Oxidative etching was used to produce gold seeds of different sizes and crystal habits. Following detailed characterization, the seeds were grown under different conditions. Our results bring new insights toward understanding the effect of size and crystallinity on the growth of anisotropic particles, whilst identifying guidelines for the optimisation of new synthetic protocols of predesigned seeds.
Ultrafast
laser irradiation can induce morphological and structural
changes in plasmonic nanoparticles. Gold nanorods (Au NRs), in particular,
can be welded together upon irradiation with femtosecond laser pulses,
leading to dimers and trimers through the formation of necks between
individual nanorods. We used electron tomography to determine the
3D (atomic) structure at such necks for representative welding geometries
and to characterize the induced defects. The spatial distribution
of localized surface plasmon modes for different welding configurations
was assessed by electron energy loss spectroscopy. Additionally, we
were able to directly compare the plasmon line width of single-crystalline
and welded Au NRs with single defects at the same resonance energy,
thus making a direct link between the structural and plasmonic properties.
In this manner, we show that the occurrence of (single) defects results
in significant plasmon broadening.
The irradiation of spherical gold nanoparticles (AuNPs) with nanosecond laser pulses induces shape transformations yielding nanocrystals with an inner cavity. The concentration of the stabilizing surfactant, the use of moderate pulse fluences, and the size of the irradiated AuNPs determine the efficiency of the process and the nature of the void. Hollow nanocrystals are obtained when molecules from the surrounding medium (e.g., water and organic matter derived from the surfactant) are trapped during laser pulse irradiation. These experimental observations suggest the existence of a subtle balance between the heating and cooling processes experienced by the nanocrystals, which induce their expansion and subsequent recrystallization keeping exogenous matter inside. The described approach provides valuable insight into the mechanism of interaction of pulsed nanosecond laser with AuNPs, along with interesting prospects for the development of hollow plasmonic nanoparticles with potential applications related to gas and liquid storage at the nanoscale.
The implementation of plasmonic nanoparticles in vivo remains hindered by important limitations such as biocompatibility, solubility in biological fluids, and physiological stability. A general and versatile protocol is presented, based on seeded emulsion polymerization, for the controlled encapsulation of gold and silver nanoparticles. This procedure enables the encapsulation of single nanoparticles as well as nanoparticle clusters inside a protecting polymer shell. Specifically, the efficient coating of nanoparticles of both metals is demonstrated, with final dimensions ranging between 50 and 200 nm, i.e., sizes of interest for bio-applications. Such hybrid nanocomposites display extraordinary stability in high ionic strength and oxidizing environments, along with high cellular uptake, and low cytotoxicity. Overall, the prepared nanostructures are promising candidates for plasmonic applications under biologically relevant conditions.
Pinhole free, uniform and conformal oxidation barrier on Cu and Fe powder.• Proper agitation of the powder is required and performed by a rotating ALD reactor.• Al2O3 coating of 8 nm on Cu powder causes a shift of oxidation temperature of 200 °C • Al2O3 coating of 25 nm on Fe powder causes a shift of oxidation temperature of 400 °C
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