Fluorescent triazolyl-coumarin carbon spheres synthesized from waste tyres for Fe3+ detection

The recycling and re-use of waste tyres is an important area for global research to find ways in alleviating the hazardous impact of these hardy materials on the environment. The use of recycled waste tyres as carbon source... [ view full abstract ]

The recycling and re-use of waste tyres is an important area for global research to find ways in alleviating the hazardous impact of these hardy materials on the environment. The use of recycled waste tyres as carbon source to synthesize fluorescent chemosensing carbon spheres for the detection of harmful chemicals in water is proposed in this work. Three key problems are addressed at once: i) re-using waste tyre products ii) synthesis of low-cost carbon nanomaterial iii) detection of harmful compounds within environment systems. The carbon spheres were synthesized from waste tyre pyrolysis oil using chemical vapour deposition (CVD) at 950 ^oC with ferrocene as catalyst. Characterization of the carbon spheres were done using TEM, SEM, Raman, TGA and XRD. The two-unit triazolyl-coumarin was synthesized through a multi-step procedure with the “click-reaction" as one of the steps. The carbon spheres were functionalized with the triazolyl-coumarin units through Steglich esterification to yield fluorescent carbon spheres. Functionalization was confirmed using XPS, FT-IR and TGA. Complexation studies were done using UV/Vis and fluorescence with a wide range of elements; Ag⁺, Al³⁺, Co²⁺, Cr³⁺, Cu²⁺, Fe³⁺, Hg²⁺, Li⁺, Ni²⁺, Pb²⁺ and Zn²⁺. The triazolyl-coumarin carbon spheres showed reasonable sensitivity and selectivity towards Fe³⁺ in water with a quenching effect in fluorescence. It was shown that the 1,2,3-triazole is a possible binding site for Fe³⁺ on the triazolyl-coumarin carbon sphere, determined through the comparison of emission responses of the fluorescent carbon spheres,starting carbon sphere and a reference compound. Titration studies with Fe³⁺ were also done with results indicating an exponential decay of quenching in the fluorescence up to 70%. Ferric ion (Fe³⁺) is a crucial element used in the maintanance of biochemical processes within living systems. Detection of Fe³⁺ is therefor crucial for monitoring the limits within the environment and living systems.