Au(I) N-heterocyclic carbenes from bisimidazolium amphiphiles: synthesis, cytotoxicity and incorporation onto gold nanoparticles

A gold(I) N-heterocyclic carbene 4 from a bis-imidazolium-amphiphile was synthesized and characterized. The cytotoxicity against HT-29 colon carcinoma and MDA-MB-231 breast adenocarcinoma cells was assessed for the NHC complex 4, the imidazolium salt precursor 2, and its methyl analogue 3, indicating that compounds 2–4 are promising cytotoxic agents. Furthermore, the ability of these compounds to be associated with gold nanoparticles was also explored, in order to develop an anticancer drug delivery system. The free ligands displayed more activity when compared with the ligands immobilized on the gold nanoparticles. The synthesized gold particles incorporating the bis-imidazolium salts either 2 or 3 showed monodisperse spherical shape with sizes of approximately 5 nm

Developing Biotemplated Data Storage: Room Temperature Biomineralization of L1<inf>0</inf> CoPt Magnetic Nanoparticles

L10 cobalt platinum can be used to record data at approximately sixfold higher densities than it is possible to on existing hard disks. Currently, fabricating L10 CoPt requires high temperatures (≈500 °C) and expensive equipment. One ecological alternative is to exploit biomolecules that template nanomaterials at ambient temperatures. Here, it is demonstrated that a dual affinity peptide (DAP) can be used to biotemplate L10 CoPt onto a surface at room temperature from an aqueous solution. One part of the peptide nucleates and controls the growth of CoPt nanoparticles from solution, and the other part binds to SiO2. A native silicon oxide surface is functionalized with a high loading of the DAP using microcontact printing. The DAP biotemplates a monolayer of uniformly sized and shaped nanoparticles when immobilized on the silicon surface. X-ray diffraction shows that the biotemplated nanoparticles have the L10 CoPt crystal structure, and magnetic measurements reveal stable, multiparticle zones of interaction, similar to those seen in perpendicular recording media. This is the first time that the L10 phase of CoPt has been formed without high temperature/vacuum treatment (e.g., annealing or sputtering) and offers a significant advancement toward developing environmentally friendly, biotemplated materials for use in data storage

Modulating Semiconductor Surface Electronic Properties by Inorganic Peptide–Binders Sequence Design

The use of proteins and peptides as part of biosensors and electronic devices has been the focus of intense research in recent years. However, despite the fact that the interface between the bioorganic molecules and the inorganic matter plays a significant role in determining the properties of such devices, information on the electronic properties of such interfaces is sparse. In this work, we demonstrate that the identity and position of single amino acid in short inorganic binding protein-segments can significantly modulate the electronic properties of semiconductor surfaces on which they are bound. Specifically, we show that the introduction of tyrosine or tryptophan, both possessing an aromatic side chain which higher occupied molecular orbitals are positioned in proximity to the edge of GaAs valence band, to the sequence of a peptide that binds to GaAs (100) results in changes of both the electron affinity and surface potential of the semiconductor. These effects were found to be more pronounced than the effects induced by the same amino acids once bound on the surface in a head–tail configuration. Furthermore, the relative magnitude of each effect was found to depend on the position of the modification in the sequence. This sequence dependent behavior is induced both indirectly by changes in the peptide surface coverage, and directly, probably, due to changes in the orientation and proximity of the tyrosine/tryptophan side group with respect to the surface due to the preferred conformation the peptide adopts on the surface. These studies reveal that despite the use of short protein oligomers and aiming at a non-natural-electronic task, the well-known relations between the proteins’ structure and function is preserved. Combining the ability to tune the electronic properties at the interface with the ability to direct the growth of inorganic materials makes peptides promising building blocks for the construction of novel hybrid electronic devices and biosensors

Peptide-functionalized semiconductor surfaces: strong surface electronic effects from minor alterations to backbone composition

Semiconductor surface electronic properties are shown to be sensitive to subtle changes in the backbone composition of surface-bound dipeptide ligands.</p

Surface characterization of U(AlxSi1-x)3 alloy and its interaction with O2 and H2O, at room temperature

Surface characterization and the interactions of U(AlxSi1-x)3 alloy (x = 0.57) with oxygen and water vapor were studied, utilizing X-Ray Photoelectron Spectroscopy and Direct Recoil Spectrometry, at room temperature. The U 4f spectrum of U(AlxSi1-x)3 alloy exhibits weak correlation satellites, suggesting an itinerant description of the U 5f states for this compound. The Al and Si 2p lines are chemically shifted to lower binding energies. Exposing the alloy to oxygen and water vapor results in oxidation of mainly the uranium and aluminum components, while silicon is only slightly oxidized. Oxygen was found to be a stronger oxidizer than water vapor and the trend is consistent with the more negative enthalpies of formation of metal oxides produced by the O2 reaction, as compared to H2O. During oxygen exposure, fast oxidation occurs by oxide islands nucleation and lateral growth, followed by oxidation of the sub-surface, up to ∼4 nm, at 1000 L exposure. Water initially reacts with the surface by full dissociation and oxide islands formation, which is then covered by hydroxides. Only a minor increase in the oxide thickness of up to ∼2.5 nm, was observed after coalescence.JRC.G.I.5-Advanced Nuclear Knowledg