Synthesis of short chain thiol capped gold nanoparticles, their stabilization and immobilization on silicon surface

Tethering between nanoparticles and a supporting substrate, especially in the form of covalent bonding, is a highly useful way of ensuring development of robust systems for various applications. This requires bestowing specific functionalities on nanoparticle surfaces that can also prevent aggregation between nanoparticles. In this work, short chain thiol (4-aminothiophenol)-capped gold nanoparticles functionalized with amine-termination have been synthesized and changes in their morphology by varying the process conditions as well as the dispersion medium were studied. Subsequently, the nanoparticles (which are prone to agglomerate due to amine–amine hydrogen bonding), were stabilized in solution and by anhydride capping. Finally, these stabilized nanoparticles were immobilized on a SiO2 substrate. X-ray photoelectron spectroscopy (XPS) confirmed the absence of non-reacted thiol groups in the synthesized nanoparticles and presence of nanoparticles on the Si surface after the immobilization process. Transmission electron microscope (TEM) and UV–visible spectroscopy have been used to study particle morphology. Cross-sectional HR-TEM images show direct evidence that the particles are anchored to the silicon surface.