Chemical Characterization of Nanoparticles

The Analytical Chemistry Division is helping to support nanotechnology research being conducted throughout NIST by developing and applying methods for the chemical compositional characterization of nanomaterials. Measurement capabilities being developed include the detection and quantification of nanoparticles by way of elemental signatures (for example gold or silver nanoparticles), quantification of other chemicals present in nanomaterial formulations, and techniques to distinguish between free and complexed nanoparticles or to distinguish metals present as nanoparticles from other chemical forms of the metal. The research also includes studies of the behavior of nanoparticles in analytical measurement systems.

NIST has a broad research program spread throughout the major operating units aimed at building the supporting technical capabilities that U.S. industry needs in their quest to develop new nanotech products with desirable new capabilities and bring them safely to market. The Analytical Chemistry Division is developing new capabilities to provide chemical compositional characterization of nanomaterials in support of broader NIST nanotechnology research activities including the development of nanomaterial reference materials and the characterization of nanomaterial formulations being developed for cancer treatment. The latter is a collaboration between NIST and the National Cancer Institute’s Nanotechnology Characterization Laboratory.

We have been collaborating with other NIST divisions to provide chemical compositional measurements of reference materials or other types of samples under investigation. In some cases this has required the development of new methods of analysis or studies of the behavior of nanomaterials in analytical measurement systems. To provide information about the chemical form of specific nanomaterials we have coupled various chromatographic separation techniques with sensitive element-specific detection systems such as inductively coupled plasma mass spectrometry (ICP-MS). We are also developing a system that couples an ion mobility analyzer with ICP-MS as a means of separating metal-containing nanoparticles by size and as a means of distinguishing metals present as nanoparticles from those present as dissolved ions. This type of chemical information is particularly valuable for toxicological studies.

Major Accomplishments: 

• Neutron activation analysis of a candidate carbon nanotube reference material revealed very high levels of contamination from catalysts used to produce the materials resulting in rejection of the material as a RM.
• Isotope dilution mass spectrometric analysis of a nanoemulsion submitted by the NCI Nanotechnology Characterization Laboratory (NCI-NCL) for gadolinium content.
• Value assignment of gold, chloride, citrate, and sodium mass fractions, pH, and electrolytic conductivity in RMs 8011 through 8013, Gold Nanoparticle Reference Materials.
• Determination of cadmium concentrations in quantum dot-containing samples in collaboration with CSTL’s Surface and Microanalysis Science Division.
• Analysis of tissue samples submitted by NCI-NCL for toxicological study of gold nanoparticles and the transfer of this measurement methodology to NCI-NCL for their future use.
• Development of a method based on size-exclusion chromatography with ICP-MS detection to quantitatively distinguish between free and complexed forms of gadolinium in samples submitted by NCI-NCL.