Dye Thin Films Research Articles

Electrical Properties of poly Vinyl Alcohol (PVA) doped with Alizarin orang Azo dye thin films prepared by cast method.

Electrical Properties of poly Vinyl Alcohol (PVA) doped with Alizarin orang Azo dye thin films prepared by cast method.

Silver nanoparticles produced by laser ablation for a study on the effect of SERS with low laser power on N719 dye and Rhodamine-B

ABSTRACTThe effect of surface-enhanced Raman spectroscopy (SERS) was investigated in N719 dye thin films deposited on silicon wafer with a thin film of silver nanoparticles (Ag-NPs) fabricated by laser ablation in an aqueous solution, using a NdYAG laser (λ = 1064nm). Optical absorption spectroscopy of the Ag-NPs colloidal solution shows an absorption peak at λ = 400nm, associated with a localized surface plasmon resonance in the Ag-NPs. Scanning electron microscopy (SEM) reveals that these NPs have an approximately spherical shape, with their diameter being tunable by laser power intensity. Raman spectroscopy measurements were performed using low laser power to avoid damage to the N719 dye films. Thus, a small Raman signal is obtained. The Raman intensity was greatly increased when the N719 film was deposited on a substrate with a thin film of Ag-NPs due to the SERS effect. The process was also used in Rhodamine-B to clearly demonstrate the SERS effect obtained by the use of these NPs produced by laser ablation.

"Synthesis and Optical Properties of Polystyrene Doped with DCM Thin Films "

"In the present work Polystyrene (PS) polymer doped with DCM laser dye thin films have been prepared on glass substrate using casting method. The final samples of PS doped with DCM thin films were treated with different annealing temperatures at (30, 40, 50, 60) oC. Optical absorption and transmission spectra of the prepared thin films were recorded using UV-VIS double beam spectrometer in the wavelength range from 190 to 1100 nm. The results shown that the allowed direct electronic transitions energy gap increased from 2.08 up to 2.25e.V as the temperature increasing from 30 to 60oC, whereas the allowed indirect electronic transition energy gap increase from 2.02 up to 2.17 eV as the temperature increase from 30 to 60oC. The effect of temperature on the optical properties such as Urbach’s energy, Refractive index, Extinction coefficient, Critical angle, Brewster angle, and Finesse coefficient of PS doped with DCM thin films also studied in this work.

Novel Photoalignment Method Based on Low-Molecular-Weight Azobenzene Dyes and Its Application for High-Dichroic-Ratio Polarizers.

Photoalignment is a simple technique for the manipulation of molecular orientations, which has been widely used in liquid crystal displays. Here, we propose a novel photoalignment method, in which an azobenzene dye thin film is deposited by thermal evaporation and in situ exposed to linearly polarized light simultaneously. We obtain polarizers with a dichroic ratio of up to 62, which is the highest value ever realized by a photoalignment method. Moreover, the polarizing thin film has a thickness of just 200 nm, compatible with flexible substrates, making it perfect for use as a dichroic polarizer in ultrathin and flexible displays.

Phase, microstructural analysis, and humidity-sensing properties of orange dye and cuprous-oxide composite

The effect of humidity on the phase, microstructure, and electrical properties of an organic compound orange dye (C17H17N5O2) and cuprous-oxide (Cu2O) micro-composite thin film has been investigated. 5 wt% commercially available orange dye and 30–40 wt% Cu2O were used to prepare an aqueous solution. The solution was layered in the form of a thin film on a pre-deposited copper glass substrate using a drop-casting technique under normal gravity conditions. A gap was made in the middle of the surface to get ohmic type electrodes at the ends of the glass substrate. In this way, a Cu/Cu2O–OD/Cu humidity sensor was fabricated. A self-made setup was used to carry out the experiment. Impedance of these samples was observed to decrease by 57–84 times and capacitance increased by 20–26 times with an increase in humidity from 62 to 98% RH. These observations demonstrated that impedance was more sensitive to the variations in humidity as compared to capacitance.

Coherent Random Lasing from Dye Aggregates in Polydimethylsiloxane Thin Films.

