Coumarin Laser Dyes Research Articles

Editorial comment

There has been relatively little controversy in the management of upper ureteral stones over the years, mainly because access to the upper ureter with available ureteroscopes was always a chancy affair. Additionally, if the stone could be accessed, fragmentation was limited for practical purposes to the electrohydraulic probe or possibly the Coumarin dye laser. In the past few years, however, small, flexible, steerable ureteroscopes have become widely available, with a parallel evolution in the technique of URS, particularly with the use of the access sheath. Thus, it is now routinely possible to access the upper ureter in the vast majority of patients. Efficiency and cost of treating proximal ureteral stones: Shock wave lithotripsy versus ureteroscopy plus holmium:yttrium-aluminum-garnet laserUrologyVol. 64Issue 6PreviewTo compare the success rates, cost effectiveness, and efficiency of ureteroscopy (URS) and extracorporeal shock wave lithotripsy (ESWL) for proximal ureteral stones. Full-Text PDF

Photoacoustic investigations on the photostability of Coumarin 540-doped PMMA

In this paper, we present a laser-induced photoacoustic study on the photostability of laser dye Coumarin 540 doped in PMMA matrix and modified by the incorporation of low-molecular weight additives. The dependence of photostability of the dye on various experimental conditions, such as nature of solvents, incident optical power and dye concentration, is investigated in detail. The activation rates for the bleaching process are calculated for different concentrations and they suggest the possibility of two distinct mechanisms responsible for photodegradation. Further, analysis of the data confirms the linear dependence of photodegradation on the intensity of incident radiation. The role of different externally influencing parameters, such as wavelength and modulation frequency of incident radiation, is also discussed.

Solvation Dynamics of Coumarin 480 in TritonX-100 (TX-100) and Bile Salt Mixed Micelles

The time-resolved Stokes' shift of the laser dye Coumarin 480 (C-480) has been investigated in the Stern layer of the pure Triton X-100 (TX-100), bile salt (Sodium Deoxycholate, NaDC) and the mixed micelles of bile salt (NaDC), and TX-100 at different compositions using picosecond time-resolved emission spectroscopy. The wavelength dependent decays at the blue end and growth at the red end of the spectrum are observed for the TX-100, NaDC micelles, and mixed micelles above critical micelles concentrations. The average solvation time in pure NaDC and TX-100 are 3.35 and 1.51 ns, respectively, but in the mixed micelles, it is 2.27−3.26 ns. The solvation dynamics of the water molecule in the Stern layer of the mixed micelles is retarded several times compared to that of pure water. The relatively slow solvation dynamics in the Stern layer of the NaDC micelles is due to the motion of the Na+ ions and the water molecules confined in the micellar cavity. The interaction of the Na+ ions with the headgroup of the...

Energy Transfer in Dye-Doped Mesostructured Composites

Energy transfer between the organic laser dyes coumarin 485 and pyrromethene 567 was investigated in mesostructured silica/block copolymer thin films. The 2-D hexagonal mesostructured silica thin films were made using acidic sol−gel synthesis with poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), (EO20PO70EO20) as the structure-directing agent. The dyes were doped into the film synthesis solutions so that they underwent co-assembly with the silica and block copolymer. At a very low concentration of acceptor, one acceptor molecule for every 20 donor molecules, the donor's emission was drastically quenched, suggesting efficient energy transfer. Investigations into amplified spontaneous emission revealed that the donor/acceptor system resulted in full gain narrowing at significantly lower concentrations than systems without a donor.

Host–Guest Interactions and Laser Activity in AlPO 4-5/Laser Dye Composites

In situ inclusion of the laser dyes coumarin 466, coumarin 7, pyridine 2 and DCM has been conducted successfully in AlPO 4-5 crystals. The charged molecule pyridine 2 interacts with the framework and leads to bundle-like morphologies with increasing dye content. Uncharged molecules (DCM, coumarin 7, coumarin 466) are included, although corresponding molecular dimensions are exceeding pore size. These dyes probably induce local defects in the pore walls of AlPO 4-5 which are healed during crystal growth leading to well-developed hexagonal prisms. Spectroscopic studies show interactions of the dyes with the solid-state matrix which are reflected by shifts of absorption and emission maxima of the dyes. For the first time, laser activity is demonstrated on a perfect hexagonal single AlPO 4-5/DCM crystal.

