Dye Monomers Research Articles

Silk Fibroin‐Based Films Enhance Rhodamine 6G Emission in the Solid State: A Chemical–Physical Analysis of their Interactions for the Design of Highly Emissive Biomaterials

AbstractDescribed herein is the preparation of dye‐doped films employing silk fibroin (SF) as a biomaterial, capable of preserving the optical properties of the monomeric dye in the solid state, a critical requisite for optical and biolaser applications. A comprehensive physical–chemical characterization is reported for SF films doped with Rhodamine 6G, an ideal candidate for photonics and optoelectronics. Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD) and X‐Ray diffraction (XRD) provide information on SF secondary conformation in the presence of rhodamine. UV–vis absorption spectra and exciton CD inform on the structure of encapsulated rhodamine, while changes in dye photophysical properties illuminate the molecular mechanism of the involved host–guest interactions. SF host environment inhibits rhodamine dimer formation, indicating that SF is an optimum matrix to keep rhodamine essentially monomeric at concentrations as high as 7 mm in the film. The relevant optical properties of these films and the easiness of their preparation, make these systems optimal candidates for innovative photonic technologies.

Novel Phosphonium Dye TDV1 as a Potential Fluorescent Probe to Monitor DNA Interactions with Lysozyme Amyloid Fibrils

The applicability of the novel cationic phosphonium dye TDV1 to monitor the complexation between DNA and pathologically aggregated proteins, amyloid fibrils, was tested using the optical spectroscopy and molecular docking techniques. TDV1 has been found to be highly emissive in buffer solution and is characterized by one well-defined fluorescence peak attributed to the dye monomers. The association of the dye with the double stranded DNA was followed by the enhancement of monomer fluorescence coupled with a bathochromic shift of the emission maximum. The addition of fibrillar lysozyme (LzF) to TDV1-DNA mixture led to the further enhancement of fluorescence intensity of the monomeric dye form coupled with a hypsochromic shift of the emission maximum and an appearance of a second long-wavelength peak. An assumption has been made that the fluorescence enhancement augmenting with increasing the protein concentration in the TDV1/DNA system is produced by the interaction of the free TDV1 monomers with lysozyme fibrils as well as by the LzF-induced conformational alterations of DNA. The long-wavelength peak emerging in the presence of LzF is presumably a consequence of the J-aggregate formation upon the TDV1 association with lysozyme fibrils. The molecular docking studies showed that TDV1 monomers are incorporated into the fibril grooves associating with 7 β-strands in such a way that the dye long axis is parallel to the fibril axis. The most energetically favorable position of TDV1 is the S60-W62/G54-L56 groove in the lysozyme fibril core. In contrast, the TDV1 dimers seem to associate with the more hydrophilic side of the model β-sheet. Cumulatively, the results from the absorption and fluorescence measurements, together with the molecular docking analysis are consistent with the minor groove mode of the TDV1 binding to dsDNA. The electrostatic interactions seem to play a predominant role in the TDV1 complexation with the double stranded DNA, while the hydrophobic interactions and steric hindrances are supposed to be influential in the association of TDV1 with fibrillar lysozyme.

Spectral and Luminescent Properties and Morphology of Self-Assembled Nanostructures of an Indotricarbocyanine Dye

Spectral and luminescent properties of an indotricarbocyanine dye are studied in solutions and after deposition on quartz or silicon substrates. It is found that the dye molecules self-assemble in aqueous EtOH solutions to form H*-aggregates. The absorption band of the H*-aggregates shows a hypsochromic shift of 192 nm (5291 cm–1) relative to the absorption maximum of dye monomers (706 nm) and has a full width at half maximum of 21 nm (797 cm–1). The morphology of the H*-aggregates of the indotricarbocyanine dye is studied for the first time. It is found that the aggregates are rod-like species ~10 nm high, 100 nm wide, and several micrometers long. H-aggregates with a fluorescence maximum at 560 nm and Stokes shift of 325 cm–1 in addition to non-fluorescent H*-aggregates form in aqueous EtOH solutions and are nanoparticles with a height of 1–3 nm and lateral dimensions of ~100 nm.

Interaction of a dimeric carbocyanine dye aggregate with bovine serum albumin in non-aggregated and aggregated forms.

