Fluorescence coupled with electrochemical approach at the bulk and the interface region of hydrogen-bonding self assemblies of urea derivatives with DDP dye in aqueous solution

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 229; p. 117914
• Main Authors: Somasundaram, Gayathri, Rajaraman, Vasanthi, Mahalingam, Vanjinathan, Dhenadhayalan, Namasivayam, Rajendran, Kumaran
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 15.03.2020
• Subjects: DDP dye; Electrochemical impedance spectra; Fluorescence emission; Fluorescence lifetime; Hydrogen-bonding; Urea derivatives; DDP dye; Urea derivatives; Electrochemical impedance spectra; Hydrogen-bonding; Fluorescence lifetime; Fluorescence emission
• ISSN: 1386-1425; 1873-3557
• DOI: 10.1016/j.saa.2019.117914

Photophysical and electrochemical techniques were employed to hydrogen-bonding self assemblies forming solutes (Urea, Dimethylurea and Tetramethylurea) in the presence of 4-dicyanomethylene 2, 6-dimethyl-4H-pyran (DDP) dye. Addition of urea derivatives to DDP dye (Intramolecular Charge Transfer (ICT)) results in a fluorescence enhancement accompanied with a significant shift. Fluorescence lifetime behavior exhibits a tri-exponential decay with a large variation in the fluorescence lifetime and relative amplitude distribution. The coexistence of three different fluorescence lifetime components of DDP with urea derivatives signifies the existence of heterogeneous micro environment. The dye is surrounded by varying proportion of solute and water molecules are established from fluorescence lifetime studies. Urea derivatives govern the excited state characteristics of DDP dye resulting in the formation and promotion of different microenvironment which are clearly distinguishable. The existence of multi environment attributed to urea-water structural behaviour is authenticated by electrochemical impedance spectral studies (EIS). A large variation in the contour pattern, shape and intensity in 3D fluorescence contour spectra of dye with urea validate the existence of dye in a heterogeneous micro environment. The hydrophobicity of urea derivatives along with the hydrogen-bonding properties of urea-water and urea-urea influence the photophysical and electrochemical nature of dye is emphasized. [Display omitted] •Photophysical and electrochemical properties of DDP dye with urea derivatives is entirely different from DCM type dyes.•Absorption, emission, and fluorescence lifetime of urea derivatives with DDP dye results in a fluorescence enhancement accompanied with shift in emission maxima and hydrogen-bonding interaction exists between DDP dye with urea derivatives.•Fluorescence spectral characteristics along with electrochemical impedance spectral behaviour of dye are confined to a heterogeneous environment.