Ligand-engineered nanoparticles (NPs) have emerged as promising platforms for many applications, including biomedical imaging, sensing, and drug delivery. The surface chemistry of NPs is of great importance, as it directly dictates not only the colloidal stability of NPs but also their interaction with the environment. Multivalency (multiple receptors per particle) has been proven to be a powerful strategy for targeting. However, counter-intuitively, more targeting ligands are not always beneficial. For example, overfunctionalization of the surface can result in a high consumption of receptors per NP, causing lower cellular uptake since there are fewer receptors for other NPs to bind. Overfunctionalization can also give rise to steric clashes between the targeting groups, reducing their ability to bind to receptors. Therefore, there is often an optimal targeting ligand density to achieve the highest cell binding and cellular uptake. Gold NPs with one antibody per particle have even been reported to have better tumor accumulation than those with two antibodies, demonstrating the need for precise control of surface functionalization. Despite its clear importance for nanomedicine, fine-tuning of surface chemistry and quantification of surface functional groups have rarely been reported.