Dye-doped Films Research Articles

Spectroscopic study of wemple-didomenico empirical formula and taucs model to determine the optical band gap of dye-doped polymer based on chitosan: Common poppy dye as a novel approach to reduce the optical band gap of biopolymer

This study investigates the effect of a natural dye extracted from common poppy (Papaver rhoeas) waste flowers on the optical properties of chitosan (CS) films. The extraction of natural dyes from waste flowers can be considered a new field for research in green chemistry. CS films are flexible and biodegradable but have low optical activity and band gap, limiting their applications in optical devices. The doped CS polymer with different concentrations of Papaver rhoeas dye exhibited enhanced optical properties. Also, 30 % glycerol was added as a plasticizer to omit film brittleness. The FTIR examinations is helpful to propose a mechanism that explains the interaction of the dye with the host polymer. The UV–vis spectroscopic examination establish that the optical characteristics of the films can be modified by adjusting the dye concentration. Furthermore, optical absorption properties are described using the Tauc non-direct transition model, revealing an approximate optical band gap of 1.64 eV. This band gap defines the energy required for electron transitions, elucidating the material’s electronic characteristics. The extinction coefficient (k) and refractive index (n) of the CS-doped films’ shows a dispersion behavior at visible regions of EM radiation. The Wemple-DiDomenico single oscillator model was used to investigate the n dispersion and determine the oscillator energy equivalent to the optical band gap. Additionally, calculations have been performed on optical dielectric properties and optical conductivity. The Urbach energy was measured and used to detect the structure of the films. The findings underscore the potential applications of these natural dye-doped CS films in eco-friendly materials and optical devices.

Humidity-sensitive luminescent dye-doped polyelectrolyte films: Fabrication, characterization, and potential application as colorimetric moisture sensor

A novel type of luminescent dye-doped polyelectrolyte films, which change their light absorption and photoluminescent properties upon changing relative humidity (RH) is reported. A polyelectrolyte – poly(4-styrene sulfonic acid) (PSSA) was chosen as a matrix, while Coumarin 6 (C6) was used as a luminescent dye. The films were prepared using a dip-coating technique. Coatings with a refractive index (RI) of around 1.49 and various thicknesses in a submicrometric range were obtained by changing the withdrawal speed or concentration of the polyelectrolyte. It was found that depending on the RH, C6 in the polyelectrolyte films may exist in two equilibrium forms – monocationic and dicationic. Significant differences between these two forms upon RH level variations were observed and investigated using FT-IR and UV–Vis spectroscopic techniques. FT-IR spectroscopy confirmed the distortion of the double bond conjugation in the benzothiazole unit of the dicationic form of the dye in the dry state. The dependences of the UV–Vis absorption and luminescent properties on RH were determined. The distinct color changes of the films, ranging from faint yellow to intense pink-red, enabled the estimation of the RH level through visual inspection. Taking advantage of a straightforward preparation protocol for this newly developed material, we believe that it may be used as a humidity-sensitive coating.

Tuned the refractive index and absorption edge for Fuchsin basic dye-doped (PVA-PVP-PEG) films: Linear and nonlinear optical characterization for blocking intense laser power

The current investigation focused on creating dye-doped polymer blend films using a solution cast method with a composition of 60%PVA-30%PVP-10%PEG. These films displayed altered refractive index and absorption edge properties. Various characterization techniques, including XRD, FTIR, UV–vis spectroscopy, and optical limiting effects, were utilized to analyze the structural and optical features of the dyed films. The doped samples showed noticeable changes in the structural properties of the polymer matrix blend, as evident from their XRD and FTIR patterns. Incorporating FB dye into the blend resulted in absorption spectra appearing in multiple bands between 295 and 560 nm. For 532.8 nm He-Ne lasers, the FB/(PVA-PVP-PEG) blend was found to be ideal due to its transmittance CUT-OFF within the 200–600 nm wavelength range. The addition of FB dye had a significant impact on the optical characteristics of the polymer blend, leading to a shift in the absorption edge towards lower photon energy levels. The presence of FB dye was also observed to influence the refractive index (n) of the host polymer, indicating its potential for adjusting optical properties. Detailed investigations into the bandgap revealed a reduction in the bandgap of the host polymer due to the presence of the dye. Electronic transitions were further examined through the εi(ω) parameter during the bandgap analysis, confirming the role of the dye in altering the optical bandgap. Overall, the synthesized FB/(PVA-PVP-PEG) polymeric films hold promise for various optoelectronic applications, including lasers, optical filters, communication devices, LEDs, and optical switches.

