Characterization of reference materials: Nanoparticles and protocols

Full text: Recently, nanoparticles have been used in many commercial products, such as cosmetics, fabrics, biological and medical systems. Consequently, questions concerning the homogeneity, stability and the real dimension of these nanoscale objects are becoming more important. Therefore, the Brazilian National Institute of Metrology, Quality and Technology (INMETRO) has a direct action in production of nanoparticle reference materials, and the establishment of standard methods in accordance with International Organization for Standardization (ISO). In this work, we present the main results obtained in the characterization of nanoparticles, candidates for reference materials, carried out by different analytical techniques. These characterizations are powerful tools to the standardization of measurements methods, development of protocols and the production of reference materials. Several nanoparticles (Au, Ag and silica) and carbon based materials were analyzed, using SEM, TEM, AFM, BET, XRD, XPS and Raman spectroscopy techniques. These characterizations were done in accordance with interlaboratorial comparations with Institutes of Metrology from other countries. Concurrently, several digital imaging processing were tested with objective to get analyses that are more reliable from electron microscopy images, such as shape, size and morphology. Our results show that most of nanoparticles have large size distribution, and the reported values from different techniques vary slightly, evidencing the needs of finding high quality reference materials. Finally, new reference materials, protocols and methods of analyses have been necessary to improve our knowledge about dimensional properties of nanoparticles. These preliminary results have been useful in the development of measurement protocols. Employing the analytical techniques used for the characterization of candidates of the reference materials discussed here(author)