Improved quantum dots fluorescence quenching using organized medium: A study of the effect of naphthoquinones aiming the analysis of plant extracts

Abstract

Abstract The fluorescence quenching effect of lapachol, β-lapachone, α-lapachone and β-lapachone-3-sulfonic acid on 3MPA-CdTe quantum dots (QDs) was studied in organized surfactant systems. The use of CTAB in the working dispersions promoted several advantages such as fast probe fluorescence stabilization and the increasing of the quenching effect caused by these naphthoquinones, which eliminated the need for attenuation correction caused by inner filter effect. The cationic surfactant facilitated the solubility of the naphthoquinones and minimized the effect on the probe signal caused by the presence of different organic solvents. Working dispersions (6.0 × 10− 8 mol of QDs in 1 L of aqueous solution) were prepared in aqueous CTAB solutions (9.0 × 10− 4 mol L− 1) containing sodium phosphate buffer of pH 7.4. In order to establish a relationship between fluorescence (380/560 nm) and concentration of naphthoquinones, a Stern–Volmer model was used. The linear range obtained was from 5.0 × 10− 7 to 1.0 × 10− 5 mol L− 1. The methodology was applied in the determination of lapachol in an extract of Tabebuia impetiginosa (Pink Ipe). The suitability of using thin layer chromatography with quantum dots fluorescence probing has been demonstrated.