The coherent random laser (CRL) from dye-doped polydimethylsiloxane (PDMS) has been investigated in both nanoparticle-doped (NP-doped) thin films and pure dye thin films. Compared with the literature, the pump threshold is only 1.5 mJ/cm2 in the pure dye thin film with a low dye concentration. The spontaneously formed micro-/nanocrystals of Pyrromethene 597 (PM597) dye support both gain and random feedback in the bulk of the PDMS during the sample preparation. When the SiO2 NPs were doped, the pump threshold was reduced to 0.75 mJ/cm2. The threshold increased after the film was peeled off from glass, which indicates that the photon localization effect of the leaky-waveguide structure plays an important role in the reduction of the CRL threshold. By a change in the pump stripe length or the thickness of the film, the peak wavelength red-shifts 6.7 or 5.93 nm, respectively. The PM597 dye molecule solubility changes, and they spontaneously aggregate in the process of toluene volatilization; the PDMS cures, which is the reason for the formation of PM597 micro-/nanocrystals. This thin film random laser with a low dye concentration can be used in integrated optoelectronics and display imaging.

Orange Dye Thin Film Resistive Hygrometers

<p>An investigation on electrical properties of organic semiconductor, Orange Dye (OD), C<sub>17</sub>H<sub>17</sub>N<sub>5</sub>O<sub>2</sub>, resistive hygrometers was made in present study. Organic thin films were deposited on substrate by different thin film deposition methods, such as by vacuum evaporation method (Aluminum/Orange Dye/Aluminum), by spin-coater method from solution (Gold/Orange Dye/Gold), and in normal gravity condition by placing drops of OD solutions over the surface of tissue paper (Tin metal/Orange Dye in tissue paper/Net metal). As OD is also temperature sensitive, that is why to compensate temperature effect for the measurement of humidity dependent electrical properties, special arrangement was provided over the same substrate, but encapsulated from humidity environment. The AC (frequency of 10 Hz) and DC resistances were evaluated from current-voltage characteristics of all samples of resistive hygrometers, measured in the temperature interval range of 20-70 °C and relative humidity range of 30-80%. It was observed that the resistance of the OD decreases with a rise in temperature. Similarly, OD resistance is observed to decrease with increase in humidity level. The relative resistance ratio to relative humidity was found 30 and 12 for the samples deposited by vacuum evaporation and from solution by spin coater respectively. Humidity dependent on electrical properties of these resistive hygrometer make them attractive for use in development of industrial humidity meters.</p>

Structural, linear and third order nonlinear optical properties of drop casting deposited high quality nanocrystalline phenol red thin films

The present work is focused on the fabrication of high quality Phenol red dye thin films of three different thicknesses using low cost route for the first time. The thickness of the fabricated films was measured by thickness monitor and found to be 50, 84 and 91 nm. The powder X-ray diffraction reveals the amorphous nature of the film due to very fine layer of the deposited films. SEM and AFM studies were carried out on the deposited films and confirms their high quality with nanocrystalline morphology. To study the optical characteristics of the deposited thin films, UV–Vis–NIR absorbance, transmittance and reflectance spectra measurements were carried out. The variation in the value of energy gap, refractive index, optical, dielectric constant was observed with thickness. The nonlinear optical constants such as: $$~{\chi ^1},~{\chi ^3}{\text{and}}~{n_2}$$ were found to vary with thicknesses of the films, which are in the range of 0.3–1.8, 0.0089 × 10− 9–1.55 × 10− 9 esu and 0.003 × 10− 8–1.22 × 10− 8 esu. Results suggest that it may be a good contender to be used in optoelectronic applications.

The role of low light intensity: A cheap, stable, and solidly efficient amorphous Sb2S3 powder/hypericin composite/PVA matrix loaded with electrolyte solar cell

We report here on an inexpensive, solid and stable solar cell designed and made entirely of synthesized materials, Sb2S3/hypericin (dye) thin film on ITO‐coated glass (working electrode), aluminum (counter electrode), and PVA matrix (solid carrier) loaded with electrolyte (0.5M KI + 0.05M I2). The fact that the cell is inexpensive but also stable and solid, with efficiency of around 1.3%/cm2 at a very low light intensity of only 5% sun, makes it particularly suitable for indoor applications. At higher light intensities of 25 and 55% sun, however, the cell exhibits lower efficiency, around 0.3 and 0.07%/cm2, respectively. Development of low‐cost cell technology combined with understanding of low light utilization and setting of standard conditions should be some of the future directions the research in this area should follow. Therefore, in this work, we tried to give sufficient reasons for establishing standard conditions related to low light intensity. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1507–1516, 2017