Laser Induced Damage Study of Dye Doped Polystyrene Films deposited in Glass Substrate by Dip Coating Technique

In the present work, the Laser-induced Damage Morphology of Dye-doped Polystyrene films is investigated. The focus is on the Front and Rear side Damage Morphology at two different Pulse Repetition Frequencies, namely 1 pps and 20 pps. For this experiment, films were deposited on both sides of Borosilicate Glass. It was found that at 1 pps, the front side film is damaged without affecting the glass, while the modified beam propagates through the glass to damage the rear side film. Dendrimer-like microstructures are found on both the front and rear sides of the damaged spots, along with pits and craters. At 20 pps frequency, the front side film is damaged, including damage to the glass, resulting in a large crater on the front surface. The morphological features were studied using Fresnel equations. Polymeric films were fabricated using the Dip Coating Technique, and Film thickness was evaluated using the Prism Coupling technique.

Cavity Lasing Characteristics of Thioflavin T and Thioflavin X in Different Solvents and Their Interaction with DNA for the Controlled Reduction of a Light Amplification Threshold in Solid-State Biofilms.

The lasing characteristics of Thioflavin T (ThT) and Thioflavin X (ThX) dyes were investigated in solvents with increasing viscosity: water, ethanol, butanol, ethylene glycol, and glycerol and three forms of DNA (double-helix natural, fragmented, and aggregated). The results identified that lasing thresholds and photostability depend on three critical factors: the solvation shell surrounding dye molecules, the organization of their dipole moments, which is driven by the DNA structure, and the molecules diffusion coefficient in the excitation focal spot. The research highlights that dye doped to DNA accumulated in binding sites fosters long-range dye orientation, facilitating a marked reduction of lasing thresholds in the liquid phase as well as amplified spontaneous emission (ASE) thresholds in the solid state. Leveraging insights from lasing characteristics obtained in liquid, ASE in the solid state was optimized in a controlled way by changing the parameters influencing the DNA structure, i.e., magnesium salt addition, heating, and sonication. The modifications led to a large decrease in the ASE thresholds in the dye-doped DNA films. It was shown that the examination of lasing in cavities can be useful for preparing optical materials with improved architectures and functionalities for solid-state lasers.

Fluorescent Dye-Doped Brightening Polymer-Stabilized Bistable Cholesteric Liquid Crystal Films.

Brightening polymer-stabilized bistable cholesteric liquid crystal (PSBCLC) films with doped fluorescent dyes were prepared using the polymerization-induced phase separation (PIPS) method. The transmittance performance behavior of these films in both states (focal conic and planar) and absorbance change in multiple dye concentrations were studied using a UV/VIS/NIR spectrophotometer. The change occurring in dye dispersion morphology with different concentrations was obtained by means of the polarizing optical microscope. The maximum fluorescence intensity of different dye-doped PSBCLC films was measured using a fluorescence spectrophotometer. Moreover, the contrast ratios and driving voltages of these films were calculated and recorded to demonstrate film performance. Finally, the optimal concentration of dye-doped PSBCLC films with a high contrast ratio and a relatively low drive voltage was found. This is expected to have great potential applications in cholesteric liquid crystal reflective displays.

Fabrication, Characterization of Basic Blue 7 Dye-Doped PVA Films and Their Third-Order Nonlinear Optical Properties.

In this work, we report on the fabrication, characterization and the third-order nonlinear optical (NLO) properties of basic blue 7 (BB 7) dye‒doped polyvinyl alcohol (PVA) polymer thin films. The absorption spectra of BB 7 dye‒PVA films were measured by UV‒visible absorption studies. The functional groups of BB 7‒PVA films have been identified by FT‒IR spectroscopic analysis. The surface morphology was examined by AFM and SEM analysis which shows that the BB 7 dye‒doped PVA films have a homogenous and smooth surface. The nonlinear absorption and refraction of BB 7‒PVA films were respectively explored by open aperture and closed aperture Z‒scan technique using a 5 mW semiconductor diode laser of 635nm wavelengths. The BB 7‒PVA films exhibit the reverse saturable absorption (RSA) and self-defocusing effect and the measured third‒order nonlinear susceptibility χ(3) values of these films were found to be of the order of 10- 5 esu. The present experimental results show that BB 7‒PVA films may have potential applications in future photonic and NLO devices.

