A morphology-tailored triazine-based crystalline organic polymer for efficient mercury sensing

Abstract

Hydrothermal synthesis of a novel crystalline, highly cross-linked and thermally-stable triazine-based organic polymer with nanodendritic morphology has been reported. A Rietveld whole profile fitting method has been deployed to elucidate the crystal structure of the polymer. The polymer has been found to be composed of monoclinic melamine having space group P2₁/a. FTIR and Raman spectroscopic analysis provided a detail insight into the chemical structure of the as-synthesized polymer. XPS and NMR analyses were carried out for further understanding the different types of linkages required to create the backbone of the polymer. The unique rod-like morphology of the triazine-based polymer has been revealed by FESEM and TEM studies. Furthermore, a plausible mechanism for nanodendrite formation has been proposed. Interestingly, this polymer has been found to selectively detect Hg²⁺ ions at an extremely low concentration through fluorescence quenching with a detection limit as low as 0.03 ppb. The sensing phenomenon has also been explained in detail to understand the applicability of the material. Until now most of the existing studies have reported that triazine-based polymers for mercury ion sensing required the introduction of sulphur-based groups and subsequent fuctionalization owing to the high affinity of Hg²⁺ towards sulphur. However, the inherent impressive sensitivity of our polymer sample towards Hg²⁺ is the very first report in the field of highly crystalline triazine-based polymers without the necessity of any modification by sulphur mediation for mercury ion detection.