Amplified light harvesting for enhancing Italian lettuce photosynthesis using water soluble silicon quantum dots as artificial antennas

Abstract

Maximizing the utilization of the ultraviolet portion in the solar radiation spectrum has always been a goal for plant growth in order to minimize the harm and harvest the benefits. For this reason, fluorescent, amine-functionalized, and water-soluble silicon quantum dots (SiQDs) were fabricated with a mono-dispersed size of 2.4 nm. The SiQDs were used as artificial antennas to amplify the light harvesting ability and consequently enhance the photosynthesis in Italian lettuce. Upon ultraviolet excitation, the intense blue emission from the quantum dots matched very well to the absorption of the chloroplasts, allowing for the ultraviolet portion in solar radiation to be effectively utilized. The consumed optical energy enhanced the photosystem II activity, which made the amplification of photosynthesis possible. More importantly, in vivo, the quantum dots significantly promoted Italian lettuce seedling growth at concentrations below 30 mg L⁻¹ on the root length, seedling height, and biomass by increasing the soluble sugar and water content by 49.8% and 40.9%, respectively. Interestingly, the chlorophyll a and b content increased to 41.0 and 114.8%, respectively, with no inhibition, even at the highest dose of 200 mg L⁻¹. This study provides a new perspective on the use of quantum dots to amplify the utilization of ultraviolet light in agriculture.