The substituent effect on CW laser beam self-action manifestation under UV irradiation of azo-azomethine PMMA composites thin films

We report synthesis and study of E→Z→E photoswitching transformations of methyl-substituted azo-aldehyde and six novel corresponding azo-azomethines containing electron withdrawing/donating substituents in para-position to – CHN– bond, being analyzed by UV–Vis and 1H NMR spectroscopy techniques. Impact of donor/acceptor substituent nature on isomerization kinetics was studied in THF solutions by light activation at 390 nm. We obtained high optical quality of PMMA thin films doped with mentioned dyes. It was characterized with both angularly resolved optical elastic scattering data and nonlinear refractive/absorptive optical responses analysis via CW laser beam self-action effects manifestation at wavelength 532 nm. Pronounced self-focusing effect contribution was shown for electron donating substituents (-CH3, -OCH3) and self-defocusing one for electron withdrawing -NO2 group. UV irradiation at 254 nm provides switching from self-defocusing to self-focusing mode of -NO2 substituted dye-doped film with refractive nonlinear optical response efficiency Re(χ(3)) ≈10−2 esu on background of moderate photoinduced absorption effects manifestation.

Plasmon effect on triplet-singlet energy transfer in the dye-doped Langmuir-Blodgett films

The effect of silver plasmonic nanoparticles on triplet-singlet energy transfer in the donor-acceptor pair of organic dyes was studied. Layered dye films were prepared on the surface of glass and island silver films using the Langmuir-Blodgett method. Amphiphilic analogs of Rose bengal and polymethine dye were used as donor and acceptor of energy. A polymer monolayer was deposited between monolayers of donor and acceptor molecules to exclude the competing triplet-triplet energy transfer. The spectra of delayed fluorescence and phosphorescence of donor-acceptor films and the delayed luminescence lifetime of donor in these films have been measured. It is shown that a threefold increase in the fluorescence intensity and a twofold increase in the donor phosphorescence intensity are observed on silver island films. The successful triplet-singlet energy transfer is evidenced by both the quenching of donor centers and appearance of sensitized delayed fluorescence of the acceptor with the duration close to the donor triplet lifetime. In the presence of silver nanoparticles, in addition to enhancement in the intensity of the donor emission, an increase in the efficiency of tripletsinglet energy transfer was observed. The obtained results can be used in various optical devices.

Structural, morphological, nonlinear optical and power limiting properties of acid green 3 dye-doped PVA films

Structural, morphological, nonlinear optical and power limiting properties of acid green 3 dye-doped PVA films

Synthesis, Characterization, and Performance of Pyridomethene-BF2 Fluorescence Dye-Doped PVA Thin Film and PVP Nanofibers as Low γ-ray Dosimeters.

Currently, particular attention is paid to public health related to the field of γ-ray dosimetry, which is becoming increasingly important in medical diagnostic processes. Incorporating sensitive dyes as radiation dose sensors in different material hosts has shown promising radiation dosimetry application routes. In this perspective, the current study proposes a new fluorescent dye based on boron difluoride complex, the pyridomethene–BF2 named 2-(1-(difluoroboraneyl)-1,2-dihydroquinolin-2-yl)-2-(1-methylquinoxalin-2-ylidene) acetonitrile (DBDMA) as an indicator for low γ-ray doses. The different optical and quantum chemical parameters and the spectral behavior of the selected fluorescent dye were first studied. Then, PVP/DBDMA electrospun nanofibers and PVA/DBDMA thin films were prepared. The different UV–vis spectrophotometric and fluorescence studies revealed a clear change after exposure to different γ-ray doses. Thermogravimetric analysis exhibited excellent thermal stability of the prepared nanocomposite films, showing altered thermal behavior after γ-ray treatment. Furthermore, the SEM evaluation displayed a significant modification in the surface morphology of the two designed nanomaterials with increased radiation dose intensity. These novel forms of dosimeter designed in nanoscale composites could therefore constitute a promising and efficient alternative for rapid and accurate detection of low doses of γ-rays in various medical applications.

