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The present study reports thin films of merocyanine 540–octadecylamine (MC540–ODA) prepared by Langmuir–Blodgett (LB) and Spin–Coating (SC) methods, and their photophysical and morphological features. The addressed MC540–ODA LB films are different from the others designed by co–spreading method. Briefly, a known quantity of ODA in chloroform was slowly spread on the surface of a 10−6 M concentrated solution of MC540 in deionized water as subphase and the LB films were generated by the deposition of a MC540–ODA Langmuir film onto a solid substrate. The capability of MC540–ODA forming a stable monolayer at the air-water interface was confirmed by pressure–area (π–A) isotherm studies. The spectroscopic studies revealed that the photophysical properties of LB films strongly depended on the number of layers and deposition pressure. The SC thin films of MC540 at a constant dye concentration with and without ODA were successfully fabricated under the optimized experimental conditions. In the SC thin films, ODA molecules played a crucial role in their photophysical and morphological variations. Consequently, the varied experimental route allows to fine–tune the photophysical and morphological properties of the dye thin films. Image 1 • Langmuir-Blodgett and Spin-Coating films of MC540-ODA were fabricated. • The formation of H-dimers and H-aggregates depended on the film conditions. • MC540 LB films showed the large, overlapped and folded layers in AFM image. • The bowl and island-like nanostructures of MC540 SC films were monitored by AFM. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: Mono and multilayer of water-soluble pyronin B (PyB) and pyronin Y (PyY) mixed with stearic acid (SA) have been incorporated in Langmuir–Blodgett (LB) films. The surface pressure–area (π–A) isotherm studies pointed out that pure PyB and PyY are incapable of forming stable films at air–water interface and collapsed readily at low surface pressures. However, mixture of PyB or PyY with SA easily formed stable films at the air–water interface and they were easily transferred onto solid substrates. The average area per molecule of mixed films of PyB and PyY at the air–water interface was observed to decrease with increasing concentrations of PyB and PyY. The spectroscopic characteristics of PyB and PyY in chloroform, in SA containing chloroform and in LB films have also been investigated by using absorption and steady-state and time-resolved fluorescence spectroscopy techniques. The morphology of the LB film surfaces has been characterized by using atomic force microscopy (AFM). [Copyright &y& Elsevier]

Six ZnO thin films were grown under different oxygen flow rates by electrochemical deposition onto commercial indium tin oxide substrates. X-ray diffraction (XRD), optical absorption, and photoluminescence (PL) measurements were performed on all films. XRD measurements showed that films are highly (0002) c-axis oriented. It has been observed that the growth rates of the films are highly dependent on the oxygen flow rates. High growth rate is obtained for the midoxygen flow rates in the cell. Calculated crystallite size values have an increasing trend as the oxygen flow rate increases. Absorption measurements have revealed that the band gap energy of ZnO thin films is about 3.4 eV. PL measurements showed that two emissions are observed in all films: free exciton emission at about 3.37 eV and so-called blue emission at 2.66 eV in ZnO. Relatively low dose (5×1012 e-/cm2) and high-energy electron-irradiation (HEEI) (12 MeV) experiments were performed on all films. Their effects on the optical and structural characteristics are discussed. In addition, an annealing process was applied to understand the effect on the recovery of the HEEI-induced defects. [ABSTRACT FROM AUTHOR]

Abstract: High energy electron irradiation (HEEI) effects on the as-grown and annealed ZnO thin films grown by electrochemical deposition were investigated. Both samples were exposed to the sequential electron irradiations of 6, 12 and 15MeV energies at a fluence of 1×1012 e−/cm2. The results of X-ray diffraction suggest that a highly strong crystallographic structure can be produced by annealing process. Photoluminescence (PL) studies show that the EI produces violet emission which results from the zinc interstitial. Recombination lifetime (RL) values of the both films reveal that the high quality crystals are obtained. The decreasing trends of RL values with increasing electron energy have been explained by the formation of crystal defects due to the HEEI. [Copyright &y& Elsevier]