Key Takeaways & Executive Findings
- •• Dual-emission biomass carbon quantum dots (D-BCQDs) were synthesized from Viburnum awabuki leaves via a simple, eco-friendly ethanol solvothermal method. • The fluorescence color of D-BCQDs can be tuned from crimson to blue-gray by adjusting the solvothermal temperature (140–240 °C), with two emission peaks at 490 nm and 675 nm under 413 nm excitation. • Surface oxidation defects, nitrogen content, and sp2-C/sp3-C hybridized domains are the main factors determining the fluorescence color. • The D-BCQDs enable ratiometric detection and quantification of Fe3+ and Cu2+ ions, including simultaneous detection in mixed solutions.
Abstract
Using simple and eco-friendly ethanol solvothermal treatment, dual-emission biomass carbon quantum dots (D-BCQDs) were synthesized from biomass viburnum awabuki leaves. Under excitation with 413 nm wavelength light two emission peaks appeared at 490 and 675 nm and the dots could be tuned to emit crimson, red, purplish red, purple and blue-gray fluorescence by changing the solvothermal temperature from 140 °C to 160, 180, 200 and 240 °C, respectively. XPS and FTIR characterization indicated that the fluorescence color was mainly determined by surface oxidation defects, elemental nitrogen and sp2-C/sp3-C hybridized structural domains. The D-BCQDs could not only detect Fe3+ or Cu2+, but also quantify the concentration ratio of Fe3+ to Cu2+ in a solution containing both, demonstrating their potential applications in the simultaneous detection of Fe3+ and Cu2+ ions.
1. Introduction
Carbon quantum dots (CQDs) are emerging as an alternative to conventional semiconductor quantum dots and organic fluorescent dyes due to their exceptional photostability, low toxicity, biocompatibility and small size. These characteristics make CQDs highly promising for a wide range of applications, including metal ion sensing, bioimaging, drug delivery and photocatalysis. BCQDs prepared from natural biomass have excellent biocompatibility and fluorescence properties. However, most BCQDs emit blue-green fluorescence, which limits their applications in fluorescence sensing. Consequently, there is an urgent need to synthesize long-wavelength emission or multicolor BCQDs.
In nature, plant leaves naturally contain chlorophyll with a porphyrin structure, which exhibits strong near-infrared absorption and emission properties. This intrinsic characteristic renders them highly suitable for synthesizing long-wavelength BCQDs. For instance, Qu et al. synthesized near-infrared light BCQDs from magnolia leaves and applied them to the detection of Pd2+. In addition, researchers have synthesized long-wavelength red BCQDs using taxus and mulberry leaves as carbon sources.
Currently, three luminescence mechanisms have been identified and accepted: the quantum confinement effect, surface state luminescence (involving surface chemical groups, surface oxidation degree and surface defects) and molecular state luminescence. Consequently, researchers modify the particle size and surface state of BCQDs by precisely controlling reaction conditions, including reaction temperature, time, solvent and precursors. Additionally, heteroatom doping is implemented further to enhance the tunability and multicolor luminescence of BCQDs. However, the tunable fluorescence color mechanism of multicolor dual-emission BCQDs (D-BCQDs) has rarely been studied.
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XUE Jia-jia, GAN Mei-heng, LU Yong-gen, WU Qi-lin (2025). Fluorescence color tuning of dual-emission carbon quantum dots produced from biomass and their use in Fe3+ and Cu2+ detection. SinoTechIntel Verified Research. https://doi.org/10.1016/S1872-5805(NCM2024-39-06-12)
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Frequently Asked Questions
What are dual-emission biomass carbon quantum dots (D-BCQDs)?
D-BCQDs are carbon quantum dots synthesized from biomass (e.g., Viburnum awabuki leaves) that exhibit two distinct emission peaks under a single excitation wavelength. In this study, they show emission at 490 nm and 675 nm when excited at 413 nm, enabling ratiometric fluorescence sensing.
How is the fluorescence color of D-BCQDs tuned?
The fluorescence color of D-BCQDs can be tuned by varying the solvothermal temperature during synthesis. Temperatures of 140, 160, 180, 200, and 240 °C produce crimson, red, purplish red, purple, and blue-gray fluorescence, respectively. This is attributed to changes in surface oxidation defects, nitrogen content, and sp2-C/sp3-C hybridized domains.
What is the significance of dual-emission for ion detection?
Dual-emission allows ratiometric detection, where the ratio of the two emission intensities changes in response to the analyte concentration. This approach reduces interference from environmental factors and probe concentration, improving accuracy and sensitivity compared to single-emission probes.
Can D-BCQDs detect both Fe3+ and Cu2+ simultaneously?
Yes, the D-BCQDs developed in this study can not only detect Fe3+ or Cu2+ individually but also quantify the concentration ratio of Fe3+ to Cu2+ in a solution containing both ions, demonstrating potential for simultaneous detection.
What are the main factors determining the fluorescence color of D-BCQDs?
According to XPS and FTIR characterization, the fluorescence color is mainly determined by surface oxidation defects, elemental nitrogen content, and the ratio of sp2-C to sp3-C hybridized structural domains.
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