New polymethine dyes for liquid and polymer passive Q-switches of neodymium lasers

Spectral and nonlinear optical properties of the new tricarbocyanine dyes, derivatives of the benzo[cd]indole, which absorb efficiently in the region 1.05–1.08 µm, have been investigated. Based on these compounds, the liquid (ethanol solutions) and polymer (in a form of triplexes, where dye-doped polyurethane films are placed between two optical glass substrates) passive Q-switches for the neodymium lasers have been developed. The modulation depth of 100% at the generation of the ultrashort pulse (USP) trains has been obtained. The high-stable regime of passive mode-locking has been realized; it is characterized with the 100% probability appearance of a single pulse in an axial period with average durability 25–30 ps and energy 1–2 mJ, depending on the dye structure. Advantages of the new Q-switches over the corresponding analogues, based on organic dyes, nanotubes, graphene, inorganic semiconductors and mirrors (SESAM), LiF:F2ˉ and Cr4+:YAG, have been demonstrated.

Towards facile fabrication of photonics components from inorganic and hybrid sol-gel films. Preparation and optical properties characterization

New trends towards development of integrated optics and miniaturization of photonic devices require fabrication of miniaturized photonic components. Fabrication of waveguiding films with designed optical properties is a fundamental process for production of planar integrated devices.We report here preparation of thin layers based on TiO2 precursor (TET – titanium(IV) ethoxide) and SiO2 precursors, namely inorganic (TEOS – tetraethyl orthosilicate) or organically modified (GLYMO − 3-glycidoxypropyltrimethoxysilane) as candidates for potential application in the planar integrated circuits.The thin layers were deposited on soda-lime glass substrates using the sol-gel method and dip-coating technique and processed at relatively low temperature (up to 300 °C). Several parameters e.g. a) the type of SiO2 precursor, b) the presence of complexing agent for TET and c) heat treatment temperature were tested for their influence on thickness and refractive index of the obtained films.Furthermore, a few series of sol-gel films activated with luminescent dye (Rhodamine B) was fabricated. The influence of the above-listed parameters on luminescent properties of the films was characterized because of lack of systematic study in the literature in this aspect. Moreover, a spectrum of the light at the output of a chosen luminescent dye-doped waveguiding film excited by laser source was investigated.In addition, the subject of our investigations were films prepared at 200 °C with various amounts of TET and organically modified SiO2 precursor in concentration range not presented before. Their optical properties such as homogeneity and values of optical band gap of TiO2 clusters were explored. For selected samples the waveguide properties including the optical losses were evaluated. For the first time, hybrid films with presented composition and refractive index in range of 1.59–1.71 were used for patterning by nanoimprint technique allowing for reproduction of periodic structures, which may serve for example as grating couplers or DFB (distributed feedback) resonators.

Study on the Synthesis of ZnO Nanoparticles Using Azadirachta indica Extracts for the Fabrication of a Gas Sensor.

This paper compared the effects of A. indica plant proteins over chemical methods in the morphology of zinc oxide nanoparticles (ZnO NPs) prepared by a co-precipitation method, and ethanol sensing performance of prepared thin films deposited over a fluorene-doped tin oxide (FTO) bind glass substrate using spray pyrolysis technique. The average crystallite sizes and diameters of the grain-sized cluster ZnO NPs were 25 and (701.79 ± 176.21) nm for an undoped sample and 20 and (489.99 ± 112.96) nm for A. india dye-doped sample. The fourier transform infrared spectroscopy (FTIR) analysis confirmed the formation of the Zn–O bond at 450 cm−1, and also showed the presence of plant proteins due to A. indica dye extracts. ZnO NPs films exhibited good response (up to 51 and 72% for without and with A. indica dye-doped extracts, respectively) toward ethanol vapors with quick response-recovery characteristics at a temperature of 250 °C for undoped and 225 °C for A. indica dye-doped ZnO thin films. The interaction of A. indica dye extracts helps to decrease the operating temperature and increased the response and recovery rates of the sensor, which may be due to an increase in the specific surface area, resulting in adsorption of more oxygen and hence high response results.

Effect of nanoscale dielectric environments on concentration quenching

Abstract We have studied the dependence of concentration quenching of luminescence (donor–acceptor energy transfer) on the thickness d of dye-doped polymeric films (HITC:PMMA) and found its strong inhibition at small values of d. This phenomenon is tentatively explained by a limited number of acceptors, which donors’ excitation can reach in thin samples, if the film’s thickness is comparable to the diffusion length of the energy transfer. The latter mechanism, along with effective reduction of the dye concentration, is responsible for an inhibition of the concentration quenching of dye molecules impregnating porous alumina membranes. The elongation of emission kinetics in thick (≥3 μm) HITC:PMMA films is cautiously attributed to the samples’ crystallinity.