Host–Guest Interactions and Laser Activity in AlPO4-5/Laser Dye Composites

In situ inclusion of the laser dyes coumarin 466, coumarin 7, pyridine 2 and DCM has been conducted successfully in AlPO4-5 crystals. The charged molecule pyridine 2 interacts with the framework and leads to bundle-like morphologies with increasing dye content. Uncharged molecules (DCM, coumarin 7, coumarin 466) are included, although corresponding molecular dimensions are exceeding pore size. These dyes probably induce local defects in the pore walls of AlPO4-5 which are healed during crystal growth leading to well-developed hexagonal prisms. Spectroscopic studies show interactions of the dyes with the solid-state matrix which are reflected by shifts of absorption and emission maxima of the dyes. For the first time, laser activity is demonstrated on a perfect hexagonal single AlPO4-5/DCM crystal.

Spectroscopic properties of coumarin 2 in HCl and HNO 3 catalysed sol–gel glasses

Laser dye Coumarin 2 (C2) was incorporated in transparent xerogel via acid catalysed sol–gel method. Two different methods using HCl and HNO 3 as catalysts were employed. The absorption and fluorescence spectra of C2 in both types of solids show different characteristics. These spectroscopic properties of C2 were compared with its respective properties in ethanolic solution in acidic environment. Solids prepared by using HNO 3 as catalyst show superior absorption/emission properties than those prepared by using HCl.

Efficient and stable operation of an Ar+-pumped continuous-wave ring laser from 505–560 nm using a coumarin laser dye

A coumarin laser dye has been found to produce efficiencies and lifetimes comparable to those of the rhodamines. Coumarin 521 (coumarin 334) produces up to 400 mW of single frequency light (frequency width <1 MHz) at 520 nm in a ring laser when excited with 2.4 W of 457.9 nm light from an Ar+ ion laser. Operation with a 488 nm pump shows slightly lower efficiency. Dye lifetime to 75% full power has exceeded 1000 W h over a period of several months. Methanol and ethylene glycol are the only solvents required. This dye operates in a portion of the tuning range of a continuous-wave ring dye laser which is otherwise extremely difficult to access using an argon ion laser as the pump source. Used in conjunction with an external buildup cavity, 8–12 mW of 258 nm light is reliably produced for weeks at a time.

Quinolizin-Coumarins as Physical Enhancers of Chemiluminescence during Lipid Peroxidation in Live HL-60 Cells

We investigated whether physical enhancers of low-level chemiluminescence—coumarin laser dyes C-314, C-334, and C-525—may be used to monitor interactions of lipid peroxyl radicals during lipid peroxidation in live cells. We present data demonstrating that two quinolizin-substituted coumarins—C-525 and C-334—can be integrated into HL-60 cells and successfully used as physical enhancers of chemiluminescence induced by the lipid soluble azo-initiator 2,2′-azobis(2,4-dimethyl-valeronitrile) (AMVN). Coumarins did not inhibit AMVN-induced peroxidation of membrane phospholipids in HL-60 cells, and no consumption of these coumarins occurred in the course of AMVN-induced oxidative stress. Redox status, evaluated by intracellular GSH content, remained unchanged after treatment with the coumarins. tert-Butyl hydroperoxide and cumene hydroperoxide (more hydrophilic oxidants) induced a lower chemiluminescence signal with both coumarins. Viability of HL-60 cells was not affected by coumarins both in the presence and in the absence of oxidants. Based on these results we conclude that quinolizin-substituted coumarins represent a promising class of physical enhancers of chemiluminescence for monitoring free radical peroxidation in live cells.

A REMPI method for the ultrasensitive detection of NO and NO2 using atmospheric pressure laser ionization mass spectrometry.

We report on the development of a quasi-simultaneous highly selective method for NO and NO2 detection at the ultratrace level. Atmospheric pressure laser ionization (APLI), recently introduced by our group, is used to detect both compounds at low parts per trillion by volume (pptv) mixing ratios. APLI is based on resonance-enhanced multiphoton ionization mass spectrometry. Two-color pump-probe experiments employing a single excimer pumped dye laser combination allow for the ultrasensitive measurement of NO and NO2 within a narrow range of maximum pumping efficiency of the laser dye Coumarin 120. NO is detected via excitation of the long-lived A 2sigma+ (nu' = 1) level at 215.36 nm and subsequently ionized with 308-nm radiation provided by the excimer pump laser. NO2 is ionized after double resonant excitation of the A2B1 and 3psigma manifolds in a (1 + 1' + 1(')) process using 431.65 + 308 nm. The selectivity of the NO measurement exceeds 2,000 with respect to NO2 and N2O5. For NO2, a selectivity of >3,000 with respect to N2O5 and organic nitrates is observed. The current APLI detection limit of NO and NO2 is 0.5 and 5 pptv, respectively, with a 20-s integration time.

