Strategy for Finely Aligned Gold Nanorod Arrays Using Polymer Brushes as a Template

Abstract

The development of a strategy for the assembly of nanoscale building blocks, in particular, anisotropic nanoparticles, into desired structures is important for the construction of functional materials and devices. However, control over the orientation of rod-shaped nanoparticles on a substrate for integration into solid-state devices remains challenging. Here, we report a strategy for the fabrication of finely aligned gold nanorod (GNR) arrays using polymer (DNA) brushes as a nanoscale template. The gold nanorods modified with cationic surface ligands were electrostatically adsorbed onto the DNA brush substrates under various conditions. The orientational behavior of the GNRs was examined by spectral analyses and transmission electron microtomography (TEMT). As a result, we found several important factors, such as moderate interaction between GNRs and polymers and polymer densities on the substrate, related to the vertical alignment of GNRs on the substrates. We also developed a purification method to remove the undesired adsorption of GNRs onto the arrays. Finally, we have succeeded in the fabrication of extensive vertical GNR arrays of high quality via the easy bottom-up process.

Gold Nanorods: The Most Versatile Plasmonic Nanoparticles

“…Au NR arrays with higher number densities can be obtained by increasing the ionic strength of the Au NR solution with inorganic salts such as NaCl . Functionalization of the substrate with appropriate molecular groups, , polymer brushes, , and DNA brushes , is another common approach for the production of Au NR arrays with high number densities (Figure b).…”

Reversible changes in the orientation of gold nanorod arrays on polymer brushes

“…In our previous study, we developed a preparation method for vertically aligned GNR arrays using polymer brushes as a template. 41,42 As the polymer brushes are so matrices, it is expected that the GNR orientation can be actively tuned through some kind of stimulation. In those reports, we found that GNRs formed vertically aligned arrays when mildly cationized GNRs, which were modied with 20% cationic and 80% nonionic ligands, were attached on negatively charged polymer (DNA) brushes via moderate electrostatic interactions.…”

“…As it is expected that the rigidity of the polymer is an important factor for the change in the orientation of GNRs on polymer brushes, we next applied a exible polymer to this system. Fortunately, we have already reported that the vertical GNR alignment can also be performed on single-stranded DNA (ssDNA) brushes, 42 which are more exible and share the same lack of well-ordered structures as general synthetic polymers. 48,49 Thus, we investigated the tuning of GNR orientation by changes in the interactions between polymers and GNRs on ssDNA brushes.…”

Nanomolding of Gold and Gold–Silicon Heterostructures at Room Temperature

“…Gold nanorods are used for a wide range of applications, including plasmonics, 8,9 solar energy harvesting, 10,11 drug delivery, 12,13 biomedical imaging, 14,15 photothermal therapy, 16,17 sensitive chemical detection, 18,19 and metamaterials development. 20,21 The synthesis methods for these nanorods include templatedirected synthesis, 22,23 electrochemical growth, 24,25 seedmediated colloidal growth methods, 26,27 seedless growth, 27,28 photochemical synthesis, 29,30 and mechanical tearing of the nanocrystalline Au film. 31 Wet chemical methods are the most common synthesis processes for gold nanomaterials, where yield and control from seeded growth 32 are usually better than the unseeded ones, 33 but producing the required nanoparticle seeds themselves can be challenging.…”

“…The wide spanning technological and research applications of nanomaterials, owing to the engineering control over materials at the nanoscale, require fabrication ability with accurate dimension and shape control on the nanoscale. − Among the most utilized nanomaterials are gold and silicon, and also their combinations as heterostructures. Gold nanorods are used for a wide range of applications, including plasmonics, , solar energy harvesting, , drug delivery, , biomedical imaging, , photothermal therapy, , sensitive chemical detection, , and metamaterials development. , The synthesis methods for these nanorods include template-directed synthesis, , electrochemical growth, , seed-mediated colloidal growth methods, , seedless growth, , photochemical synthesis, , and mechanical tearing of the nanocrystalline Au film . Wet chemical methods are the most common synthesis processes for gold nanomaterials, where yield and control from seeded growth are usually better than the unseeded ones, but producing the required nanoparticle seeds themselves can be challenging .…”