This paper describes the production and characteristics of the nanoparticle test materials prepared for common use in the collaborative research project NanoChOp (Chemical and optical characterization of nanomaterials in biological systems), in casu suspensions of silica nanoparticles and CdSe/CdS/ZnS quantum dots (QDs). This paper is the first to illustrate how to assess whether nanoparticle test materials meet the requirements of a "reference material" (ISO Guide 30, 2015) or rather those of the recently defined category of "representative test material (RTM)" (ISO/TS 16195, 2013). The NanoChOp test materials were investigated with small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and centrifugal liquid sedimentation (CLS) to establish whether they complied with the required monomodal particle size distribution. The presence of impurities, aggregates, agglomerates, and viable microorganisms in the suspensions was investigated with DLS, CLS, optical and electron microscopy and via plating on nutrient agar. Suitability of surface functionalization was investigated with attenuated total reflection Fourier transform infrared spectrometry (ATR-FTIR) and via the capacity of the nanoparticles to be fluorescently labeled or to bind antibodies. Between-unit homogeneity and stability were investigated in terms of particle size and zeta potential. This paper shows that only based on the outcome of a detailed characterization process one can raise the status of a test material to RTM or reference material, and how this status depends on its intended use.
Bibliographical noteFunding Information:
The NanoChOp project was funded through the European Metrology Research Programme (EMRP NEW 03), funded by the EMRP participating countries of EURAMET and the European Union. The authors wish to thank H. Emteborg, A. Oostra, K. Teipel and M.-F. Tumba-Tshilumba (JRC-IRMM) for their advice and assistance with the processing of the materials, D. Fruge (Grace Materials Technologies) for the supply of a colloidal silica, and K. Hoffman (BAM) and T. Gerganova (JRC-IRMM) for the optical microscopy.
- Analytical quality assurance
- Materials characterization
- Reference material