Robust Synthesis of Gold Nanotriangles and their Self‐Assembly into Vertical Arrays

Abstract

We report an efficient, seed‐mediated method for the synthesis of gold nanotriangles (NTs) which can be used for controlled self‐assembly. The main advantage of the proposed synthetic protocol is that it relies on using stable (over the course of several days) intermediate seeds. This stability translates into increasing time efficiency of the synthesis and makes the protocol experimentally less demanding (‘fast addition’ not required, tap water can be used in the final steps) as compared to previously reported procedures, without compromising the size and shape monodispersity of the product. We demonstrate high reproducibility of the protocol in the hands of different researchers and in different laboratories. Additionally, this modified seed‐mediated method can be used to produce NTs with edge lengths between ca. 45 and 150 nm. Finally, the high ‘quality’ of NTs allows the preparation of long‐range ordered assemblies with vertically oriented building blocks, which makes them promising candidates for future optoelectronic technologies.

Time Optimization of Seed-Mediated Gold Nanotriangle Synthesis Based on Kinetic Studies

“…It has the same maximum position at 523 nm, which relates to the spherical particles with a diameter of ca. 10 nm [ 31 ]. It is assumed that intermediate seeds can be used as soon as their growth has finished.…”

“…Gold nanotriangles (NTs) of various sizes were synthesized following the seed-mediated procedure described by Szustakiewicz et al [ 31 ]. Firstly, initial seeds were obtained by stirring 25 μL of HAuCl 4 50 mM solution and 4.7 mL of a CTAC 100 mM solution for 2–3 min and then, under vigorous stirring, by injecting into the reaction mixture 300 μL of a freshly prepared 10 mM NaBH 4 solution.…”

“…When reproducing such complex syntheses, one has to keep in mind that parameters like speed and sequence of precursor addition significantly influence the kinetics and, thereby, the shape yield and size distribution of NPs [ 30 ]. Recently, Szustakiewicz et al reported a method involving stable intermediate seeds, in order to avoid the above-mentioned fast-addition step [ 31 ]. Furthermore, the authors described the use of a purification procedure based on depletion-forced aggregation, which, in turn, provides a higher shape yield [ 25 , 32 , 33 , 34 ].…”

Chitosan-Stabilized Noble Metal Nanoparticles: Study of their Shape Evolution and Post-Functionalization Properties

“…In view of their promising use in such various fields, a strict control of the size and shape of anisotropic noble metal nanoparticles is required. Among the available schemes of synthesis following a bottom-up approach, the so-called seeded-mediated growth method in aqueous solution [9] is particularly popular because of its versatility in producing nanoparticles of different geometry in high shape yields. The method is based on the selective reduction of a gold precursor (growth solution) on premade seeds, which act as both catalysts and nucleation points for the growth of the gold nanostructures.…”

DNA-Biofunctionalization of CTAC-Capped Gold Nanocubes

“…These small molecules make room for new and bigger ligands that contain—or are modified with—groups with even higher affinity to gold than the previous ligand [ 21 , 25 ]. This approach of particle functionalization was accomplished with several different nanoparticle shapes, such as nanorods, -spheres, -prisms, and -cubes (synthetized with cetyltrimethylammonium bromide (CTAB)) [ 20 , 21 , 22 , 26 , 27 ]. Aside from surfactants, a few small molecules or polymers have also been applied to facilitate DNA conjugation while avoiding gold nanoparticle aggregation.…”