Interactions and Attachment Pathways between Functionalized Gold Nanorods

Abstract

Nanoparticle (NP) self-assembly has been recognized as an important technological process for forming ordered nanostructures. However, the detailed dynamics of the assembly processes remain poorly understood. Using in situ liquid cell transmission electron microscopy, we describe the assembly modes of gold (Au) nanorods (NRs) in solution mediated by hydrogen bonding between NR-bound cysteamine linker molecules. Our observations reveal that by tuning the linker concentration, two different NR assembly modes can be achieved. These assembly modes proceed via the (1) end-to-end and (2) side-to-side attachment of NRs at low and high linker concentrations in solution, respectively. In addition, our time-resolved observations reveal that the side-to-side NR assemblies can occur through two different pathways: (i) prealigned attachment, where two Au NRs prealign to be parallel prior to assembly, and (ii) postattachment alignment, where two Au NRs first undergo end-to-end attachment and pivot around the attachment point to form the side-to-side assembly. We attributed the observed assembly modes to the distribution of linkers on the NR surfaces and the electrostatic interactions between the NRs. The intermediate steps in the assembly reported here reveal how the shape and surface functionalities of NPs drive their self-assembly, which is important for the rational design of hierarchical nanostructures.

Gold Nanocrystal Etching as a Means of Probing the Dynamic Chemical Environment in Graphene Liquid Cell Electron Microscopy

“…56,57 ( Figure S9) In some videos, a more perturbative, halolike feature emerges around the nanocrystal, and from HRTEM, it was determined to be Fe-(OH) 3 (H 2 O) 0. 25 56,58 ( Figure S10). When this iron oxyhydroxide grows on or close to the surface of the etching nanocrystal, the precipitate limits the etchant species from getting to the nanocrystal surface and causes a slower, but still constant, etching rate ( Figure S12).…”

Nanoparticle Characterization: What to Measure?

“…This technique makes it possible to image previously “unobserved” processes such as nucleation and growth of nanoparticles as well as their interaction and assembly . The power of LC TEM has been demonstrated by studying several aspects of synthesis and use of gold nanoparticles, namely their nucleation rates, and the dynamics and assembly between bare and functionalized particles (Figure b) . Finally, atomic‐resolution transmission electron microscopy (AR‐TEM) enables the study of dynamic processes and provides real‐time observation of changes at the molecular level with atomic sensitivity .…”

“…a) A nanoparticle suspension is sandwiched between two electron‐transparent windows (e.g., made of thin silicon nitride) to prevent the evaporation of the solution in the high vacuum environment during TEM imaging; b) formation of gold nanorod chains by sequential attachment of nanorods in solution. Adapted with permission . Copyright 2017, American Chemical Society; c) conformational changes of a biotinylated molecule grafted to the tip of a tapered single‐walled carbon nanotube.…”

New Strategy for Streptavidin Detection Using AuNRs/PAAm Hydrogel Composites

“…Cys molecules interact strongly with the gold surface by -SH groups, leaving the -NH 2 group free for further modifications. 31,32 Based on this purpose, the second step was anchor the biotin in the Cys surface, which led to a biotinylated surface proper for streptavidin detection. The N-hydroxysuccinimide group at the biotin molecule can be easily removed from the reaction with the exposed amine group of the Cys/AuNRs system.…”