Abstract
Colloidal gold nanoparticles are a widespread nanomaterial with many potential applications, but their aggregation in suspension is a critical issue which is usually prevented by organic surfactants. This solution has some drawbacks, such as material contamination and modifications of its functional properties. The gold nanoparticles presented in this work have been synthesized by ultra-fast laser ablation in liquid, which addresses the above issues by overcoating the metal nanoparticles with an oxide layer. The main focus of the work is in the characterization of the oxidized gold nanoparticles, which were made first in solution by means of dynamic light scattering and optical spectroscopy, and then in dried form by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and finally by surface potential measurements with atomic force microscopy. The light scattering assessed the nanoscale size of the formed particles and provided insight in their stability. The nanoparticles’ size was confirmed by direct imaging in transmission electron microscopy, and their crystalline nature was disclosed by X-ray diffraction. The X-ray photoelectron spectroscopy showed measurements compatible with the presence of surface oxide, which was confirmed by the surface potential measurements, which are the novel point of the present work. In conclusion, the method of laser ablation in liquid for the synthesis of gold nanoparticles has been presented, and the advantage of this physical approach, consisting of coating the nanoparticles in situ with gold oxide which provides the required morphological and chemical stability without organic surfactants, has been confirmed by using scanning Kelvin probe microscopy for the first time.
Highlights
Gold (Au) nanoparticles (NPs) are used in many applications [1,2], from biology-oriented fluorescent labeling for microscopy [3] to biomedical drug-delivery carriers [4] or vectors for thermal cancer treatment [5], on to optoelectronic applications thanks to the plasmonic properties, e.g., for surface-enhanced Raman scattering (SERS) spectroscopy [6,7]
One way to minimize the issues correlated with the organic coating is to provide the metal NPs with an alternative oxide coating soon after synthesis, which is the natural result of the laser ablation (LA) technique described in this work [31]
The particles were first measured in the same liquid medium of the synthesis for assessment of their size by dynamic light scattering (DLS) soon after synthesis
Summary
Gold (Au) nanoparticles (NPs) are used in many applications [1,2], from biology-oriented fluorescent labeling for microscopy [3] to biomedical drug-delivery carriers [4] or vectors for thermal cancer treatment [5], on to optoelectronic applications thanks to the plasmonic properties, e.g., for surface-enhanced Raman scattering (SERS) spectroscopy [6,7]. The same as for all colloidal NPs, one critical issue is the aggregation and/or instability of Au NPs in suspension, and this is usually addressed by means of organic surfactants [24,25,26]. These organic coatings are effective, yet contaminate the material and may give rise to side effects on the functional properties of the NPs, especially in view of their optical response [27,28] and mechanical or morphological behavior when used, for example, in composites [29,30]. Is the oxide passivating layer more stable than any possible organic ligand, due to the intrinsic properties of oxides (i.e., chemical inertness, thermal stability, physical properties such as hardness), and it is intrinsically limited to the NP surface
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
