Promoting the Growth of Mung Bean Plants through Uptake and Light Conversion of NaYF₄:Yb,Er@CDs Nanocomposites

In recent years, the application of nanomaterials in promoting plant growth and augmenting photosynthesis has aroused great interest. Herein, carbon dots (CDs) are combined with NaYF₄:Yb,Er to achieve an enhanced upconversion red emission. The effects of the obtained NaYF₄:Yb,Er@CDs nanocomposites on the growth of mung bean plants are investigated. It is found that an appropriate concentration of the NaYF₄:Yb,Er@CDs nanocomposites (0.5 mg/mL) can enhance the water absorption ability of hydroponic mung beans and promote their growth after incubation for 7 days. Confocal imaging shows that the nanocomposites can transfer from the roots to the stems and leaves. Interestingly, after spraying the nanocomposite solution on the surface of the mung bean seedling leaves and placing them under sunlight for 2 weeks, the root/stem lengths and wet/dry weight clearly increase. Moreover, the photosynthetic rate of the mung bean seedling is found to increase by more than 2 times, while the transpiration rate and stomatal conductance are improved by 144 and 148%, respectively. Such a promoting effect is ascribed to the ability of the NaYF₄:Yb,Er@CDs nanocomposites to convert near-infrared (NIR) radiation into red light, which is beneficial for plant photosynthesis. This work provides a promising strategy for promoting plant growth by the application of nanomaterials.