Gold nanorods: Synthesis, characterization and applications (original) (raw)
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Geometric curvature controls the chemical patchiness and self-assembly of nanoparticles
Nature Nanotechnology, 2013
Section 1. Synthesis, Functionalization, and Analysis of Nanoobjects S1.1 Synthesis and Functionalization of Nanoobjects Spherical (d ≈ 16 nm) gold nanoparticles stabilized with excess hexydecyl-trimethylammonium bromide (CTAB) were synthesized using a three step, seeded growth procedure. 1 A seed solution of ~3.5 nm citrate stabilized gold particles was prepared by the addition of 0.6 mL of 0.1 M sodium borohydride into a 20 mL aqueous solution of 2.5x10-4 M HAuCl 4 and 2.5x10-4 M trisodium citrate. The addition of borohydride was performed under vigorous stirring; one minute after the injection, the stirring was stopped and the particles were allowed to age for 2 hours. To create ~8 nm CTAB stabilized particles, 1 mL of the above described seed solution was added to 9 mL of a growth solution (2.5x10-4 M HAuCl 4 •3H 2 O and 0.08 M CTAB) followed by the addition of 50 µL of 0.1 M ascorbic acid. The particles were allowed to grow for 30 minutes prior to the next growth step. The second growth step was performed under the same conditions, but 1 mL of the 8 nm particles was used to seed the growth solution. CTAB stabilized gold nanorods (NRs) were synthesized using a seed mediated growth procedure. 2 Seed particles were prepared by the addition of 0.6 mL of 10 mM sodium borohydride to 10 mL of 0.1 M CTAB aqueous solution and 4.2x10-4 M HAuCl 4 under vigorous stirring. This solution was allowed to age for 1 hour. The growth solution for the nanorod synthesis consisted of a 203.4 mL aqueous solution of 0.1 M CTAB, 5.9x10-5 M AgNO 3 , and 5.4x10-4 M HAuCl 4. 1.1 mL of 0.1 M ascorbic acid was added to the growth solution immediately followed by 250 µL of the seed solution. This solution was stirred vigorously during the addition of ascorbic acid and seed solutions, but was then left to rest for at least 6 hours before further use. CTAB stabilized gold-silver core-shell nano-dumbbells (NDs) were synthesized under alkaline conditions from the above described CTAB stabilized AuNRs. 3 Briefly, 200 mL of the above described CTAB stabilized AuNRs were added to 450 mL of DI water and 165 mL of 0.5 M glycine buffer solution adjusted to pH=10 using NaOH.
Overgrowth of Gold Nanorods by Using a Binary Surfactant Mixture
Langmuir, 2014
Seed-mediated surfactant-assisted growth is widely used as the most effective method for gold nanorod (NR) synthesis. Using prepared nanorods as seeds for further overgrowth can increase the dimensional tunability of the final particles. However, overgrowth in usual cetyltrimethylammonium bromide (CTAB) surfactant solutions leads to poor control of the final particle shape and size. In this work, we report an improved strategy to demonstrate the controllable overgrowth of gold NRs in the binary surfactant mixture sodium oleate (NaOL) + CTAB. This approach overcomes the difficulty of growing NR suspensions with small amounts of impurities. By controlling the total amount of added NR seeds, it is possible to tune the average length, diameter, and plasmon resonances of overgrown particles in a wide range. Together with the original NaOL + CTAB method developed by Murray and co-workers (Nano Lett. 2013, 13, 555), this overgrowth approach expands the dimensional and plasmonic tunability of the fabrication technology without any decrease in the monodispersity and purity of samples.
Shape control in gold nanoparticle synthesis
Chemical Society Reviews, 2008
In this tutorial review, we summarise recent research into the controlled growth of gold nanoparticles of different morphologies and discuss the various chemical mechanisms that have been proposed to explain anisotropic growth. With the overview and discussion, we intended to select those published procedures that we consider more reliable and promising for synthesis of morphologies of interest. We expect this to be interesting to researchers in the wide variety of fields that can make use of metal nanoparticles.
Nano Letters, 2014
Density Functional Theory simulations including dispersion provide an atomistic description of the role of different compounds in the synthesis of gold-nanorods. Anisotropy is caused by the formation of a complex between the surfactant, bromine, and silver that preferentially adsorbs on some facets of the seeds, blocking them from further growth. In turn, the nanorod structure is driven by the perferential adsorption of the surfactant, which induces the appearance of open {520} lateral facets.
Crystal Growth & Design, 2008
A seed-mediated approach was applied to synthesize gold (Au) nanoparticles (NP) by using twin tail alkylammonium cationic surfactants such as 12-6-12 and 12-0-12 as capping agents in aqueous phase at ambient conditions. The growth of Au NP was monitored by changing the amount of seed. Spherical NP (10-50nm) and nanorods (aspect ratio ) 2-3) were obtained in the presence of 12-6-12 as capping agent; their shape and size systematically deformed because of anisotropic growth with a decrease in the amount of seed. In contrast, when 12-0-12 was used as a capping agent, no anisotropic growth was observed. An effective liquid/solid interfacial adsorption of 12-0-12 prevented anisotropic growth which led to precise morphologies. This was not observed in the case of 12-6-12 because of the presence of a spacer which restricted an effective interfacial adsorption because of the steric factors. XPS and FTIR studies clearly indicated the presence of a surfactant film on the surface of Au NP, while XRD analysis demonstrated a difference in the preferential adsorption of 12-6-12 and 12-0-12 at different crystal planes of fcc geometry which resulted in a difference in their capping behaviors.
Rationally Designed Ligands that Inhibit the Aggregation of Large Gold Nanoparticles in Solution
Journal of the American Chemical Society, 2008
Experimental Section Materials. Water was purified to a resistance of 18 MW using an Academic Milli-Q Water System from Millipore Corporation. The following chemicals were purchased from the indicated suppliers and used without purification: carbon tetrachloride (Acros), toluene and chloroform (EM Science), tetrahydrofuran, hexadecanethiol (n-C 1 6), and tetra-noctylammonium bromide (Aldrich). The adsorbates 2-tetradecylpropane-1,3-dithiol (C16C2), 2-methyl-2-tetradecylpropane-1,3-dithiol (C16C3), and 1,1,1-tris(mercaptomethyl)pentadecane (t-C16) were synthesized as described previously. S1-S3 The strategy used to prepare the monodentate ligand 2,2-dimethylhexadecane-1-thiol (DMC16) is outlined below in Scheme S1. S4 Detailed procedures for each step are provided in the subsequent paragraphs. Quantitative determination of the molecular packing density of the SAM formed from DMC16 on flat gold was performed using an established procedure, S1-S3,S5 which gave a value of 72% molecules per unit area relative to 100% for n-alkanethiols. Gold nanoparticles (~20-50 nm in diameter) were prepared by the reduction of HAuCl 4 with trisodium citrate. S6 While the bulk of our experiments were conducted with 30 nm gold nanoparticles, the observations reported here were consistent across the entire range of sizes examined (i.e., ~20-50 nm). All glassware used in the preparation and storage of the gold nanoparticles was treated with aqua regia, rinsed with water, and cleaned with piranha solution (7:3 concentrated H 2 SO 4 / 30 wt% H 2 O 2). Caution: Piranha solution reacts violently with organic materials and must be handled carefully! Scheme S1. Synthesis of 2,2-Dimethylhexadecane-1-thiol (DMC16)