Photoluminescent Green Carbon Nanodots from Food-Waste-Derived Sources: Large-Scale Synthesis, Properties, and Biomedical Applications

TLDR

Green carbon nanodots derived from food waste are highly water‑soluble due to abundant surface oxygen groups. The authors synthesize green carbon nanodots from diverse food waste at a yield of ~120 g per 100 kg, then test their cytotoxicity in CHO‑K1, C2C12, and COS‑7 cells up to 2 mg mL⁻¹ for 24 h. The green nanodots, produced at ~120 g per 100 kg of food waste, are ~4 nm in size, emit 400–470 nm light, remain photostable (≈8 % loss over 10 days), exhibit low cytotoxicity in CHO‑K1, C2C12, and COS‑7 cells, serve as effective bioimaging probes, and their synthesis byproducts enhance seed germination, indicating broad potential in biomedical imaging, optoelectronics, and agriculture.

Abstract

We have developed a simple approach for the large-scale synthesis of water-soluble green carbon nanodots (G-dots) from many kinds of large food waste-derived sources. About 120 g of G-dots per 100 kg of food waste can be synthesized using our simple and environmentally friendly synthesis approach. The G-dots exhibit a high degree of solubility in water because of the abundant oxygen-containing functional groups around their surface. The narrow band of photoluminescence emission (400-470 nm) confirms that the size of the G-dots (∼4 nm) is small because of a similar quantum effects and emission traps on the surfaces. The G-dots have excellent photostability; their photoluminescence intensity decreases slowly (∼8%) under continuous excitation with a Xe lamp for 10 days. We carried out cell viability assay to assess the effect of cytotoxicity by introducing G-dots in cells such as Chinese hamster ovary cells (CHO-K1), mouse muscle cells (C2C12), and African green monkey kidney cells (COS-7), up to a concentration of 2 mg mL(-1) for 24 h. Due to their high photostability and low cytotoxicity, these G-dots are excellent probes for in vitro bioimaging. Moreover, the byproducts (not including G-dots) of G-dot synthesis from large food-waste derived sources promoted the growth and development of seedlings germinated on 3DW-supplemented gauze. Because of the combined advantages of green synthesis, high aqueous stability, high photostability, and low cytotoxicity, the G-dots show considerable promise in various areas, including biomedical imaging, solution state optoelectronics, and plant seed germination and/or growth.