A RESEARCH group at the National Institute of Standards and Technology (NIST) has developed a new measurement tool for nanotechnology.
The NIST team developed a chemical analysis technique which uses the shifting ultrasonic pitch of a small quartz crystal in order to test the purity of a few micrograms of material. This allows testing of samples close to a thousand times smaller than comparable commercial instruments.
According to the NIST, nanotechnology and other developments have resulted in the objects of scientific research getting smaller and smaller, resulting in increased research into instrumentation at those scales.
The new NIST technique is a based on thermogravimetric analysis (TGA). This involves heating a sample of material slowly, with changes in mass measured as the temperature increases. The technique measures the reaction energy needed to decompose, oxidize, dehydrate, or otherwise chemically change the sample with heat.
To adopt TGA for smaller masses, the NIST researchers used a sensitive quartz crystal microbalance to measure the minute changes in mass.
The microbalance is a small piezoelectric disk of quartz sandwiched between two electrodes. Applying an AC current across the electrodes causes the crystal to vibrate at a stable and precise ultrasonic frequency. Adding the microsample lowers the resonant frequency, which climbs back up as the microsample is heated and breaks down.
The new microbalance TGA allows the use of the technique with samples about a thousand times smaller than conventional TGA instruments. It has been applied to measure the organic surface coatings biologists put on gold nanoparticles to modify them for particular applications.
More details regarding this technique can be found in the paper “Quartz crystal microbalances for microscale thermogravimetric analysis”, found at http://pubs.acs.org/doi/abs/10.1021/ac102030z