An Optically Reconfigurable Förster Resonance Energy Transfer Process for Broadband Switchable Organic Single-Mode Microlasers

An Optically Reconfigurable Förster Resonance Energy Transfer Process for Broadband Switchable Organic Single-Mode Microlasers

Strong exciton-plasmon coupling in dye-doped film on a planar hyperbolic metamaterial.

We experimentally demonstrate the direct strong coupling between the S0→S1 absorption transition of rhodamine 6G (R6G) dye molecules and the surface plasmon polaritons of a hyperbolic metamaterial (HMM) substrate. The surface plasmon mode was excited by a guided mode of the R6G-doped polymer thin film on the HMM. The coupling strengths of the interactions between the surface plasmon and two molecular exciton modes are greater than the average linewidths of the individual modes indicating a strong coupling regime. This is the first, to the best of our knowledge, experimental demonstration of the direct strong coupling between the resonance mode supported by the HMM and the dye molecules on the HMM surface, not embedded in the HMM structure. The study may provide the foundation for the development of novel planar photonic or electronic devices.

Effect of metallic substrates and cavities on emission kinetics of dye-doped polymeric films

We have studied emission kinetics in dye-doped polymeric films (HITC:PMMA), deposited on top of glass and silver and embedded in Fabry–Perot cavities (metal-insulator-metal waveguides). For highly doped films on glass, we observed strong concentration quenching, as evidenced by a dramatic shortening of the emission kinetics, consistent with our previous studies. However, for the same dye-doped films on top of silver, slower emission kinetics were observed despite the high decay rates of individual dye molecules near the metallic surface. The concentration quenching rates in Fabry–Perot cavities were nearly identical to those of HITC:PMMA films deposited on top of silver. These findings are explained within a theoretical model for the inhibition of Förster energy transfer near a metallic surface. Furthermore, the emission kinetics of the dye-doped films on top of silver were approximately single exponential—consistent with the strong coupling of excited molecules with propagating surface plasmons.

Fabrication of Bilayer Dichroic Films Using Liquid Crystal Materials for Multiplex Applications.

A bilayer dichroic-doped liquid crystal (BDLC) film is fabricated via the uniaxial alignment method and a photopolymerization process. It is found to be useful in dichroic color filters, dual-mode circular polarizers, and chirality detectors. Two kinds of dichroic films with different absorbing wavelengths are cross-stacked to show various colors and contrasts depending on the polarization direction of the incident linearly polarized light, which is comparable with the conventional single-layer dichroic dye-doped (SDLC) film that only shows the contrast difference. This platform can be used in many other applications beyond the applications presented in this study, such as multicolor holograms, optical signal encryption, and electrically tunable devices.

Synthesis, optical limiting behavior, thermal blooming and nonlinear studies of dye-doped polymer films

Homogenous (poly (6,6′-(2-hydroxy-5-(phenyldiazenyl)-1,3-phenylene) bis (methylene) bis (2-ethylphenol)) (PHPP) film has been properly deposited using the spin coating method. In this paper, the polymer film was characterized by Atomic Force Microscopy (AFM), histogram characterization, intensity distribution of the film, and scan of the microscopic surface. The bandgap $$E_{\text{g}}$$ value was investigated by different ways. The Nonlinear Refractive Index (NLR) and Nonlinear Absorption (NLA) of the Flu-doped polymer, PbPc-doped polymer, and CuPc-doped polymer are determined using the Z-scan technique. Experimentation was conducted via a 532 nm diode laser and 3.554 KW/cm2 incident laser intensity. The effects of concentration of dye-doped PHPP films on the behavior optical limiting have been discussed. Additionally, multiple induced self-diffraction patterns generated in dye-doped PHPP polymer films using the same diode laser were observed through the study. The thermooptic coefficient (dn/dT) of the Flu-doped polymer, PbPc-doped polymer, and CuPc-doped polymer has been formed equivalent to − 0.409 × 10−5 K−1, − 0.88 × 10−5 K−1, and − 1.133 × 10−5 K−1, respectively.