sorption is ultimately accompanied by dye aggregation in the film, which results in shifts and splitting of features in the monomer absorbance spectrum. The formation of nonluminescent aggregates was also confirmed by emission spectroscopy. Desorption of the dye from the film resulted in a reversal of film physical changes. Spectroscopic results were quantitatively accounted for by constructing an opti...

In situ synthesis of dye-doped stainless-steel-net-supported mesostructured silica film for solid-state laser material

Optically active stainless-steel-net-supported mesostructured SBA-15 films have been fabricated by a simple sol–gel synthesis. Laser dye rhodamine 6G is doped in situ in the films to produce solid state dye lasers. Characterization by optical microscopy and field-emission scanning electron microscopy reveals that the surface of the film is smooth and macroscopic homogeneous without any crack and the stainless steel net acts as a good framework of the film. Mesoscopic ordering of the film is demonstrated by a combination of small-angle X-ray diffraction analysis and transmission electron microscopy investigation. The spectroscopic properties of the solid-state laser materials are measured by the second harmonic of a Q-switched Nd:YAG laser at 532 nm. A distributed feedback laser (DFB laser) is revealed through the gain narrowing of the band over threshold energy of 30 μJ and the occurring of superlinear dependence. The grids of the stainless steel nets are regarded as laser resonant structures for feedback of light, and the aperture of the grids plays an important role on the films’ optical performance. Such dye-activated mesostructured materials have potential application for the fabrication of solid state dye lasers and microphotonic devices.

Energy transfer between rhodamine 3B and oxazine 4 in synthetic-saponite dispersions and films

The objective of this study was the investigation of energy transfer between the laser dyes rhodamine 3B (R3B) and oxazine 4 (Ox4) adsorbed on the surface of synthetic Sumecton saponite (Sum). The process of energy transfer was studied for both saponite dispersions and oriented solid films. The electronic properties, luminescence, and the energy transfer process were described by UV–vis absorption and fluorescence spectroscopy. For the efficiency of the energy transfer process, the concentrations of energy donor and acceptor components on a clay mineral surface were found to be essential. A side reaction of the molecular assembly formation reduced both the luminescence and energy-transfer yields, mainly due to fluorescence quenching. The quenching was more problematic for the solid film specimens, where an appropriate modification of the inorganic host with hydrophobic alkylammonium cations was used to achieve a higher luminescence. Due to the higher tendency of Ox4 to form nonluminescent aggregates at higher concentrations, the lowering of the Ox4 concentration further improved the luminescent properties of the films. In this case, the energy transfer occurring in the solid film from R3B to Ox4 was clearly proven.

Molecular-dynamics simulations of pyronine 6G and rhodamine 6G dimers in aqueous solution

We have carried out molecular-dynamics (MD) simulations on dimers of the positively charged laser dyes pyronine 6G (P6G) and rhodamine 6G (R6G) in aqueous solution, generating trajectories of 2.5 ns for various computational protocols. We discuss how the choice of atomic partial charges and the length of the trajectories affect the predicted structures of the dimers and compare our results to those of earlier MD-simulations, which were restricted to only 0.7 ns. Our results confirm that monomers of P6G easily undergo relative rotations within the dimer, but we found new conformations of the R6G dimer at longer simulation times. In addition, we analyzed in detail the energy change during the formation of dimers. With suitable corrections, the electrostatic energy from an Ewald treatment agrees with the results from an approach relying on a residue-based cutoff. For P6G, we show that the strong solvent-mediated electrostatic attraction between the monomers is counteracted by an almost equally large solvent-induced entropy contribution to yield a small driving force to dimer formation, in very good agreement with the free-energy change from a thermodynamic-integration procedure. Thus, earlier rationalizations of the dimer formation, based only on energy arguments, yield a qualitatively wrong picture.

Continuous-wave solid-state dye laser

We report the first realization of a cw solid-state dye laser. The laser medium consists of a laser dye (Rhodamine 6G) dissolved in a photopolymer. The UV-cured solution is sandwiched between two DVD substrates. The resonator design was derived from a conventional liquid solvent dye laser geometry. The laser radiation can be tuned from 565 to 615 nm by using a birefringent filter. A pump power of 2 W leads to a cw output power of more than 20 mW.

Functionalized SU-8 patterned with x-ray lithography

In this work we demonstrate the feasibility of x-ray lithography on SU-8 photoresist doped with the laser dye Rhodamine 6G, while retaining the photoactive properties of the embedded dye. Two kinds of structures are fabricated via soft x-ray lithography and characterized: a laser and an amplified spontaneous emission light source that couples out light normal to the chip plane. In addition we examine the influence of the x-ray irradiation on the fluorescence of thin films of dye doped SU-8. The dye embedded in the SU-8 is optically excited during characterization by an external light source tuned to the absorption band of the dye.