Nanomaterials have already been incorporated into a large range of commercial products including pharmaceuticals, sunscreens, automobile additives, personal care products, detergents and plastics. Although nanotechnology is changing the way we live, the accidental release of nanomaterials into the environment poses an unknown public health risk. Due to the significant physical and chemical differences between materials in nanoparticle form and bulk material form, new methods are needed to assess nanomaterial safety.
Workers, consumers and living organisms are exposed to nanomaterials through inhalation, dermal contact or water exposure. Understanding the environmental, health and safety effects of nanomaterials through scientifically-based and consensus-based standard test methods is critical for assessment of nanotechnology safety and will lead to increased commerce on a global level. A common issue encountered in such studies is accurate nanoparticle concentration expression, given the critical importance of the dose-response relationship. Furthermore, particle concentration can be alternatively expressed as mass, number of particles (molar) or surface area units, often complicating inter-study comparisons. Accurate gravimetric measurement using analytical balances may not be practical in the sub-microgram range, as this is approaching the sensitivity limit for most instruments.
The quartz crystal microbalance (QCM) is a nanogram-resolution mass-sensing technique based on the piezoelectric effect. The technique is quite versatile, as it possesses a wide detection range and can be applied to deposited mass measurements in the gas or liquid phase. Deposition of a liquid drop on one of the faces of an oscillating crystal causes a shift in its resonant frequency, enabling accurate residue film mass measurements following solvent evaporation. We apply quartz crystal microgravimetry to accurately quantify nanoparticle concentrations in size-selected colloidal suspensions in a low boiling point solvent. By depositing a fixed volume of the nanoparticle colloidal solution and determining the dry residue mass after solvent evaporation, we measured the nanoparticle concentration and expressed it in mass per unit volume. Concentration data on size-selected nanoparticle batches enables the calculation of the nanoparticle extinction coefficient and will facilitate practical applications of absorption-based nanoparticle concentration determination when accurate quantitation of a small nanoparticle sample is required.
Silver nanomaterials are increasingly being used as antimicrobial agents in medical devices. A recent joint study with the Food and Drug Administration's Center for Devices and Radiological Health assessed the in vitro hemolytic potential of silver particles in human blood to determine which physical and chemical particle properties contribute to mechanisms of red blood cell damage.
NIST staff are active participants in ISO TC 229 (Nanotechnologies) technical groups.