Effect of Concentration Ratio of Precursor-Surfactant Solution on The Performance of Boron-doped ZnO Nanotubes Dye Sensitized Solar Cells

Boron doped zinc oxide (ZnO) nanotubes have successfully been grown using seed-mediated hydrothermal method at various concentrations of precursor-surfactant solution. The growth of ZnO nanotubes was carried out at a temperature of 90°C for 8 hours and a drop in temperature to 50°C for 16 hours. In this study, the effect of concentration ratio of precursor-surfactant was evaluated. Samples were characterized using UV-Vis Spectroscopy, X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray (EDX). UV-Vis spectra of the samples showed that the ZnO nanotubes were grown on the Flourine Tin Oxide (FTO) and the strong absorption occurred in the wavelength range of 300-400 nm, which is typical spectrum for hexagonal-nanostructure. XRD patterns showed five diffraction peaks at 2θ = 32.05°, 34.5°, 36.35°, 47.75° and 56,9°. The analysis of EVA Diffrac Plus confirmed the peaks were represented to the lattice of (100), (002), (101), (102), and (110) respectively. FESEM images of the samples showed the hexagonal-shaped ZnO nanotubes with an average diameter of 50-340 nm and an average thickness of 1.2 - 4.4 μm observed for all samples. Uniformity the size and shape of ZnO nanotubes become higher as concentrations of ZNH decreased. The EDX spectra of the samples showed the percentage of weight of Zn, O, and B was 69.35%, 21.60% and 4.76% respectively, while the percentage of their atoms was 33, 06%, 42.08% and 13.71% respectively. The B-doped ZnO nanotubes solar cells were fabricated by arranging a sandwich structure, consisting of the FTO, ZnO nanotubes, dye, electrolyte and platinum thin film. I-V characteristics of cell were carried out under irradiation of 100 mWcm<sup>-2</sup> halogen lamp. The I-V curves produced the highest efficiency from the cells utilizing the B-doped ZnO nanotubes with their concentration ratio of precursor-surfactant of 0.1 M : 0.04 M as the active material, which was 0.352%. This value is much higher than that of pure ZnO nanotube based DSSC of 0.05%.

Effect of Concentration Ratio of Precursor-Surfactant Solution on The Performance of Boron-doped ZnO Nanotubes Dye Sensitized Solar Cells

Boron doped zinc oxide (ZnO) nanotubes have successfully been grown using seed-mediated hydrothermal method at various concentrations of precursor-surfactant solution. The growth of ZnO nanotubes was carried out at a temperature of 90°C for 8 hours and a drop in temperature to 50°C for 16 hours. In this study, the effect of concentration ratio of precursor-surfactant was evaluated. Samples were characterized using UV-Vis Spectroscopy, X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray (EDX). UV-Vis spectra of the samples showed that the ZnO nanotubes were grown on the Flourine Tin Oxide (FTO) and the strong absorption occurred in the wavelength range of 300-400 nm, which is typical spectrum for hexagonal-nanostructure. XRD patterns showed five diffraction peaks at 2θ = 32.05°, 34.5°, 36.35°, 47.75° and 56,9°. The analysis of EVA Diffrac Plus confirmed the peaks were represented to the lattice of (100), (002), (101), (102), and (110) respectively. FESEM images of the samples showed the hexagonal-shaped ZnO nanotubes with an average diameter of 50-340 nm and an average thickness of 1.2 - 4.4 μm observed for all samples. Uniformity the size and shape of ZnO nanotubes become higher as concentrations of ZNH decreased. The EDX spectra of the samples showed the percentage of weight of Zn, O, and B was 69.35%, 21.60% and 4.76% respectively, while the percentage of their atoms was 33, 06%, 42.08% and 13.71% respectively. The B-doped ZnO nanotubes solar cells were fabricated by arranging a sandwich structure, consisting of the FTO, ZnO nanotubes, dye, electrolyte and platinum thin film. I-V characteristics of cell were carried out under irradiation of 100 mWcm<sup>-2</sup> halogen lamp. The I-V curves produced the highest efficiency from the cells utilizing the B-doped ZnO nanotubes with their concentration ratio of precursor-surfactant of 0.1 M : 0.04 M as the active material, which was 0.352%. This value is much higher than that of pure ZnO nanotube based DSSC of 0.05%.

