Luminescent Organic Dye Research Articles

Fibered luminescent concentrator: A bridge between flashlamp devices and laser technologies for skin therapy.

Laser skin therapy and intense pulsed light (IPL) therapy are both light-based treatments used for various skin concerns. They have been used since decades and each system have their own specificity, advantages, and drawbacks. However specific treatment is still not accessible with standard techniques due to difficulties having a source with both laser and IPL advantages. We describe a new concept, the fibered luminescent concentrator-FLC, based on luminescent concentrators capable of concentrating spectrally and spatially an IPL source, resulting in a multi-color fibered device. The FLC utilizes luminescent materials arranged in parallelepiped shapes polished on all faces. The IPL broadband spectrum is absorbed by the luminescent molecules and is re-emitted to a red shifted wavelength. The emitted spectral bandwidth ranges from green to dark red, depending on the type of luminescent concentrator. This light is then spatially concentrated by total internal reflections in the parallelepiped and guided through a fiber to the final operator. We have developed three different solid luminescent concentrators based on a transparent polymer sheet (PMMA) doped with luminescent organic dye molecules for yellow and red emission, and an alexandrite crystal for emission in the dark red spectrum. We demonstrate that our new non-laser FLC device can concentrate spectrally and spatially the light with no temporal deformation and offers real opportunities for treatments where the IPL is less well-adapted. The FLC is an additional tool for existing conventional systems such as laser or IPL sources. It is easily adaptable to any IPL source and is a very good complement, especially for wavelengths where the laser cannot easily produce light, such as the yellow band.

Ammonia and temperature sensing applications using fluorometric and colorimetric microparticles and polymeric films doped with BODIPY-emitters.

Fourfunctionalized BODIPY derivatives(BDP1 to BDP4) were synthesizedand their optical properties investigatedboth in solution and when incorporated into a solid matrix. Recognizing the versatility of BODIPY derivatives and the increasing interest in developing new luminescent organic dyes embedded in polymers, the BODIPY derivatives were dispersed into two types of polymeric matrices: Poly(methyl methacrylate) (PMMA) and Thermoplastic Polyurethane (TPU), both as films and microparticles. This resulted in eight new BODIPY-doped polymer films and eight types of BODIPY-doped polymeric microparticles for use in aqueous solutions. The integration of the BODIPY dyes into the polymeric matrices combines the unique properties of the polymer films, such as porosity, flexibility, and elasticity, with the excellent photophysical characteristics of the BODIPYs. Importantly, the dispersion minimized issues such as aggregation-caused quenching commonly observed in solid-state luminescent materials. The thermometric responses of all polymer films were evaluated by studying their solid-state emission spectra in the 25-200°C temperature range. The reversibility of these temperature-induced changes was also assessed, revealing excellent recovery of luminescence. These promising results suggest these materials could have applications as fluorescent thermometric sensors. Furthermore, we explored the potential of the brominated (BDP3) and chalcogenated (BDP4) BODIPY derivatives as ammonia sensors. The two derivatives produced yellow fluorescent products upon interaction with the analyte. Kinetic studies using solid-state emission spectra of BDP4@TPU and BDP4@PMMA showed significant differences in reaction rates (minutes for BDP4@TPU and hours in the case of BDP4@PMMA) attributable to the higher permeability of TPU when compared with PMMA. Detection and quantification of ammonia concentration were conducted by means of simple photographic analysis, measuring the "R" (red) and "G" (green) components of RGB color parameters. Theresults from the photographic method correlated well with the results from fluorimetric spectroscopy studies. The photographic analysis is straightforward, portable, and does not require expensive equipment. Finally, we successfully applied polymeric microparticles doped with BODIPYs to detect ammonia in water, demonstrating their effectiveness without the need for organic solvents. This highlights their potential for environmental monitoring and other applications requiring sensitive and selective detection methods.

