Preparation of Polystyrene- and Silica-Coated Gold Nanorods and Their Use as Templates for the Synthesis of Hollow Nanotubes

Abstract

We report the preparation of polystyrene and silica-coated Au nanorods (aspect ratio 13 with 16 nm short axis). The coating resulted in a modification of the optical properties of the Au nanorods. Dissolution of the Au core from the polystyrene-and silica-coated Au nanorods using KCN enabled the formation of hollow polystyrene and silica nanotubes.Metal nanoparticles of different shapes and sizes, particularly gold, silver, and copper, have attracted considerable attention from the inorganic, materials, and physical community. 1 For nanoparticles made in solution, uncontrollable aggregation effects can be detrimental to many applications (e.g., electronics). Common stabilizers such as polymers, surfactants, and dendrimers have been used to increase nanoparticle stability. 2 Coating nanoparticles by in situ polymerization reactions provides an alternative method to increasing nanoparticle stability.3 Another potential use of coated nanoparticles is to make precursors to hollow nanoparticles. Hollow nanoparticles are an interesting and increasingly important class of materials with diverse applications, ranging from drug delivery, 4 cell and enzyme transplantation, 4b,5 contaminated waste removal, 6 and gene therapy. 7 Controlling the shape of the hollow nanoparticles is a great challenge. 8 Most of the work done in this field makes use of spherical inorganic cores. We have recently synthesized high aspect ratio cylindrical Au nanorods. 9 We here report a method of coating these nanorods with polystyrene and silica, followed by subsequent dissolution of the Au nanorods to form hollow nanotubes of the coating material.A solution of Au nanorods in the presence of the surfactant cetyltrimethylammonium bromide (CTAB) was prepared as described earlier. 9 The particle concentration in terms of Au atoms was 2.5 × 10 -4 M. Polystyrene coating of the particles was accomplished by the emulsion polymerization of styrene in the presence of CTAB-coated Au nanorods. Typically, 1 µL of styrene (Aldrich) was added to 10 mL of the Au nanorod solution. The solution was stirred for 5 min and 4 µL of a 0.1 M solution of the initiator ammonium persulfate (APS) was added. The polymerization was allowed to take place, and after 15 min the stirring was stopped. The solution was allowed to sit at room temperature for about 1 h before analysis. The polystyrene-coated Au nanoparticles were separated from spheres and excess CTAB by centrifugation and resuspended in deionized water for characterization by TEM and UV-visible absorption spectroscopy.For silica coating, Au nanorods were first separated from spheres and excess CTAB as described earlier.9 Next, a Au nanorod solution that was 0.01-0.1 wt % nanorod concentration was prepared. For typical silica coating, 10 µL of a

Development of Fabrication of Giant Nanomembranes

“…Preparation of the layer-bylayer assembled ultrathin hollow polymer shells (or nanotubes) has been extensively investigated by Caruso et al [15][16][17][18][19] and by other groups. [20][21][22][23][24][25][26] The preparation of free-standing ultrathin films by this approach has been studied by several groups. Onda et al have prepared enzyme-containing alternate films on porous filter membranes and examined sequential enzyme catalysis.…”

Layer-by-layer accumulation of cadmium sulfide core—silica shell nanoparticles and size-selective photoetching to make adjustable void space between core and shell

“…Among the nanocomposites, studies of surface coating of nanoparticles with different materials to produce core-shell structures have attracted attention , because physical and chemical properties of core materials can be modified or tailored by the shell components with negligible change in shape and size of the core particles. Also core-shell nanoparticles have been useful as precursors for the preparation of hollow structures by removing core materials through chemical etching or combustion [22][23][24][25][26][27][28][29][30], and partial removal of the core has enabled preparation of novel nanostructures inside the shell, such as the encapsulation of metal nanoparticles in hollow sphere and the void formation between the core and shell [31][32][33][34][35][36][37]. To utilize these nanoparticles in solid devices, such as optoelectronic devices and sensors, it is necessary to immobilize core-shell nanoparticles onto solid substrates.…”

Analyses of protein corona on bare and silica-coated gold nanorods against four mammalian cells

“…[11][12][13][14] A volume of 3 mL of the AuNRs solution was centrifuged to remove excess CTAB and was redispersed in distilled water. A solution containing 5.58 μL of MPS in 20 mL of ethanol was prepared, and 80 μL of the solution was added to the AuNRs solution under vigorous magnetic stirring for 30 minutes to achieve a silica coating of intermediate thickness (around 3 nm).…”