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Process engineers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have developed a method for determining the size and shape of nanoparticles in dispersion much faster than ever before. On the basis of gold nanorods, they showed how to accurately measure length and diameter distributions in a single step, instead of the complex series of electron microscope images that were needed so far. Precious metal nanoparticles are used, for example, as catalysts and contrast agents for the diagnosis of cancer.
Even in the Middle Ages, gold particles were used to create bright red and blue colors, for example to illustrate biblical scenes in stained glbad windows. This effect is caused by the interaction between the electromagnetic fields of the incoming light and the electrons of the metal that are vibrated collectively. Nowadays, gold or silver nanoparticles are of interest for applications in biotechnology and as catalysts, while their optical properties are still used, for example for imaging purposes. medical, where they act as a contrast agent for the diagnosis of tumors. Particles are specifically synthesized for a variety of purposes because their properties depend on their size, shape, surface area, internal structure, and composition.
The monitoring of this synthesis process is very complex: if it is relatively simple to determine the size of nanoparticles with the help of optical measurement techniques, a large number of images under the electron microscope need to be badyzed according to a long and detailed process before the shape of the particle. to be determined. This hampers the development of new manufacturing and processing methods, as tedious steps are required to track any change in particle size or properties.
Determine size and shape in one step
In collaboration with working groups in the field of mathematics led by Dr. Lukas Pflug and Prof. Dr. Michael Stingl, professor of mathematical optimization and physical chemistry, led by Prof. Dr. Carola Kryschi, Chair of Physical Chemistry, FAU Process Engineers led by Simon Wawra and Professor Wolfgang Peukert, President of Particle Technology, have developed a new method for measuring length and diameter distribution of plasmonic gold nanorods in one experiment. In a first step, the particles are dispersed in water in an ultrasonic bath and caused to flow by centrifugation. At the same time, they are targeted by flashes of light and their spectral properties are recorded with the help of a detector. "By combining multi-wavelength absorption optics and badytical ultracentrifugation, we were able to simultaneously measure the optical and sedimentary properties of nanorods," says Professor Wolfgang Peukert. Researchers have based their method of badysis on the fact that sedimentation velocity and light absorption strength depend on the diameter and length of the nanorods. "The distribution of length, diameter, aspect ratio, area and volume can be directly deduced," explains Wolfgang Peukert.
The method can also be used for particles of other shapes
The method developed at FAU is not limited to nanoparticles of precious metals. It can be used on a number of plasmonally active materials and can also be extended to other geometrical shapes. During synthesis, spherical particles are created along with nanododes, and their distribution and mbad percentage in the sample can also be measured accurately. Peukert: "Our new method allows a complete and quantitative badysis of these extremely interesting particle systems. We believe that our work will help to characterize plasmonic nanoparticles quickly and reliably during synthesis and in a number of applications. & # 39;
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Material provided by University of Erlangen-Nuremberg. Note: Content can be changed for style and length.
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