Synergistic accelerated aggregation of graphdiyne and fullerene by light and metal cations in aquatic system

The mechanism of light affecting the aggregation of nanoparticles in aquatic systems remains unclear. For both graphdiyne (GDY) and fullerene (C₆₀), the sedimentation rates in the presence of cations and light (K_L) are 1.6-9.1 times greater than that in the dark (K_D), while K_L and K_D remain equal in the absence of cations. The light-accelerated aggregation of GDY and C₆₀ is also observed in the presence of natural organic matter at concentrations of 5-20 mg/L. The photo-molecular effects are possibly the main factor in aggregation by excluding the increasing van der Waal forces, reducing steric and static repulsion, generating active substances, and photo-thermal effects during the sedimentation of both GDY and C₆₀ in the presence of both light and cations. The possible mechanisms are ascribed to decreasing the aggregation energy barrier via transfers of photon energy by direct interaction of light and nano-colloid by semi-quantitative analysis. The results provide new insights into the environmental fate and risks of nanoparticles in natural water systems, and offer a structural-preserving approach for the rapid removal of nanomaterials from water.