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Red/Green Tunable-Emission Carbon Nanodots for Smart Visual Precision pH Sensing

Zhao, Jiang Lin; Luo, Qing Ying; Ruan, Qin; Chen, Kai; Liu, Cui; Redshaw, Carl; Jin, Zongwen


Jiang Lin Zhao

Qing Ying Luo

Qin Ruan

Kai Chen

Cui Liu

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Professor Carl Redshaw
Professor of Inorganic Materials Chemistry and REF Lead for Chemistry

Zongwen Jin


The development of novel carbon nanodots (CDs) with excellent optical properties and promising applications is an attractive but a challenging area. Herein, we demonstrate that the fluorescence properties of CDs can be optimized by simple modification of the molecular structure of the carbon source. Significantly, the final optimized CDs 1 exhibit a rare extremely acidic (pH 1-3) sensitivity. A distinguishable red/brown/green fluorescence color change is achieved for visual readout by simply tuning the pH to 1, 2, or 3. The distinguishable color change combined with ratiometric fluorescence changes greatly improves the naked-eye visual resolution up to 0.2 pH units, which is higher than that of commercial precision pH test strips. Furthermore, a smartphone was employed in a portable, low-cost, rapid, and precise pH measurement method, which satisfied the requirement of point-of-care testing. Inspired by the reversible color change of red/brown/green tri-fluorescence on tuning the pH to 1, 2, or 3, a simple yet efficient molecular logic circuit has been designed. Given the unique pH-dependent photoluminescence properties, these CDs have been further applied in the anti-counterfeiting and information encryption field, making the "burn after reading"encryption technology a reality.


Zhao, J. L., Luo, Q. Y., Ruan, Q., Chen, K., Liu, C., Redshaw, C., & Jin, Z. (in press). Red/Green Tunable-Emission Carbon Nanodots for Smart Visual Precision pH Sensing. Chemistry of materials : a publication of the American Chemical Society,

Journal Article Type Article
Acceptance Date Jul 21, 2021
Online Publication Date Jul 23, 2021
Deposit Date Jul 24, 2021
Publicly Available Date Oct 27, 2022
Journal Chemistry of Materials
Print ISSN 0897-4756
Electronic ISSN 1520-5002
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Keywords Color; Fluorescence; Cadmium sulfide; Aromatic compounds; pH
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©2021 The authors. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder

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