Antenna Dyes Research Articles

Multiple Pathways in the Triplet States Population for a Naphthalenediimide-C60 Dyad.

The link of an antenna dye with an electron spin converter, in this case naphthalenediimide and C60, produces a system with a rich photophysics including the detection of more than one triplet state on the long timescale (tens of μs). Beside the use of optical spectroscopies in the ns and in the fs time scale, we used time-resolved Electron Paramagnetic Resonance (TREPR) to study the system evolution following photoexcitation. TREPR keeps track of the formation path of the triplet states through specific spin polarization patterns observed in the spectra. The flexibility of the linker and solvent polarity play a role in favouring either electron transfer or energy transfer processes.

Optimization of All-Polymer Optical Fiber Oxygen Sensors with Antenna Dyes and Improved Solvent Selection Using Hansen Solubility Parameters.

We present an all-polymer optical fiber sensor for the sensing of dissolved oxygen by phase-fluorometry. The sensing matrix is applied as a film on the fiber end-surface, and consists of poly-methylmethacrylate (PMMA), the oxygen quenchable luminophore platinum-octaethylporphyrin (PtOEP) and the luminophore coumarin 545T for increasing the brightness of PtOEP by way of resonance energy transfer (RET), also called light harvesting. We show that by using Hansen Solubility Parameters (HSPs), it is possible to quantitatively formulate a solvent mixture with a good solubility of the polymer matrix and the luminophores simultaneously. Our approach can readily be extended to other polymers and luminophores and is therefore a valuable tool for researchers working with photoluminescence and polymeric matrices.

Photocontrollable NO-releasing compounds and their biological applications.

Photocontrollable nitric oxide (NO)-releasing compounds, or caged NOs, are very useful to expose cells or tissues to NO in a spatiotemporally well-controlled manner, e.g., for precise investigations of biological responses to NO and NO-related signaling pathways. We have developed photocontrollable NO releasers based on two mechanisms: photoinduced isomerization reaction of a dimethylnitrobenzene moiety conjugated with a pi-electron system, and photoinduced electron transfer of a moderately electron-rich N-nitroso aminophenol moiety linked with an antenna dye moiety. In this review, we describe the development of our photoinduced NO releasers based on these mechanisms, and present examples of cellular and ex vivo applications.

Photon Upconversion in a Molecular Lanthanide Complex in Anhydrous Solution at Room Temperature

Molecular photon upconversion luminescence was observed from an ion-associated complex of an erbium chelate of 2-thenoyltrifluoroacetone and a near-infrared-emitting cyanine dye in anhydrous solution at room temperature. In the complex erbium was sensitized by the organic antenna dye excited at 808 nm. The result was characteristic erbium emission at 510–565 nm with second-order dependence on the excitation power, suggesting a dye-sensitized energy transfer upconversion mechanism. Compared to inorganic upconverting nanoparticles, the organic molecular dye-sensitized complexes are expected to offer higher molar absorptivity, smaller well-defined size, and simpler addition of functional groups.

Visible Discrimination of Broadband Infrared Light by Dye-Enhanced Upconversion in Lanthanide-Doped Nanocrystals

Optical upconversion of near infrared light to visible light is an attractive way to capture the optical energy or optical information contained in low-energy photons that is otherwise lost to the human eye or to certain photodetectors and solar cells. Until the recent application of broadband absorbing optical antennas, upconversion efficiency in lanthanide-doped nanocrystals was limited by the weak, narrow atomic absorption of a handful of sensitizer elements. In this work, we extend the role of the optical antenna to provide false-color, visible discrimination between bands of infrared radiation. By pairing different optical antenna dyes to specific nanoparticle compositions, unique visible emission is associated with different bands of infrared excitation. In one material set, the peak emission was increased 10-fold, and the width of the spectral response was increased more than 10-fold.

Thickness dependence of device parameters in solid state dye sensitized solar cells

A solid-state dye-sensitized solar cell (SDSC) was fabricated with a very thin (~ 650 nm) mesoporous TiO2 electrode and a donor-antenna (D-A) dye by using 2,2',7,7'- tetrakis - (N,N-di-p-methoxyphenyl-amine) 9,9'- spirobifluorene (Spiro OMeTAD) as hole conductor. A highly transparent thin electrode sensitized with D-A dye showed a short circuit current (Isc) of 4.10mA/cm2, an open circuit voltage (Voc) of 782 mV and an efficiency of 1.79 % at an illumination intensity of 100 mW/cm2 (1 sun, AM 1.5G). TiCl4 treatment of mesoporous TiO2 layer resulted in Isc of 6.18 mA/cm2, Voc of 737 mV and an efficiency of 2.12% at the same illumination intensity. This investigation demonstrates the possibility of fabrication of SDSC by way of using a very thin and transparent TiO2 electrode together with a high molar extinction coefficient D-A dye, and the effect of TiO2 layer thickness on solid-state solar cell performances is discussed. Keywords: Donor - antenna dye, sensitization, solid-state dyesensitized solar cell, TiO2, transparent electrode. Doi: 10.4038/jnsfsr.v39i1.2921 J.Natn.Sci.Foundation Sri Lanka 2011 39 (1): 35-42

