Sterical ligand stabilization of nanocrystals versus electrostatic shielding by ionic compounds: a principle model study with TEM and XPSElectronic supplementary information (ESI) available: Statistical size analysis of TEM micrographs, scheme illustrating the size change during purification, XPS survey and Au4f detail spectra. See DOI: 10.1039/c6ra27454d

• Main Authors: Mohrhusen, Lars, Osmi, Milena
• Format: Journal Article
• Language: English
• Published: 24-02-2017
• ISSN: 2046-2069
• DOI: 10.1039/c6ra27454d

Colloidal metal nanoparticles are usually fabricated
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the reduction of metal salt precursor compounds in liquid phase. To prevent agglomeration, organic capping agents are used. Commonly, it is neglected that ionic compounds may coadsorb when present in the mixture. However, we shall show that ionic adsorbates play a key role in size and growth control. We present a universal case study on gold nanoparticles with various amine ligands to reveal two competitive stabilization mechanisms
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quantitative X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Gold nanocrystals were obtained starting with a single phase room temperature synthesis. The stabilization turned out to be a combination of sterical and electrostatic shielding depending on the ligand molecule properties. We can adjust the ratio of both contributions
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simple liquid phase ligand exchange procedures at moderate temperatures as shown with XPS. Apparently, ions further have the power to steer different ripening processes. HR-TEM studies proved that there is no influence on nanoparticle morphology during heat treatment or ligand exchange. Introducing a lack of stabilization by weaker sterical ligands offers an auspicious new way for the synthesis of porous nanomaterials. The novel findings illustrate that electrostatic stabilization by coadsorbed ionic compounds can play a crucial role in understanding various experimental results and thus the colloidal synthesis of nanomaterials in general appears in a new light.
Electrostatic
versus
sterical ligand stabilization: competitive stabilization mechanism play a key role in the control of nanomaterial properties.