The interaction of fluorescent dyes with serum proteins has garnered significant interest owing to potential for non-covalent labeling and imaging applications. In this work, dimeric benzothiazole-based trimethine cyanine dyes are synthesized and their interaction with bovine serum albumin studied. The dimeric cyanine dyes mainly exist as H-dimers and H-aggregates in aqueous solution. A combination of absorbance, fluorescence, circular dichroism spectroscopy and atomic force and fluorescence microscopy indicate the formation of dye-BSA complexes. Binding of one of the dimeric dyes on BSA with a Ka of 1.49×105M-1 results in disruption of dye self-aggregates and unfolding of the dyes into the monomeric or open conformation. Fluorescence enhancement experienced by the dimeric dyes upon interaction with BSA is superior to that registered by Thioflavin T. Surfactant SDS has been used to further tune the self-aggregation of the dimeric dye resulting in a 200-fold fluorescence enhancement in presence of BSA. Interaction of a dimeric dye with BSA under conditions favoring protein aggregation is found to result in faster dye binding and the resulting fluorescence enhancement is easily visualized by fluorescence microscopy. The interaction of a dimeric cyanine dye aggregate with BSA is promising for non-covalent labeling applications in sharp contrast to the monomeric dye counterpart.

A comparative study of assembly and disassembly process of dimeric and monomeric cyanine dyes with DNA templates

Cyanine dyes have attracted more and more interest due to their controllable assembly and disassembly process with biomolecular templates. The self-assembly of cyanine dye not only depend on the environment, but also on their structures. Here, we report assembly and disassembly of two cyanine dyes, a dimeric cyaine dye (TC-P4) and its corresponding monomer (TC). In PBS, these dyes could form aggregates. The parallel c-myc G-quadruplex as a template causes the transformation of TC-P4 from H-aggregates to dimer and monomer; while duplex and single-stranded DNAs could not. The interaction between these DNAs motifs and TC could all induce the appearance of monomer band. Parallel c-myc G-quadruplex could enhance the fluorescence intensity of TC-P4 and TC. The self-assembly and disassembly of TC and TC-P4 could be regulated and used as probes for G-quadruplex recognition from duplex and single-stranded DNAs in solution.

Highly-efficient sensitizer with zinc porphyrin as building block: Insights from DFT calculations

To further improve the photoelectronic conversion efficiency of dye-sensitized solar cell, a series of novel D-π-A dyes with Zn porphyrin as building block are evaluated with theoretical calculations. The effect of relative position of Zn-porphyrin (ZP) on the overall performance of D-π-A dye has been investigated by means of density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches. Through the analyzing the molecular geometry, electronic structure, transport properties and light harvesting and utilization of monomer dyes, dye-III is confirmed to be the most suitable one for DSSC application, due to its smaller HOMO-LUMO energy gap, broader absorption coverage, better transport capability, and larger short-circuit current density. Quantum dynamics simulation illustrates novel dyes constructed in current contribution are faster in electron transfer at dye@TiO2 interface. The overall efficiency of DSSC could be boosted if ZP unit was incorporated close to the acceptor group in D-π-A dye. Our work is expected to provide theoretical guideline for further designing and screening prospective sensitizers for DSSC.

Highly Fluorescent Merocyanine and Cyanine PMMA Copolymers.

Polymerizable merocyanine and cyanine dye monomers are synthesized and applied in a statistical copolymerization with methylmethacrylate, giving a series of highly fluorescent poly(methyl methacrylate) (PMMA) copolymers. Photophysical properties of yellow to red merocyanine- and of pink to dark purple cyanine-containing copolymers are studied by fluorescence spectroscopy in solid state as well as in different solvents. The highest quantum yield measured in the solid state is observed for copolymers with the lowest dye content: 16% for merocyanine-based and 13% for cyanine-based copolymers, respectively. Fluorescence properties in solution show positive solvatochromism for both merocyanine monomer and copolymer. Copolymer, in comparison to monomer, is hypsochromically shifted to lower wavelengths which point toward H-aggregation of the chromophores in the copolymer matrix.

Influence of the interaction with DNA on the spectral-fluorescent and photochemical properties of some meso-substituted polymethine dyes

Spectral-fluorescent and photochemical properties of meso-substituted thiacarbocyanine dyes 3,3′-dimethyl-9-phenylthiacarbocyanine and 3,3′-diethyl-9-(2-hydroxy-4-methoxyphenyl)thiacarbocyanine in solutions and their interaction with DNA were studied. The dyes form noncovalent complexes with DNA, which is accompanied by changes in the absorption spectra and an increase in the fluorescence intensity of the dyes. The data obtained suggest that the dyes are in the form of trans-isomers both in solvents of different polarity and in complexes with DNA. It was shown that the interaction of the dyes with DNA is a complex process involving monomeric dye molecules and aggregates of the dyes. The primary photochemical processes of the dyes in solutions and in complexes with DNA were studied by flash photolysis technique. Upon flash photoexcitation in solutions, the formation and decay of the photoisomers of the dyes were observed, with no generation of the triplet states. In the complex with DNA, no signal of photoisomers was detected; in the absence of oxygen, the formation of the triplet state of the dyes was observed. The decay kinetics of the triplet state of the dyes were two-exponential. The process of quenching of the triplet state of the dyes by oxygen in a complex with DNA was studied, the respective quenching rate constants were estimated, being lower than the diffusion-controlled value.

