Atomic Force Microscopes for Nanoparticle Characterization

The Atomic Force Microscope (AFM) allows for 3D characterization of nanoparticles with sub-nanometer resolution. Nanoparticle characterization using Atomic Force Microscopy has a number of advantages over dynamic light scattering, electron microscopy and optical characterization methods.

Some of the unique advantages of nanoparticle characterization with an AFM include:

  • Characterization of nanoparticles that are .5 nm in diameter and larger.
  • Nanoparticle mixture distributions below 30 nm.
  • Characterization of variable geometry nanoparticles.
  • Direct visualization of hydrated nanoparticles/liquid medium.
  • Characterization of nanoparticle physical properties such as magnetic fields.

Characterization of nanoparticles that are .5 nm in diameter and above

An outstanding feature of the Atomic Force Microscope is that it can directly create images of nanoparticles with dimensions between 0.5 nm and 50+ nm. Nanoparticle size distributions are directly calculated from AFM images.

Colbalt nanoparticles 1 nm & 3 nm AFM scan    CdSe quantum dots AFMs for nanoparticle characterization

On the left is a sample of 1 nm and 3 nm colbalt nanoparticles. At the right is a CdSe quantum dot sample deposited on a polymer film.

100-nm gold nanoparticles AFM scan    200 nm gold nanoparticles AFM scan

 

On the left is a sample of 100 nm gold nanoparticles. On the right is a sample of 20 nm gold nanoparticles.

AFM scan of CdSe quantum nanoparticles    3D image of CdSe nanoparticles 1.5 µm x 1.5 µm

Image of 2.7 nm diameter CdSe quantum dot nanoparticles. At left is a 2-D view, at right is the image in 3-D.

Nanoparticle Mixtures

The AFM can easily identify and characterize bi-modal distributions of nanoparticles. AFMWorkshop's built-in nanoparticle analysis software makes nanoparticle characterization fast and easy.

AFM scan of polystyrene nanoparticles

Above, an image shows a bimodal distribution of polystyrene nanoparticles (20 nm and 100 nm)

2 -20nm CdSe quantum-dots    AFM software, line profiles of 3 separate nanoparticles

At the left is an image of 2-20 nm nanoparticles. On the right are line profiles for the 3 separate nanoparticles identified in the image at left)

Variable geometry nanoparticles

The AFM can evaluate variable nanoparticle geometry, from traditional spherical nanoparticles to more exotic fractal geometries of nanoparticle clusters.

AFM scan of nanoparticles 2 µm x 2 µm     Gold NanoTriangles, AFM scan

On the left is sample of nanoparticles with "donut" shaped structures. On the right is an image of Gold NanoTriangles.

AFM analysis of hydrated samples/liquid medium

The atomic force microscope's ability to measure conductive or non-conductive samples in air allows for characterization of complex polymers and biological samples. For samples that need to be kept hydrated or in a controlled liquid or pH solution, AFMWorkshop offers a fluid cell option that allows for AFM analysis in liquid.

Nanoparticle Physical Properties

Many AFM modes may be used to measure nanoparticle physical properties such as magnetic fields, mechanical properties, electrical properties, and thermal conductivity.

Nanoparticle Size Analysis

A specialized AFMWorkshop optional Nanoparticle Analysis Software measures the critical dimensions of AFM nanoparticle images. This is possible because an AFM measures the entire three dimensional structure of the nanoparticles.

AFM Nanoparticle size analysis 3 µm x 3 µm

 

 

A 3µm x3 µm image of nanoparticles displayed as a three dimensional projection. These nanoparticles range in size from 4nm to 12nm in diameter.

 
 

AFM nanoparticle analysis software screen image

Specialized software algorithms allow the nanoparticles in the image to be identified and then counted. Additionally, critical sample image dimensions such as height, volume, surface area, and perimeter may be calculated and displayed.

 
Histogram of AFM nanoparticle analysis

Using data from the image analysis software module, a histogram of the nanoparticle distributions can be calculated.