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In this paper, solvent effects on the linear and nonlinear optical responses of thiazine dyes were investigated. Spectroscopic and open aperture Z-scan techniques were used for studying linear and nonlinear responses of azure A and methylene blue dyes. The experimental results show that linear and nonlinear optical properties of used dyes depend highly on the molecular structure and their surrounding media characteristics. The calculated contribution of various media- induced interactions indicate that solvent hydrogen bond acceptor and solvent dipolarity and polarizability abilities have significant effects on the linear and nonlinear absorption characteristics of thiazine dyes. Moreover, by transition of the linear optics domain to nonlinear optics, similar resonance structures were obtained for thiazine dyes. So, the spectroscopic technique can be considered as a simple method for prediction of dominant resonance structures and effective solvent polarity parameters on the third-order nonlinear properties of azure A and methylene blue dyes. Key words: nonlinear optics, spectroscopy, Z-scan, thiazine, solvent. Nous etudions ici les effets du solvant sur les proprietes optiques lineaires et non lineaires de colorants thiazines. Nous utilisons des techniques spectroscopiques et de Z scan pour etudier les reponses lineaires et non lineaires des colorants azur A et methylene bleu. Les resultats experimentaux montrent que les proprietes lineaires et non lineaires dependent fortement de la structure moleculaire et des caracteristiques de leur milieu ambient. La contribution calculee de l'interaction induite de differents milieux indique que les capacites d'accepteur de lien hydrogene du solvant et ses habilites dipolaire/polarisable ont des effets significatifs sur les caracteristiques d'absorption des colorants thiazines. Ainsi, la technique spectroscopique peut etre consideree comme une methode simple pour predire les structures de resonances dominantes et les parametres de polarite effectives du solvant sur les proprietes non lineaires du troisieme ordre des colorants azur A et methylene bleu. [Traduit par la Redaction] Mots-cles: optique non lineaire, spectroscopie, Z scan, thiazine, solvant., 1. Introduction Recently, nonlinear optical materials, especially organic molecules, due to their good photo-thermal stability, dissolvability, and easy preparation characteristics, have received serious consideration. In addition, these remarkable properties increase [...]

Absorption and fluorescence spectra of some Sudan dyes (Sudan III, Sudan IV, and Sudan Black B) were recorded in various solvents in the range of 300-800 nm at room temperature. The solvatochromic behavior of these substances and their solvent-solute interactions were analyzed by means of the linear solvation energy relationship concept suggested by Kamlet and Taft. The obtained results express the effect of solvation on the tautomerism and molecular configuration (geometry) of Sudan dyes in solvent media. Furthermore, analysis of solvent-solute interactions suggests different forms of resonance structures of Sudan dyes in polar and low-polar solvents. Keywords: diazo Sudan dye, solvent-solute interaction, Kamlet-Taft parameter, tautomeric resonance structure, linear solvation energy relationship. Nous avons enregistre les spectres d'absorption et de fluorescence de certains colorants Soudan (Soudan III, Soudan IV et noir Soudan B) dans divers solvants dans la gamme de 300 a 800 nm a temperature ambiante. Nous avons analyse le comportement solvatochromique de ces substances ainsi que leurs interactions solvant-solute selon le concept de relation lineaire d'energie de solvatation propose par Kamlet et Taft. Les resultats obtenus expriment l'effet de la solvatation sur le tautomerisme et la configuration moleculaire (geometrie) des colorants Soudan en solution. En outre, l'analyse des interactions solvant-solute laisse entrevoir differentes formes des structures de resonance de ces colorants, selon le degre de polarite des solvants. [Traduit par la Redaction] Mots-cles: colorant diazoique Soudan, interaction solvant-solute, parametre Kamlet-Taft, structures de resonance tautomeriques, relation lineaire d'energie de solvatation., Introduction Azo dyes are one of the largest and most important classes of colorants. Usage of azoic dyes in textiles, food, paper printing, nonlinear optical devices, and liquid crystalline displays [...]

The plasma reactors are of great interest in ammonia synthesis because of their green performance, small-scale process capabilities, and various design and application options. The purpose of this research is to synthesize water-soluble ammonia by plasma electrolysis which utilizes nitrogen atmospheric pressure plasma generated by DC discharge. Then, we investigate the influence of the plasma characteristics such as the electron temperature and density on the resultant ammonia concentration. For this purpose, the model of the Hoffman electrolysis apparatus was designed for separating the anodic and the cathodic parts, producing plasma, and finally interacting with an aqueous solution surface. This procedure allows us to compare the mechanism of the classical electrolysis with plasma electrolysis. The concentration of synthesized ammonia resulting from the reaction of active species in the interaction between plasma and the liquid surface on the cathode side of the device was obtained. The plasma electron temperature and density were measured by the standard Boltzmann plot method and the Stark broadening of H β via optical emission spectroscopy (OES), respectively, and their effects on the interaction between plasma and the water surface were investigated, which leads to nitrite and ammonia synthesis. The intensity of the emitted light varied as the discharge voltage was increased according to 8kV, 9kV, 10kV, and 11kV. As a result, the plasma electron temperature, density, and the synthesis of additional water-soluble ammonia parameters increase. Multiple parameter linear regression was used to evaluate the effect of varying the voltage on these parameters, which was positive. [ABSTRACT FROM AUTHOR]