![]() The fourth sample, Au-2-041-3, was measured using MADLS, and while the distribution was mostly uniform, there was an unexpected small peak below 10nm. By identifying that these rings are not representative of the sample means that this sample can be sold. Therefore, it is likely during the drying process some of the surfactant in the dispersion has dried around the particles causing these visible rings. If the rings were around the particles when dispersed then the DLS distribution would be much wider and higher in size. By measuring the sample using MADLS, it can be seen the distribution is narrow and within specifications. However, there are rings around many of the particles and it is unclear if these are a true reflection of the particle size when dispersed or if this is a result of the drying process. This means that while the MADLS measurements are well suited to detecting particles that are larger than the majority of the sample, they are less able to identify a sample that contains particles which fall under the specification.įor the third sample, the TEM image shows a uniform size distribution that falls within specifications for the particles themselves. The MADLS measurements was unable to pick this up because the scattering of the sample is much more skewed towards the larger sizes masking that of the tail of smaller particles. However, the TEM measurements disagree, as while the majority of the populations fall within the expected range, there is a tail of particles below the target size which means it does not meet specifications. Measuring the second sample, Au-2-017-6, with MADLS would suggest that this sample is on specification as a narrow distribution is measured. It is likely that these are being masked in the MADLS measurement by the scattering of the larger particles. The TEM image also shows that there are multiple large particles but also shows the expected 10nm particles. Therefore, this sample has failed to meet the specifications. Measuring the first sample, Au-2-016-7, with DLS showed the size populations to be much larger than the target size of 10 nm, to the point that the 10nm peak does not appear in the distribution. Zetasizer measures the hydrodynamic diameter of the gold, while TEM only measures the core particle diameter, therefore this is the primary reason for the discrepancy. These samples were also measured using TEM with at least 100 particles being measured for each sample.įor all of the samples, the Peak by Intensity values as measured by the Zetasizer are higher than those measured by TEM due to the effects of stabilising ligands, ionic surfactants and hydration layers, which increase the hydrodynamic size of the dispersed gold. Target sizes of 10nm, 15nm, 20nm and 50nm were measured on the Zetasizer Ultra using MADLS in DTS0012 plastic cuvettes. The samples tested in this study were gold nanoparticle samples synthesized by Particle Works during the early development of the Ultraspherical Gold Nanoparticle product range. In this study, samples of Particle Works gold nanoparticles were measured using both TEM and Multi-Angle Dynamic Light Scattering (MADLS) with the Zetasizer Ultra to determine whether the samples were of high enough quality to be sold. ![]() These include Adaptive Correlation, Multi-Angle Dynamic Light Scattering (MADLS) and Depolarized Dynamic Light Scattering (DDLS). The Zetasizer Ultra has multiple features that help to reduce the time taken for measurements to be carried out while providing much more detail on sample properties. Particle Works were therefore keen to explore whether the Zetasizer Ultra could be used to reduce the amount of TEM analysis required. However, TEM is a time-consuming and expensive technique that requires an experienced user to perform analysis. Currently, Particle Works use TEM as the primary technique for characterizing their samples for QC. For example, Particle Works, a brand of Blacktrace Holdings, produce gold nanoparticles which must be highly monodisperse and have high batch-to-batch consistency, with CV values as low as 5% for the size distribution and 2.5% for the batch consistency. When producing particles of a known size, the monodispersity of the samples in terms of both size and shape is important and often requires a high-resolution technique such as Transmission Electron Microscopy (TEM) to look at these sample properties. Non-Metallic Mineral Mining and Quarrying.
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