Experimental and Theoretical Evaluation of a Commercial Luminescent Dye for PVT Systems

Combining photovoltaic (PV) and photo-thermal (PT) energy collection strategies in a single system can enhance solar energy conversion efficiencies, leading to increased economic returns and wider adoption of renewable energy sources. This study focuses on incorporating a commercial luminescent organic dye (BASF Lumogen F Red 305) into ethylene glycol to explore its potential for PVT applications. The optical and electrical characteristics of the working fluid were evaluated at different temperatures under direct solar irradiance. Pristine ethylene glycol reduced the maximum PV cell temperature by 10 °C. The inclusion of luminescent dye at various concentrations further reduced the maximum temperature, with the lowest concentration achieving a 7 °C decrease compared to pristine ethylene glycol. The highest dye concentration (0.50 wt%) resulted in a significant temperature reduction of 12 °C. While electrical conversion efficiencies decreased with increasing dye concentration, all concentrations exhibited higher fill factors compared to the bare PV cell during the 100-min illumination period. A ray-tracing model was employed to analyze the behavior of the luminescent dye and quantify transmitted energy for electricity and thermal energy production. Different concentrations showed varying energy outputs, with lower concentrations favoring electrical energy and higher concentrations favoring thermal energy. Economic assessment revealed the viability of certain concentrations for specific countries, highlighting the trade-off between thermal and electrical energy generation. These findings provide valuable insights for PVT system applications in different geographical and economic contexts.

Hybrid spherical microresonators with luminescent organic dyes FITC and DCM

Luminescent hybrid spherical microresonators of two types consisting of monodisperse spherical silica particles with a diameter of 3.5 μm coated with either FITC dye molecules or a 200 nm thick mesoporous silica shell containing DCM dye are fabricated. The luminescence spectra of microresonators are studied and the experimental emission spectra are simulated using the method of spherical wave transfer matrices. The ratio of intensities of emission lines into whispering gallery modes with different polarizations and the same polar and radial indices is analyzed. It is shown that the ratio depends on the orientation of the dipole moment of the radiative transition of dye molecules relative to the surface of spherical silica particles. Keywords: spherical microresonator, whispering gallery modes, organic dyes, photoluminescence.

Red-Emitting Latex Nanoparticles by Stepwise Entrapment of β-Diketonate Europium Complexes.

The core-shell structure of poly(St-co-MAA) nanoparticles containing β-diketonate Eu3+ complexes were synthesized by a step-wise process. The β-diketonate Eu3+ complexes of Eu (TFTB)2(MAA)P(Oct)3 [europium (III); 4,4,4-Trifluoro-1-(2-thienyl)-1,3-butanedione = TFTB; trioctylphosphine = (P(Oct)3); methacrylic acid = MAA] were incorporated to poly(St-co-MAA). The poly(St-co-MAA) has highly monodispersed with a size of 300 nm, and surface charges of the poly(St-co-MAA) are near to neutral. The narrow particle size distribution was due to the constant ionic strength of the polymerization medium. The activated carboxylic acid of poly(St-co-MAA) further chelated with europium complex and polymerize between acrylic groups of poly(St-co-MAA) and Eu(TFTB)2(MAA)P(Oct)3. The Em spectra of europium complexes consist of multiple bands of Em at 585, 597, 612 and 650 nm, which are assigned to 5D0→7FJ (J = 0-3) transitions of Eu3+, respectively. The maximum Em peak is at 621 nm, which indicates a strong red Em characteristic associated with the electric dipole 5D0→7F2 transition of Eu3+ complexes. The cell-specific fluorescence of Eu(TFTB)2(MAA)P(Oct)3@poly(St-co-MAA) indicated endocytosis of Eu(TFTB)2(MAA)P(Oct)3@poly(St-co-MAA). There are fewer early apoptotic, late apoptotic and necrotic cells in each sample compared with live cells, regardless of the culture period. Eu(TFTB)2(MAA)P(Oct)3@poly(St-co-MAA) synthesized in this work can be excited in the full UV range with a maximum Em at 619 nm. Moreover, these particles can substitute red luminescent organic dyes for intracellular trafficking and cellular imaging agents.

White-light-emitting triphasic fibers as a phosphor for light-emitting diodes.

