Solvent Selection for Alkanethiol-Coated Nanopowders
NanoComposix alkanethiol-stabilized Au and Ag nanopowders can be fully dispersed into a variety of solvents without particle agglomeration. The particles are sterically-stabilized – as compared with charge-stabilized particles – meaning that the alkanethiol coating at the surface of the particle provides a physical barrier that prevents particle sintering in the dried state, as well as providing a hydrophobic coating that allows the particles to be reversibly dried and re-suspended in organic solvents.
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To redisperse the particles, we recommend adding an appropriate solvent from the Table below to the dried powder and vortexing for 30 seconds. After redispersion, samples should be stored at 4°C and away from light, as described in our Storage and Handling instructions.
|Solvent Refractive Index, n||Nanopowder Solubility|
Effect of Solvent on Nanoparticle Optical Properties
UV-visible spectroscopy can be used to detect the presence of aggregation or changes in particle size; such effects are readily observed in the absorption spectrum as a change in the width of the plasmon peak and/or the appearance of a secondary peak that is red-shifted from the plasmon peak. Samples of a hexane dispersion of 4 nm-diameter dodecanethiol-coated Ag nanoparticles were dried and re-suspended in a variety of organic solvents. The absorption spectrum of the resuspended sample is compared with that of the original hexane dispersion in the figures below.
Small changes in the UV-visible absorption spectra of the redispersed samples are seen when compared with the original hexane dispersion. The shifting and broadening of the the spectra are typical of those seen during solvent transfer due to a change in the refractive index of the solvent, and are not due to changes in particle size or agglomeration.