LUMINESCENT HYBRID MATERIALS BASED ON KAOLINITE AS PROMISING SENSORS FOR ORGANIC CONTAMINANTS DETECTION

Abstract

The goal of this work was obtain a new luminescent hybrid material, stable, and selective for detection of organic pollutants such as caffeine, acetylsalicylic acid and trimethoprim using the luminescent properties of organic fluorescent dyes for contaminant detection. Methods: Rhodamine B and 3-aminopropyltriethoxysilane (APTES) were reacted at 190oC, under vigorous magnetic stirring. After 24 h reaction, the temperature lowered to 60oC and the precursor kaolinite intercalated with dimethylsulfoxide (KaDMSO) was added to the reaction mixture. The system was very slowly heated up to 190oC (about 4h of heating) and maintained at this temperature for 24 h. Powder X-ray diffraction (PXRD), fluorescence spectroscopy and thermal analysis (TGA) were used to characterize the structure and properties of natural and grafted clays. Results : The silane and Rhodamine B molecules promoted the delamination of the clay due to their large molecular size, weakening the hydrogen bonds between Si-O and Al-OH layers in the interlayer space. PXRD revealed that, after APTES and Rhodamine B reaction the typical reflection of intercalated DMSO was not observe confirming the displacement of this molecule, the diffraction reflections reduced the intensity probably due to non-stacking of kaolinite layers promoted by the organic molecules; rhodamine B and APTES grafted into lateral hydroxyls promoted kaolinite delamination. Conclusion: The synthesized material (KaRhAPTES) was immobilized along the kaolinite structure, which makes the component extremely attractive for applications in the area of sensors.