Five-branched gold nanostars are obtained using Triton X-100 in a seed-growth synthesis. They have the uncommon feature of two intense localized surface plasmon resonances (LSPRs) in the 600-900 and 1100-1600 nm ranges. Both LSPRs convert laser radiation into heat, offering two photothermally active channels in the NIR and SWIR ranges.

By replacing cetyltrimethylammonium bromide (CTAB) with the zwitterionic lauryl sulfobetaine (LSB) surfactant in the classical seed-growth synthesis, monocrystalline gold nanostars (m-NS) and pentatwinned gold asymmetric nanostars (a-NS) were obtained instead of nanorods. The main product under all synthetic conditions was a-NS, which have branches with high aspect ratios (AR), thus leading to LSPR absorptions in the 750-1150 nm range. The percentage of m-NS versus a-NS, the aspect ratio of the a-NS branches, and consequently the position of their LSPR absorption can be finely tuned simply by regulating the concentration of reductant, the concentration of surfactant, or the concentration of the "catalytic" Ag(+) cation. The m-NS have instead shorter and larger branches, the AR of which is poorly influenced by synthetic conditions and displays an LSPR positioned around 700 nm. A growth mechanism that involves the direct contact of the sulfate moiety of LSB on the surface of the nano-object is proposed, thereby implying preferential coating of the {111} Au faces with weak interactions. Consistent with this, we also observed the straightforward complete displacement of the LSB surfactant from the surface of the nanostars. This was obtained by the simple addition of thiols in aqueous solution to yield extremely stable coated a-NS and m-NS that are resistant to highly acidic, basic, and in similar to in vivo conditions.

Asymmetric branched gold nanoparticles are obtained using for the first time in the seed-growth approach a zwitterionic surfactant, laurylsulfobetaine, whose concentration in the growth solution allows to control both the length to base-width ratio of the branches and the LSPR position, that can be tuned in the 700-1100 nm near infrared range.

Monolayers of gold nanostars (GNS) are grafted on mercaptopropyltrimethoxysilane-coated glass slides. In the formed monolayers the localized surface plasmon resonance of GNS can be tuned in the 700-1100 nm range. Upon laser excitation of the nearIR LSPR an efficient photothermal response is observed, inducing local hyperthermia and efficient killing of Staphylococcus aureus biofilms.

We developed an all-optical method to measure the temperature on gold (nanorods and nanostars) and magnetite nanoparticles under near-infrared and radiofrequency excitation by monitoring the excited state lifetime of Rhodamine B that lies within =/~20 nm from the nanoparticle surface. We reached high temperature sensitivity (0.029 ± 0.001 ns/°C) and low uncertainty (±0.3 °C). Gold nanostars are =/~3 and =/~100 times more efficient than gold nanorods and magnetite nanoparticles in inducing localized hyperthermia.

Under the action of near-infrared radiation, shape anisotropic gold nanoparticles emit two-photon luminescence and release heat. Accordingly, they have been proposed for imaging, photothermal therapies and thermo-controlled drug delivery. In all these applications particular care must be given to control the nanoparticle − cell interaction and the thermal efficiency of the nanoparticles, while minimizing their intrinsic cytotoxicity. We present here the characterization of the cell interaction of newly developed branched gold nanostars, obtained by laurylsulfobetaine-driven seed-growth synthesis. The study provides information on the size distribution, the shape anisotropy, the cellular uptake and cytotoxicity of the gold nanostars as well as their intracellular dynamic behavior by means of two-photon luminescence imaging, fluorescence correlation spectroscopy and particle tracking. The results show that the gold nanostars are internalized as well as the widely used gold nanorods and are less toxic under prolonged treatments. At the same time they display remarkable twophoton luminescence and large extinction under polarized light in the near-infrared region of the spectrum, 800−950 nm. Gold nanostars appear then a valuable alternative to other elongated or in-homogeneous nanoparticles for cell imaging.

Monolayers of photothermally responsive gold nanostars on PEI-coated surfaces display two localized surface plasmon resonances (LSPRs) in the near-IR region that can be laser-irradiated either separately, obtaining two different T jumps, or simultaneously, obtaining a T jump equal to the sum of those obtained with separate irradiations.

Many natural products have been used as a model for the development of new drugs and agrochemicals. Following this strategy 11 rubrolide analogues, bearing electron-withdrawing and -donating groups at both benzene rings, were prepared starting from commercially available mucobromic acid. The ability of all compounds to inhibit the photosynthetic electron transport chain in the chloroplast was investigated. The rubrolide analogues were effective in interfering with the light-driven ferricyanide reduction by isolated chloroplasts. The IC(50) values of the most active derivatives are in fact only 1 order of magnitude higher than those of commercial herbicides sharing the same mode of action, such as Diuron (0.27 μM). QSAR studies indicate that the most efficient compounds are those having higher ability to accept electrons, either by a reduction process or by an electrophilic reaction mechanism. The results obtained suggest that the rubrolide analogues represent promising candidates for the development of new active principles targeting photosynthesis to be used as herbicides.