Radially oriented cellulose triacetate chains on gold nanoparticles

Abstract

Cellulose triacetate (CTA) derivatives having a disulfide group at the reducing-end (CTA2S, CTA13S, CTA41S), with number average degrees of polymerization (DP n s) 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 (HAuCl 4 ) 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.

Water-soluble low-molecular-weight cellulose chains radially oriented on gold nanoparticles

“…The ds and its standard deviations showed no substantial difference before and after deacetylation, indicating that the gold nanoparticles were stable under alkaline condition. In the case of CTAAu nanoparticles, the interparticle distance between nanoparticles agreed well with CTA molecular chain length (Enomoto-Rogers et al 2010). However, in the case of CELLAu nanoparticles prepared in this work, the interparticle distances were irregular and could not be controlled by chain length of cellulose molecule.…”

“…The ds of the gold cores of CELL2Au, CELL13Au, and CELL41Au were 6.1, 6.1, and 11.5 nm, respectively. The ds of the gold cores of CTA2Au, CTA13Au, and CTA41Au were 8.7, 7.9, and 13.4 nm, respectively, according to our previous work (Enomoto-Rogers et al 2010). The ds and its standard deviations showed no substantial difference before and after deacetylation, indicating that the gold nanoparticles were stable under alkaline condition.…”

“…The gold nanoparticles grafted with cellulose triacetate (CTA) chains with the DP n of 2, 13, and 41, were prepared as reported in our previous article (Enomoto-Rogers et al 2010), and described as CTA2Au, CTA13Au, and CTA41Au, respectively. Cellohexaose was obtained from Seikagaku Cooperation (Tokyo, Japan).…”

“…As a method to control the orientation of cellulose chains by immobilization of the reducing-end of cellulose, we have recently prepared cellulose triacetate (CTA) bearing a single disulfide group at the reducing-end, and succeeded in preparation of the CTA-self-assembled gold nanoparticles (CTAAu) (Enomoto-Rogers et al 2010). CTA chains on the surface of gold nanoparticles were radially oriented in a head-to-tail manner, where a head is the reducing-end, and a tail is the non-reducing-end.…”

Coating matters: the influence of coating materials on the optical properties of gold nanoparticles

“…This method is known as the LbL (Layerby-Layer) technique [87] , and is widely applied not only to stabilize gold nanoparticle dispersions, but also to confer them with a desired surface charge, which is determined by the charge of the outmost polyelectrolyte layer [85]. Besides synthetic charged polymers, also bio-polymers [88] such as DNA [89 -93] , dextran [94] , cellulose [95,96] , chitosan [97,98] and various peptides and proteins can adsorb onto the nanoparticle surface, and have been widely used to make gold nanoparticles suitable for bio-applications. Moreover, polyelectrolyte multilayers can also serve as primers to make gold nanoparticles suitable for further surface modifi cations or coatings, such as silica [99] or pNIPAM microgels [100] .…”