Hi
I am looking for a way to synthesize amide functionalized gold nanoparticles from mercaptocarboxylic acid functionalized gold nanoparticles. In order to keep these particles stable, the surface carboxylic acid ligands are deprotonated using ammonium hydroxide. I would like to find slow coupling agents that can help the carboxylate ions to bind with alkyl amines and preferably speeden up the reaction with heat.
Regards
Rifat
Dear Rifat,
Commonly found carboxylic groups can be reacted with primary amines by means of a condensation reaction to yield amide bonds. For this, a water-soluble carbodiimide (e.g. EDC) is commonly used. For more on this method, please see Figure 4 (a) in the publication contained in the following link:
Common conjugation reaction for particles with carboxylic acid function: the water-soluble carbodiimde EDC forms an unstable intermediate, a so-called ‘activated’ carboxylic group. This can either hydrolyse or react with a primary amino group under formation of a stable amide bond.
Figure 4 (a)
Hermanson G. T. (2008) Bioconjugate techniques (Academic Press, San Diego, CA), 2nd edn.
http://rsta.royalsocietypublishing.org/content/368/1915/1333
Another source which can be utilized to prepare your desired product is the following:
Phase Transfer of Large Gold Nanoparticles to Organic Solvents with Increased Stability
Article in Langmuir 23(3):1414-8 · February 2007
DOI: 10.1021/la0617560 · Source: PubMed
Abstract
In this paper, we describe a new procedure to phase transfer large gold nanoparticles (diameters > 45 nm) from aqueous solution to organic solvents. This is accomplished using a covalent amide coupling reaction that incorporates dicyclohexylamine (DCHA) headgroups on the surface of mercaptoacetic acid (MAA) functionalized gold nanoparticles. Gold nanoparticles are first synthesized in aqueous solution by the citrate-reduction method, and nanoparticle size is controlled by the molar ratio of the reducing agent (sodium citrate) and the gold precursor (KAuCl4). MAA is then adsorbed to the surface of the gold nanoparticles followed by an amide-coupling reaction to covalently attach DCHA to the surface-immobilized MAA. The bulky dicyclohexyl groups entropically stabilize gold nanoparticles in organic solvents. This procedure was used to reliably transfer gold nanoparticles with diameters between 45 and 100 nm from aqueous solution to organic solvents such as dimethyl sulfoxide and chloroform.
https://www.researchgate.net/publication/6562144_Phase_Transfer_of_Large_Gold_Nanoparticles_to_Organic_Solvents_with_Increased_Stability
Hoping this will be helpful,
Rafik
Article Phase Transfer of Large Gold Nanoparticles to Organic Solven...
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