White-light-emitting materials have received significant attention because of their potential application in lighting, displays, and sensors. However, it is a challenge to obtain white light from one phosphor, because the basic requirement of the white light emission spectrum is that it should be wide enough to cover the entire visible light region. In this study, we have designed and demonstrated a white-light-emitting PMMA–CBS-127/PVP–coumarin 6/PAN–rhodamine B (PSCR) fibrous membrane, which was prepared through a triphasic electrospinning method. Three luminescent organic dyes, CBS-127 (4.77 wt%, blue), coumarin 6 (0.1 wt%, green), and rhodamine B (0.42 wt%, red), were elaborately selected and doped into PMMA, PVP, and PAN, respectively. The resulting flexible PSCR membranes show white light emission (cover the entire visible-light region from 382 to 700 nm) with Commission Internationale de L'Eclairage (CIE) coordinates of (0.31, 0.32), which is very close to ideal white light with CIE coordinates (0.33, 0.33). In addition, the PSCR membranes maintained high-quality white light emission after about 10 weeks of storage. The PSCR membranes can be used as the phosphor converting layer in white light-emitting diodes (WLEDs) through a remote membrane packaging method. A bright white emission is achieved at an applied voltage of 9 V. Therefore, the results indicate that PSCR membranes are potentially attractive candidates for application in WLEDs and displays.

Luminescent organic dyes containing a phenanthro[9,10-D]imidazole core and [Ir(N^C)(N^N)]+ complexes based on the cyclometalating and diimine ligands of this type.

A family of diimine (N^N) and cyclometalating (N^C) ligands based on a phenanthro-imidazole aromatic system: 2-pyridyl-1H-phenanthro[9,10-d]imidazole (N^N); 2-R-1-phenyl-1H-phenanthro[9,10-d]imidazole, R = phenyl (N^C4), 3-iodophenyl (N^C5) and 4-nitrophenyl (N^C6) were prepared. It was found that N^C4 and N^C5 show π-π* fluorescence typical of aromatic systems of this sort, whereas the donor-acceptor architecture of N^C6 leads to strong emission solvatochromism and acidochromism, indicating the charge transfer character of the fluorescence observed. Six iridium(iii) complexes (1-6) [Ir(N^C#)2(N^N)]+, where # = 1-6 and N^C1 = 2-phenylpyridine, N^C2 = 2-(benzo[b]thiophen-2-yl)pyridine, and N^C3 = methyl 2-phenylquinoline-4-carboxylate, were also synthesized and characterized. The complexes obtained display moderate to bright phosphorescence with quantum yields up to 46% in degassed solution. The photophysical characteristics of 1-6 were studied in detail. DFT and TD DFT calculations were used for the assignment of electronic transitions responsible for the absorption and emission of these compounds. The variations in the cyclometalating ligand structure give rise to rich photophysics of the complexes obtained. It was found that the orbitals of both N^C and N^N ligands make a major contribution to the formation of emissive excited states and a delicate balance between the energy of the ligands' frontier orbitals determines the emission character.

Towards rare-earth-free white light-emitting diode devices based on the combination of dicyanomethylene and pyranine as organic dyes supported on zinc single-layered hydroxide.

A new luminescent composite film resulting from the dispersion of luminescent organic dyes in a single-layered hydroxide (SLH)-type inorganic matrix has been developed. Two fluorescent organic dyes emitting visible light upon blue LED excitation were investigated in this study: dicyanomethylene (DCM) and pyranine (HPTS). These dyes exhibit broad emission bands that cover a large part of the visible spectrum. The concept developed in our work consisted in keeping SLH in its wet form to ensure a good dispersion of the fluorescent dyes prior to immobilizing the hybrid materials in a silicone polymer to achieve luminescent composite films. We demonstrate that these coatings stacked upon each other and placed above a blue LED lead to white-light emission with suitable photometric parameters for applications in lighting or display devices: colour temperature of 5409 K and colour rendering index (CRI) of 81.