Comparison of dye (oxazine and thiazine) materials as a photosensitizer for use in photogalvanic cells based on molecular interaction with sodium dodecyl sulphate by spectral study

The photochemistry of dye is playing a significant role for understanding the mechanism of electron transfer reactions in photoelectrochemical devices such as photogalvanic cells, DSSC, semiconductor photo-catalysis, photoconductors, etc. Oxazines (Brilliant Cresyl Blue and Nile Blue O) and thiazines (Azur A, Azur B, Azur C, Methylene Blue and Toluidine Blue O) dyes have been used widely as a photosensitizer with and without surfactants in the photogalvanic cells for solar power conversion and storage. Since, the stability and solubility of photosensitizers (dyes) are increased in the presence of surfactant and these properties lead to enhance the electrical output of the photogalvanic cells. Therefore, here we have studied the extent of interaction of different dyes with sodium dodecyl sulphate (SDS), find out the order of stability of dye–SDS on the basis of magnitudes of shifting in λmax of dye monomer and try to correlate order of dye–SDS interaction with already reported electrical output data of photogalvanic cells. Brilliant Cresyl Blue, Nile Blue O, Azur A and TB O have shown red shifting while Azur B, Azur C and MB have shown blue shifting in their λmax value with SDS, which indicates formation of dye–surfactant complex. But, the extent of formation of complex for different dyes with SDS was different due to change in their alkyl groups. Dyes with red shifting have greater stability in excited state as well as higher electrical output data of the cell than dye with blue shifting. On the basis of both red and blue shifting, order of stability of dyes–SDS complex was found as: Brilliant Cresyl Blue > Toluidine Blue O > Azur A > Nile Blue > Azur B > Methylene Blue > Azur C. The order of electrical output values of these dyes in photogalvanic cells have also been supported by literature data in the presence of SDS. Hence, the dye–surfactant complex which would have greater stability in excited state might be more useful for improvement of conversion efficiency and storage capacity of photogalvanic cells in the future.

Competitive Binding of Organic Dyes between Cucurbiturils and Octa Acid.

Employing six cationic water-soluble organic dye molecules as probes, we have attempted to qualitatively understand the factors that govern the attraction between such molecules and the anionic water-soluble host, octa acid (OA). Examination of the competitive host–guest complexation between cucurbit[8]uril (CB[8]) and OA using absorption and emission spectroscopy revealed that the dye molecules included within CB[8] could be “pulled out” by OA. However, an order of magnitude higher concentration of OA was required to shift the equilibrium toward OA, suggesting that attraction between the anionic host OA and the cationic dye molecules such as cresyl violet perchlorate and methylene blue is weaker than the hydrophobic and cation–dipolar interaction between these dye molecules and CB[8]. The importance of Coulombic attraction between OA and dye molecules is also revealed by monomer-to-dimer conversion upon addition of OA to an aqueous solution of monomeric dye molecules. Under conditions where the dye-to-OA ratio is high, freely dissolved monomeric dye molecules are attracted to the exterior of OA and aggregate as dimers on the exterior wall of OA. On the other hand, at high ratios of OA to dye molecules, the dye molecules adsorb as monomers on the exterior of OA. Thus, the monomer-to-dimer ratio in aqueous solution can be controlled by adjusting the ratio of dye to OA molecules. The results presented are of value in qualitatively understanding the relative binding properties of ionic guests with ionic hosts. Studies are qualitative in nature, and further detailed quantitative studies planned for the future are likely to provide deeper understanding of the interaction between water-soluble dye molecules, OA, and CB.

