New aspects of gold nanorod formation via seed-mediated method

Abstract

Gold nanorods (AuNRs) were obtained via a wet chemistry technique, in aqueous medium, employing crystallisation seeds. The kinetics of formation, the aspect ratio, and the selectivity of the particles were evaluated according to the parameters of synthesis: the growth-driving agent, seed, and gold precursor concentrations. In 2-4 h, the rod particles attained the expected size and shape under kinetic control, and were stable for at least 2 days. In order to obtain good quality AuNRs in good yields, without enrichment, we suggest keeping the growth-driving agent/gold molar ratio, the Au I /seed ratio, and the concentration of the reagents in the final solution within specific ranges. For example, even if good molar ratios between the reagents are maintained, relatively highly concentrated reaction solutions lead to AuNRs with lower aspect ratios. The main properties of the prepared colloidal systems and the nanoparticles were evaluated by UVvis spectroscopy and transmission electron microscopy, respectively.

Aptamer-conjugated, fluorescent gold nanorods as potential cancer theradiagnostic agents

“…No observed when GNRs were kept in the mother solution with native CTAB concentration. Recently, analogous spectrophotometric changes following the synthesis have been reported by da Silva [42]. Interestingly, the authors observed such variations when CTAB was not removed from the GNRs'solution.…”

“…[22] The lack of a molecular level understanding of the fabrication mechanism leads to major difficulties in controlling the reproducibility and poses questions on the interplay of different variables determining the shape and the AR. Moreover, the occurrence of aging phenomena [23] still needs adequate characterization, and further compromises the fine control of the size and the structure of GNRs. Secondly, GNRs obtained by seed-mediated growth are capped by a double layer of cetyl trimethyl ammonium bromide (CTAB), a surfactant that plays a critical role in driving the seeds' growth towards the cylindrical shape.…”

New Aspects of the Gold Nanorod Formation Mechanism via Seed-Mediated Methods Revealed by Molecular Dynamics Simulations

“…Briefly, in the seed-mediated synthesis of AuNRs, the growth of these anisotropic nanoparticles is mediated by the addition of metallic gold atoms at the surface of previously prepared small gold nanoparticles (seeds), by a controlled reduction of Au­(I) species at the surface of the seeds that grow in an anisotropic way due to the presence of cetyltrimethylammonium bromide (CTAB) as a growth-driving agent. ,, Indeed, many studies of these standard synthesis methods and adaptations thereof have appeared in the literature. In particular, the effects of the seed size, cosurfactants, additives, temperature, , surfactant chain length, and headgroup structure have been investigated.…”

Self-Assembly of Metal Nanoparticles, an Important Process to the Development of New Nanostructured Materials and Devices

“…Vale também comentar que agentes de modificação de superfície podem apresentar uma maior afinidade por um tipo de faceta cristalina da nanopartícula que outra. Essa propriedade é importante tanto para a geração de nanopartículas anisotrópicas, 40 quanto para realizar automontagens com orientações especificas das nanopartículas, gerando, consequentemente, arranjos nanoestruturados singulares. 99 Devido à promoção de interações químicas específicas e seletivas, muitos conectores são à base de biomoléculas (proteínas, peptídeos, filamentos da cadeia do DNA etc.).…”