Sensitivity Control of Dye-Doped Polymeric Fiber-Optic Strain Sensor Using Radiative Emission-Absorption Mechanism

Principle of a novel fiber-optic strain sensor using dye-doped polymer optical fiber (POF) was demonstrated in the earlier ECS meeting[1]. This time, we demonstrate the ability to tune the sensitivity of this sensor by varying the numerical aperture of the fiber. The sensor uses radiative emission-absorption mechanism and it is capable in sensing stress (strain) by simple viewing of the large-core cross section. Conventional well-known fiber-optic strain sensors such as BOTDR or FBG types require spectral analysis to determine the strain value. Our sensor does not require expensive equipment such as spectral analyzer or well-tuned light source that are required in conventional fiber-optic strain sensors. A pair of luminescent organic dyes, Coumarin 540A and Rhodamine 6G, that functions as donor and acceptor of excitation energy were doped in core and cladding of the fiber, respectively. By taking this structure, stress applied to the fiber could be detected as an increase in cladding intensity. This happens because emission of core dye leaks to the cladding due to the deformation, and it excites the cladding dye[2]. POFs with three different NA were fabricated by varying the amount of high-refractive index dopant in the core[2]. Using the fabricated POF, change in near field pattern and output visible spectrum upon different fiber bending diameter were detected. 406 nm output pigtail laser was used in order to excite the donor dye efficiently. Pigtail end was coupled to the test fiber with direct contact to the core center of the test fiber in which no cladding excitation was expected. Fibers were stressed in various magnitudes by bending them in different loop diameters, namely, 1.5 cm, 3 cm, and 6 cm. Single loop was created in the middle point of the whole length. Relaxed condition, which the fiber was naturally straightened with no loop, was also investigated. Output beam from the test fiber was analyzed using Near Field Pattern measuring system (Hamamatsu C9664-01G02) and spectral analyzing system (JASCO MF-3500). As a result, linear change in sensor sensitivity was observed as the NA increases. Therefore, it was suggested that sensitivity of the sensor is controllable by further optimization of the waveguide parameters. Therefore, the proposed results suggests a potential for an enhanced fiber-optic stress detection with simpler and inexpensive accessory components. [1] Kamimura and Furukawa, 232nd ECS meeting. [2] Kamimura and Furukawa,Appl. Phys. Lett. 111, 063301 (2017)

4-Phenyl-1,8-naphthalimides: Brightness and tuning emission over widely visible gamut in different aggregated states

Luminescent organic dyes with tuning emission in widely visible gamut are still interesting challenging. Herein, we report two naphthalimide derivatives (NAPP, NAPTPA), which can output the variable emission colors covering the whole visible spectra from purple to far-red in aqueous solution. Both naphthalimide derivatives can exhibit bright emission in aqueous solution by introducing a phenyl ring into 4-site of naphthalimide, which acts as a π-bridge in delocalized system and not affects the intramolecular charge transfer process of naphthalimide dyes. Comparison with three analogues (NAPDMP, NAPMOP and NAPDMA), we evidenced the bright emissions in aqueous solution are from the amorphous emission different from the common crystal emission of naphthalimide dyes. We further fabricated the NAPP and NAPTPA into different nanoparticles matrixes to construct the multi-color toolbox, which could output four colors (purple, blue, green and red) in aqueous solution and yellow emission in crystal. Moreover, the white emission system was obtained through solution doping method.

Stress Detection Using Polymer Optical Fiber with FRET Pair Dyes

Noble fiber-optic strain sensor using dye-doped polymer optical fiber (POF) was proposed, and its ability to sense stress (strain) by simple viewing of the large-core cross section was proposed. Conventional well-known fiber-optic strain sensors such as BOTDR or FBG types require spectral analysis to determine the strain value. Our sensor does not require expensive equipments such as spectral analyzer or well-tuned light source that are required in conventional fiber-optic strain sensors. A pair of luminescent organic dyes, Coumarin 540A and Rhodamine 6G, that functions as donor and acceptor of excitation energy were doped in core and cladding of the fiber, respectively. By taking this structure, stress applied to the fiber could be detected as an increase in cladding intensity. This happens because emission of core dye leaks to the cladding due to the deformation, and it excites the cladding dye. Using the fabricated POF, change in near field pattern upon different fiber bending diameter was detected. Lasers with three different wavelengths were used; namely, 406 nm, 532 nm, and 635 nm. 406 nm is the optimum wavelength for exciting the Coumarin 540A of the core efficiently. 532 nm excites Rhodamin 6G well, but does not excite Coumarin 540A well. 635 nm excites neither dyes. Pigtail end was coupled to the test fiber with direct contact to the core center of the test fiber in which no cladding excitation was expected. Fibers were stressed in various magnitudes by bending them in different loop diameters, namely, 1.5 cm, 3 cm, and 6 cm. Single loop was created in the middle point of the whole length. Relaxed condition, which the fiber was naturally straightened with no loop, was also investigated. Output beam from the test fiber was analyzed using Near Field Pattern measuring system (Hamamatsu C9664-01G02). In addition, dye-doped POF with lower numerical aperture had shown enhancement in sensitivity. Therefore, it was suggested that sensitivity of the sensor is controllable by further optimization of the waveguide parameters. Therefore, the proposed results suggests a potential for an enhanced fiber-optic stress detection with simpler and inexpensive accessory components.