Exciton Dynamics from Strong to Weak Coupling Limit Illustrated on a Series of Squaraine Dimers

We present a joint theoretical and experimental study on the light-induced exciton relaxation dynamics in a series of three squaraine dimers spanning the range from weak to intermediate to strong excitonic coupling strength regime. As revealed by transient-absorption spectroscopy and mixed quantum-classical dynamics simulations that explicitly take into account excitation by the laser pulse, three different types of exciton dynamics could be observed, although the investigated systems exhibit very similar spectral features. While in the strongly coupled system (Frenkel limit), the exciton remains delocalized over both dye monomers, in the system with intermediate coupling, transient localization–delocalization on a femtosecond time scale can be observed. Finally, in the weakly coupled heterodimer (Förster limit), efficient exciton transfer, mediated by transient delocalization that correlates with a strong nonadiabatic coupling, takes place. By delivering the first systematic microscopic study on different regimes of exciton transfer, our findings shed new light on the possible mechanisms of energy transport in organic molecular excitonic materials.

Solvatochromic fluorescence in an immiscible two-phase system of alcohols and hydrophobic polymers: Distinction between light alcohol and water, ink printing

A solvatochromic dye monomer with an allyl group (ASCD) was polymerized together with methyl methacrylate (MMA) or styrene (St) to obtain hydrophobic fluorescent polymers. The wettability of the polymers to alcohols was examined by monitoring the fluorescence (FL) changes over time. On the one hand, when the ASCD-incorporated poly MMA (PMMA) film was exposed to liquid alcohols, a remarkable red-shift occurred instantly in the FL emission spectra for light alcohols such as methanol, ethanol, and propanol whereas for heavier alcohols, a blue-shift occurred first and subsequently a red-shift occurred gradually. On the other hand, the ASCD-incorporated poly St (PSt) film exhibited less significant FL change upon contact with the light alcohols owing to the relatively higher hydrophobicity. In contrast to the case of alcohols, the polymer films exhibited no FL response to water even after prolonged exposure. Particularly, the ASCD-incorporated PSt film showed a reversible and reproducible FL change during the repeated methanol and water contact cycle, indicating a high potential for use as a sensor to discriminate between light alcohol and water. Moreover, when the ASCD-incorporated PMMA was ground mechanically and added to the alcohols, the nanoparticle powder was dispersed very well in the alcohols. When the colloidal solution was deposited onto a paper as an ink, high-resolution FL images were obtained on the surface of the paper.

Characterization and Thermal Study of Schiff-Base Monomers and Its Transition Metal Polychelates and Their Photovoltaic Performance on Dye Sensitized Solar Cells

Azo dye monomer 4,4′-(4,4′-biphenylylenebisazo)-disalicylaldehyde-4n-butylphenyl aniline (H2A) is synthesised by the reaction of 4,4′-bis[(salicylaldehyde-5)-azo]biphenyl (Azo) and n-butylaniline in the 1:2 molar ratio and its metal polychelates are also synthesized with Co(II), Ni(II), Cu(II), and Zn(II) metal ions. The synthesized compounds are characterized by 1H, 13C NMR, Fourier transform infrared (FT-IR) spectroscopy, electronic spectra (UV-Vis), elemental analysis (C, H, N, O), gas chromatography-mass (GCmass) spectrometry, magnetic susceptibility and molar conductivity techniques. Thermal properties of the title compounds are studied using the thermogravimetric analysis (TGA). The metal molar ratio in all of the polychelates is found to be consistent with 1:1 (metal/ligand) stoichiometry. The influence of organic dyes H2A and the [CuA(H2O)2] n polychelate are investigated as photosensitizers on the photovoltaic parameters by current–voltage (I–V) measurements on TiO2 photoelectrode dye sensitized solar cells (DSSCs). The [CuA(H2O)2] n metal polychelate demonstrates the best performance as compared to the cell sensitized with H2A.

Halogen-containing thiazole orange analogues - new fluorogenic DNA stains.

Novel asymmetric monomeric monomethine cyanine dyes 5a–d, which are analogues of the commercial dsDNA fluorescence binder thiazole orange (TO), have been synthesized. The synthesis was achieved by using a simple, efficient and environmetally benign synthetic procedure to obtain these cationic dyes in good to excellent yields. Interactions of the new derivatives of TO with dsDNA have been investigated by absorption and fluorescence spectroscopy. The longest wavelength absorption bands in the UV–vis spectra of the target compounds are in the range of 509–519 nm and these are characterized by high molar absorptivities (63000–91480 L·mol−1·cm−1). All investigated dyes from the series are either not fluorescent or their fluorescence is quite low, but they become strongly fluorescent after binding to dsDNA. The influence of the substituents attached to the chromophores was investigated by combination of spectroscopic (UV–vis and fluorescence spectroscopy) and theoretical (DFT and TDDFT calculations) methods.

