Effect of Dipolar Interactions on the Assembly Process of Iron Oxide Nanoparticles Promoted by the CuAAC “Click” Chemistry Reaction

Abstract

Nanoparticle assemblies are very attractive because they allow the fine-tuning of magnetic properties by taking advantage of collective behavior ruled by interparticle interactions. Nevertheless, great efforts to control the spatial arrangement of nanoparticles still have to be developed in order to integrate such nanomaterials in devices for applications in fields such as sensors and recording media. Herein, we report on the assembly of iron oxide magnetic nanoparticles promoted by copper-catalyzed alkyne–azide cycloaddition (CuAAC) “click” reaction. Azido-terminated nanoparticles were assembled onto alkyne-terminated gold substrates. The assembly mechanism was investigated by monitoring the density of nanoparticles as a function of their size and concentration. The kinetics of the assembly process is exponential and is favored by the increase of the nanoparticle size and of the concentration. We show that the assembly of nanoparticles is controlled by the random sequential adsorption (RSA) mechanism below a critical size. In contrast, large nanoparticles allow strong dipolar interactions which participate actively in the assembly process, thus they avoid the RSA pathway. These two different mechanism pathways have a significant influence on the spatial arrangement of nanoparticles. The RSA results in rather isolated small nanoparticles at the earliest reaction times which become gradually a discontinuous monolayer. In contrast, the dipolar interaction assisted RSA mechanism (DIA-RSA) favors linear or 2D small assemblies which quickly grow in tight-packed monolayers of nanoparticles. Finally, the magnetic collective properties of these assemblies are markedly favored by the increase of the nanoparticle size.

Increasing the size of Fe3-δO4 Nanoparticles by Performing a Multistep Seed-Mediated Growth Approach

“…H C decreases from 219 Oe (IOC) to 96 Oe (IOCS4) according to the increase of the nanoparticle size. These results agree with stronger dipolar interactions. ,, In addition, the H C of IOCS1 (80 Oe) was expected to be higher and may be ascribed to shorter interparticle distances as mentioned above.…”

“…These results agree with stronger dipolar interactions. 19,49,50 In addition, the H C of IOCS1 (80 Oe) was expected to be higher and may be ascribed to shorter interparticle distances as mentioned above. The M R /M S ratio (Table 4), also called the alignment ratio, is used to describe the mean orientation of the magnetic moments of the nanoparticles.…”

Chemical design of high performance SPR biosensor based on a dielectric nanoparticle assembly supported onto a gold thin film

“…28 Indeed, dipolar interactions contribute to the assembly process, which results in closer nanoparticles (up to 80% hcp ). 29 Atomic force microscopy (AFM) provided complementary information on the structure of the nanoparticle assembly (Fig. 2b and c).…”