Ask an Expert: Is it easier to work with bare gold nanoparticles. If yes, where can I buy bare gold nanoparticles? 

"Bare" gold nanoparticles is actually a misnomer, as gold nanoparticles must have a stabilizing agent to prevent irreversible aggregation.

When you see the term "bare" nanoparticles, typically this indicates that the particles are provided in the same stabilizing agent with which they were synthesized. For gold nanospheres, this means citrate; for gold nanorods, CTAB or citrate.

NanoHybrids provides Gold NanoSpheres in a 2 mM citrate solution and Gold NanoRods in 1 mM CTAB.

Since the stabilizing agents of "bare" nanoparticles are easily displaced by thiols or amines these particles offer great flexibility to perform surface modifications and conjugations. Drawbacks of "bare" gold nanoparticles include reduced stability and cytotoxicity if unmodified. Generally, PEGylated gold nanoparticles can be employed to reduce immunogenicity, and can also be supplied with a variety of surface functionalizations.

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Related links:

Ask an expert: What is the difference between citrate, CTAB, PEG & Silica coatings?

Ask an expert: How do I prevent aggregation of gold nanoparticles?

Gold nanoparticles & Antibody conjugations