Preparation of N-doped carbon quantum dots and their applications in the selective sensing of Mercury (II)

Yan, Xiangyu (2021) Preparation of N-doped carbon quantum dots and their applications in the selective sensing of Mercury (II). Masters thesis, Memorial University of Newfoundland.

[img] [English] PDF - Accepted Version
Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.

Download (3MB)

Abstract

This master’s thesis presents a comprehensive study on the optimal design and synthesis of nitrogen-doped carbon quantum dots (N-CQDs) from small molecule carbon and nitrogen precursors and their application as fluorescence sensor for the detection of heavy metal ions. By employing the Box-Behnken design (BBD), the optimal synthetic condition for hydrothermal method was obtained, which led to the achievement of the high quantum yield of 51.7% for N-CQDs. The as-prepared N-CQDs are with brownish-yellow color and showed a bright blue light irradiation. To stabilize the N-CQDs, immobilization of N-CQDs onto a glutaraldehyde cross-linked chitosan was then performed to prepare the N-CQDs@GACTS hydrogel film for the selective sensing of Hg2+ ion. FTIR and XPS analyses revealed that N-CQDs were embedded into the GACTS matrix mainly through weak hydrogen bond or electrostatic attraction. Among the three tested heavy metal ions (Cd²⁺, Hg²⁺ and Pb²⁺), the N-CQDs@GACTS hydrogel film exhibited remarkable sensing sensitivity and selectivity of Hg²⁺. The excellent selectivity could be attributed to a stronger interaction between the hydrogel film and Hg²⁺ ion. Due to the strong oxidizing ability and chelating power, Hg²⁺ can be more readily combined with polar groups on the surface of N-CQDs@GACTS hydrogel to form new complexes by either chelation or electrostatic attraction, which provokes an effective electron transfer for the fluorescence quenching of the N-CQDs@GACTS hydrogel. The prepared N-CQDs@GACTS hydrogel demonstrates enhanced practicality in terms of fast response, sensitivity, selectivity, and economical pricing. It has great potential for practical applications in selectively detecting Hg²⁺ from either drinking water or wastewater.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/15066
Item ID: 15066
Additional Information: Includes bibliographical references (pages 72-91).
Keywords: Carbon quantum dots, Nitrogen doped, Design of experiment, Heavy metal sensing
Department(s): Engineering and Applied Science, Faculty of
Date: February 2021
Date Type: Submission
Library of Congress Subject Heading: Quantum dots--Design; Quantum dots--Synthesis; Nitrogen; Mercury.

Actions (login required)

View Item View Item

Downloads

Downloads per month over the past year

View more statistics