Dual‐Emission Carbon Dot Nanozymes Mitigate Salt Stress and Enhance Photosynthesis for Crop Germination and Growth

Bifunctional carbon dot (CD) nanozymes with dual‐emission properties and superoxide dismutase (SOD)‐like activity are synthesized via microwave method. CDs can simultaneously emit blue and red light under the same excitation wavelength, which effectively overlap with chloroplasts absorption spectra, thereby enhancing energy transfer and photosynthetic efficiency. For hydroponic seedling, CDs significantly promote growth of corn ( Zea mays L .), increasing fresh weight, shoot length, chlorophyll content, net photosynthetic rate and stomatal conductance by 30.8%, 27.8%, 14.4%, 54.4% and 65.2%, respectively. Furthermore, CDs significantly alleviate oxidative damage in seeds and seedlings through their SOD‐like activity, increasing seed germination rate by 41.5% under NaCl (200 mM) stress. In NaCl (200 mM)‐treated soil, CDs enhanced corn salinity tolerance by triggering coordinated responses including reactive oxygen species scavenging, osmotic adjustment, and metabolic reprogramming. Transcriptome analysis revealed that CDs can regulate key pathways, including energy metabolism, amino acid metabolism, and the synthesis of secondary metabolites. Additionally, by passivating the surface functional groups of CDs, it investigates the specific functional groups contributing to their fluorescence and SOD‐like activity, offering valuable insights for future design on similar nanomaterials. This study provides practical strategies for enhancing crop productivity and resilience in saline‐alkali soils.