Sample preparation for the quick sizing of metal nanoparticles by atomic force microscopy

Abstract

Two alternative pretreatment methods for depositing metal nanoparticles on mica for atomic force microscopy (AFM) imaging are presented. The treated substrates are flat and clean, thus they are amenable of use to characterize very small nanoparticles. The methods do not require any instrumentation or particular expertise. As they are also very quick, the need for storage of the prepared substrates is avoided altogether. These proposed methods, which are compared with the results of transmission electron microscopy analysis, allow the quick sizing and characterization of nanoparticles with the atomic force microscope and could thus help expanding the user community of nanoparticle researchers who could use the AFM for their characterization needs.

PMMA‐based core‐shell nanoparticles with various PTFE cores

“…The interparticle distances for neighboring particles can be evaluated directly from the micrographs 23. Such distance is a measure of the packing of the particles and of their diameter, in case of ordered compact packing of hard‐shell particles.…”

“…Micrographs are then subjected to flattening using the microscope constructor software. The interparticle distances are measured semiautomatically using a custom‐developed software utility 23…”

Atomic Force Microscopy Probing of Receptor–Nanoparticle Interactions for Riboflavin Receptor Targeted Gold–Dendrimer Nanocomposites

“…Similar observations have been noted with Mg 2+ treated mica surfaces, and the immobilization appears to depend on the size of the nanoparticles with larger AuNPs not adhering to the MgCl 2 treated mica surface. 68 3-(Aminopropyl)triethoxysilane (APTES) treated mica is also commonly used for immobilizing biological material and has been used extensively in imaging DNA on mica substrates. 67 Mica substrates treated with 0.01% APTES solution were found to be favorably disposed toward achieving electrostatic immobilization of unconjugated AuNPs (Figure 3A).…”

Analysis of Non‐Covalent Bioconjugation of Colloidal Nanoparticles by Means of Atomic Force Microscopy and Data Clustering

“…Because all AuNP hybrids are negatively charged due to the citrate or DNA layer on their surface, it was necessary to activate mica by deposition of Mg 2 + ions, as it is typically carried out for immobilization of DNA and DNA-protein conjugates. [19,37] This method led to high surface coverages of the hybrid nanoparticles 1-6 on the mica substrates. Table 1 summarizes the observed surface coverages as well as height and FWHM values, obtained from the AFM measurements.…”

“…Notable recent advances in this respect concern the determination of the stoichiometry of QD-bioconjugates using highpressure size-exclusion chromatography and scanning transmission electron microscopy, [11] circular dichroism (CD) spectroscopy [12] or dynamic light scattering (DLS) techniques. [13,14] Atomic force microscopy (AFM) is a standard technique for nanoparticle analysis, [15][16][17][18][19][20] and it has also been used for the analysis of nanoparticle-biomolecule hybrids, [21,22] for example, as a means for detection of biomolecular recognition events. [23,24] However, AFM analysis is prone to artefacts, which stem from side products or other contaminants of the sample, and its lateral resolution is often insufficient to visualize the presence or absence of biomolecules tethered to colloidal nanoparticles.…”