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UV-vis and NMR spectroscopy together with size-exclusion chromatography (SEC), dynamic light scattering, and transmission electron microscopy (TEM) have been used to characterise an entirely novel and unique example of gold nanoparticles that can dissolve in any conventional solvent. Eugene Zubarev and co-workers at Rice University, Texas, have devised what they describe as a very efficient method for making well-defined gold nanoparticles with equal numbers of hydrophobic and hydrophilic arms. The V-shaped arms are alternately distributed across the surface of 2 nanometre gold core particles. The solubility of these nanoparticles in a wide range of solvents means that they should be amenable to further processing with various chemical modifiers. Such nanoparticles have potential in optoelectronics, catalysis, and biomedical applications. Previous researchers have added a polymer coating to gold nanoparticles, and further modified these appendages with other molecules, including DNA strands. However, there are difficulties in controlling the distribution of the connection points on the particle surface using their methods. Zubarev and colleagues reasoned that if an amphiphilic block copolymer with a fixed hydrophobe-hydrophile ratio were linked to the gold particles they might gain more control over the patterning of the product. As such, the team developed a two-stage synthesis involving formation of the amphiphilic molecule and subsequent attachment to the gold nanoparticles. They used SEC to follow the rapid coupling reaction while TEM allowed them to characterise the gold particles revealing that each cluster contains around 270 atoms. Mass calculations then show that at least 65 V-shaped molecules are attached to the surface of each particle. The highly pure nature of the particles makes them amenable to NMR studies confirming the chemistry of the surface groups. The team is currently investigating the behaviour of these modified gold nanoparticles. Related links:
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Zubarev - Golden boy of soluble nanoparticles |