Upconversion Luminescent Chemodosimeter Based on NIR Organic Dye for Monitoring Methylmercury In Vivo

While most luminescent organic dyes display intense Stokes fluorescence, some of them exhibit unique single‐photon frequency upconversion luminescence (FUCL). Compared to conventional anti‐Stokes luminescence of lanthanides and two‐photon excitation, FUCL materials display adjustable spectrum area and require a much lower excitation power. Although this is very beneficial for biological applications in the perspective of reducing photodamage to biological samples and photobleaching of the dyes, the utilization of FUCL for biosensing and bioimaging in vivo has not been reported. In this study, we developed a near‐infrared (NIR) rhodamine derivative (FUC‐1) as a chemodosimeter, which displays weak luminescence but undergoes thiolactone ring‐open process leading to luminescence turn‐on in response to mercury(II) cation or methylmercury with good selectivity and high sensitivity in aqueous solution. Interestingly, FUC‐1 displays particular FUCL, excitation at 808 nm leads to luminescence at 745 nm. Compared to Stokes luminescence resulted from excitation at 630 nm, the use of FUCL lowers the detection limit of Hg2+ to be 0.207 nM. FUC‐1 has been used for FUCL bioimaging of methylmercury in live cells and mice. To the best of our knowledge, this is the first example of FUCL biosensing and bioimaging in vivo using visible and NIR fluorescence of small‐molecular dyes.

Measurement method for photoluminescent quantum yields of fluorescent organic dyes in polymethyl methacrylate for luminescent solar concentrators

A method for measuring the photoluminescent quantum yields (PLQY) of luminescent organic dyes is presented. The self-absorption probability calculated at different dye concentrations is used to determine the absolute quantum yield from the observed values. The results for a range of commercially available dyes show high quantum yields, even at high concentrations, and an absence of quenching. The PLQY of several dye mixtures are also presented. The results indicate an absence of any reduction of PLQY in a dye mixture as compared with the individual PLQY of the dyes.

Photostability of laser dyes incorporated in formamide SiO2 ORMOSILs

The sol–gel process provides a low temperature chemical route for the preparation of rigid transparent matrix materials. Under this process, luminescent organic dye molecules were incorporated into organically modified silicate (ORMOSIL) host matrices. The photostability of these laser dyes encapsulated in a solid matrix was studied using optical absorption and luminescence. The photochemical mechanisms of the dye response under N2 laser irradiation were studied using UV and fluorescence spectra measurement. The evolution of the maximum of the emission and excitation curves as function of accumulated irradiated energy was fitted by exponential equations. The matrix protects the dye from the oxidation and dimerization reactions. The dye molecules exhibited photobleaching due to their photodegradation. The ORMOSIL doped with Nile blue exhibits good photostability after 6 h of irradiation.

Laser behavior and photostability characteristics of organic dye doped silicate gel materials

The solgel process is a solution synthesis technique which provides a low temperature chemical route for the preparation of rigid transparent matrix materials. Luminescent organic dye molecules have been incorporated via the solgel method into organically modified silicate (ORMOSIL) polymer host matrices. Optical gain, laser oscillation, and photostability of rhodamine and coumarin dyes doped into ORMOSIL gels are reported. The gel laser materials exhibit peak gain values of 40 cm(-1) and show improved photostability with respect to comparable polymeric host materials.