Template‐Free Self‐Assembly of Dimeric Dicarbocyanine Dyes

AbstractSymmetrical dicarbocyanine dyes are known to cooperatively assemble on DNA templates. With the goal of developing dyes that are capable of template‐free self‐assembly, two N‐linked dimeric benzothiazole containing pentamethine cyanine dyes have been synthesized. UV‐visible spectroscopy of the dimeric dyes reveals very strong propensities for self‐assembly unlike their monomeric dye counterparts. The N‐propyl linked dye exhibits pronounced H‐aggregation at micromolar dye concentrations with the absorption maxima blue‐shifted by nearly 200 nm. In contrast, an N‐hexyl linked dye preferentially folds into H‐dimers. Similar aggregates of the monomeric dicarbocyanine dyes are known to be observed at much higher dye concentrations or in presence of suitable templates such as DNA molecules. The aggregate species of the dimeric dyes are identified based on shifts in their absorbance maxima and quenched fluorescence. The calculated electronic structure of the dimeric dyes supports their observed aggregation behaviour. Further, introduction of DNA molecules with AT‐tracts leads to transformation of the spontaneously formed dimeric dye H‐aggregates and H‐dimers into DNA‐bound dye species.

Orthogonally Functionalized Donor/Acceptor Homo- and Heterodimeric Dyes for Dye-Sensitized Solar Cells: An Approach to Introduce Panchromaticity and Control the Charge Recombination.

Organic dyes possessing conjugated π-framework forms closely packed monolayers on photoanode in dye-sensitized solar cell (DSSC), because of the limitation to control the orientation and the extend of intermolecular π-π interaction, self-aggregation of dyes leads to reduced cell performance. In this report, a series of homodimeric (D1-D1 and D2-D2) and heterodimeric (D1-D2 and D2-D4) donor/acceptor (D/A) dyes containing spiroBiProDOT π-spacer were designed and synthesized by utilizing Pd-catalyzed direct arylation reaction and correlates the device performance with monomeric dyes (D1 and D2). Both the thiophenes (π-spacer) of spiroBiProDOT were functionalized with same or different donor groups which led to homodimeric and heterodimeric chromophores in a single sensitizer. The homodimeric spiro-dye D1-D1 showed higher power conversion efficiency (PCE), of 7.6% with a Voc and Jsc of 0.672 V and 16.16 mA/cm2, respectively. On the other hand, the monomeric D1 exhibited a PCE of 3.2% (Voc of 0.64 V and Jsc of 7.2 mA/cm2), which is lower by 2.4 fold compared to dimeric analogue. The spiro-unit provides flexibility between the incorporated chromophores to orient on TiO2 due to four sp3-centers, which arrest the molecular motions after chemisorption. This study shows a new molecular approach to incorporate two chromophores in the dimeric dye possessing complementary absorption characteristics toward panchromatic absorption. The attenuated charge recombination at TiO2/Dye/redox couple interface in case of D1-D1, owing to better passivation of TiO2 surface, was elucidated through impedance analysis. The FT-IR spectrum of D1-D1 adsorbed on TiO2 film indicated both the carboxylic units were involved in chemisorption which makes strong coupling between dye and TiO2.

Nature of the optical band shapes in polymethine dyes and H-aggregates: dozy chaos and excitons. Comparison with dimers, H*- and J-aggregates.

Results on the theoretical explanation of the shape of optical bands in polymethine dyes, their dimers and aggregates are summarized. The theoretical dependence of the shape of optical bands for the dye monomers in the vinylogous series in line with a change in the solvent polarity is considered. A simple physical (analytical) model of the shape of optical absorption bands in H-aggregates of polymethine dyes is developed based on taking the dozy-chaos dynamics of the transient state and the Frenkel exciton effect in the theory of molecular quantum transitions into account. As an example, the details of the experimental shape of one of the known H-bands are well reproduced by this analytical model under the assumption that the main optical chromophore of H-aggregates is a tetramer resulting from the two most probable processes of inelastic binary collisions in sequence: first, monomers between themselves, and then, between the resulting dimers. The obtained results indicate that in contrast with the compact structure of J-aggregates (brickwork structure), the structure of H-aggregates is not the compact pack-of-cards structure, as stated in the literature, but a loose alternate structure. Based on this theoretical model, a simple general (analytical) method for treating the more complex shapes of optical bands in polymethine dyes in comparison with the H-band under consideration is proposed. This method mirrors the physical process of molecular aggregates forming in liquid solutions: aggregates are generated in the most probable processes of inelastic multiple binary collisions between polymethine species generally differing in complexity. The results obtained are given against a background of the theoretical results on the shape of optical bands in polymethine dyes and their aggregates (dimers, H*- and J-aggregates) previously obtained by V.V.E.