Optical Study on Deposed Polystyrene Doped DCM Laser Dye Thin Films at Different Temperature

Polystyrene (PS) polymer doped with DCM laser dye thin films have prepared on glass substrate using casting method. The obtained PS doped with DCM thin films were treated at different annealing temperatures such (30, 40, 50, 60, 70) °C. It was observed from result that the allowed direct electronic transitions energy gap was increased from 2.21 up to 2.3e.V as the temperature increasing from 30-70°C. And the allowed indirect electronic transition energy gap rose from 0.06 to 0.15e.V as the temperature increasing. The allowed indirect phonon energy also was decreased at the same range of temperature. The different effect of temperature variation was observed on the optical properties of PS doped with DCM thin films.

Optical Study on Deposed Polystyrene Doped DCM Laser Dye Thin Films at Different Temperature

Polystyrene (PS) polymer doped with DCM laser dye thin films have prepared on glass substrate using casting method. The obtained PS doped with DCM thin films were treated at different annealing temperatures such (30, 40, 50, 60, 70) °C. It was observed from result that the allowed direct electronic transitions energy gap was increased from 2.21 up to 2.3e.V as the temperature increasing from 30-70°C. And the allowed indirect electronic transition energy gap rose from 0.06 to 0.15e.V as the temperature increasing. The allowed indirect phonon energy also was decreased at the same range of temperature. The different effect of temperature variation was observed on the optical properties of PS doped with DCM thin films.

Thickness dependent optical dispersion and nonlinear optical properties of nanocrystalline fluorescein dye thin films for optoelectronic applications

In the current work, the authors have fabricated the good quality nanocrystalline thin films of Fluorescein dye with different thicknesses (i.e. 145, 175 and 210nm) using cost effective spin coating technique for the first time. Structural examination was done by X-ray diffraction. Surface morphology was assessed by atomic force microscopy which verified that the fabricated thin films are of high quality with nanostructure morphology. UV–vis-NIR transmittance and reflectance spectra were recorded and various optical parameters were calculated. The enhancement in the values of optical band gap, refractive index, optical dielectric constant was observed with thickness. The nonlinear optical constants such as:χ1,χ3and n2 were also enhanced with increasing the thicknesses of the films and found to be in the range of 1.88–2.25, 0.15–0.32esu and 1.0×10−13 to 1.8×10−12esu. All the results suggest that it may be useful in optoelectronic applications.

Electrochemical detection of nitrite on poly(pyronin Y)/graphene nanocomposites modified ITO substrate

The present study reports on an easy preparation of poly(pyronin Y)/graphene (poly(PyY)/graphene) nanocomposites thin films on indium tin oxide coated glass substrates (ITO). The thin films of poly(PyY)/graphene nanocomposites are prepared by a novel method consisting of three steps; (i) preparation of graphene oxide (GO) thin films on ITO by spin-coating method, (ii) self-assembly of PyY molecules from aqueous solution onto the GO thin film, (iii) surface-confined electropolymerization (SCEP) of the adsorbed PyY molecules on the GO thin film. The as-prepared poly(PyY)/graphene nanocomposites thin films are characterized by using electroanalytical and spectroscopic techniques. Afterwards, the graphene-based polymeric dye thin film on ITO is used as an electrode in an electrochemical cell. Its performance is tested for electrochemical detection of nitrite. Under optimized conditions, the electrocatalytical effect of the nanocomposites thin film through electrochemical oxidation of nitrite is better than that of GO coated ITO.

