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. (C) 2011 Elsevier B.V. All rights reserved.