Radially oriented cellulose triacetate chains on gold nanoparticles

Cellulose triacetate (CTA) derivatives having a disulfide group at the reducing-end (CTA2S, CTA13S, CTA41S), with number average degrees of polymerization (DP_ns) of 2, 13 and 41, respectively, were prepared. The CTA-self-assembled gold nanoparticles (CTA2Au, CTA13Au, and CTA41Au) were obtained through the reduction of gold salt (HAuCl₄) with CTASs. The diameters (d) and the interparticle distances (L) of the gold cores were analyzed by transmission electron microscopy (TEM) observations. The d values of CTA2Au, CTA13Au, and CTA41Au, were 8.7, 7.9, and 13.4 nm respectively. The L values of CTA2Au, CTA13Au, and CTA41Au, were 2.8, 6.3, and 20.9 nm, respectively, and agreed well with the molecular length (l) of CTAS chains (ls of CTA2S, CTA13S, CTA41S = 2.0, 7.5, 21.5 nm, respectively). The hydrodynamic diameters (D) of CTAAu nanoparticles in chloroform solution, measured by dynamic light scattering (DLS), were larger than the d values and increased with the increase in the molecular length of the CTA chains. The CTAS chain was found to work as an excellent stabilizer of the gold nanoparticles in both solid state and solution. The molecular length of CTA chains controlled the size and the alignment of the gold nanoparticles. As a result, the radially oriented CTA chains on the gold nanoparticles were successfully prepared.