How to measure nanoparticle size: methods and equipment

Size is an important property when characterizing nanoparticles. Accurate measurement of nanoparticle size is therefore essential for scientists working with these tiny particles. Several methods and equipment are available for measuring nanoparticle size, each with its advantages and limitations. In this article, we will explore the different options for measuring nanoparticle size and help you understand how to choose the best method or equipment for your needs.

One of the best methods for measuring nanoparticle size is nanoparticle tracking analysis (NTA). NTA involves using a microscope and a high-resolution camera to track the movement of individual nanoparticles in a fluid. By analyzing the movement of the nanoparticles (known as Brownian motion), it is possible to determine their size and size distribution. NTA is a non-invasive method that can be used to measure the size of a wide range of nanoparticles made of metals, polymers, or biomolecules such as proteins or nucleic acids. NTA is also capable of measuring single nanoparticles, making it a valuable tool for understanding the properties of individual particles. However, the application of accurate NTA measurements is typically limited to nanoparticles larger than 80 nm.

Another common method for measuring nanoparticle size is dynamic light scattering (DLS). This method involves shining a laser beam through a suspension of nanoparticles and measuring the scattered light. The size of the nanoparticles can be calculated based on the intensity of the scattered light and the angle at which it is scattered. DLS is a quick and non-invasive method that can be used to measure the size of a wide range of nanoparticles including viruses, lipid nanoparticles, liposomes and extracellular vesicles. However, it is not as precise as some other methods and may not be suitable for measuring very small nanoparticles (<10 nm).

Transmission electron microscopy (TEM) is a highly precise method for measuring nanoparticle size. It involves using a high-energy electron beam that is cast on a grid that contains the nanoparticles. The resulting image can then be used to determine the size of the nanoparticles can be measured by analyzing the image. TEM is a highly precise method that can be used to measure the size of individual nanoparticles, but it is time-consuming and is destructive to the sample. In addition, it requires specialized equipment and trained operators, making it less accessible to some researchers.

Scanning electron microscopy (SEM) is another method for measuring nanoparticle size. It involves using a focused beam of electrons to create an image of the nanoparticles. The size of the nanoparticles can be measured by analyzing the image. SEM is a highly precise method that can be used to measure the size of individual nanoparticles, but it requires specialist training, is time-consuming and can be destructive to the sample.

Atomic force microscopy (AFM) is another method for measuring nanoparticle size. It involves using a very fine probe to scan the surface of the nanoparticles and measure their size. AFM is a highly precise method that can be used to measure the size of individual nanoparticles but determines the size when the nanoparticle is adsorbed to a surface in a dried state. Performing experiments in liquids can be performed but requires appropriate probes and specialist training. Furthermore, AFM is time-consuming and may not be suitable for measuring numerous batches or numbers of particles.

Laser diffraction is a method for measuring nanoparticle size that involves shining a laser beam through a suspension of nanoparticles and measuring the diffracted light. It is a quick and non-invasive method that can be used to measure the size of a wide range of nanoparticles, including metals, polymers, and biomolecules. However, it may not be as precise as some other methods and may not be suitable for measuring very small nanoparticles.

When choosing a method or equipment for measuring nanoparticle size, it is important to consider the expected characteristics of the nanoparticles being studied and the requirements of the application. Factors to consider include the size range of the nanoparticles, a representative sample size, the accuracy and precision required, and the cost and availability of the method or equipment.

In conclusion, there are several methods and equipment available for measuring the size of nanoparticles. Each method has its advantages and limitations, and the appropriate method will depend on the specific characteristics of the studied nanoparticles. By understanding the different options available, researchers and scientists can choose the best method for characterizing the size of their nanoparticles.

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