Optical properties and fluorescence quenching of carbazole containing (D–π–A) push–pull chromophores by silver nanoparticles: a detailed insight via an experimental and theoretical approach

Abstract

(4Z)-4-[(9-Ethyl-9H-carbazol-3-yl)methylidene]-2-phenyl-1,3-oxazol-5(4H)-one (ECPO) was prepared by the one-pot multi-component reaction of 9-ethyl-9H-carbazole-3-carbaldehyde, hippuric acid, anhydrous sodium acetate and acetic anhydride under microwave irradiation. The structure of ECPO was confirmed by elemental analysis and spectral studies (¹H and ¹³C NMR, FT-IR) and theoretically by Density Functional Theory (DFT). The experimental and simulated electronic absorption and fluorescence spectra of ECPO have been studied in solvents of different polarities. They are in good agreement with each other. The data were used to study solvatochromic properties such as excitation coefficient, Stokes shift, oscillator strength, transition dipole moment, and fluorescence quantum yield. The wavelength maxima showed red shifts with increasing solvent polarity from n-hexane to DMSO. ECPO undergoes solubilization in different micelles and may be used as a probe for determining the critical micelle concentration (CMC) of CTAB and SDS. The interaction of colloidal silver nanoparticles (AgNPs) with ECPO dye was studied in ethanol and ethylene glycol using steady state fluorescence quenching measurements. The Stern–Volmer quenching rate constant (K_sv) was calculated to be 5.28 × 10⁷ M⁻¹ and 3.48 × 10⁷ M⁻¹ in ethanol and ethylene glycol, respectively. ECPO's highly promising NLO character was complemented by NBO investigation.