Effects of gold nanoparticles on photophysical behaviour of chlorophyll and pheophytin

The increasing application of engineering nanoparticles (ENPs) in various commercial products justifies the need for studying their impact on living organisms and environment. The interaction between gold nanoparticles (AuNPs) with different diameters (5, 10, and 20 nm) and two photosynthetic pigments ― chlorophyll (Chl) and pheophytin (Pheo) ― was investigated using optical techniques and computational simulations. UV–Vis absorption, steady-state fluorescence, and time-resolved fluorescence showed that AuNPs affected the optical features of the studied photosynthetic pigments. Moreover, the optical and computational results show that an analogous Pheo molecule (chlorin) was less susceptible than an analogous chlorophyll molecule (Mg-chlorin) to interact with AuNPs. Therefore, AuNPs interact with both Chl and Pheo so that they may change the operation of the plant photosystems in case of uptake and internalisation in plants.