Plasmon Controlled Shaping of Metal Nanoparticle Aggregates by Femtosecond Laser-Induced Melting

In this work, we show how to control the morphology of femtosecond laser melted gold nanosphere aggregates. A careful choice of both laser fluence and wavelength makes it possible to selectively excite different aggregate substructures to produce larger spherical nanoparticles, nanorods, and nanoprisms or necklace-like 1D nanostructures in which the nanoparticles are interlinked by bridges. Finite integral technique calculations have been performed on the near-field concentration of light in the nanostructures which confirm the wavelength dependence of the light concentration and suggest that the resulting localized high intensities lead to nonthermal melting. We show that by tuning the wavelength of the melting light it is possible to choose the spatial extension of the ensembles of NPs heated thus allowing us to exhibit control over the morphology of the nanostructures formed by the melting process. By a proper combination of this method with self-assembly of chemically synthesized nanoparticles, one can envisage the development of an innovative high-throughput high-resolution nanofabrication technique.

Synthesis of functionalized gold nanoparticles capped with 3-mercapto-1-propansulfonate and 1-thioglucose mixed thiols and "in vitro" bioresponse

The synthesis, characterization and assessment of biological behavior of innovative negatively charged functionalized gold nanoparticles is herein reported, for potential applications in the field of radiotherapy and drug delivery. Gold nanoparticles (AuNPs) functionalized with two capping agents, i.e., the 3-mercapto-1-propansulfonate (3-MPS) and 1-β-thio-D-glucose (TG), have been on purpose synthesized and fully characterized. Advanced characterization techniques including X-Ray Photoelectron Spectroscopy (XPS) were applied to probe the chemical structure of the synthesized nanomaterials. Z-potential and Dynamic Light Scattering measurements allowed assessing the nanodimension, dispersity, surface charge and stability of AuNPs. Transmission Electron Microscopy (TEM) and Flame Atomic Absorption Spectroscopy (FAAS) were applied to the "in vitro" HSG cell model, to investigate the nanoparticles-cells interaction and to evaluate the internalization efficiency, whereas short term cytotoxicity and long term cell killing were evaluated by means of MTT and SRB assays, respectively. In conclusion, in order to increase the amount of gold atoms inside the cell we have optimized the synthesis for a new kind of biocompatible and very stable negatively charged TG-functionalized nanoparticles, with diameters in a range that maximize the uptake in cells (i.e., ∼15nm). Such particles are very promising for radiotherapy and drug delivery application.

Negatively charged gold nanoparticles as a dexamethasone carrier: stability in biological media and bioactivity assessment in vitro

AuNP and AuNP/DXM stability and drug release kinetics in different biological media.

Silver nanoparticles linked by a Pt-containing organometallic dithiol bridge: study of local structure and interface by XAFS and SR-XPS

Silver nanoparticles (AgNPs) functionalized with an organometallic bifunctional thiol containing Pt(ii) centers, generated in situ from trans-trans-[thioacetyl-bistributylphosphine-diethynylbiphenyl-diplatinum(ii)], were synthesized with different sulphur/metal molar ratios (i.e. AgNPs-1 and AgNPs-2) with the aim to obtain nanosystems of different mean size and self-organization behaviour. AgNPs spontaneously self-assemble, giving rise to 2D networks, as previously assessed. In this work a deeper insight into the chemico-physical properties of these AgNPs is proposed by means of synchrotron radiation induced X-ray photoelectron spectroscopy (SR-XPS) and X-ray absorption fine structure spectroscopy (XAFS) techniques. The results are discussed in order to probe the interaction at the interface between a noble metal and a thiol ligand at the atomic level and the aim of this study is to shed light on the chemical structure and self-organization details of nanosystems. The nature of the chemical interaction between the dithiol ligand and the Ag atoms on the nanoparticle surface was investigated by combining SR-XPS (S2p, Ag3d core levels) and XAS (S and Ag K-edges) analysis. UV-visible absorption and emission measurements were also carried out on all samples and compared with TD-DFT calculations so as to get a better understanding of their optical behavior and establish the nature of the excitation and emission processes.

Gold nanoparticles and gold nanoparticle-conjugates for delivery of therapeutic molecules. Progress and challenges

Gold nanoparticles and their conjugates as drug delivery vehicles for selective targeting of cancer cells.

Dielectric relaxations of ionic thiol-coated noble metal nanoparticles in aqueous solutions: electrical characterization of the interface

The radiowave dielectric properties of organothiol monolayer-protected Au and Ag metallic nanoparticles have been investigated in the frequency range of 10 kHz to 2 GHz, where a dielectric relaxation, due to the polarization of the ionic atmosphere at the aqueous interface, occurs. The simultaneous measurement of the particle size, by means of dynamic light scattering technique, and of the particle electrical charge, by means of laser microelectrophoresis technique, allow us to describe the whole dielectric behavior at the light of the standard electrokinetic model for charged colloidal particles. Au and Ag metallic nanoparticles experience a large charge renormalization, in agreement with the counterion condensation effect for charged spherical colloidal particles. The value of the effective valence Z(eff) of each nanoparticle investigated has been evaluated thanks to the dielectric parameters of the observed relaxation process and further confirmed by direct current electrical conductivity measurements. All in all, these results provide support for the characterization of the electrical interfacial properties of metallic nanoparticles by means of dielectric relaxation measurements.