Synthesize of nitrogen doped carbon quantum dots by the hydrothermal method and its application for detection of iodide anion using paper based smart phone detection system.

Abstract

The purpose of this research is to design a Whatman paper based sensor for quantitative measurement of iodide anion by its quenching effect on the fluorescence intensity of the nitrogen doped carbon quantum dots (N-doped CQDs) using a smart phone as a detection system. In this project, N-doped CQDs were synthesized by a hydrothermal method using citric acid as a source of carbon and hexamethylenediamine as a source of nitrogen. In order to characterize of the synthesized N-doped CQDs, Fourier transform infrared spectrophotometry (FT-IR), Energy-dispersive X-ray spectroscopy (EDX) and dynamic light scattering (DLS) was used. After designing of the paper based sensor, an aliquot of the mixture of the N-doped CQDs:Glue (glue roles as the stabilizing agent) was injected on the hydrophilic zone of the paper and then by injection of different concentrations of iodide anion, the reduction of the fluorescence intensity was measured using the smart phone camera. By optimizing the critical parameters affecting the quenching efficiency of the N-doped CQDs including the size of the hydrophilic zone, the volume ratio of the N-doped CQDs:Glue, type of the Whtaman filter paper and the pH of sample solution, the proposed method was used for determination of iodide ion. The results show that two calibration curves in the ranges of 1-10 and 15-200 mmol L^-1 iodide were obtained for determination of iodide anion. Also, the detection limit (LOD) of 3 mmol L^-1 and the relative standard deviation (RSD) in the range of 2.6-2.9 % were obtained for the iodide anion in the range of 50-150 mmol L^-1. The main advantages of the propsed method are rapidity, inexpensively, simplicity, availability and no need of expert for operation.