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Here, we demonstrated a bio-probe based on Europium(III)-8-allyl-2-oxo-2H-chromene-3-carbaldehyde (AOCC) complex for sensing of N-acetylamino acids, nucleotides, nucleobases and CT-DNA in solution using time-resolved Luminescence method. The stoichiometry of the complex has been optimized to be 1:3 metal: ligand ratio. The limits of detection were in the range of 0.044 - 0.13 μM. The binding constants (K) and thermodynamic parameters of biomolecules under examination with Eu (III)–(AOCC)3 complex have been determined. Selectivity of Eu(III)-(AOCC)3 complex towards various biomolecules was studied utilizing ratiometric methods, where the binding affinities of these biomolecules towards Eu(III)-(AOCC)3 complex have been calculated. The binding mode between CT-DNA and Eu(III)-(AOCC)3 has been investigated using steady-state luminescence and viscosity method. The luminescence emission of this complex was found to be modulated to different degrees when interacting biomolecules under investigation and DNA. This can be considered as a model for a sensor for detecting these biologically compounds.

A new luminescent europium- o -(4-methoxy benzoyl) benzoic acid [ o -(4-anisoyl)] complex in ethanol–water (5:5 v/v) solution was used for selective determination of organophosphorus pesticides. The interaction of new and selective luminescent europium complex with different pesticides was studied using electroanalytical methods and fluorescence technique. The results indicate that the pesticides azinphos ethyl, chlorfenvinphos, diazinon and isofenphos, exhibit quenching effect on the characteristics emission peak for Eu(III) at λ = 614 nm. The luminescence variations values using the probe Eu-( o -(4-anisoyl)) 2 fit Stern–Volmer equation, where the detection limits are 1.93, 2.82, 3.78 and 1.80 μmol L −1 for azinphos ethyl, chlorfenvinphos, diazinon and isofenphos, respectively. The binding constants at different temperatures were calculated. Also, it was found that the quenching mechanism is dynamic type for chlorfenvinphos, diazinon and isofenphos while static type for azinphos ethyl. Effect of some relevant interferents on the detection of pesticides has been investigated.