Thin films of organic dyes with silver nanoparticles: enhancement and spectral shifting of fluorescence due to excitation of localised surface plasmons

Localised surface plasmon resonances of silver nanoparticles were used for modification of spectral response of organic dye thin films. Silver nanoparticles were deposited in the form of an island film on the quartz substrate. Three kinds of organic thin films with different absorption spectra were used: coumarin, rhodamine, and malachite green. A prominent increase of the thin films absorption was observed. Along with the enhancement of the dye absorption, shifts of the plasmon frequencies were observed. In the presence of silver nanoparticles either fluorescence quenching or enhancement was observed depending on the thickness of the dye layers. In the presence of silver nanoparticles maximum of the dye fluorescence shifts by 30 nm. To enhance the fluorescence of organic thin films we used poly(methyl metacrylate) as a matrix isolating molecules from the metallic surface. In this case, five-fold enhancement of the dye fluorescence was registered.

The thin films of pyronin dyes doped with poly(vinyl sulphate) on glass substrate: Preparation and characterization

The thin films of pyronin B (PyB) and pyronin Y (PyY) mixed with poly(vinyl sulphate) (PVS) on glass substrate from aqueous solution were fabricated using a simple spin-coating film technique. The photophysical properties of the thin films were examined by UV–Vis, steady-state fluorescence and time-resolved fluorescence spectroscopy techniques. The dye thin films on the glass substrate were prepared at various [PVS]/[dye] ratios. The interactions of pyronin dyes with PVS caused the formation of monomeric and H-aggregate thin films of the dyes. H-aggregates of pyronin dyes in the thin film quenched their fluorescence intensities while the monomeric dye films have strong fluorescence. Moreover, the presence of H-aggregates in the thin film also decreased the fluorescence lifetimes of dyes. The morphological variations in the thin films depending on the dye concentration were investigated by AFM. The morphological analysis of the thin films revealed that the thin films including H-aggregates were predominant in fibril-like structures while the monomeric thin films displayed the same morphologies compared to that observed in pristine PVS film. When the spectroscopic and morphological results were evaluated, it was concluded that H-aggregates of pyronin dyes were formed due to the adsorption of the dyes on PVS backbone.

Fabrication of cyanine dye thin films grown by a layer-by-layer method

We report the optical properties of the cyanine dye molecule thin film fabricated by a layer-by-layer method. While the absorbance and the film thickness increase with the dipping time, the use of a multilayer structure enables fabrication of the thin film without the creation of the molecule bundle that suppresses light scattering and the large absorbance obtained for the shorter dipping time. Exciton dynamics are studied by using a pump-probe technique; the signal shows two decay components in the multilayer sample that originate from the fast intramolecular relaxation and from the slow exciton relaxation. The temporal profiles show at the high signal-to-noise ratio. These results indicate that the thin film without the creation of the molecule bundle fabricated by the layer-by-layer method can be used for ultrafast all-optical switches.

Shift of absorption energy during thin dye film growth: interpretation by geometric models of the growth morphology

We measure absorption spectra of two different perylene molecules in thin films with thicknesses varied between 1 and 30nm physical vapor deposited on glass substrates. Atomic force microscopy (reveals the formation of crystallized needles for N, N`-dimethyl perylene tetracarboxylic acid diimide and amorphous round-shaped islands for 1,6,7,12-tetrachloro-N,N`-dimethyl perylene tetracarboxylic. For both molecules, a spectral shift of the lowest energy transition to lower energies was observed with increasing film thickness. Common models taking electric fields, electronic coupling or exciton confinement into account cannot completely describe the observed spectral shift. Here we show that the experimental values can be fitted with an advanced layering model based on the energetic difference between bulk and interface/surface materials. In contrast to the known simple d−1 model, which describes the energetic shift for the special case of a layer-by-layer growth, we extend this idea to other film morphologies.

Waterproof material for liquid crystals photoalignment based on azo dyes

We have designed and synthesized azo dyes with reversible intermolecular bonds, which can be used as materials for liquid crystal photoalignment. The generation of anisotropic structures in azo dye thin film is possible due to the presence of intermolecular hydrogen or coordination (metal–oxygen) bonds. All thin film materials are resistant to air moisture, while photoalignment material with reversible hydrogen bonds is inert to direct water contact. In this paper, we study photoalignment dynamics of obtained materials and discuss possible formation of intramolecular and intermolecular hydrogen bonds within the photoalignment dye layer.