Light Harvesting as a Simple and Versatile Way to Enhance Brightness of Luminescent Sensors

The emissive output of indicator dyes in luminescent sensors can be amplified by the addition of antenna dyes with a higher brightness. The highly concentrated antenna dye molecules absorb the excitation light and transfer the energy to an indicator dye. This harvesting of light makes thin sensor layers (thickness <500 nm) and nanometer sized sensor particles with exceptionally high brightness and compatible with the most powerful LEDs available. The performance of sensor layers of ∼250 nm thickness employing light harvesting was investigated and compared with established sensors. The principle is demonstrated for oxygen and ammonia sensors. An overview of possible application of light harvesting to various reagent mediated optical sensing schemes is given.

Position of the non-template DNA in the Polymerase II elongation complex revealed using single-molecule Fluorescence Resonance Energy Transfer

Single Molecule Fluorescence Resonance Energy Transfer (FRET) was used as a quantitative tool to localize non-template DNA in the RNA Polymerase II (Pol II) elongation complex.We measured the FRET efficiencies between ‘antenna dye molecules’ (ADMs) attached to the non-template DNA and several ‘satellite dye molecules’ (SDMs) attached to known positions within the Pol II elongation complex using the recently developed Nano Positioning System (NPS) (1). NPS combines x-ray crystallographic information, single-molecule FRET data and bayesian parameter estimation, a probability based analysis method, to compute the three dimensional probability density for the position of ADMs. Within the bayesian framework, we were able to account for errors in the determined Forster radii, errors in the measured FRET efficiencies and uncertainties in the SDM positions (due to the attachment of the SDMs via flexible linkers) as well as for geometric constraints.We determined positions of the non-template DNA at +1, -2, -4, -7 (within the transcription bubble) and -12, -15, -18 of the up-stream DNA. Together with the high resolution x-ray structure and our earlier studies (2) determining the position of the nascent RNA this study completes the picture of the Pol II elongation complex.1. A. Muschielok, J. Andrecka, A. Jawhari, F. Bruckner, P. Cramer and J. Michaelis, A nano-positioning system for macromolecular structural analysis. Nature Methods, accepted.2. J. Andrecka, R. Lewis, F. Brueckner, E. Lehmann, P. Cramer and J. Michaelis, Tracking the position of mRNA in RNA polymerase II elongation complexes. PNAS 105, 135-140 (2008).

Kodak Professional Ektar 100 Film

This new film with ISO 100 speed, high saturation, and ultravivid color offers the finest, smoothest grain of any color negative film available today. This film incorporates KODAK VISION Motion Picture Film Technology to achieve its extremely fine grain. It is ideal for scanning and offers extraordinary enlargement capability from a 35 mm negative. This paper will describe the new components and their features. These include emulsion improvements: optimized tabular grain technology, advanced cubic crystals, antenna dye sensitization, and improved spectral sensitivity. Chemical improvements are also described: advanced development accelerators, a new high-efficiency masking coupler, and improved DIR couplers.

Highly Efficient Solar Cells using TiO2 Nanotube Arrays Sensitized with a Donor-Antenna Dye

Donor antenna dyes provide an exciting route to improving the efficiency of dye sensitized solar cells owing to their high molar extinction coefficients and the effective spatial separation of charges in the charge-separated state, which decelerates the recombination of photogenerated charges. Vertically oriented TiO(2) nanotube arrays provide an optimal material architecture for photoelectrochemical devices because of their large internal surface area, lower recombination losses, and vectorial charge transport along the nanotube axis. In this study, the results obtained by sensitizing TiO(2) nanotube arrays with the donor antenna dye Ru-TPA-NCS are presented. Solar cells fabricated using an antenna dye-sensitized array of 14.4 microm long TiO(2) nanotubes on Ti foil subjected to AM 1.5 one sun illumination in the backside geometry exhibited an overall conversion efficiency of 6.1%. An efficiency of 4.1% was obtained in the frontside illumination geometry using a 1 microm long array of transparent TiO(2) nanotubes subjected to a TiCl(4) treatment and then sensitized with the Ru-TPA-NCS dye. Open circuit voltage decay measurements give insight into the recombination behavior in antenna-dye sensitized nanotube photoelectrodes, demonstrating outstanding properties likely due to a reduction in the influence of the surface traps and reduced electron transfer from TiO(2) to ions in solution.

