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Preparation and Evaluation of Fluorescent Carbon Dots from Tea and Coffee Extracts

Undergraduate #144
Discipline: Chemistry and Chemical Sciences
Subcategory: Biomedical Engineering

Anissa Kennedy - Winston-Salem State University
Co-Author(s): Melissa Chang, Maria Ngu-Schwemlein, and Ng Sing Muk



Carbon dots (C-dots) are a fascinating new class of nanomaterials that are promising molecular templates for various different types of applications including imaging, sensing, drug delivery, photo-catalysis, and more. However, previously reported methods for the preparation of C-dots have several limitations, including the use of costly or toxic chemicals and expensive equipment. Therefore, there is a need to establish new sources that are more sustainable to preserve the environment. The objective of this study is to assess the formation of fluorescent carbon dots from sources that will support a green environment. We hypothesized that carbonization of beverage biowaste, such as tea or coffee, could generate fluorescent carbon dots. Black tea and select coffee beans were subjected to thermal carbonization at 250°C, and extracted with water to yield fluorescent carbon dots. Their fluorescent sensing potential was evaluated by titration with some common metal ions. Fluorescence emission measurements were conducted on a Cary Eclipse spectrofluorimeter. Control experiments using room temperature extracts from raw tea or coffee did not yield any fluorescence. The results from this study show that fluorescent carbon dots are readily prepared from biowaste as a facile way to produce carbon dots. They are soluble in water to form a stable and transparent yellowish solution that emits fluorescence with a strong band following excitation at 330 nm. Its fluorescence was independent of the metal ion type except for iron (III), whereby it exhibited a concentration dependent emission quenching.

In conclusion, carbon dots derived from tea or coffee by thermal carbonization exhibit significant fluorescent properties. They offer a “greener” and more sustainable approach to preparing carbon-based nanoparticles. Future research in the functionalization of these carbon dots is a worthwhile pursuit to design multifunctional carbon dots for environmental and biomedical applications.

Funder Acknowledgement(s): We acknowledge support from the National Science Foundation HBCU-TIP and LSAMP programs, and an American Association for the Advancement of Science WIRC-MI grant.

Faculty Advisor: Maria Ngu-Schwemlein,

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This material is based upon work supported by the National Science Foundation (NSF) under Grant No. DUE-1930047. Any opinions, findings, interpretations, conclusions or recommendations expressed in this material are those of its authors and do not represent the views of the AAAS Board of Directors, the Council of AAAS, AAAS’ membership or the National Science Foundation.

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