Uptake and impact of carbon dots and their copper complex on tomato health

Abstract

Nanomaterials are being increasingly studied for their use in agriculture to promote healthy crop growth and mitigate the damaging effects of plant diseases. Copper is among the elements delivered and managed with nanoenabled-agriculture practices, but it is challenging to balance copper levels because some doses mitigate disease, but in excess, it can be harmful and interrupt photosynthetic function. Carbon dots (CDs) are an emerging, sustainable class of fluorescent nanomaterials with affinity for copper ions that possess good biocompatibility and low toxicity, making them an ideal candidate for use in crop applications. Here, a range of CDs were synthesized from citric acid and urea with varied affinity for copper ions. We investigated how chelated copper affects CD fluorescence and structure, and we propose a mechanism for the chelation of Cu²⁺ by CDs. Additionally, the effects of the Cu–CD complex on both healthy and disease-bearing tomato plants were evaluated. The data show that the complex had no toxic effects on the plant and can increase seedling biomass by 44–61% when applied through a vacuum seed infiltration method. The desorption of copper from the Cu–CD complex exhibited a slow-release profile, indicating that CDs could be an effective tool for mitigating excess copper in plants.