However, it is important to consider that a change to tether length would also influence the density of tethers, which in turn could influence the resulting AuNP densities. To factor this influence, the areal densities of the different tethers were independently determined for different tethered amine layers using SPR. The 4-ATP was found to exhibit highest molecular coverage of 5 molecules/nm 2 (green bar in Fig. ). This decreased to 1.8 molecules/nm 2 for the 3.2 nm long tethers, while continuing to remain the same for 4.5 nm and 7.8 nm long tethers (red, blue and dark green bars in Fig. ). The 79.5 nm long tether resulted in the least coverage of 0.3 molecule/nm 2 (cyan bar in Fig. ). Thus, the increase in AuNP density as a function of the tether length was achieved despite the decrease in tethers density. The grafting density of tethers is known to determine the conformation of PEG tethers, which in turn could influence the adsorption densities. Thus, it is essential to check whether all the tethers are in the same conformation despite the different length and molar mass. In order to do so, we have calculated the Flory radius as following: 𝑅𝑅 𝑓𝑓 = 𝛼𝛼𝑛𝑛 𝜐𝜐 where 𝜐𝜐 = 3/5, 𝛼𝛼 = 0.35 𝑛𝑛𝑚𝑚 for an ethylene glycol monomer and 𝑛𝑛 indicates the number of monomers in the chain. We estimated 𝑛𝑛 to be roughly equal to 8, 13, 21, 214, respectively for the 3.2 nm, 4.5 nm, 7.8 nm and 79.5 nm long tethers (Table ). Flory radius as calculated above is to be compared with the average distance between individual tethered receptor estimated as below.