Imaging the cellular uptake of tiopronin-modified gold nanoparticles

Well-dispersed gold nanoparticles (NP) coated with tiopronin were synthesized by X-ray irradiation without reducing agents. High-resolution transmission electron microscopy shows that the average core diameters of the NPs can be systematically controlled by adjusting the tiopronin to Au mole ratio in the reaction. Three methods were used to study the NP uptake by cells: quantitative measurements by inductively coupled plasma mass spectrometry, direct imaging with high lateral resolution transmission electron microscopy and transmission X-ray microscopy. The results confirmed that the NP internalization mostly occurred via endocytosis and concerned the cytoplasm. The particles, in spite of their small sizes, were not found to arrive inside the cell nuclei. The synthesis without reducing agents and solvents increased the biocompatibility as required for potential applications in analysis and biomedicine in general.     

A Tunable Multicolor Photoluminescent Nanocarbon Prepared from Castor Oil Soot

We herein report a straightforward soot‐based synthesis and characterization of the negatively charged, hydrophilic, photoluminescent nanocarbon. The photoluminescent nanocarbon was prepared by refluxing castor oil soot in nitric acid. The as‐obtained fluorescent nanocarbon shows multiple colors under UV exposure and was characterized with surface morphological and spectral studies. Additionally, the photoluminescence nature of the nanocarbon was tunable by changing the pH or the dilution factor. During the course of the investigation, it has been found that, the photoluminescence nature observed here is not attributed to the presence of poly aromatic hydrocarbons, but solely due to the trait of the fluorescent nanocarbon. These results indicate that interparticle surface plasmon resonance plays a key role in the exhibition of photoluminescence. Furthermore, the feasibility of photoluminescent nanocarbon as a plausible tool for cell imaging and electrochemical application of the oxidized nanocarbon has also been examined.     

A compact synchrotron‐based transmission X‐ray microscope

A compact transmission X‐ray microscope has been designed and implemented based on a cylindrical symmetry around the optical axis that sharply limits the instabilities due to thermal mechanical drift. Identical compact multi‐axis closed‐loop actuation modules drive different optical components. The design is modular and simplifies the change of individual parts, e.g. the use of different magnification and focusing devices. This compact instrument can be easily transported between laboratory and synchrotron facilities and quickly put into operation. An automated alignment mechanism simplifies the assembly of different modules after transportation. After describing the design details, the results of the first tests are presented.     

Roles of interface and oxide trap density in the kinked current behavior of Al/SiO2/Si(p) structures with ultra-thin oxides

A clear current kinked phenomenon was observed in Al/SiO₂/Si(p) structures with nanoscale (<2.5 nm) SiO₂ in a forward biased region. It was found that the kinked points are dependent on oxide thickness and are not the same as flat-band voltages. A model regarding the oxide voltage dropping efficiency with the consideration of interface trap density ( $D_{\mathrm{it}}$ ) and effective charge number density ( $Q_{\mathrm{eff}}/q$ ) was proposed for the observation. It is noted that the kinked point is severely affected by the oxide quality and uniformity. However, Al/SiO₂/Si(n) structures in a forward biased region do not exhibit this current kinked phenomenon because the dropping behavior of oxide is absolutely different from Al/SiO₂/Si(p) structures.     

One-pot tuning of Au nucleation and growth: from nanoclusters to nanoparticles

We describe a simple and effective method to obtain colloidal surface-functionalized Au nanoparticles. The method is primarily based on irradiation of a gold solution with high-flux X-rays from a synchrotron source in the presence of 11-mercaptoundecanoic acid (MUA). Extensive tests of the products demonstrated high colloidal density as well as excellent stability, shelf life, and biocompatibility. Specific tests with X-ray diffraction, UV-visible spectrometry, visible microscopy, Fourier transform infrared spectroscopy, dark-field visible-light scattering microscopy, and transmission electron microscopy demonstrated that MUA, being an effective surfactant, not only allows tunable size control of the nanoparticles, but also facilitates functionalization. The nanoparticle sizes were 6.45 ± 1.58, 1.83 ± 1.21, 1.52 ± 0.37 and 1.18 ± 0.26 nm with no MUA and with MUA-to-Au ratios of 1:2, 1:1, and 3:1. The MUA additionally enabled functionalization with l-glycine. We thus demonstrated flexibility in controlling the nanoparticle size over a large range with narrow size distribution.     

Extended utility of molten-salt chemistry: unprecedented synthesis of a water-soluble salt-inclusion solid comprised of high-nuclearity vanadium oxide clusters

Polyoxometallates (POMs) are desirable in materials applications ranging from uses as catalysts in selective oxidation reactions to molecular-like building blocks for the preparation of new extended solids. With the use of an unprecedented approach involving high temperature, molten salt methods, a fascinating series of salt-inclusion solids (SISs) that contain high nuclearity POMs has been isolated for the first time. Cs(11)Na(3)(V(15)O(36))Cl(6) (1) was synthesized using the eutectic NaCl/CsCl flux (mp 493 °C) which serves as a reactive solvent in crystal growth and allows for the SIS formation. Its framework can be viewed as an "ionic" lattice composed of alternately packed counterions of Cl-centered [V(15)O(36)Cl](9-) clusters (V15; S = 11/2) and multinuclear [Cs(9)Na(3)Cl(5)](7+) cations. In light of the structural analysis, 1 was proven to be soluble in water giving rise to a dark green solution that is similar in color to single crystals of the title compound. Infrared spectroscopy of the solid formed from fast evaporation of the solution supports the presence of dissolved V15 clusters. Also noteworthy is the magnetization of 1 at 2 K, which reveals an s-shaped plot resembling that of superparamagnetic materials.     

Synthesis of Nucleobase‐Functionalized Carbon Nanotubes and Their Hybridization with Single‐Stranded DNA

For the first time ssDNA (25‐aptamer of mixed dA, dT, dG, and dC) was wrapped around functionalized single‐walled carbon nanotubes (SWCNTs), whose external surfaces were attached to multiple triazole‐(ethylene glycol)‐dA ligands. This method of hybridization involved the formation of hydrogen bonds between dT of ssDNA and dA of functionalized SWCNTs. It deviates from the reported π–π stacking between the nucleobases of DNA and the external sidewalls of nanotubes. The structural properties of the functionalized SWCNTs and its ssDNA complex were characterized by spectroscopic (including CD and Raman), thermogravimetric, and microscopic (TEM) methods. The results thus obtained establish a new platform of DNA delivery by use of nanotubes as a new vehicle with great potential in biomedical applications and drug development.