Dynamic quenching of porphyrin triplet states by two-photon absorbing dyes: Towards two-photon-enhanced oxygen nanosensors

Two-photon-enhanced dendritic nanoprobes are being developed for two-photon (2P) laser scanning microscopy of oxygen [R.P. Briñas, T. Troxler, R.M. Hochstrasser, S.A. Vinogradov, J. Am. Chem. Soc. 127 (2005) 11851–11862]. In these molecular constructs, phosphorescence of metalloporphyrins is coupled to two-photon absorption (2PA) of electronically separate antenna dyes via intramolecular Förster-type resonance energy transfer (FRET). In the originally developed probes, competing electron transfer (ET) between the antennae and the long-lived triplet states of metalloporphyrins partially quenched the phosphorescence, reducing the probe's sensitivity and dynamic range. The rate of such ET can be reduced by tuning the redox potentials of the chromophores. In order to identify the optimal metalloporphyrin-2P antenna pairs, we performed screening of several phosphorescent Pt porphyrins (FRET acceptors) and 2P dyes (FRET donors) using dynamic quenching of phosphorescence. Phosphorescence lifetimes of Pt porphyrins were measured as a function of the dye concentration in organic solutions. The obtained Stern–Volmer quenching constants were correlated with the corresponding ET driving forces (Δ G ET), calculated using the Rehm–Weller equation. FRET pairs with minimal quenching rates were identified. The developed approach allows convenient screening of candidate-compounds for covalent assembly of 2P-enhanced triplet nanodevices. Systematic electrochemical measurements in a series of Pt porphyrins with varying peripheral substitution and conjugation pathways are presented.

New KODAK PROFESSIONAL PORTRA Films: Re-Engineered for Improved Performance

The Kodak Professional Portra family of films was originally launched in 1998. Since then, Kodak has made many advances in color negative film technology. The films introduced at Photokina 2006, the Kodak Professional Portra 160 NC and VC, and the 400 NC and VC films, have been reformulated to improve performance. This paper will describe the new components and their features. These include emulsion improvements: optimized T-Grain technology, antenna dye sensitization, and improved spectral sensitivity. Chemical improvements are also described: Advanced development accelerators, a new high-efficiency masking coupler, and improved DIR couplers.

Light‐Harvesting Metallosupramolecular Squares Composed of Perylene Bisimide Walls and Fluorescent Antenna Dyes

The fluorescent dye 4-dimethylamino-1,8-naphthalimide was incorporated at the bay area of N,N'-bispyridyl perylene bisimide to afford a fourfold-functionalized perylene bisimide ligand. Through self-assembly directed by metal-ion coordination, a multichromophore supramolecular entity composed of sixteen dimethylaminonaphthalimide antennas and a perylene bisimide-walled square core was subsequently constructed from this linear ditopic ligand and 90 degrees metal corner [Pd(dppp)](OTf)2 (dppp=1,3-bis(diphenylphosphino)propane; OTf=trifluoromethanesulfonate) in good yield. The isolated metallosupramolecular square was characterized by elemental analysis and 1H, 13C, and 31P{1H} NMR and UV/Vis spectroscopy. Furthermore, by means of 1H NMR diffusion-ordered spectroscopy (DOSY) the dimension of this assembly was evaluated by employing a previously reported perylene bisimide ligand and its square assembly as references. The results obtained confirm the square framework of the current assembly. The optical properties of this multichromophore dye assembly were investigated by UV/Vis and steady-state and time-resolved fluorescence spectroscopy. It was revealed that light captured by dimethylaminonaphthalimide antennas could be efficiently transported to the perylene bisimide core by a fluorescence resonance mechanism (energy-transfer efficiency E=95%), and this resulted in almost exclusive detection of intense perylene bisimide emission, irrespective of the excitation wavelength applied. The present square scaffold containing aminonaphthalimide antenna dyes exhibits more than seven times higher fluorescence quantum yield (Phifl=0.37) than a previously reported pyrene-bearing perylene bisimide-walled square (Phifl=0.05). Thus, this multichromophore square assembly with aminonaphthalimide antenna dyes is an artificial model for the cyclic light-harvesting complexes in purple bacteria.

