Biomimetic preparation of silicon quantum dots and their phytophysiology effect on cucumber seedlings

In this study, a biomimetic synthetic strategy was proposed for a facile preparation of red fluorescent silicon quantum dots (SiQDs) using unicellular algae of diatoms as reaction precursor. The resultant nontoxic SiQDs of ∼2.0 nm diameter display remarkable red luminescence, high quantum yield (∼15%) and narrow full width at half maximum (FWHM, ∼35 nm). Specifically, as-prepared SiQDs show promise as regulators of plant growth. After cultivating cucumber seedlings with SiQDs, the growth of cucumber seedlings has been significant promoted within a wide range of SiQDs concentrations (0.01-0.3 mg mL^-1). The total weight of cucumber seedlings significantly increased by 51.91% (P < 0.001) compared with weight of the control group after incubation for 10 days. Moreover, it was discovered that the growth of cucumber seedlings is positively correlated with the water uptake rate of roots. After a 5 day incubation, the optimum concentration of SiQDs significantly increased water uptake rate of roots by 74.6% compared with that of the control group. Real-time fluorescence quantitative polymerase chain reaction (RT-PCR) analysis revealed that the expression of aquaporin gene in cucumber roots treated with SiQDs increased significantly compared to that of the control group. This is the first report regarding a phytophysiology effect of red fluorescent SiQDs on cucumber seedlings growth. The results widen the range of applications of SiQDs in plant science.