Biopolymer-based nanodots assembly on paper for pH-dependent separation of a mixture of oppositely charged dyes Tuhin Bhattacharjee a,c , Rita Rabha a,c , Devasish Chowdhury ,b , Gitanjali Majumdar a,c a Department of Chemistry, Assam Engineering College, India, b Material Nanochemistry Laboratory, Physical Science Division, Institute of Advanced Studies in Science and Technology, India, c Assam Science and Technology University, India In the presented work, we have synthesized biopolymer-derived carbon nanodots directly on paper using chitosan via a thermal assisted approach [1]. The formation of the biopolymer-based nanodots was confirmed using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscope (FESEM). The nanodot paper was further characterized using UV-Vis spectrophotometer and emission spectroscopy, Energy Dispersive X-Ray (EDX), X-ray Diffraction (XRD), and Laser Confocal Microscopy (LCSM) to confirm the deposition of nanodots. The paper showed selectivity for negatively charged dyes in acidic and neutral pH while in basic pH, there was no adsorption of anionic dye. Thereby, the basic medium was exploited as a medium to desorb anionic dye from nanodot paper with slight agitation and up to 76% can be recovered. The X-ray Photoelectron spectroscopy (XPS), Fourier Transformed Infrared (FTIR), and Zeta potential measurements confirm the interaction of the dye with the carbon dots on the paper and were used to deduce a possible mechanism. The selectivity was found to be above 98% for a pair of different cationic and anionic dyes. This work demonstrates the ability of natural bio-precursors in the separation of oppositely charged materials. Furthermore, using paper as support, we have created a cheaper and more sustainable approach for dye separation [2]. References 1. Tuhin Bhattacharjee, Mirjufa Islam, Devasish Chowdhury, Gitanjali Majumdar,In-situ generated carbon dot modified filter paper for heavy metals removal in water, Environmental Nanotechnology, Monitoring & Management, Volume 16,2021,100582. https://doi.org/10.1016/j.enmm.2021.100582. 2. Tuhin Bhattacharjee, Rita Rabha, Devasish Chowdhury, Gitanjali Majumdar,Carbon Dot grafted pH sensitive smart paper for highly efficient separation ofanionic/cationic dyes from a mixture, Sustainable Materials and Technologies , Volume 33, 2022, e00489,. https://doi.org/10.1016/j.susmat.2022.e00489.
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