Correlation between lasing and photophysical performance of dyes in polymethylmethacrylate

Laser dyes rhodamine 6G, rhodamine B, coumarin 30 and coumarin 2 are embedded in polymethylmethacrylate (PMMA) matrix. These materials are pumped by nitrogen laser to study their lasing action. Lasing properties and photophysical properties of these materials are correlated. Photostability of the dye/PMMA samples is also studied. Rhodamine B is found to be the most photostable dye while coumarin 2 is the least photostable dye in PMMA host.

Polymer thin-film distributed feedback tunable lasers

We report on measurements of laser emission from poly-methylmethacrylate and poly-vinyl carbazole polymer films doped with rhodamine-6G, DCM and coumarin laser dyes in an optically pumped distributed feedback scheme. We obtain tunability on a broad spectral range for all samples. We show the impact of waveguiding in the polymer film on reducing the laser threshold. We also show that the number of laser modes increases with the polymer film thickness, following the guided mode dispersion.

Modular Approach to the Accelerated Convergent Growth of Laser Dye-Labeled Poly(aryl ether) Dendrimers Using a Novel Hypermonomer

The synthesis of novel dendrimers functionalized with laser dyes both at the periphery and at the core, along with all relevant model compounds necessary for accurate photophysical studies, is described. The utilized synthetic strategy involves a modular approach in which a variety of peripheral and core moieties can be placed on a dendritic structure bearing electrophilic peripheral groups and a nucleophilic core. Specifically, the target macromolecules required functionalization with the laser dyes coumarin 2 (periphery) and coumarin 343 (core) due to the possibility of energy transfer from the former to the latter dye. In addition, the preparation of a novel, highly soluble and reactive hypermonomer utilized in the rapid and efficient synthesis of high-generation dye-labeled dendrimers and model compounds is outlined.

Effects of a modulation of the pump-polarization in a degenerate pump/probe experiment

The effects of the pump-polarization in a degenerate pump/probe experiment are analyzed. It is shown that modulating the pump polarization from linear to circular induces a modulation in the probe absorption change that allows to separate various contributions that are mixed in the signal. An experimental demonstration is carried out in a laser dye (Coumarin 500).

Emission properties of dye-polymer-opal photonic crystals

The effect of the incomplete photonic bandgap (PEG) provided by the opal template upon the emission properties of the laser dyes (Coumarin G and perylene derivative) dissolved in the solidified polymer has been studied. The bandgap of dye-polymer opal composite is highly anisotropic because of the insufficient refractive index contrast (RIG), moreover, the extent of anisotropy depends on the volume fraction of the polymer. The anisotropic bandgap enforces the corresponding directionality of the emission, but the emission anisotropy is restricted, as compared with the bandgap anisotropy, within the energy range of the Stokes shift between emission and absorption spectra of the dye. The bands of amplified spontaneous emission, which show the same anisotropy as the bandgap, have been observed. Besides, the isotropic amplified spontaneous emission band has been detected at the high intensity excitation, which band was tentatively understood as the result of the weak localization of photons in the gain medium with embedded scatterers.

Source-Corrected Two-Photon Excited Fluorescence Measurements between 700 and 880 nm

Passively mode-locked titanium:sapphire (Ti:S) lasers are capable of generating a high-frequency train of transform-limited subpico-second pulses, producing peak powers near 105 W at moderate average powers. The low energy per pulse (<20 nJ) permits low fluence levels to be maintained in tightly focused beams, reducing the possibility of saturating fluorescence transitions. These properties, combined with a wavelength tunability from approximately 700 nm to 1 μm, provide excellent opportunities for studying simultaneous two-photon excitation (TPE). However, pulse formation is very sensitive to a variety of intracavity parameters, including group velocity dispersion compensation, which leads to wavelength-dependent pulse profiles as the wavelength is scanned. This wavelength dependence can seriously distort band shapes and apparent peak heights during collection of two-photon spectral data. Since two-photon excited fluorescence is proportional to the product of the peak and average powers, it is not possible to obtain source-independent spectra by using average power correction schemes alone. Continuous-wave, single-mode lasers can be used to generate source-independent two-photon data, but these sources are four to five orders of magnitude less efficient than the mode-locked Ti:S laser and are not practical for general two-photon measurements. Hence, a continuous-wave, single-mode Ti:S laser has been used to collect a source-independent excitation spectrum for the laser dye Coumarin 480. This spectrum may be used to correct data collected with multimode sources; this possibility is demonstrated by using a simple ratiometric method to collect accurate TPE spectra with the mode-locked Ti:S laser. An approximate value of the two-photon cross section for Coumarin 480 is also given.

The role of laser-induced autofluorescence spectroscopy in bladder tumor detection. Dependence on the excitation wavelength.

