Interactions of Environmental Pollutant Aromatic Amines With Photo Excited States of Thiophene Substituted 1,3,4-Oxadiazole Derivative: Fluorescence Quenching Studies

Journal of Fluorescence - In the present work, the fluorescence quenching of novel thiophene substituted1,3,4-oxadiazole derivative 2-(4-(4-vinylphenyl)...     

Effect of expired doxofylline drug on corrosion protection of soft steel in 1 M HCl: Electrochemical,quantum chemical and synergistic effect studies

The corrosion inhibition property of expired Doxofylline (DF) was tested for soft steel in 1 M hydrochloric acid solution by adopting mass change and electrochemical measurement techniques. At 200 ppm concentration of DF, maximum of 72.84% inhibition efficiency was noticed. However with addition of 50 ppm of KI, it enhances the percentage inhibition efficiency up to 88.48%. DF resists both anodic and cathodic reactions and functioned as mixed-inhibition mechanism. At higher temperatures, electrochemical impedance response noticed that, the diameter of the semicircle decreases as solution temperature increases As a result, in both absence and presence of the inhibitor the R_p values were decreased. Quantum chemical studies revealed about structural and electronic effects in relation to the inhibition efficiencies. Surface morphology of both inhibited and corroded soft steel was assessed by means of scanning electron microscopy (SEM)) and atomic force microscope (AFM). The SEM images of soft steel reflect the inhibitive property of the DF at optimized concentration and a significant decrease in the surface roughness was observed (surface roughness was reduced from 606 nm to 294 nm as measured by AFM)). UV-Visible absorption peaks signifies that CC and CO groups from the inhibitor were interacted with iron cations, which is the evidence for the formation protective film over the soft steel surface.     

Resonance Energy Transfer Studies from Derivatives of Thiophene Substituted 1,3,4-Oxadiazoles to Coumarin-334 Dye in Liquid and Dye-Doped Polymer Media

In the present work, we have carried out energy transfer studies using newly synthesised derivatives of thiophene substituted 1,3,4-oxadiazoles namely, 2-(-4-(thiophene-3-yl)phenyl)-5-(5-(thiophene-3-yl)thiophene-2-yl)-1,3,4-oxadiazole [TTO], 2-(-4-(benzo[b]thiophene-2-yl)phenyl)-5-(5-(benzo[b]thiophene-2-yl)-1,3,4-oxadiozole [TBO] and 2-(4-(4-(trifluoromethyl)phenyl)phenyl)-5-(5-(4-(trifluoromethyl)phenyl)thiophen-2-yl)-1,3,4-oxadiazole [TMO] as donors and laser dye coumarin-334 as acceptor in ethanol and dye-doped polymer (poly(methyl methacrylate) (PMMA)) media following steady-state and time-resolved fluorescence methods. Bimolecular quenching constant (k _q), translation diffusion rate parameter (k _d), diffusion length (D _l), critical transfer distance (R ₀), donor- acceptor distance (r) and energy transfer efficiency (E _T) are calculated. It is observed that, critical transfer distance is more than the diffusion length for all the pairs. Further, bimolecular quenching constant is also more than the translation diffusion rate parameter. Hence, our experimental findings suggest that overall energy transfer is due to Förster resonance energy transfer (FRET) between donor and acceptor in both the media and for all the pairs. In addition, considerable increase in fluorescence intensity and energy transfer efficiency is observed in dye-doped polymer matrix systems as compared to liquid media. This suggests that, these donor-acceptor pairs doped in PMMA matrix may be used for applications such as energy transfer dye lasers (ETDL) to improve the efficiency and photostability, to enhance tunability and for plastic scintillation detectors.