Dodecanethiol is a hydrophobic molecule that provides particles with solubility in organic solvents and compatibility with non-polar polymer composite materials as well as promoting dispersion in low surface-energy solvents for coating applications requiring uniform particle deposition. The thiol group provides a very strong bond to the gold particle surface, leaving the hydrophobic alkyl chain exposed to solution. The dodecane thiol gives steric stability by providing a physical barrier that prevents particle aggregation in the dried state and allows particles to be dried and re-suspended in organic solvents without particle agglomeration. See list of compatible solvents.
Dodecanethiol is only available for sub-10 nm sizes of gold and silver; for larger sizes requiring organic compatibility, we recommend polystyrene.
Representative Source: 1-dodecanethiol (Sigma Aldrich, 471364)
Molecular Weight: 202.40
To redisperse the particles, we recommend adding an appropriate solvent from the Table below to the dried powder and vortexing for 30 seconds. The list below is not comprehensive and represents only a subset of compatible solvents; other nonpolar solvents may also be compatible. After redispersion, samples should be stored at 4°C and away from light, as described in our Storage and Handling instructions.
| Refractive Index, n | Polarity Index | Dry Particle Solubility | |
|---|---|---|---|
| Toluene | 1.50 | 2.4 | High |
| Chloroform | 1.45 | 4.1 | High |
| Dichloromethane | 1.42 | 3.1 | High |
| Hexane | 1.38 | 0.1 | High |
| THF | 1.41 | 4.0 | High |
| DMF | 1.43 | 6.4 | None |
| DMSO | 1.48 | 7.2 | None |
| Acetonitrile | 1.34 | 5.8 | None |
| Isopropanol | 1.38 | 3.9 | None |
| Ethanol | 1.36 | 5.2 | None |
| Methanol | 1.33 | 5.1 | None |
| Water | 1.34 | 10.2 | None |
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.