Our environment is heavily polluted with microplastics. The term microplastics usually refers to particles with a size of 5 millimeters or smaller; in the environment they are fragmented into smaller units of 1 µm or smaller, then called nanoplastics. Pollution with plastic occurs in oceans, soils, consumer products and food, it endangers the health of these systems and of humans.
Finding and identifiying nanoparticles in the 100 nm range remains a challenge. Meeting both objectives is essential: the high resolution imaging capabilities of Scanning Electron Microscopy (SEM) is key to find micro- and nanoplastic particles (M/NPs) where Raman spectroscopy provides analysis of organic specimens. Thus the analysis of nanometer sized particles benefits from the correlation of the two techniques.
On this web page, you will learn how to use
- SEM for imaging and filter particle segmentation
- AI guided software for classification and quantification
- Raman spectroscopy for chemical identification
- A multi-modal combination of all three techniques
Healthy oceans, seas, coastal and inland waters are vital for our societies and the future of our planet.Funding Program 'Horizon Europe' by the European Union
When using machine learning for particle analysis you may start with imaging the MNPs on a filter via SEM. The software ZEISS ZEN Intellesis automatically identifies particles with a deep learning model on a SEM image.
The user trains the classification model by mouse clicks on a few images, indicating different objects and assigning particle types manually. The resulting model distinguishes particle properties like diameter, orientation or chemical properties after correlation with Raman spectroscopy results, e.g. different polymers like PVC, PA, PS, and PE.
Time-consuming segmentation steps on hundreds of images are done by machine learning algorithms (including Deep Learning). ZEN Intellesis Object Classification, a Python-powered tool offers pixel classification with real multichannel feature extraction and segmentation. By pre-trained networks even complex multidimensional, multi-modal data can be analyzed, regardless of their origin.
SEM is able to find nanometer sized particles being well within the range of both micro- and nanoplastics. But SEM alone cannot distinguish between types of particles, especially organic ones. The correlation with Raman enables the detection of the latter. Laboratories already equipped with a standalone Raman, are enabled to use it in combination with a standalone ZEISS SEM.
A so-called NanoGPS chip from Horiba is used as a marker on your specimen to aid relocation of the point of interest in both SEM and Raman. The software module ZEISS ZEN Connect offers a correlative workspace tailored for multi-modal experiments. It supports the import of Horiba Raman maps and enables image-based navigation in the SEM. Additionally, connection of multi-modal data, overlay, and alignment of images and analytical results are possible with ZEN Connect.
An alternative to using two separate systems is to perform Raman-SEM correlations with a fully integrated solution. RISE (Raman Imaging and Scanning Electron Microscopy) is the combination of WITec Confocal Raman Imaging with a ZEISS FE-SEM all in one instrument.
Combining the chemical sensitivity of Raman with the SEM allows you to analyze nanoplastic particles more efficiently, accurately and reliably than before. The sample with its regions of interest stays in the vacuum chamber, is transferred from one objective, SEM or Raman, to the other. The workflow is streamlined and convenient to use, from SEM imaging to Raman spectroscopy, delivering complementary information of the specimen - a chemical fingerprint.
Characterization of microplastics and nanoplastics requires a scale-bridging combination of microscopies and spectroscopies. In this Nature Research webinar, Dr. Silke Christiansen specifies the challenges of scale-bridging analytics and analytical techniques required to truly correlate physical and chemical properties at particle levels.
Watch on-demand and learn about:
- The challenges of true correlation of multi-modal analytics on individual M/NPs on filters and in more complex samples such as tissue
- The power of correlative Raman-SEM to master true signal correlation on individual micro- and nanoplastic particles
- How to develop a dedicated sample preparation workflow to correlate a wealth of analytical modalities
Presenter: Dr. Silke Christiansen, Fraunhofer Institute for Ceramics Materials and Systems
Get in touch with us to find out more about micro- and nanoplastics analysis with ZEISS solutions for your research, book a demo at our customer center, or get a quote. We are looking forward to hearing from you.