Efficient UV emission from carbon dots derived from a green-tea extract

Henry Opoku; Junkai Ren; Xin Zhou; Peijuan Zhang; Shi Tang; Dongfeng Dang; Ludvig Edman; Jia Wang

doi:10.26599/NR.2025.94907321

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Research Article | Open Access

Efficient UV emission from carbon dots derived from a green-tea extract

Henry Opoku^¹, Junkai Ren^¹, Xin Zhou^², Peijuan Zhang^³, Shi Tang^¹, Dongfeng Dang^³, Ludvig Edman^{¹^,⁴}

(), Jia Wang^{¹^,⁴}

()

1Department of Physics, Umeå University, SE-90187 Umeå, Sweden

2Department of Medical and Translational Biology, Umeå University, SE-90187 Umeå, Sweden

3Engineering Research Center of Energy Storage Materials and Devices, Ministry of Education, School of Chemistry, Xi’an Jiaotong University, Xi’an 710049, China

4Wallenberg Initiative Materials Science for Sustainability, Department of Physics, Umeå University, SE-90187 Umeå, Sweden

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Ultraviolet (UV)-emitting carbon dots were synthesized by hydrothermal reaction of a renewable feedstock, a green-tea extract. When dissolved in water, they emit with a peak wavelength of 384 nm and a photoluminescence quantum yield of 17%. When they are dissolved in poorer solvents, the emission blue-shifts and the photoluminescence quantum yield increases significantly, which suggests that the carbon dots emit by aggregation-induced emission.

Abstract

Emissive carbon dots (CDs) that are synthesized from biomass can be highly sustainable, but the number of reported biomass-derived CDs that emit in the ultraviolet (UV) range is small. Moreover, current commercial UV-emitting materials rely heavily on the use of non-sustainable resources, such as rare metals, heavy metals, and petroleum chemicals. This yields that the development of efficient biomass-derived UV-CDs is desired. Here, we report on the hydrothermal conversion of a common green-tea extract (Polyphenon 60) into UV-CDs, which feature a photoluminescence (PL) peak wavelength of 384 nm, a full width at half maximum of 72 nm, and a photoluminescence quantum yield (PLQY) of 17% in water. By shifting to a lower-polarity solvent of 3-phenoxyanisole, the PLQY is strongly enhanced to 81%, and the PL peak blue-shifts to 370 nm, while the maximum solubility is lowered. These observations support the notion that the UV-CDs feature aggregation-induced emission and that they are endowed with hydrophilic surface groups. Moreover, the findings of excitation-wavelength-independent PL and a nanosecond-level short emission lifetime reveal that it is a single distinct fluorophore that produces the UV emission. We finally report preliminary results that the UV-CDs exhibit potential for inhibiting the proliferation of cancer cells.

Keywords

carbon dots ultraviolet (UV) emission biomass aggregation-induced-emission cell proliferation inhibitor

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References

[1]

Meng, W. X.; Bai, X.; Wang, B. Y.; Liu, Z. Y.; Lu, S. Y.; Yang, B. Biomass-derived carbon dots and their applications. Energy Environ. Mater. 2019, 2, 172–192.