Chain length effect of diamine linkers on the self-assembled structure of large gold nanoparticles over glass substrates

Bi-functional diamines with different chain lengths were investigated to control the packing density of large gold nanoparticles (ca. 60–80 nm) over glass substrates. Diamine linkers induced the lateral immobilization of neighboring gold nanoparticles (GNPs) on the amine-functionalized glass surface. The molecular bridging force of diamines was proportional to the number of CH2 groups: 1,4-diaminobutane (C-4) < 1,8-diaminooctane (C-8) < 1,12-diaminododecane (C-12). Even though the aggregation of Au colloids was more sensitive to C-12 diamines, the uniform and densely-packed array of GNPs over glass substrates were accomplished by the addition of C-8 diamines possessing optimal chain length with a balanced binding force on Au colloids.