Immobilization of Magnetic Nanoparticles onto Conductive Surfaces Modified by Diazonium Chemistry

Abstract

Core-shell γ-Fe(2)O(3)@SiO(2) nanoparticles (NPs) substituted by PEG and NH(2) groups may be immobilized on metal surfaces (glassy carbon or gold) substituted by 4-carboxyphenyl groups through electrostatic interactions. Such immobilization is evidenced by (i) IRRAS owing to the Si-O band, (ii) SEM images, which show that the surface coverage by the NPs is nearly 100%, and (iii) the NPs film thickness measured by ellipsometry or AFM, which corresponds to about one NPs monolayer. Such NPs film is permeable to redox probes, which allows us to propose electrochemical methods based on direct or local measurements as a way to inspect the NPs assembly steps through their ability to alter mass and charge transfer. This process also applies to patterned polystyrene surfaces, and selective immobilization of NPs substituted by amino groups was carried out onto submillimeter patterns obtained by local oxidation. Biological applications are then expected for hyperthermia activation of the NPs to trigger cellular death. Finally, some tests were performed to further derivatize the immobilized NPs onto surfaces through either a covalent bond or electrostatic interactions. Future work will be dedicated to the recovery of such Janus NPs from the substrate surface.

Mussel-Inspired Direct Immobilization of Nanoparticles and Application for Oil–Water Separation

“…In contrast, only very low amount of Fe 3 O 4 nanoparticles coats the sponge treated in Fe 3 O 4 dispersion without dopamine at the same pH (Figure c), indicating the important role of dopamine in the nanoparticle adhesion process. The results imply that dopamine can directly “glue” Fe 3 O 4 nanoparticles to the sponge skeleton, while avoiding specific modification of nanoparticles and substrates of the previous reports. − …”

“…Immobilization of nanoparticles (NPs) onto complex two- (2D) and three-dimensional (3D) structures has a wide spectrum of applications in optics and electronics, , biomedicine, , sensors, , energy storage, catalysis, and so on. , A number of strategies have been proposed for achieving this goal, which mainly involved the modification of either nanoparticles or target surfaces with polymers, supramolecular assemblies and molecules containing functional groups such as mercapto, pyridyl, amino,, diazonium salt, etc. The immobilization mechanism mainly depends on noncovalent interactions − or covalent bonding , between nanoparticles and surfaces.…”

High-Density Single-Layer Coating of Gold Nanoparticles onto Multiple Substrates by Using an Intrinsically Disordered Protein of α-Synuclein for Nanoapplications

“…For that purpose, many approaches have been introduced on the basis of charge interaction, Langmuir–Schaefer transfer, Langmuir–Blodgett technique, and thermal annealing, which would contribute to the preparation of nanodevices such as optoelectronic sensors and low-power consumption memories. Their use, however, has been hindered by the requirement of specific surface modifications with chemicals, − polymers, or supramolecules, the utilization of complex instruments, and the need of extreme conditions for NP thermal annealing . Concerning various types of materials to produce nanodevices, a simple and universal procedure for NPs to be graffitized on a diverse set of substrates in the form of tightly packed particles in a single layer has been needed.…”

Electrochemical Detection of Single Microbeads Manipulated by Optical Tweezers in the Vicinity of Ultramicroelectrodes

“…Electrochemistry of nano- and microparticles is of high interest for detecting the presence, the size, or the chemical signature of single objects. It is also a powerful approach to understand diffusion and reaction in the vicinity of individual objects or in confined volumes such as microbead agglomerates or nanoparticle opals. − Detection of single particle has thus been achieved using electrochemical techniques with both signal-on and signal-off approaches. − For example, Compton et al have extensively studied the effect of inert particles blocking the surface of an electrode . The authors positioned mechanically a bead of radius 125 μm on an electrode of radius 59 μm and studied its influence on cyclic voltammograms at different scan rates. , They were first able to extract the size of the particle from the voltammetric data.…”

“…With the optical tweezers ensuring positioning control, the UME is static and inert objects are manipulated in its vicinity. Equivalently to SECM and as presented in Figure B, the insulating microbeads are expected to alter the diffusional fluxes of the electroactive species and thus the intensity of the electrochemical signal. ,, The diffusion hindrance afforded by a single bead or an assembly of beads is then analyzed electrochemically depending on their levitating or landing locations.…”