Highly Efficient Solid State Dye-Sensitized TiO2 Solar Cells Using Novel Donor Antenna Dyes

not Available.

Downhill Energy Transfer via Ordered Multichromophores in Light-Harvesting Capsules

A variety of light-harvesting capsules were successfully constructed by assembling polyelectrolyte complexes and antenna dyes of graduated absorption energy into nanoscale walls (thickness of a single layer around 2 nm). Two-step downhill energy transfer was demonstrated with absorption and fluorescence spectroscopy for the first time on light-harvesting capsules. Energy transfer occurs parallel to the capsule surface if the dyes are coadsorbed to the preassembled capsule wall. Energy transfer perpendicular to the surface was achieved by sequentially assembling the dyes in different layers of the wall. Although perpendicular energy transfer is less efficient because of longer intermolecular distances, utilization of J-aggregates and optimization of dye combinations and dye ratios yielded an efficient energy cascade along three components. The light-harvesting capsules are analogous to the light reactions of photosynthesis in chloroplasts.

Mimicking Photosynthetic Two-Step Energy Transfer in Cyanine Triads Assembled into Capsules

A two-step energy transfer cascade was constructed in the wall of hollow microcapsules by means of defined assembly of three cyanine dyes, thiacyanine (antenna), thiacarbocyanine (receiver and antenna), and indodicarbocyanine (receiver), in the wall plane and perpendicular to it. The efficiency of the energy transfer steps has been measured by fluorescence spectroscopy. The unidirectional energy transfer perpendicular to the surface was smaller than for the lateral one. The antenna dyes on the outer surface of the capsules harvest the light energy and conduct it downhill by Forster resonance energy transfer to the capsule interior in analogy to chloroplasts in nature. However, the obtained efficiency is much smaller, though some improvement was reached by using J-aggregate-forming dyes.

The influence on the triplet state in antenna rhodamine dyes of intramolecular energy transfer and charge transfer

The triplet lifetimes of 2,5-diphenyloxazole-rhodamine dyes and trichromophoric antenna rhodamines have been measured by nanosecond laser flash photolysis and phosphorescence decay measurements. The intramolecular energy transfer and intramolecular charge transfer in these dye systems have been discussed. These may affect the lasing efficiency as well as the emission wavelength of the antenna dyes. The oxygen influence on the energy transfer has also been discussed.

Luminescent oxygen channeling immunoassay: measurement of particle binding kinetics by chemiluminescence.

A method for monitoring formation of latex particle pairs by chemiluminescence is described. Molecular oxygen is excited by a photosensitizer and an antenna dye that are dissolved in one of the particles. 1 delta gO2 diffuses to the second particle and initiates a high quantum yield chemiluminescent reaction of an olefin that is dissolved in it. The efficiency of 1 delta gO2 transfer between particles is approximately 3.5%. The technique permits real-time measurement of particle binding kinetics. Second-order rate constants increase with the number of receptor binding sites on the particles and approach diffusion control. By using antibody-coated particles, a homogeneous immunoassay capable of detecting approximately 4 amol of thyroid-stimulating hormone in 12 min was demonstrated. Single molecules of analyte produce particle heterodimers that are detected even when no larger aggregates are formed.

Studies on Intramolecular Energy Transfer and Charge Transfer in Trichromophoric Antenna Rhodamine Dyes

The triplet lifetime of some trichromophoric antenna rhodamine dyes have been measured by nanosecond laser flash photolysis and phosphorescence decay method．The intramolecular triplet energy transfer and intramolecular charge transfer in these dyes have been discussed． These processes may affect the lasing efficiency as well as the emission wavelength of the antenna dyes． The experimental results support the existence folded conformation in the antenna rhodamine dyes linked with CH2-CH2．

Fluorescence and lasing properties of rhodamine dyes

New rhodamine dyes with amino endgroups that are rigidized by 5- and 6-membered rings have been synthesized. The fluorescence quantum yield in ethanolic solution is, independent of temperature, close to unity. A derivative with amino groups incorporated in a single 6-membered ring lases more efficiently than rhodamine 6G. In an attempt to improve pumping by an excimer laser the rhodamine chromophore was connected via methylene bridges with 2,5-diphenyloxazole (PPO) which absorbs strongly at 308 nm. In these antenna dyes complete energy transfer from PPO to rhodamine is observed, yet lasing efficiency is influenced by some unexpected excited state interaction between the chromophores. We studied with other multichromophoric dyes also the influence of nitrobenzene and anthracene moieties on the fluorescence efficiency of the rhodamine chromophore. Linkages consisting of two methylene groups permit a stronger interaction between chromophores than those consisting of a single methylene group.