We assessed the ability of laser-induced autofluorescence spectroscopy to distinguish neoplastic urothelial bladder lesions from normal or nonspecific inflammatory mucosa. Three different pulsed laser excitation wavelengths were used successively: 308 nm (xenium chloride excimer laser), 337 nm (nitrogen laser) and 480 nm (coumarin dye laser). The excitation light was delivered by a specially devised multifiber catheter connected to a 1-mm core diameter silica monofiber introduced through the working channel of a standard cystoscope with saline irrigation. The captured fluorescence light was focused onto an optical multichannel analyzer detection system. Performance of this device was evaluated in 25 patients after obtaining consent and immediately before transurethral resection of a bladder tumor. Spectroscopic results were compared with histological findings. At 337- and 480-nm excitation wavelengths, the overall fluorescence intensity of bladder tumors was clearly decreased compared to normal urothelial mucosa regardless of tumor stage and grade. At the 308-nm excitation wavelength, the shape of the tumor spectra, including carcinoma in situ, was markedly different from that of normal or nonspecific inflammatory mucosa. No absolute intensity determinations were required in this situation, since a definite diagnosis could be established based on the fluorescence intensity ratio at 360 and 440 nm. This spectroscopic study could be particularly useful in designing a simplified autofluorescence imaging device for detection of occult urothelial neoplasms.

Evolution of dendritic patterns during alloy solidification: onset of the initial instability.

The evolution of a dendritic pattern from a planar solid-liquid interface during directional solidification of a binary alloy was investigated experimentally. The model alloy used was the transparent organic crystal succinonitrile doped with the laser dye coumarin 152. The buildup of solute ahead of the initially stable planar interface and the subsequent instability of the planar front were measured in detail and compared with recent theoretical calculations by Warren and Langer [Warren, J. A. & Langer, J. S. (1993) Phys. Rev. E 47, 2702- 2712]. The fluorescence of coumarin 152 was used for direct observations of the evolution of the solute concentration profile ahead of the initially planar solid-liquid interface. UV absorption was used to produce thermal perturbations of the sample that generated spatially periodic modulations of the planar interface. This technique allows for measurement of both positive and negative linear growth coefficients (determined from the growth or decay rate of the modulation after the perturbation is switched off) for a large range of wave vectors. Measurements of the evolution of the concentration profile and the linear growth coefficients, and the occurrence of the initial instability, were in good agreement with the Warren-Langer predictions.

Ground and excited state dipole moments of coumarin laser dyes: Investigation by electro-optical absorption and emission methods

Modified electro-optical absorption and emission methods were used to measure the dipole moments of four efficient coumarin laser dyes (CU1, CU4, CU120, CU334) in the equilibrated ground, excited Franck-Condon and equilibrated excited states. The measurements were performed in cyclohexane (CU1, CU120, CU334) and dioxane (all CUs) at room temperature. Our results show that the charge distribution in CU4 differs substantially from that in the other CUs. The equilibrated ground and excited state dipole moments measured by electro-optical methods are compared with those derived from other measurement techniques and from semiempirical calculations. The possible role of twisted intermolecular charge transfer (TICT) state formation is discussed.

Laser Induced Autofluorescence Diagnosis of Bladder Tumors: Dependence on the Excitation Wavelength

Purpose We assessed the ability of laser induced autofluorescence spectroscopy to distinguish neoplastic urothelial bladder lesions from normal or nonspecific inflammatory mucosa. Materials and Methods Three different pulsed laser excitation wavelengths were used successively: 308 nm. (xenium chloride excimer laser), 337 nm. (nitrogen laser) and 480 nm. (coumarin dye laser). The excitation light was delivered by a specially devised multifiber catheter connected to a 1 mm. core diameter silica monofiber introduced through the working channel of a standard cystoscope with saline irrigation. The captured fluorescence light was focused onto an optical multichannel analyzer detection system. Device performance was evaluated in 25 patients after obtaining consent and immediately before transurethral resection of a bladder tumor. Spectroscopic results were compared with histological findings. Results At 337 and 480 nm. excitation wavelengths the overall fluorescence intensity of bladder tumors was clearly decreased compared to normal urothelial mucosa regardless of tumor stage and grade. At the 308 nm. excitation wavelength the shape of the tumor spectra, including carcinoma in situ, was markedly different from that of normal or nonspecific inflammatory mucosa. No absolute intensity determinations were required in this situation, since a definite diagnosis could be established based on the fluorescence intensity ratio at 360 and 440 nm. Conclusions This spectroscopic study could be particularly useful to design a simplified autofluorescence imaging device for detection of occult urothelial neoplasms.