Measurement of nanoparticle concentration using quartz crystal microgravimetry.
Various nanoscale items (e.g., nanoparticles and nanotubes) have been actively investigated due to their unique physicochemical properties. A common issue encountered in such studies is accurate expression of nanoparticle concentration. Given the critical importance of the dose-response relationship, we present the use of quartz crystal microgravimetry (QCM) to accurately measure nanoparticle concentration in a colloidal suspension. Application of a small drop of the nanoparticle suspension in a volatile solvent to the crystal surface leaves a dry nanoparticle residue after solvent evaporation after which the shift in the crystal resonant frequency is recorded. The instrument was calibrated using a set of serial dilutions of Si and Ag nanopowder in methanol, rhodamine B in methanol, and ferrocene in cyclohexane. Using QCM, a linear response for nanoparticle concentrations up to 1300 μg/mL was determined. The developed method was used to determine the concentrations of size-selected, octyl-terminated Si nanocrystal samples with median diameters in the range 1.1-14.8 nm and also to calculate size-dependent nanocrystal extinction coefficients.
Biochemical Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Vytas
V
Reipa
Geoffrey
G
Purdum
Jonghoon
J
Choi
D002627:Chemistry, Physical; D053768:Metal Nanoparticles / Q000737:chemistry*; D043942:Nanotubes / Q000737:chemistry; D010316:Particle Size; D011791:Quartz / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry
D011791:Quartz; D012825:Silicon