Complexation of 5-aminovaleric acid zwitterions in aqueous/methanol solution by heterotopic tri-cationic receptors.

Heterotopic tri-cationic receptors based on 4,10,16-triaza-18-crown-6 are capable of efficient and selective binding of the zwitterionic form of 5-aminovaleric acid (5-AVA) in aqueous/methanol solution. The cooperative participation of both cation and anion binding domains of this receptor in 5-AVA complexation was established by 1H NMR experiments and DFT calculations. Heterotopic receptors and fluorescein were used for the preparation of indicator displacement assay and this assembly was applied to selective optical sensing of 5-aminovaleric acid.

Covalently Linked Bis(Amido-Corroles): Inter- and Intramolecular Hydrogen-Bond-Driven Supramolecular Assembly.

Four bis-corroles linked by diamide bridges were synthesized through peptide-type coupling of a trans-A2 B-corrole acid with aliphatic and aromatic diamines. In the solid state, the hydrogen-bond pattern in these bis-corroles is strongly affected by the type of solvent used in the crystallization process. Although intramolecular hydrogen bonds play a decisive role, they are supported by intermolecular hydrogen bonds and weak N-H⋅⋅⋅π interactions between molecules of toluene and the corrole cores. In an analogy to mono(amido-corroles), both in crystalline state and in solutions, the aliphatic or aromatic bridge is located directly above the corrole ring. When either ethylenediamine or 2,3-diaminonaphthalene are used as linkers, incorporation of polar solvents into the crystalline lattice causes a roughly parallel orientation of the corrole rings. At the same time, both NHCO⋅⋅⋅NH corrole hydrogen bonds are intramolecular. In contrast, solvation in toluene causes a distortion with one of the hydrogen bonds being intermolecular. Interestingly, intramolecular hydrogen bonds are always formed between the -NHCO- functionality located further from the benzene ring present at the position 10-meso. In solution, the hydrogen-bonds pattern of the bis(amido-corroles) is strongly affected by the type of the solvent. Compared with toluene (strongly high-field shifted signals), DMSO and pyridine disrupt self-assembly, whereas hexafluoroisopropanol strengthens intramolecular hydrogen bonds.

Reduced Self-Aggregation and Improved Stability of Silica-Coated Fe3O4/Ag SERS-Active Nanotags Functionalized With 2-Mercaptoethanesulfonate.

Nanocomposites combining magnetic and plasmonic properties are very attractive within the field of surface-enhanced Raman scattering (SERS) spectroscopy. Applications presented so far take advantage of not only the cooperation of both components but also synergy (enhanced properties), leading to multi-approach analysis. While many methods were proposed to synthesize such plasmonic-magnetic nanoparticles, the issue of their collective magnetic behavior, inducing irreversible self-aggregation, has not been addressed yet. Thus, here we present a simple and fast method to overcome this problem, employing 2-mercaptoethanesulfonate (MES) ions as both a SERS tag and primer molecules in the silica-coating process of the previously fabricated Fe3O4/Ag nanocomposite. The use of MES favored the formation of silica-coated nanomaterial comprised of well-dispersed small clusters of Fe3O4/Ag nanoparticles. Furthermore, adsorbed MES molecules provided a reliable SERS response, which was successfully detected after magnetic assembly of the Fe3O4/Ag@MES@SiO2 on the surface of the banknote. Improved chemical stability after coating with a silica layer was also found when the nanocomposite was exposed to suspension of yeast cells. This work reports on the application of 2-mercaptoethanesulfonate not only providing a photostable SERS signal due to a non-aromatic Raman reporter but also acting as a silica-coating primer and a factor responsible for a substantial reduction of the self-aggregation of the plasmonic-magnetic nanocomposite. Additionally, here obtained Fe3O4/Ag@MES@SiO2 SERS nanotags showed the potential as security labels for the authentication purposes, retaining its original SERS performance after deposition on the banknote.

New cubic cluster phases in the Mg-Ni-Ga system.

