# Enhanced herbicidal activity of coumarin via carbon dot nanoformulation: synthesis and evaluation

## TL;DR

Researchers developed a new method using carbon dots to enhance the weed-killing power of coumarin, reducing the need for chemical pesticides.

## Contribution

A novel carbon dot nanoformulation of coumarin is shown to significantly enhance herbicidal efficacy against weeds.

## Key findings

- Cm-CDs completely inhibit the germination of S. viridis and prevent development of P. oleracea at lower concentrations than coumarin alone.
- Cm-CDs reduced the dry weight of P. oleracea and S. viridis by 69.3% and 63.61%, respectively, causing wilting and growth cessation.
- Cm-CDs show stronger herbicidal toxicity than coumarin in both germination and pot experiments.

## Abstract

The integration of nanocarriers with biochemicals can markedly enhance the stability and efficacy of these agents, which will help to diminish the reliance on chemical pesticides, and contribute to the advancement of sustainable agricultural practices.

We prepared nanometer carbon dots (CDs) from black wolfberry (Lycium ruthenicum Murr.) and synthesized coumarin‐loaded carbon dots (Cm‐CDs) nanocomposites. The CDs exhibited a uniform distribution and high stability, with a coumarin loading rate of 65.45%. Experimental results on the herbicidal activity of both coumarin and Cm‐CDs against Portulaca oleracea and Setaria viridis showed that, compared with coumarin alone, Cm‐CDs completely inhibit the germination of S. viridis or prevent further development of P. oleracea post‐germination at lower concentrations. The application of Cm‐CDs has the potential to significantly diminish the biomass of P. oleracea and S. viridis (the dry weight decreased by 69.3% and 63.61% respectively), leading to a cessation of growth and the manifestation of wilting symptoms (P < 0.05). This indicates that the binding of coumarin to CDs markedly enhances the herbicidal efficacy of coumarin. Both coumarin and Cm‐CDs exhibit consistent alterations in biomass, hormone levels, antioxidant enzyme activity, malondialdehyde (MDA) content, root morphology, and vitality, however, the effects observed with Cm‐CDs were consistently more pronounced than those associated with coumarin (P < 0.05).

In both the germination bioassay and the pot experiment, Cm‐CDs demonstrated stronger herbicidal toxicity. Both coumarin and Cm‐CDs exhibit identical modes of action on P. oleracea and S. viridis. This study confirms that CDs can serve as effective nanocarriers to markedly enhance the herbicidal biological activity of coumarin in controlled conditions. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

We synthesized carbon nanocarriers from black wolfberry and combined them with coumarin to prepare coumarin‐loaded carbon dots (Cm‐CDs) nanocomplexes, which could significantly enhance the inhibitory effect of coumarin on weeds.