Shape-controlled synthesis of NIR absorbing branched gold nanoparticles and morphologystabilization with alkanethiols

Abstract

Gold nanoparticles are ideal candidates for clinical applications if their plasmon absorptionband is situated in the near infrared region (NIR) of the electromagnetic spectrum. Variousparameters, including the nanoparticle shape, strongly influence the position of thisabsorption band. The aim of this study is to produce stabilized NIR absorbingbranched gold nanoparticles with potential for biomedical applications. Hereto,the synthesis procedure for branched gold nanoparticles is optimized varyingthe different synthesis parameters. By subsequent electroless gold plating theplasmon absorption band is shifted to 747.2 nm. The intrinsic unstable nature ofthe nanoparticles’ morphology can be clearly observed by a spectral shift andlimits their use in real applications. However, in this article we show how thestabilization of the branched structure can be successfully achieved by exchanging theinitial capping agent for different alkanethiols and disulfides. Furthermore, whenusing alkanethiols/disulfides with poly(ethylene oxide) units incorporated, anincreased stability of the gold nanoparticles is achieved in high salt concentrationsup to 1 M and in a cell culture medium. These achievements open a plethora ofopportunities for these stabilized branched gold nanoparticles in nanomedicine.