The crystal structure of new Mg9Ni6Ga14 and Mg3Ni2Ga compounds were investigated by single-crystal diffraction. Both structures can be described as three-core-shell cluster compounds. In the Mg6Ni9Ga14 structure, the [Ni6Ga6] icosahedron is encapsulated within the [Mg20] dodecahedron, which is again encapsulated within a [Ni18Ga42] fullerene-like truncated icosahedron, thus the three core-shell cluster [Ni6Ga6@Mg20@Ni18Ga42] results. In the Mg3Ni2Ga structure, the [Mg6] octahedron is encapsulated within the [Ni12Ga6] flattened icosahedron in vertices of which there are 12 nickel atoms, and six lateral edges are centered by gallium atoms, which in turn is encapsulated within a [Mg36] pseudo-rhombicuboctahedron with 12 additional atoms centering the lateral faces; thus for Mg3Ni2Ga the three-shell cluster is [Mg6@Ni12Ga6@Mg36].

Toward the synthesis, fluorination and application of N-graphyne.

The discovery of properties and applications of unknown materials is one of the hottest research areas in materials science. In this work, we navigate a route towards these goals by the development of a new type of graphyne nanostructure. It is synthesised by a Sonogashira cross-coupling reaction of 1,3,5-triethynylbenzene with cyanuric chloride resulting in an extended carbon-based material called TCC. Also, we modify the obtained TCC via fluorination using XeF2 at various concentrations to investigate the effect of fluorination on the triple bonds and the conjugated structure of graphyne. In this study, we put special emphasis on the determination of the impact of the fluorine content and the type of CF functionalities on the morphology, chemical and electronic structure, biocompatibility, electrical conductivity and possible applicability as anode materials for Li-ion batteries. The obtained results indicate that the character of C-F bonds influences the final properties of fluorinated materials. The polar C-F bonds are preferable for cell proliferation while CF2 groups are most suitable for battery devices, however, the appearance of PTFE-like units may have a negative impact on battery specific capacitance as well as on cell viability.

Easy Synthesis and Characterization of Holmium-Doped SPIONs.

The exceptional magnetic properties of superparamagnetic iron oxide nanoparticles (SPIONs) make them promising materials for biomedical applications like hyperthermia, drug targeting and imaging. Easy preparation of SPIONs with the controllable, well-defined properties is a key factor of their practical application. In this work, we report a simple synthesis of Ho-doped SPIONs by the co-precipitation route, with controlled size, shape and magnetic properties. To investigate the influence of the ions ratio on the nanoparticles’ properties, multiple techniques were used. Powder X-ray diffraction (PXRD) confirmed the crystallographic structure, indicating formation of an Fe3O4 core doped with holmium. In addition, transmission electron microscopy (TEM) confirmed the correlation of the crystallites’ shape and size with the experimental conditions, pointing to critical holmium content around 5% for the preparation of uniformly shaped grains, while larger holmium content leads to uniaxial growth with a prism shape. Studies of the magnetic behaviour of nanoparticles show that magnetization varies with changes in the initial Ho3+ ions percentage during precipitation, while below 5% of Ho in doped Fe3O4 is relatively stable and sufficient for biomedicine applications. The characterization of prepared nanoparticles suggests that co-precipitation is a simple and efficient technique for the synthesis of superparamagnetic, Ho-doped SPIONs for hyperthermia application.

Towards potent but less toxic nanopharmaceuticals - lipoic acid bioconjugates of ultrasmall gold nanoparticles with an anticancer drug and addressing unit.

Modification of ultrasmall gold nanoparticles (AuNPs) with the lipoic acid derivative of folic acid was found to enhance their accumulation in the cancer cell, as compared to AuNPs without addressing units. The application of lipoic acid enabled the control of the gold nanoparticle functionalities leading to enhanced solubility and allowing for attachment of both the folic acid and the cytotoxic drug, doxorubicin. More robust attachment of doxorubicin to the nanoparticle through the amide bond resulted in toxicity comparable with that of the drug alone, opening a new perspective for designing more potent, but less toxic nanopharmaceuticals. The increased uptake was accompanied by pronounced nuclear accumulation and observable cytotoxicity. Doxorubicin binding via covalent amide bonds enhanced stability of the whole drug vehicle and provided much better control over doxorubicin release in the cell environment, as compared to physical adsorption or pH sensitive bonding commonly used for anthracycline carriers. Confocal microscopy revealed that the bond was stable in the cytoplasm for 22 h. The ability to slow down the rate of drug release may be crucial for the application in sustained anticancer drug delivery. Biological analyses performed using MTT assay and confocal microscopy confirmed that the ultrasmall AuNPs with the lipoic acid derivative of folic acid exhibit relatively low cytotoxicity, however when loaded with a chemotherapeutic, they cause a significant reduction in the cell viability.