Parameters affecting the synthesis of carbon dots for quantitation of copper ions

Yu-Syuan Lin; Yaling Lin; Arun Prakash Periasamy; Jinshun Cang; Huan-Tsung Chang

doi:10.1039/c9na00137a

Parameters affecting the synthesis of carbon dots for quantitation of copper ions

Nanoscale Adv. 2019 May 14;1(7):2553-2561. doi: 10.1039/c9na00137a. eCollection 2019 Jul 10.

Authors

Yu-Syuan Lin¹, Yaling Lin¹, Arun Prakash Periasamy¹, Jinshun Cang², Huan-Tsung Chang^{1

3}

Affiliations

¹ Department of Chemistry, National Taiwan University Taipei 10617 Taiwan changht@ntu.edu.tw.
² Department of Chemical Engineering, Yancheng Institute of Industry Technology Yancheng Jiangsu 224005 China.
³ Department of Chemistry, Chung Yuan Christian University Taoyuan City 32023 Taiwan.

Abstract

A simple, eco-friendly, and low-cost electrochemical approach has been applied to the synthesis of carbon dots (C dots) from histidine hydrochloride in the absence or presence of halides (Cl, Br, and I) at various potentials up to 10 V. The as-formed C dots refer to C dots, Cl-C, Br-C, and I-C dots. The time-evolution UV-vis absorption and photoluminescence (PL) spectra provide more detailed information about the formation of C dots. Upon increasing the reaction time from 1 to 120 min, more and more C dots are formed, leading to increased PL intensity. The halides play two important roles in determining the formation of C dots; controlling the reaction rate and surface states. When compared to chloride and bromide, iodide has a greater effect on varying surface states and inducing PL quenching through intersystem crossing. The PL intensities of the four types of C dots all decrease upon increasing Cu²⁺, Hg²⁺, and Ag⁺ concentrations. In the presence of 0.8 mM I^-, I-C dots compared to C dots, Cl-C dots, and Br-C dots are slightly better for quantitation of Cu²⁺. Fourier transform infrared spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy results of I-C dots reveal the interactions of Cu²⁺ with the surface ligands (imidazole and histidine). The I-C dot probe in the presence of 0.8 mM I^- is selective toward Cu²⁺ over the tested metal ions such as Hg²⁺ and Ag⁺. The assay provides a limit of detection of 0.22 μM for Cu²⁺ at a signal-to-noise ratio of 3. Practicality of this probe has been validated by the analyses of tap, lake, and sea water samples, with negligible matrix effects.