Unusual Nonemissive Behavior of Rubrene J-Aggregates: A Rare Violation.

Structure-property correlations in rubrene (RB) colloidal J-aggregates were unravelled by steady state and time-resolved spectroscopy in conjunction with excited state density functional calculations. The RB J-aggregate with a slippage angle θ = 30.4°, estimated from the monomeric transition dipole moment directions, exhibited a broad fwhm of 1073 cm-1 and a 5 nm red-shifted absorption band carrying a transition dipole moment (M⃗λagg = 1.80 D) almost equivalent to the monomeric dye (M⃗λmon = 1.89 D). A significantly low magnitude of exciton coupling energy, ΔEexc = -358 cm-1 for the rhombic-RB colloidal J-aggregates resulted owing to the weaker electronic communication between the largely separated RB subunits (r = 7.2 Å) and a restricted exciton delocalization over the RB J-dimer (N = 2). The RB J-dimer exhibited a perfect balance between the computed singlet (2.53 eV) and the triplet (1.29 eV) exciton energies for singlet fission (SF). Supporting this, the PL decay profile of the J-aggregates revealed a delayed fluorescence, substantiating triplet pair formation via SF. The experimental evidence for the long-lived triplet formation was furthermore confirmed by its transient absorption (T1 → TN) at 530 nm. Consequently, a high probability for SF and a low probability for triplet-triplet recombination, leading to a dramatic lowering in photoluminescence quantum yield from 0.172 down to 0.035 was noted. The electronic structure calculations for the RB J-dimer followed TD-DFT-M062X/6-31G+(d,p) level of theory following integral equation formalism polarizable continuum model (IEFPCM) in water. S1 excited state for RB J-dimer was carefully analyzed using integral overlap of electron and hole density distribution (ϕ) and the defined t-indexes along all three spatial directions, and was found to be of locally excited in character.

Concentration quenching of laser dyes fluorescence in variety of solid matrices and liquid solutions

Organic dye lasers are widely used in science and technology. Impregnation of dyes into polymers demonstrates many technical advantages, especially in the case when the dye monomer solution is filled inside the cavities of nanoporous glasses and then polymerized within the pores (PFNPG-P composite). This allows to create a rigid true solid-state active elements. Peculiarities of luminescence in such compositions are the subject of the work. Luminescence of 12 laser dyes was studied in liquid solutions (ethanol, MMA) and solid matrixes such as PMMA and PFNPG-P composite. Concentration dependences were measured for pyrromethenes, phenalemines, xanthenes and other types of dyes to define the quenching threshold of luminescence.

Rose bengal in poly(2-hydroxyethyl methacrylate) thin films: self-quenching by photoactive energy traps

The effect of dye concentration on the fluorescence,ΦF, and singlet molecular oxygen,ΦΔ, quantum yields of rose bengal loaded poly(2-hydroxyethyl methacrylate) thin films (∼200 nm thick) was investigated, with the aim of understanding the effect of molecular interactions on the photophysical properties of dyes in crowded constrained environments. Films were characterized by absorption and fluorescence spectroscopy, singlet molecular oxygen (1O2) production was quantified using a chemical monitor, and the triplet decay was determined by laser flash-photolysis. For the monomeric dilute dye, ΦF = 0.05 ± 0.01 and ΦΔ = 0.76 ± 0.14. The effect of humidity and the photostability of the dye were also investigated. Spectral changes in absorption and fluorescence in excess of 0.05 M and concentration self-quenching after 0.01 M are interpreted in the context of a quenching radius model. Calculations of energy migration and trapping rates were performed assuming random distribution of the dye. Best fits of fluorescence quantum yields with concentration are obtained in the whole concentration range with a quenching radius rQ = 1.5 nm, in the order of molecular dimensions. Agreement is obtained only if dimeric traps are considered photoactive, with an observed fluorescence quantum yield ratio ΦF,trap/ΦF,monomer ≈ 0.35. Fluorescent traps are capable of yielding triplet states and 1O2. Results show that the excited state generation efficiency, calculated as the product between the absorption factor and the fluorescence quantum yield, is maximized at around 0.15 M, a very high concentration for random dye distributions. Relevant information for the design of photoactive dyed coatings is provided.